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Table of Content
    Volume 28 Issue 1
    10 January 2004
    Research Articles
    Reproductive Characteristics of Globba lancangensis and Their Evolutionary Implications
    LIU Zhi-Qiu, CHEN Jin, BAI Zhi-Lin
    Chin J Plan Ecolo. 2004, 28 (1):  1-8.  doi:10.17521/cjpe.2004.0001
    Abstract ( 2331 )   PDF (365KB) ( 1153 )   Save
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    Andromonoecy, i.e. presence of both male and bisexual (hermaphroditic) flowers on the same individuals of a species, is quite common in both wind- and animal-pollinated seed plants, while its ecological and evolutionary implications are still not fairly understood. In this paper we demonstrate an andromonoecious mating system in a native perennial herb, Globba lancangensis (Zingiberaceae), found in Xishuangbanna, SW China. Firstly, we describe the floral biology of this species: pollen viabilities, fruit-set ratios, behaviors of visiting insects and so forth, and then compare the morphological differences between male and hermaphroditic flowers. Secondly, we present the results of experiments designed to determine its breeding system, and to test whether this system has a self-incompatibility mechanism. Thirdly, we show the variations of sexual expression in this species with emphasis on the change of male : hermaphrodite ratios. Finally, we discuss the ecological and evolutionary implications of the variations in reproductive characteristics.Male and hermaphroditic flowers differed in several dimensions. Hermaphroditic flowers have significantly larger ovaries, longer corolla tubes, marginally wider staminodes and longer labellums. Hermaphroditic flowers have 48.4±12.2 (n=32) ovules in each ovary while male flowers have almost no viable ovules in their much smaller ovaries. Male flowers have 1 372±312 (n=32) pollen grains per anther, which is marginally more than that in hermaphroditic flowers with 1 099±346 (n=32). Male flowers also have a significantly longer anther appendage than hermaphroditic flowers. In natural populations, both male and hermaphroditic flowers open at 2∶30-3∶00 and the anthers dehisce at 5∶30-6∶00. There is no significant difference between male and hermaphroditic flowers in flower-opening and anther-dehiscing time. However, the male flowers shed at 13∶30-14∶00 while hermaphroditic flowers may stay until 4∶00 next morning. The pollen viabilities of hermaphrodite flowers were higher until 16∶00 in contrast to male flowers whose pollen viabilities decreased abruptly after noon. A ramet may present either a single male or a single hermaphrodite flower for many days during flowering, making itself temporally androdioecious, and may thus promote outcrossing. The existence of male flowers may offer offsets of pollen for the perfect flowers, which have relatively low P/O ratios (23±7, n=32). Thus, G. lancangensis may achieve its seed set by regulating the ratios of male to hermaphroditic flowers in community. There were no significant differences in fruit-set ratios between hand-selfing (17.2% or 17.7%) and hand-crossing (16.4% or 15.3%) but significant differences in seed-set ratios (seed/ovule ratios) were seen (5.71% or 6.89% vs. 42.76% or 42.99%), which suggested that this plant might maintain the mechanism of self-incompatibility. In contrast to previous reports that butterflies were visitors for Globba, two species of bees, Megapis dorstata and Nomia strigata, are the main visitors for G. lancangensis, while the former is the effective pollinator. G. lancangensis may encourage out-crossing by means of both andromonoecy and self-incompatibility.

    Size-Dependent Reproduction and Sex Allocation in Five Species of Ranunculaceae
    ZHAO Zhi-Gang, DU Guo-Zhen, REN Qing-Ji
    Chin J Plan Ecolo. 2004, 28 (1):  9-16.  doi:10.17521/cjpe.2004.0002
    Abstract ( 2276 )   PDF (335KB) ( 1328 )   Save
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    Reproductive allocation and sex allocation are central to plant life-history theory. Especially in recent years, more and more ecologists and evolutionists have focused on the sex allocation theory. Reproductive allocation discusses the trade-off between growth and reproduction, and sex allocation primarily studies the optimal allocation of resources to two sexes, which may explain the diversity of breeding systems in plants. To examine the adaptation of size-dependent resource allocation and discuss the effective factors on resource allocation, the variations of reproductive and sex allocation of five insect-pollinated hermaphrodite species in Ranunculaceae were studied in two populations, located separately at East Tibetan Alpine Meadow (3 500 m) and Sub-Alpine Meadow (2 900 m). Sampling positions were located in Maqu (101°53′ E, 35°58′ N) and Hezuo (102°53′ E, 34°55′ N) in Gansu Province, respectively. From June to September in 2001, we sampled stochastically by the different phenology of five species at floral stage including under- and above-ground parts. The samples collected were individually enclosed into sampling bottles and fixed in FAA (alcohol, formaldehyde, acetic acid, 8∶1∶1). The samples were heated to constant weight for 10 h at 65 ℃. Each individual was dissected into different parts, such as flowers (androecium, gynoecium and corolla etc.), roots, stems and leaves, then were weighed under the Sartorius Balances (10-4 g), and P/O (pollen/ovule ratios per flower) were counted in haemacytometer under the microscope. Individual size is represented by vegetative biomass. Reproductive allocation is the proportion of biomass of total flowers to vegetative biomass; sex allocation is the proportion of androecium biomass to biomass of total flowers. We used the power function Y=aXb to analyse relationships between individual size and reproductive components.Our results showed: 1) in all five species, the reproductive investment increases but the proportion of reproduction (reproductive allocation) decreases with increased individual size, which is consistent with the previous conclusions, indicating size-dependency of reproductive allocation at flowering. 2) there is significant negative size-dependent sex allocation in these species, in that the larger individual allocates more resources to female function (i.e. gynoecium). This means that plants can adjust the resource allocation between the two sexes by its status at flowering to gain higher fitness. However, the relationship between P/O (pollen/ovule ratio) and size is complicated and differs among species. 3) the trade-off between male and female allocation existed, and is influenced by environment. This result confirms the assumption of sex allocation theory

    Effects of Co-Inoculation with Two Ectomycorrhizal Fungi on Quercus liaotungensis Seedlings
    YAN Xiu-Feng, WANG Qin
    Chin J Plan Ecolo. 2004, 28 (1):  17-23.  doi:10.17521/cjpe.2004.0003
    Abstract ( 2424 )   PDF (289KB) ( 842 )   Save
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    Quercus liaotungensis, a special Quercus species of China, is one of the dominant species in the warm temperate deciduous broad-leaved forests, China. Gomphidius viscidus and Russula foetens are two species of ectomycorrhizal fungi being symbiosis and formation of ectomycorrhizae with Q. liaotungensis in the natural circumstance. The positive effect of the inoculation with G. viscidus and R. foetens on Q. liaotungensis seedling growth, and the improvement induced by co-inoculation with a mixed inoculum of G. viscidus and R. foetens have been reported in our early work. In the present paper, a controlled experiment was conducted in pots to investigate the effects of different inoculation amounts and different inoculation ratios of G. viscidus and R. foetens. Q. liaotungensis seeds were collected in autumn of 2001 from the natural forest of Mt. Donglingshan in the Beijing area. Before germination, seeds were rinsed in running tap water overnight, surface disinfected by shaking for 60 min in 0.5% KMnO4 and washed in four changes of sterile distilled water. Seeds were germinated in sterile sand, and seedlings were transplanted to pots (diameter 20 cm, depth 20 cm) with a sterile mixture of soil and sand in a greenhouse. The sterile mixture had a pH of 6.9, an organic matter content of 3.76%, and total N, P, K levels of 0.30%, 0.12% and 2.61%, respectively. On June 2, 2002, every 15 pots of Q. liaotungensis seedlings were randomly grouped for inoculation treatment. Three levels of inoculation amount of 12, 18 and 24 g·pot-1 were created at the ratio of 1∶1 of G. viscidus∶R. foetens, and three ratios of 2∶1, 1∶1 and 1∶2 of G. viscidus∶R. foetens were inoculated at the inoculum amount of 18 g·pot-1. After 3 months of inoculation, the mycorrhizal infection rate and the percentages of G. viscidus and R. foetens mycorrhizae were observed. The height, dry weight, nitrogen and phosphorus contents of root, stem and leaf, net photosynthesis rate of the mycorrhizal seedlings and non-mycorrhizal seedlings were measured, and biomass, nitrogen and phosphorus contents of the whole plant, root/shoot ratio and leaf water content were calculated.The infection rate of mycorrhizae of Q. liaotungensis seedlings and the percentage of G. viscidus mycorrhizae increased but the percentage of R. foetens mycorrhizae decreased when the inoculation amount was higher. The maximum biomass, height, net photosynthesis rate and total nitrogen and phosphorus contents of whole plant of Q. liaotungensis seedlings all showed in plants with inoculation amount of 18 g·pot-1. As to inoculation ratio, with the inoculum ratios of 2∶1, 1∶1 and 1∶2 of G. viscidus and R. foetens, the infection rates of total ectomycorrhizae were 96.54%, 91.02% and 92.13% respectively, and no significantly difference among them. As the proportion of G. viscidus in the inoculum decreased, the percentage of G. viscidus mycorrhizae decreased from 42.49% to 23.33%, and that of R. foetens mycorrhizae rose from 57.51% to 76.67%. With an inoculation amount of 18 g·pot-1 at a ratio of 1∶1 G. viscidus∶R. foetens, the seedlings of Q. liaotungensis have maximal biomass, net photosynthesis rate, and total nitrogen content of the whole plant which was significantly higher than seedlings under other inoculation ratio conditions. Total phosphorus content of the whole plant of Q. liaotungensis was enhanced by the increasing ratio of R. foetens.

    Effect of Morphological and Physiological Variations in the Ecotypes of Alligatorweed,Alternanthera philoxeroides on the Pupation Rate of Its Biocontrol Agent Agasicles hygrophila
    MA Rui-Yan, WANG Ren
    Chin J Plan Ecolo. 2004, 28 (1):  24-30.  doi:10.17521/cjpe.2004.0004
    Abstract ( 2102 )   PDF (248KB) ( 887 )   Save
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    Alternanthera philoxeroides, which originated in South America, is a noxious weed species in the warm temperate and subtropical regions of China, infesting rivers, lakes, ponds, and irrigation canals, as well as many terrestrial habitats. A host-specific flea beetle, Agasicles hygrophila, introduced from the USA in 1986 as a biological control agent, has become widely established in South China and has effectively controlled the weed in many water bodies. It has been observed, however, that the beetle’s ability in controlling the weed in terrestrial habitats has been limited, apparently due to its poor and/or greatly varying pupation rates. This study analyses the mechanism underpinning the relationship between the beetle’s pupation rate and the morphological and physiological characters of the three ecotypes of its host plant, viz. the weed growing in the water bodies (hydrophytes), that growing in wet soil with 15%-30% moisture content and the roots sometimes saturated with water (hygrophytes), and that growing in terrestrial soil with 5%-15% moisture content and the roots never saturated with water. Anatomical studies showed that hydrophytes do not have secondary structures in the stems, whereas stems of the hygrophytes and xerophytes have tight cortex cells and abundant crystals. The 7 morphological and anatomical characters of the alligatorweed analyzed in this study showed significant differences among the ecotypes of the weed as well as between the internodes of the same ecotype. Results of the principal component and clustering analysis placed these characters into three groups, which coincided with the distinctive levels of the beetle’s pupation rate and the effect of controlling the weed observed in both potted plants and the field experiments. A stepwise regression model was established between the pupation rate of A. hygrophiia and the 7 morphological and anatomical characters of the alligatorweed stems and internodes: y=1.533 2-0.248 3x3-0.051 2x4-1.634 9x5-0.957 7x6 (R2=0.999 9). The pupation rate of the beetle was found to be in simple positive correlation with the lengths of the internodes and the external diameter of the stems and the diameter of the pith cavity of the alligatorweed. The pupation rate was found to be in simple negative correlation with the density and thickness of the cortex parenchyma, and the thickness of the vascular cylinder and the pith cavity parenchyma. It is concluded that the pupation rate and the biological control effect of the flea beetle on A. philoxeroides are affected primarily by the thickness of vascular cylinder, cortex parenchyma, pith cavity parenchyma and the density of cortex parenchyma of its host plant. This is a rather different explanation for the poor performance of the beetle on terrestrial alligatorweed from the observations of other researchers in the USA, Australia and China.

    Photosynthetic Acclimation to Different Growth Light Environments in Seedlings of Three Tropical Rainforest Syzygium Species
    QI Xin, CAO Kun-Fang, FENG Yu-Long
    Chin J Plan Ecolo. 2004, 28 (1):  31-38.  doi:10.17521/cjpe.2004.0005
    Abstract ( 2456 )   PDF (411KB) ( 936 )   Save
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    Light is one of the most important factors that affect the regeneration and succession of tropical rain forests. Tropical trees with different successional status have different acclimation capacities to different growth light environments. In the present study, gas exchange and diurnal variation of chlorophyll fluorescence parameters were measured in the seedlings of three tropical rainforest Syzygium species, which are early (S. szemaoense), middle (S. cumini) and late (S. latilimbum) successional species. The seedlings were cultivated under three different light regimes (fully open site, 42% and 14% daylight). Their leaf mass per unit area (LMA) and chlorophyll content were also determined. The early successional species had the highest light- saturated photosynthetic rate (Pmax) and photosynthetic acclimation capacity to the variation of growth light environments, the next was the middle successional species. The late successional species had the lowest Pmax values and its photosynthesis was strongly suppressed when grown in full light. Nevertheless, grown under both the full light and 42% daylight, all the three species did not suffer from irreversible photoinhibition, as indicated by their dawn values of maximal photochemical efficiency of PS Ⅱ (Fv/Fm) larger than 0.8, and their φPSⅡ was able to recover on the same day. Dynamic (reversible) photoinhibition occurred in all species, the degree of which increased with growth light level. Among species, the degrees of dynamic photoinhibition were similar. The non-photochemical fluorescence-quenching rate (NPQ) increased with the growth light level for all species. However, in the fully open site, the NPQ rates in the morning were higher in the late and middle successional species than in the early successional species. This compensated for the lower photosynthetic rates of the former two species, and probably plays a role in preventing photodamage to these species under full light. Leaf dark respiration rate per unit area (Rd) and leaf mass per area (LMA) tended to increase with the growth light level. Under the same light regimes, Rd was higher in early than in middle and late successional species. The LMA values of late successional species were higher than for the other two species. This could be favorable for this shade-tolerant species to prevent herbivory. For all of the three species grown in 14% daylight, area-based Pmax, photosynthetic light saturation point, light compensation point, Rd and LMA were reduced, while chlorophyll content per unit dry weight were increased compared to those in the other two light regimes. This showed their favorable acclimation to low light. Nevertheless, under 14% daylight the seedlings of both the early and middle species died, only the seedlings of the late successional species were still alive. This indicates that this late successional species has high capacity to acclimate to low light.

    Photosynthetic Functions of Different Senescing Leaves in the Canopy of Super high-yield Rice ‘Hua-An3’
    WANG Qiang, WEN Xiao-Gang, LU Cong-Ming, ZHANG Qi-De
    Chin J Plan Ecolo. 2004, 28 (1):  39-46.  doi:10.17521/cjpe.2004.0006
    Abstract ( 2066 )   PDF (400KB) ( 825 )   Save
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    In order to improve rice yields to feed a growing population, China has carried out a `Super High-Yield Rice Project’ since 1996. Tremendous progress was made during the `Ninth Five-Year Plan’and several new varieties of rice hybrids were released. `Hua-an 3’(`X07S’×`Zihui100’) is a new high yield variety that has yields of more than 10 500 kg·hm-2; this compares with yields of 7 500-8 500 kg·hm-2 in the traditional hybrid rice `Shanyou 63‘ (‘Zhenshan 97A‘בMinghui 63‘). The photosynthetic functions and pigments of the upper most 5 senescing leaves of the canopy of `Hua-an 3‘ were studied by techniques of fluorescence induction kinetics, low temperature (77K) fluorescence emission spectrum and HPLC. The results showed that the maximal quantum yield of PSⅡ photochemistry (Fv/Fm), efficiency of excitation energy captured by open PSⅡ reaction centers (Fv′/Fm′), quantum yield of PSⅡ electron transport (ΦPSⅡ), photochemical quenching coefficient (qP), and the content of photosynthetic pigments, especially chlorophyll (Chl), neoxanthin (N), lutein (L) and β-carotene (β-Car), of the flag leaf were higher than those of other leaves but its excitation pressure (1-qP) was lower. It was shown that the content of the core antenna complex CP47 in photosystemⅡ (PSⅡ) and photosystem Ⅰ (PS Ⅰ) of the flag leaf also was higher than in other leaves, but the content of its non-active aggregate of light harvesting complex in PSⅡ (LHCⅡ) derived from the Gaussian analysis of low-temperature (77K) fluorescence emission spectra was lower than that of the other leaves. Our research results are as follows: 1) at later growth and development stages of rice, the dry matter of grain was mainly provided by most photosynthesis occurred in the uppermost 3 leaves in the canopy; 2) in the course of leaf senescence, the senescence of photosynthetic reaction centers was quicker than that of the antenna system; 3) one of the photoprotective pathways in hybrid rice may be through an increase in the content of PS Ⅰ, absorption of more light energy, and stimulating a high speed electron transport cycle in order to protect the photosynthetic apparatus under photoinhibitory conditions; 4) in the course of leaf senescence of rice, partial chlorophyll b was probably reduced to chlorophyll a, to decrease the content of LHCⅡ, thus reducing the amount of energy absorbed by LHCⅡ and decreasing the amount of photoinhibitory damage.

    Relationship Between Spectral Vegetation Indices and LAI in Rice
    XUE Li-Hong, CAO Wei-Xing, LUO Wei-Hong, WANG Shao-Hua
    Chin J Plan Ecolo. 2004, 28 (1):  47-52.  doi:10.17521/cjpe.2004.0007
    Abstract ( 1959 )   PDF (262KB) ( 1798 )   Save
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    Leaf area index (LAI) is an important parameter in crop growth status monitoring and yield forecasting. A vegetation index (VI) based on spectral reflectance measurements has been proposed as a reliable nondestructive method for quickly estimating LAI. To determine the best broadband index for estimating LAI in rice (Oryza sativa), field canopy reflectance values were measured over the whole rice growth cycle using a portable multi-spectral radiometer, and LAI were simultaneously determined by destructive sampling. Several vegetation indices such as normalized difference vegetation index (NDVI), ratio vegetation index (RVI), soil-adjusted vegetation index (SAVI) and the like were derived from these spectral measurements and their correlation with respect to LAI quantified. Also, their relative predictive powers were estimated by comparing determine coefficient (R2), root mean square error (RMSE) and precision and accuracy. The results showed that the power of VI for LAI assessment was the best during vegetative growth, and mainly depended on the range of variation in the experimental data. Vegetation indices accurately tracked changes in LAI when data were analyzed across a broad range of different growth stages and nitrogen levels. RVI, RDVI, and R810/R560 showed a power relation with LAI, while NDVI, PVI, DVI, SAVI and TSAVI showed an exponential relation. R810/R560 produced the best estimate of LAI among these indices. The regression equation was tested by independent datasets and the estimation accuracy was about 91.22% with RMSE of 0.480 5 and average relative error of -0.013. The results indicated that LAI monitoring in rice by means of the ratio index of near infrared band to green band from broadband spectral signatures appears very promising.

    Carbohydrate Reserves in the Rhizome of Leymus chinensis in Response to Nitrogen Addition
    PAN Qing-Min, BAI Yong-Fei, HAN Xing-Guo, ZHANG Li-Xia
    Chin J Plan Ecolo. 2004, 28 (1):  53-58.  doi:10.17521/cjpe.2004.0008
    Abstract ( 2152 )   PDF (297KB) ( 843 )   Save
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    Carbohydrates serve as food reserves for grasses at times when photosynthesis cannot supply sufficient carbon for maintenance and growth such as when grasses are completely defoliated during the winter and early spring. L. chinensis, a rhizomatous graminoid that commonly dominates the steppe in semiarid areas of northern China, stores enough carbohydrates in the rhizome before winter to ensure that it can survive the hard environmental conditions of the winter. Nitrogen (N) fertilization is a common technique used to increase forage productivity in many countries; however, fertilization is not widely used in the steppe grasslands of northern China. Nitrogen fertilization significantly affects the non-structural carbohydrates during both growth and dormant periods of some grass species, but the effect of N fertilization on carbohydrate storage in the L. chinensis rhizome remains unclear. We conducted an N addition experiment with different rates and different application times of N to L. chinensis in fenced plots at the Inner Mongolia Grassland Ecosystem Research Station, Chinese Academy of Sciences. In the first experiment, NH4NO3 was applied at six treatment levels (0, 1.75, 5.25, 10.5, 17.5, 28 g N·m-2) on July 5 every year. In the second experiment, the timing of N application was studied by applying 17.5 g N·m-2 NH4NO3 on two dates, April 20 and July 5. In both experiments, 9 replicate plots (5 m x 5 m) were used for each treatment in a complete randomly designed experiment. L. chinensis rhizome samples were collected from the field on Sep. 20. Rhizomes were washed with cold water, oven-dried at 80 ℃ for 24 hours and ground to pass through a 100 μm mesh screen. Stored carbohydrates in the rhizome of L. chinensis were analyzed using a Sugar-PAKTM I column, a specific column for carbohydrate components assay, in High Performance Liquid Chromatography (HPLC). The results showed that the stored carbohydrates of the L. chinensis rhizome consisted of fructan, mannitol, sucrose, fructose, and glucose. Fructan, which contributed 60% of total non-structural carbohydrates (TNC), was the predominant stored carbohydrate followed by mannitol, which contributed 20% of TNC. Both fructose and glucose were less than 15% of TNC and sucrose was only 6% of TNC. Hence, sucrose, a main component of stored carbohydrates in other grasses, was only a minor component of L. chinensis. Nitrogen rates significantly influenced the contents of fructan, mannitol and total carbohydrates, but had little effects on glucose, fructose and sucrose content in the L. chinensis rhizome. The total carbohydrate, fructan and mannitol concentrations increased in the rhizome with increasing N application rates from 0 to 17.5 g N·m-2, but carbohydrate reserves were reduced at application rates of 28 g N·m-2. The timing of N application also significantly influenced the contents of carbohydrate reserves; L. chinensis stored more carbohydrates in the rhizome when N was applied in July than that in April. In conclusion, fructan and mannitol are important stored carbohydrates in the rhizome of L. chinensis. Both N application rates and timing of application significantly affect the levels of carbohydrate reserves, especially fructan and mannitol in the L. chinensis rhizome.

    Measurement and Simulation of Cucumber Canopy Transpiration in a Subtropical Modern Greenhouse Under Winter Climate Conditions
    LUO Wei-Hong, WANG Xiao-Han, DAI Jian-Feng, DING Wei-Min, GUO Shi-Rong, LI Shi-Jun
    Chin J Plan Ecolo. 2004, 28 (1):  59-65.  doi:10.17521/cjpe.2004.0009
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    Canopy transpiration of crops grown in greenhouses affects greenhouse air temperature and humidity and is therefore important for the optimization of greenhouse climate control. In this study, cucumbers (Cucumis sativus) were grown in a subtropical modern greenhouse under winter climate conditions, canopy transpiration was measured every 30 minutes and greenhouse microclimatic factors were sampled with 1 second interval and 30 minutes average values were saved in a datalogger and mean values of canopy resistance rc and boundary layer resistance ra were estimated based on experimental measurements made in the greenhouse. The Penman-Monteith equation was used to estimate canopy transpiration rates. The results showed that the diurnal time course of canopy transpiration rates followed that of the net radiation above the canopy with the daily maximum value occurring at 12∶00. In contrast, maximum water vapor pressure deficit (VPD) occurred between 13∶00 and 14∶00. These results indicate that under winter climate conditions of China, subtropical greenhouse microclimate conditions are characterized by low VPD level and that daytime variations of crop canopy transpiration rates depend primarily on net radiation above the canopy. The daily maximum values of net radiation and VPD above the canopy and crop canopy transpiration rates were below 350 W·m-2, 2.0 kPa and 200 W·m-2, respectively; the ratio of latent heat caused by crop transpiration to the net radiation above the canopy in winter averaged 46%; and rc and ra were 100 s·m-1 and 600 s·m-1, respectively. The crop canopy transpiration rate and total cumulative crop transpiration calculated by Penman-Monteith equations using both the actual rc and ra values and the mean values of rc and ra agreed well with the measured results. The determination of the ratio of latent heat to the net radiation above the canopy (46%) and the characteristic values of rc (=100 s·m-1) and ra (600 s·m-1) facilitates the development of a crop transpiration model to optimize greenhouse climate and irrigation control systems. More experiments are needed to determine if these values are valid for other sites and types of greenhouses.

    Responses of Gas Exchange Parameters of Goldspur Apple Tree to Soil Water Variation
    ZHANG Guang-Can, LIU Xia, HE Kang-Ning, WANG Bai-Tian
    Chin J Plan Ecolo. 2004, 28 (1):  66-72.  doi:10.17521/cjpe.2004.0010
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    Goldspur Apple (Malus pumila cv. Goldspur) is one of the main fruit trees planted on the Loess Plateau in a semi-arid region. Gas exchange parameters in leaves of ten-year-old trees were studied under different soil water conditions with a LI-6200 portable photosynthesis system and a LI-1600 portable steady state porometer, in order to explore the effects of soil water stress on the photosynthesis and the suitable soil water content (SWC) for water-saving irrigation of the apple orchard. The experimental site is located in Tuqiaogou watersheds, Yukou town, Fangshan county, Shanxi province, China, a part of a gully-hilly area of Loess Plateau in the middle reaches of the Yellow River. It lies at 37° 36′ 58″ N, 110° 02′ 55″ E, with an average altitude of about 1 200 m and a maximum altitude of 1 446 m. The average annual precipitation is 416.0 mm, with the precipitation in June, July, August and September being more than 70% of the total amount. Annual potential evaporation is 1 857.7 mm and the greatest evaporation occurs in April to June. The soil belongs to medium soil and lossal soil and the average soil bulk density is about 1.2 g·cm-3, and mean field capacity (FC) is approximately 21.0%. In the study on responses of gas exchange parameters to soil water, eighteen apple trees were selected as experimental samples and divided into six groups (three trees per group and signed by Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ and Ⅵ). The soil water gradient was obtained in six groups by providing different water supply. During soil water treatment, SWC measured with LNW-50A neutron probe on June 12, June 16 and June 20, 1999 were as follows: group Ⅰ (22.4%, 18.7% and 16.7%), Ⅱ (20.1%, 17.4% and 16.2%), Ⅲ (18.2%, 16.7% and 14.8%), Ⅳ (15.9%, 13.6% and 11.9%),Ⅴ (11.7%, 10.5% and 9.6%) and Ⅵ (6.2%, 5.6% and 5.0%). A LI-6200 portable photosynthesis system was used to measure the photosynthesis parameters including photosynthetic rate (Pn), stomatal conductance (Gs) and intercellular CO2 concentration (Ci), while at the same time transpiration rate (Tr) was measured with a LI-1600 portable steady state porometer. The water use efficiency (WUE) and stomatal limiting value (Ls) were calculated according to formula WUE=Pn/Tr and Ls=1-Ci/Ca. These gas exchange parameters were measured on the same day that SWC was observed on June 12, June 16 and June 20, 1999, and the duration of observation was at 9∶00-11∶00 am each time.The results showed that when SWC was within a range about 60%-86% of field capacity (FC), Pn and Tr were maintained in a relative steady state and higher level, but below 60%-86% of FC, both Pn and Tr decreased obviously with decreasing soil moisture. The SWC range to support WUE at a relative steady state and higher level was about 50%-71% of FC. When SWC was less than 48% of FC, Gs and Ls declined with decreasing of soil moisture, while Ci increased rapidly. Based on the analysis of stomatal limitation of photosynthesis using two criteria (Ci and Ls) suggested by Farquhar and Sharkey, it implied that the predominant cause of restricting Pn had turn into non-stomatal limitation under severe water stress. According to the main intention of water-saving irrigation for enhancing water use efficiency, it is concluded that the suitable range of SWC was about 50%-71% of FC, as the most severe degree of soil water stress tolerated for photosynthesis was about 48% of FC.

    Studies on the Adaptation of Taxus media cv. Hicksii to Natural Temperature Reduction
    LU Zhan-Gen, ZHOU Wen-Jie, ZHAO Chang-Qiong, CHEN Jing, TAN Feng
    Chin J Plan Ecolo. 2004, 28 (1):  73-77.  doi:10.17521/cjpe.2004.0011
    Abstract ( 2195 )   PDF (211KB) ( 981 )   Save
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    The adaptation of 3-year-old Taxus media cv. Hicksii leaves to natural temperature reduction was studied. The results showed that the semilethal low temperature(LT50)of Taxus media decreased increasingly with the reduction of air temperature, from -8.13 ℃(in mid November ) to -13.01 ℃(in mid January ). The contents of osmoregulatory substances such as soluble sugar, soluble protein and free proline increased to the the different degree, but the content of starch decreased. The contents of endogenetic hormones such as ABA rose continuously and negatively correlated to LT50 (the coefficient of correlation was -0.971 06). On the contrary, the contents of ZRs, GA1/3 and IAA reduced ,which the content of ZRs was positively correlated to LT50 (the coefficient of correlation was 0.949 72). In summary, the adaptive changes of these substances including osmoregulatory substances and endogenetic hormones of leaves of Taxus media cv. Hicksii led to the reduction of LT50, thus make Taxus media cv. Hicksii suit the low temperature condition cuitivated in Chongqing and pass the winter safely.

    A GIS-Based Gradient Analysis of the Urban Landscape Pattern of Shanghai Metropolitan Region
    ZHANG Li-Quan, WU Jian-Ping, ZHEN Yu, SHU Jiong
    Chin J Plan Ecolo. 2004, 28 (1):  78-85.  doi:10.17521/cjpe.2004.0012
    Abstract ( 3218 )   PDF (350KB) ( 1274 )   Save
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    Urbanization is arguably the most dramatic form of land transformation that profoundly influences natural environment, biological diversity and human life. Understanding the causes, processes, and consequences of land use and land cover change is essential in ecology as well as in landscape and urban planning, and urbanization represents the extreme form of land transformation. Quantifying landscape pattern and its change is essential for the monitoring and assessment of the ecological consequences of urbanization. As the largest city in the country, metropolitan Shanghai is now the fastest growing area among all major Chinese cities that have more than 13 million residents. Using the 1994 GIS_based land use data set and combining gradient analysis with landscape metrics, we attempted to quantify the spatial pattern of urbanization in the Shanghai metropolitan area. Seventeen landscape metrics were computed along a 64 km long and 6 km wide west_east transect and another 66 km long and 6 km wide south_north transect, crossing at the urban center, with a moving window. The research was designed to address two questions: 1) do different land use types have their own unique spatial signatures (e.g., the shape of the change curve along an urban_rural transect)? 2) can urbanization gradients be detected using landscape pattern analysis? The results of transect analysis with landscape_level metrics showed that the spatial pattern of urbanization could be reliably quantified using landscape metrics with a gradient analysis approach, and the location of the urbanization center could be identified precisely and consistently with multiple indices of the 17 landscape metrics used in this study. Urbanization in the metropolitan Shanghai region has resulted in dramatic increases in patch density, edge density, and patch and landscape shape complexity, and sharp decreases in the largest and mean patch size, agriculture land use type, and landscape connectivity. The general pattern of urbanization was that the increasingly urbanized landscape became compositionally more diverse, geometrically more complex, and ecologically more fragmented. Although some of these changes were discernable visually from the land use maps, landscape metrics provided a useful way of quantifying these changes so that they could be further used to relate ecological patterns and processes in this urban landscape. In addition, our results supported a series of hypotheses on landscape structural responses along a human modification gradient: that, with increasing urbanization, patch density increases while patch size and landscape connectivity decrease. However, our results on patch shape seemed to disagree with the hypothesis that patch shape becomes more regular as human modification to landscapes intensifies. Our interpretation is that, when the degree of urbanization is high, not only the density, but also the shape complexity, of patches will increase. Future studies are needed to further confirm these findings.

    Dynamics of Species Diversity of Communities in Restoration Processes in Horqin Sandy Land
    ZHANG Ji-Yi, ZHAO Ha-Lin, ZHANG Tong-Hui, ZHAO Xue-Yong
    Chin J Plan Ecolo. 2004, 28 (1):  86-92.  doi:10.17521/cjpe.2004.0013
    Abstract ( 2110 )   PDF (221KB) ( 2071 )   Save
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    Characteristics of Plant Community and Soil Properties in the Plantation Chronosequence of Caragana microphylla in Horqin Sandy Land
    SU Yong-Zhong, ZHAO Ha-Lin, ZHANG Tong-Hui, LI Yu-Lin
    Chin J Plan Ecolo. 2004, 28 (1):  93-100.  doi:10.17521/cjpe.2004.0014
    Abstract ( 2325 )   PDF (357KB) ( 1334 )   Save
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    Horqin sandy land (42°41′- 45°15′ N, 118°35′-123°30′ E) is one of the typical areas of seriously degraded ecosystem characterized by sandy desertification in northern China. Reestablishing artificial vegetation on shifting sand dunes is one of the effective measures to control desertification in this region. Caragana microphylla (a leguminous shrub) artificial sand-fixing forest planted in different periods of time provides an opportunity for studying the patterns and mechanisms of restoration of soil and vegetation in seriously degraded ecosystems. In this paper, characteristics in soils and plant communities in an age sequence of 0, 5, 13, 21, and 28-year-old C. microphylla plantations were examined to assess the processes and mechanisms of restoration in soil fertility and plant species following shrub establishment. Soil samples were taken from two depths (0-5 cm and 5-20 cm) under the shrub canopy and in the mid-row location between shrubs. Some selected soil properties were measured and plant species was investigated. The results showed the following:1) Shrub establishment and development improved soil texture and water-holding capacity (WHC), enhanced organic C and total N accumulation, decreased pH and bulk density, and improved microbial activity as reflected by potential soil respiration. In an age sequence of 0-28-year-old C. microphylla plantations, silt and clay contents and WHC at the 0-5 cm depth in soils significantly increased with increasing restoration time. Soil organic carbon buildup in soils of the 0-5 cm depth under the shrub canopy increased 4.6, 13.3, 16.5, and 20.5 fold, respectively, from the non-vegetated mobile sand dunes (0.284 g·kg-1, age 0) after 5, 13, 21, and 28-years of occupancy, and in the alley, this increase was 1.9, 8.1, 11.1, and 13.3 fold, respectively. Total N accumulation followed the same pattern with respect to the plantation age. At the 5-20 cm depth, silt and clay contents, and organic C and total N levels were significantly lower than those at the 0-5 cm depth, but they were still higher than those found at corresponding depth in the non-vegetated mobile sand land (age 0). 2) The incremental rates in soil organic C and total N were faster in the early establishment stages (0-13 year) than in the late successional stages (13-28 year). 3) C. microphylla exhibited significant enrichment effect with higher C and N contents under their canopies. With increased plantation age, the area of `islands of fertility’ expanded and enrichment ratios decreased. 4) Shrub establishment and development facilitated the colonization and development of herbaceous species by ameliorating stressful environmental conditions. With the increase of restoration time, the simple artificial shrub community developed towards a complex shrubby-grass community. The restoration of soil fertility induced by re-vegetation is a complicated ecological process that is simultaneously affected by many biotic and abiotic variables. In erosion-prone Horqin sandy land, shrub establishment and development not only offered an important safeguard against soil erosion by wind, but also leaves of shrubs trapped dust materials enriched with nutrients and deposited them under the shrub canopies. The litter input and root turnover to the soil, and N fixation by C. microphylla contributed to C and N accumulation. Also, the improved microbial activity enhanced the release of nutrients from litter. Accordingly, the amelioration of soil and environmental conditions with shrub development facilitated the increase of plant species.

    Storage and Composition of Soil Seed Banks of Different Degraded Karst Vegetation Types in South-Eastern Yunnan
    SHEN You-Xin, JIANG Jie, CHEN Sheng-Guo, CAI Guang-Li, ZHANG Ping
    Chin J Plan Ecolo. 2004, 28 (1):  101-106.  doi:10.17521/cjpe.2004.0015
    Abstract ( 2434 )   PDF (240KB) ( 1103 )   Save
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    Degradation of the natural environment in karst area, especially in southern China, is a serious issue to be considered. It is difficult to restore vegetation through planting, as is done in other degraded ecosystems, since many karst areas are full of sheer craggy cliffs and outcrops of rock, with shallow and patchy soil. Encouraging regeneration of vegetation becomes crucial. Seeds buried in soil are one of the important sources for plant regeneration. Exploration of the soil seed bank will provide the basis for evaluating the restoration potential of degraded land, and also serve for restoration purposes. A comparison study was carried out to examine the soil seed banks of different karst vegetation types representing different degradation/restoration stages at three typical karst locations in southern Yunnan Province (23°16′-23°59′N, 104°24′-104°58′E). These vegetation types were: 1) secondary forest; 2) scrub; 3) grassland. Ten soil samples of 10 cm×10 cm×10 cm, further divided into 0-2 cm, 2-5 cm, and 5-10 cm depth fractions were taken from two 50 m transect lines with a 10 m interval for each vegetation type at each location. Soil samples were washed through a coarse sieve (4 mm) and a fine sieve (0.21 mm) and then put into a local greenhouse for germination and taxon identification.It was found that there were abundant seeds stored in karst soil of secondary forest, scrub and grassland at each location. Seed densities varied between 4 090-14 930 seeds·m-2, and the number of species identified varied between 23-35 among all of the soil seed banks. Seed density and number of species identified were higher under secondary forest, and little difference was found between that of scrub and of grassland. Within the top 0-10 cm of soil, seeds per volume decreased gradually from 0-2 cm depth layer to 2-5 cm and then 5-10 cm layer. The rate of this decrease was relatively lower under secondary forest. Herb was the richest whether counted in number of species or seed density, shrub came next, and tree and liana seeds were scarce in all soil seed banks across different vegetation types and locations. Tree and shrub species and their seed density were higher under secondary forest, but lower in grassland. A few species dominated the seed bank with higher seed density and accounted for a high proportion of the seed bank. The percentage of the three richest species exceeded 40% in all of the soil seed banks. High similarity was found between one and another soil seed bank. The similarity index between any two seed banks varied between 0.6-0.7 within the same location, and 0.4-0.6 across locations. 9.3% of the total species could be found in all of soil seed banks studied. The dominant species was common. The top three species in terms of seed number were three of Ageratum conyzoides, Conyza stricta, Eupatorium adenophorum, Emilia sonchifolia, Elsholtzia fruticosa, and Spiraea martinii var. pubescens in all studied soil seed banks. Washing soil samples through sieves encouraged the germination of seeds, especially the small herbaceous seeds, and made the karst seed bank density higher compared with other studies. Soil storage condition, mainly related to the vegetation coverage strongly influenced the depth distribution of seeds. Seed physiology, sampling time, and the fragmentation of karst vegetation were the main reasons behind the higher proportion of herb species and seeds, as well as the higher similarity between seed banks.

    Effects of Recreation on Plants in Zhangjiajie National Forest Park
    SHI Qiang, ZHONG Lin-Sheng, WANG Xiao-Fei
    Chin J Plan Ecolo. 2004, 28 (1):  107-113.  doi:10.17521/cjpe.2004.0016
    Abstract ( 2299 )   PDF (266KB) ( 940 )   Save
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    The effects of recreation on the environment of tourism resorts are almost unavoidable, and these particularly affect vegetation. With the greatly increasing number of visitors and the intensive increase in air pollutants released from hotels and restaurants, the plants in Zhangjiajie National Forestr Park have been polluted and seriously damaged. In order to show the effects of recreation on the growth of plants, on the internal chemical components of plant leaves and on the damage degree of tree trunks, controlled experiments were used to investigate and analyze changes in contents of fluoride and SO2 in the leaves of several tree species, and growth rates of Cunninghamia lanceolata were compared between polluted and non-polluted areas. The degree of tree bark wounding caused by visitors along both sides of the tourism roads was also investigated. The results showed that the contents of fluoride and SO2 in the leaves of C. lanceolata, Cryptomeria fortunei and Pterocarya hupehensis in polluted areas increased 1.6-16 times in comparison to that of non-polluted areas; the annual diameter increment of C. lanceolata growing near the reception area was reduced 32.3%-57.1% compared with that of the control area; a great amount of scars on the tree trunks along the two sides of the tourism roads in Jinbianxi area and Huangshizhai area were cut by visitors, and these scars were distributed among the part of the trunks 1.2-1.6 m above the ground. The wound degree was mainly related to tree species, smoothing degree of the tree bark, and the distances from tree to the edge of tourism roads and the directions the trunks face. To protect the vegetation in the park, it is vital to improve the park’s fuel structure, reduce the amount of reception sites and improve the environmental education of visitors.

    Advances in Plant Proteomics
    LIANG Yu, JING Yu-Xiang, SHEN Shi-Hua
    Chin J Plan Ecolo. 2004, 28 (1):  114-125.  doi:10.17521/cjpe.2004.0017
    Abstract ( 2598 )   PDF (432KB) ( 3990 )   Save
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    Proteomics is one of the most active research fields in the post-genomic era. The concepts, research methods and major applications of proteomics in plant science are briefly introduced in this paper. The term “proteomics" comes from two words, “protein" and “genome" and refers to the proteins expressed by the whole genome or the presence and action modes of all the proteins in a cell, tissue, organ, and whole organism. It is generally acknowledged that the field of plant proteomics was based much on the development and improvement of techniques and methods, such as two-dimensional electrophoresis (2D-E), mass spectrometry (MS), protein chips, yeast two-hybrid system, and proteomic databases. In population genetics, proteomic techniques are helpful in studies of genetic diversity and mutation. In individual plants, proteomic studies are helpful in understanding the response of plants to biotic and abiotic environmental factors. Proteomic differences among different plant tissues or organs could be used to better understand tissue differentiation and development of the plant embryo. Proteomic differences also exist between organelles in plant cells, and plant proteomic studies could be used to understand mechanisms that control many physiological processes. Different perspectives of proteomics were also discussed in this paper.

    Several Controversial Viewpoints in Studying the Cavitation of Xylem Vessels
    FAN Da-Yong, XIE Zong-Qiang
    Chin J Plan Ecolo. 2004, 28 (1):  126-132.  doi:10.17521/cjpe.2004.0018
    Abstract ( 2350 )   PDF (296KB) ( 1580 )   Save
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    Xylem cavitation/embolism, a topic that has received extensive attention, is generally seen as a potential threat for living plants because it lowers the conductivity of the axial water-conducting system. In this paper, several controversial viewpoints about studying the cavitation of xylem vessels were listed, and current efforts and advances in this field were reviewed. Ultrasonic sensors can be used to directly detect the occurrence of xylem cavitation; however, this method has some limitations. Almost all current methods used to study xylem cavitation/embolism, except for the ultrasonic sensor, requires destructive sampling. Recently, a noninvasive method based on high-resolution magnetic resonance imaging technique was introduced. Large discrepancies existed between the results of pressure chamber tests and xylem pressure probe, both of which were used to detect the tension of xylem vessels. There are at least four possible reasons to explain this discrepancy. The relationship between the anatomical characteristics and the ability of xylem vessel to resist cavitation is complex and it may show a species-specific response. The underlying mechanism of stomatal closure induced by xylem cavitation is still unclear. There is no general conclusion about the relationship between xylem vessel resistance to cavitation and the capacity of plants to adapt to water-stress. What about the embolized vessels refilled by water? It is risky to attribute this process solely to the mechanism of root pressure, because there is now some evidence that other mechanisms are involved. In general, further efforts are needed to clarify and resolve these uncertainties and discrepancies in order for us to better understand the cavitation of xylem vessels and the water-conducting system of plants.

    A Study on Genetic Diversity Centers of Tibet Cultivated Barley
    WANG Jian-Lin, HU Dan
    Chin J Plan Ecolo. 2004, 28 (1):  133-137.  doi:10.17521/cjpe.2004.0019
    Abstract ( 2018 )   PDF (156KB) ( 913 )   Save
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    Tibet is a most beautiful place, located in southwestern China. She has been called “the roof of the world” and “the third pole of the earth”. A combination of unique geological history, complex land surface and climatic zones, various soil types, and different wild vegetation makes Tibet a very typical area of vertical agricultural ecosystem. The ecosystem in Tibet may be the most complex and variable in the world. Unique and complex environments, long agricultural history, different cropping systems, and natural and artificial selection endow Tibetan barely with the richest genetic diversity, which makes Tibet one of the first barley gene centers in the world. Today, whenever and wherever scientists talk about the origin of barley, they always mention Tibet. Since the beginning of this century, Tibet has been drawing attention of scientists from all over the world. Before 1950, because of the known political reasons, some foreign scientists entered and exploited in some collections of Tibetan barley, but they could not capture the whole range of Tibetan barley resources. After the establishment of P. R. China, the Tibetan social system was changed peacefully, and great progress has been made on research of Tibetan barley germplasms. 3 502 accessions of barley germplasm have been collected from Tibet. All of the collections have been cataloged and reserved in the long-term national gene bank. All of these collections have been evaluated and verified on agronomy traits, disease resistance, abiotic stress tolerance, and nutrient content and quality. They were also grouped based on their living habits, botanical and genetic characters. Some elite germplasms were screened out and used in cross breeding programs. Good achievement has been obtained and many high quality papers published. However, the genetic diversity centers and its mode of spread were not studied yet. The author focused on barley genetic diversity centers and its spread mode. The genetic diversity, comprehensive collection of variability of 12 traits and the distribution of 3 204 accessions collected from Tibet and quantitative genetic method are presented in this paper. The results show that: 1) cultivated barley in 28°-30° N × 88°-94° E was highest in accessions, genetic diversity and comprehensive collection of variability; 2) cultivated barley in 30°-31°N×96°-98° E of Hengduan Mountains takes second place. The genetic diversity centers and spread modes of genetic diversity were put forward according to the distribution centers, genetic diversity and comprehensive collection of variability.

    Biomass and Nutrient Allocation of Lilium pumilum
    YANG Li-Ping, ZHOU Xiao-Feng
    Chin J Plan Ecolo. 2004, 28 (1):  138-142.  doi:10.17521/cjpe.2004.0020
    Abstract ( 2045 )   PDF (184KB) ( 1278 )   Save
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    In order to understand the relationship between biomass and nutrient allocation of Lilium pumilum, a wildly spread perennial herb in China mainly used for medicinal purposes (bulbs are harvested) and as an ornamental, a study on the biomass of vegetative organs, reproductive organs and allocation of N and P in different developmental stages was carried out . The experimental material was obtained from the garden of Northeast Forestry University where L. pumilum had been seeded in a high bed of black soil in spring 1998 under conditions of full sunlight and received treatment of manual weeding, watering and no fertilization.In 2000, samples were taken from May to November from blooming plants of L. pumilum at 6 different stages: bud stage (May 24th); middle period of bud spreading (June 11th); floral phase (June 26th); early fruit-set phase (July 26th); fructescence (August 29th); and seed maturation phase (October 3rd). Thirty individual plants together with their intact underground organs were carefully washed. Every plant was divided into bulb, stem, leaf, bud, flower and fruit (shell and seed), placed into envelopes, dried at 80 ℃, and weighed. We determined the mean biomass of each organ at each growth period and then calculated the ratio of the mean biomass to total biomass. Also, two replicate samples of each tissue were analyzed for N and P content and the average percentweight of total-N and total-P was recorded.The results showed that the percent mean biomass averaged across all developmental stages decreased in the following order: bulbs (60.17%): leaves (13.28%): stems (12.84%): reproductive organs (9.18%); and roots (5.78%). The large investment in the bulb might be a self-protective mechanism for a population of perennial bulbaceous plants as a means for maintaining their long term development. The bulb reached maximum biomass at the early bud stage, and seed maturation phase and the minimum at floral stage. If we want these results indicate that to harvest edible bulbs, the fruitlet should be removed at the post floral stage to increase bulb biomass at the post floral stage and thus improve the bulb harvest. Bulbs should be harvested at the period of maximum biomass, that is, at the bulb stage and seed maturation phase. Seasonal biomass dynamics of reproductive organs were negatively correlated with non-reproductive organs.The results revealed that the mean percent total-N in tissues averaged across all development stages decreased in the following order: leaves (2.19%); reproductive organs (1.50%); bulbs (1.16%); roots (1.03%); and stems (0.99%). Total-N tissue concentrations reached their peak during leaf sprouting and early leaf spreading phase; this occurred when the N content of the reproductive organs were positively correlated with leaf N content and negatively correlated with that in the bulb. The mean total-P content decreased in the following order: reproductive organs (0.035 6%); bulbs (0.031 6%); stems (0.027 8%); roots (0.026 6%); and leaves (0.026 4%). The total-N content of the reproductive organs was positively correlated with that in the stem. This research also revealed that the content of total-N and total-P in aboveground organs tended to increase while organs underground tended to decrease with changing seasons.

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