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Table of Content
Volume 28 Issue 2
10 February 2004

Research Articles
RESPONSE OF OXYGEN EVOLUTION ACTIVITY OF PHOTOSYSTEM II,PHOTOSYNTHETIC PIGMENTS AND CHLOROPLAST ULTRASTRUCTURE OF HYBRID POPLAR CLONES TO LIGHT STRESS
ZHANG Shou-Ren, GAO Rong-Fu, WANG Lian-Jun
Chin J Plan Ecolo. 2004, 28 (2):  143-149.  doi:10.17521/cjpe.2004.0021
Abstract ( 2035 )   PDF (390KB) ( 1009 )
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The photosynthetic rate, oxygen evolution activity of the PSⅡ center, and chloroplast ultrastructure of three hybrid poplar clones under light stress were investigated using an oxygen electrode, IRGA (infra-red CO2 gas analyzer), chlorophyll fluorometer and transmission electron microscopy. The photosynthetic rate and PSⅡ oxygen evolution varied negatively with the pretreatment-PFD (Photon Flux Density), whereas the chlorophyll a/b varied positively with the pretreatment-PFD for two triploid clones. Both the maximal and effective PSⅡ efficiencies of the diploid clone B11 were much higher than those of the two triploid clones B346 and B342. The non-photochemical quenching of triploid B346 was higher than in the B342 and B11 clones. The photosynthetic capacity and resistance to light stress for the diploid clone was higher than in triploid clones. There was no close relationship between chlorophyll content and photosynthetic rate, there was seasonal variation in CHL content and CHLa/b, and the ratio of CHLa to CHLb decreased with enhancing pretreatment-PFDs. The chloroplast protein inhibitor streptomycin (SM) blocked the re-synthesis process of D1 protein. Transmission electron micrographs showed that 1h strong irradiance exposure could result in the decomposition of the lamellar structure of grana. Clones B11 and B342 were more resistant to light stress than clone B346.

EFFECTS OF NOCTURNAL CHILLING TEMPERATURE ON CHLOROPHYLL FLUORESCENCE PARAMETERS IN SEEDLINGS OF TWO RAVINE RAINFOREST SPECIES GROWN UNDER DIFFERENT LIGHT INTENSITIES
FENG Yu-Long, CAO Kun-Fang, FENG Zhi-Li
Chin J Plan Ecolo. 2004, 28 (2):  150-156.  doi:10.17521/cjpe.2004.0022
Abstract ( 2081 )   PDF (318KB) ( 939 )
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We tested the hypothesis that fog can ameliorate the harmful effects of natural nocturnal chilling temperature on tropical plants in Xishuangbanna, Yunnan, China by decreasing growth light intensity in the morning during the foggy and cool seasons. The effects of nocturnal chilling temperature (4-6 ℃) on the chlorophyll a fluorescence was explored in seedlings of two tropical ravine rainforest tree species, Anthocephalus chinensis and Barringtonia macrostachya. A. chinensis is a fast growing, pioneer tree species in the ravine rainforest and B. macrostachya is an intermediate canopy layer tree species and its seedlings distribute in the understory. Seedlings of the two species were grown under four different light intensities (8%, 25%, 50% and 100% full sunlight), and diurnal, stress-induced photoinhibition, and reversible inactivation and/or damage of PSⅡ reaction centers measured. Our results demonstrated that the effects of nocturnal chilling temperature on photoinhibition were significantly intensified under stronger growth light intensities, but its effects were very small under weak growth light intensity (8% sunlight). Fog can decrease light intensity by 60%-90% in the morning during the foggy and cool season; hence, the results presented above indicate that fog can ameliorate the harmful effect of natural nocturnal chilling temperature on Xishuangbanna tropical plants through decreasing growth light intensity. Under intermediate growth light intensity (50% sunlight), stress-induced photoinhibition occurred in untreated B. macrostachya seedlings but not in A. chinensis; furthermore, under the same treatment conditions, the extent of photoinhibition was stronger in B. macrostachya than in A. chinensis. These results suggest that B. macrostachya is more sensitive to temperature-induced photoinhibition. At intermediate and low growth light intensities (25% sunlight), thermal dissipation was greater in A. chinensis than in B. macrostachya after nocturnal chilling temperature treatment, suggesting that protection against photodamage is stronger in A. chinensis. During the period of nocturnal chilling temperature treatment, photoinhibition in the two species was associated with an increase of thermal dissipation and the aggravation of reversible inactivation and/or damage to the PSⅡ reaction center.

PHOTOSYNTHETIC CHARACTERISTICS OF SIX PLANT SPECIES IN A FOREST STEPPE OF THE LOESS PLATEAU, CHINA
XU Hong-Mei, GAO Qiong, HUANG Yong-Mei, JIA Hai-Kun
Chin J Plan Ecolo. 2004, 28 (2):  157-163.  doi:10.17521/cjpe.2004.0023
Abstract ( 2119 )   PDF (343KB) ( 1002 )
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Diurnal net photosynthetic and transpiration rates of six plant species on the Loess Plateau were measured in the field during May, July, and September 2002. Photosynthetic characteristics of these species were quantified by applying a model of net photosynthesis and stomatal conductance to the field data. The results indicated that the model could explain up to 79% and 59% of the variation in the net photosynthetic rate and stomatal conductance, respectively. Hippophae rhamnoides and Artemisia capillaris had higher net photosynthetic rates than the other species because these species had high biochemical photosynthetic efficiencies whereas the other species had low photorespiration coefficients. An afternoon depression in photosynthetic rates in Robinia pseudoacacia, Hippophae rhamnoides L. subsp. sinensis Rousi, Artemisia gmelinii and A. capillaris was explained by decreased stomatal conductance, and, in Malus pumila and Caragana korshinskii, the reduction was due to decreased biochemical photosynthetic capacity. These field results provide a basis for future laboratory studies to better understand the ecophysiological properties of these plants.

EFFECTS OF PLANTING DENSITY ON CANOPY PHOTOSYNTHESIS, CANOPY STRUCTURE AND YIELD FORMATION OF HIGH-YIELD COTTON IN XINJIANG, CHINA
ZHANG Wang-Feng, WANG Zhen-Lin, YU Song-Lie, LI Shao-Kun, FANG Jian, TONG Weng-Song
Chin J Plan Ecolo. 2004, 28 (2):  164-171.  doi:10.17521/cjpe.2004.0024
Abstract ( 2311 )   PDF (323KB) ( 1507 )
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Cotton (Gossypium hirsutum) is an important crop in the Xinjiang Province in Northwest China, and high yields of high quality cotton can be produced under irrigation in the arid, continental climate of this region. In order to increase cotton yields in Xinjiang, we studied the effects of planting density (three treatments: 60 000 plants·hm-2, 180 000 plants·hm-2 and 300 000 plants·hm-2) on canopy photosynthetic rate, canopy structure and yield formation in two cotton varieties, Xinluzao 6' and Xinluzao 7'. Our results showed that canopy photosynthetic rates increased with planting density before full boll stage. Canopy photosynthetic rates of Xinluzao 6' and Xinluzao 7' at a planting density of 300 000 plants·hm-2 were 29.58 μmol CO2·m-2·s-1 and 26.16 μmol CO2·m-2·s-1 respectively, which was 10.4% and 6.5% higher than that of the medium density treatment of 180 000 plant·hm-2. In later growth periods after full boll stage, the canopy photosynthetic rate was maintained at a relatively high level in the medium density treatment, remained low in the low density treatment, but decreased rapidly in the high density treatment due to the decline of the leaf area index (LAI). LAI increased with planting density before full boll stage and attained maximum LAI at full boll stage. Generally, the canopy photosynthetic rate at each growth stage was significantly correlated with LAI (R=0.935*-0.998*, n=5) except for the Xinluzao 6' in later full boll stage. The mean foliage angle of inclination, an important index for describing canopy structure, increased with planting density, whereas two other indices of canopy structure, the canopy transmission coefficient for radiation penetration and canopy transmission coefficient for diffuse penetration, decreased with planting density.Very high planting densities negatively impacted the canopy structure, resulting in a rapid decline of canopy photosynthetic rate. The accumulation of colonial photosynthetic product increased with an increase in planting density during the growth period. In the high density treatment, colonial photosynthetic product accumulation of Xinluzao 6' and Xinluzao 7' was 13 700 kg·hm-2 and 13 153 kg·hm-2, respectively, which was 1.5% and 2.0% higher than that of the medium density treatment, and 34.3% and 54.6% higher than that of the low density treatment. The allocation of photosynthetic product to flower buds and bolls was enhanced from full flower stage to later full boll stage in the medium and high density treatments. Total boll number per unit area increased with planting density. Weight per boll in the medium density planting was 5.61 g and 5.48 g in the two varieties, which was 2.6% and 11.5% heavier than in the high density treatment for the two varieties and 8.7% and 13.5% heavier than in the low density treatments. The canopy photosynthetic rate at full flower stage and boll opening stage were significantly correlated with lint yield. Therefore, the enhancement of the canopy photosynthetic rates during the full boll and opening boll stage could lead to increased of yields of lint.

CORRELATION BETWEEN LEAF NITROGEN STATUS AND CANOPY SPECTRAL CHARACTERISTICS IN WHEAT
XUE Li-Hong, CAO Wei-Xing, LUO Wei-Hong, ZHANG Xian
Chin J Plan Ecolo. 2004, 28 (2):  172-177.  doi:10.17521/cjpe.2004.0025
Abstract ( 2064 )   PDF (289KB) ( 1239 )
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Non-destructive monitoring and diagnosis of plant nitrogen (N) status is necessary for precision N management. The present study was conducted to determine if canopy reflectance could be used to evaluate leaf N status in wheat (Triticum aestivium) of two cultivars, Huaimai 18' and Xuzhou 26'. Ground-based canopy spectral reflectance, leaf N concentration and leaf N accumulation were measured at seven growth stages (jointing, booting, heading, anthesis, initial filling, mid-filling and late filling) under four different treatments of N fertilization (0, 12, 21 and 30 g N·m-2). Analyses were made on the relationships of seasonal canopy spectral reflectance, ratio indices (R(λ1,λ2)=ρλ1/ρλ2) and normalized difference indices (ND(λ1,λ2)=|ρλ1－ρλ2|[]ρλ1+ρλ2) to leaf N concentration and N accumulation in wheat under different N treatments at different growth stages and during the whole growing season. The results showed that canopy spectral reflectance in the near infrared increased with increasing N content, whereas reflectance in the visible band decreased. Leaf N status was significantly correlated with the ratio or normalized difference indices in both cultivars. Regression models of leaf N status to spectral indices based on single growth stages did not improve the prediction over whole growth cycle; hence, a single regression model based on the whole growth cycle should be adequate for diagnosing N status in wheat plants. The relationships between leaf N concentration and spectral indices were better than those of leaf N accumulation. The best indices were the combination of a MIR (mid-infrared) band (1 220 nm) and red band (660 nm) for leaf N concentration (LNC=3.894 5×R(660, 460)-1.028 7, R2=0.834　2; LNC=3.918 7×e-2.179 6ND(660,460), R2=0.835 2) and the combination of the red band (660 nm) and blue band (460 nm) for leaf N accumulation LNA=1.55×e0.115 3R(1 220, 660), R2=0.724　2; LNA=0.219 4×e4.091 4ND(1 220, 660), R2=0.629 9). These results indicate that canopy spectral reflectance can be used to non-destructively monitor leaf N status in wheat plants.

CORRELATION ANALYSIS BETWEEN VEGETATION NEAR-GROUND REFLECTANCE SPECTRAL CHARACTERISTICS AND BIOMASS FOR INNER-MONGOLIA STEPPE
WANG Yan-Rong
Chin J Plan Ecolo. 2004, 28 (2):  178-185.  doi:10.17521/cjpe.2004.0026
Abstract ( 2003 )   PDF (340KB) ( 862 )
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The spectral reflectance characteristics and biological parameters were measured for 15 grassland community types in Inner-Mongolia from 1994 to 2001. In addition, for seven community types, the seasonal variation of these parameters were measured in 1996 and 2001. At large spatial scales, the spectral reflectance was significantly different among meadow-steppe, typical-steppe and desert-steppe and could be distinguished by PCA with lower than 20% mean error. At medium to small scales, the ability to discriminate among community types in typical steppe was higher than at larger spatial scales (the mean error was about 15%) but lower in both the meadow-steppe and desert-steppe. The results of correlation analysis indicated that the spectral reflectance characteristics of biomass and vegetation indices showed strongly significant correlations with spatial scales and community types. The strength of the correlation tended to decrease from small spatial scales to large scales. Linear models were best able to predict biomass from the spectral reflectance characteristics of communities that had high vegetation cover or biomass with an estimated reliability greater than 90%. Non-linear models were the best predictors of communities with low vegetation cover (<40%) and had an estimated reliability of about 85%. From June to September, there were no remarkable differences among the estimated biomass models among different months which implied that we can utilize a common model to monitor the seasonal change of biomass for these grassland types.

WATER RELATIONS AND STOMATAL CONDUCTANCE IN NINE TREE SPECIES DURING A DRY PERIOD GROWN IN A HOT AND DRY VALLEY
GAO Jie, CAO Kun-Fang, WANG Huan-Xiao
Chin J Plan Ecolo. 2004, 28 (2):  186-190.  doi:10.17521/cjpe.2004.0027
Abstract ( 2343 )   PDF (288KB) ( 1107 )
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The valleys along the rivers in southwestern China are hot and dry because of the rain shadow effect. The primary vegetation on the slopes in these valleys is savanna. However, due to heavy human disturbance, the vegetation on these slopes has been devastated or severely degraded, resulting in severe water and soil erosion. Rehabilitation or revegetation of these slopes is urgently needed. Some eucalypt and legume trees have been introduced for the purpose of revegetation, and these have shown fast growth during the first seven years. However, it is not known how these trees cope with the hot and dry stresses during the dry period. In the present study, we monitored the water status, stomatal conductance and osmotic regulation, and their seasonal changes of 9 tree species in a hot and dry valley. The height and diameter of these trees attained over 5 years of growth also were compared. The mean height of the 9 species ranged from 0.7 to 7.6 m, the diameter from 2.6 to 6.7 cm. Four species (Eucalyptus dulebsis, Acacia leptocarpa, A. auriculiformis and A. cunninghamii) showed fast growth, two species (E. citriodora, Leucaena leucocephala) had intermediate growth and the remaining species (A. mangium and Robinia pseudoacacia) had slow growth. The physiological measurements showed that as drought conditions progressed, all species decreased their leaf water potentials and stomatal conductance. However, the decrease was more rapid in A. leptocarpa, A. auriculiformis, A. cunninghamii and Eucalyptus dulebis. During the peak drought period (March and April), these species also reached the lowest water potentials (predawn water potential lower than -1.0 MPa) and nearly closed their stomata (A. leptocarpa, A. auriculiformis, A. Cunninghamii) or remained at low stomatal conductance (Eucalyptus dulebsis, A. holosericea and Dodonaea wiscosa) while the remaining species maintained relatively high water potentials and a low stomatal conductance (Eucalyptus citriodora and Leucaena leucocephala) or nearly closed stomata (A. mangium). Nevertheless, during the drought period, no species showed leaf wilting, except R. pseudoacacia and the native species Vitex negundo and Terminalia franchetii, which were deciduous. All species increased osmoregulation capacity, as indicated by the decrease of osmotic potentials at full saturation, and the increase of osmoregulation substances. Osmoregulatory substances increased over time in the following sequence: K+, free Pro, other free amino acids and soluble sugars. It appeared that K+ was important in osmoregulation at the beginning of the drought, while soluble sugars were important in the late drought period. E. dulebsis, A. auriculiformis and A. cunninghamii exhibited the highest osmoregulation capacities. Our results show that most of the introduced species are suitable to grow in these hot and dry habitats because of, among other things, they have strong capacities of water-absorption and water conservation.

CARBON CONSUMPTION OF ROOTS AND ITS RELATIONSHIP TO YIELD FORMATION IN SPRING WHEAT AS AFFECTED BY SOIL MOISTURE
LIU Hong-Sheng, LI Feng-Min, XU Hao
Chin J Plan Ecolo. 2004, 28 (2):  191-197.  doi:10.17521/cjpe.2004.0028
Abstract ( 2331 )   PDF (270KB) ( 869 )
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A potted plant experiment was conducted under an auto-rain-shelter to investigate C consumption of roots and its relationship to yield formation of spring wheat (Triticum aestivum) as affected by soil moisture. Two cultivars of plants, Longchun 8139-2' (L) and `Dingxi 24' (D), were grown in a split PVC pot 100 cm long and 10 cm in diameter in a mixture of deep loessial soil and vermiculite (1∶5.2 g/g). Three soil water treatments were employed: wet (W, 75%-85% of field water capacity); medium drought (M, 45%-55% of field water capacity); and serious drought (S, 25%-35% of field water capacity). Water regimes were controlled by watering every 5 days and destructive sampling was performed at jointing, anthesis and mature stage to measure plant biomass in shoots and roots. Respiration in roots and rhizosphere was measured by infrared gas analysis system at these stages. Root exudation was calculated from the rhizosphere respiration. Of the total carbon consumed by roots during jointing and anthesis, 26% of daily C consumption was allocated to root biomass, 58% to root respiration and 16% to root exudation, when averaged across all treatments. During the maturing period, no significant differences in the daily decrease of C allocated to root biomass in the W and M treatments were found between the two cultivars, but, in the S treatment, the daily decrease of C allocated to root biomass was significantly more in D cultivars than in L, and the lowest daily C consumption from root respiration and exudation also occurred in D cultivars in the S treatments. This resulted in a greater than 100 times reduction in the ratio of root biomass C to total C invested in roots, and a 7.89 times and 3.37 times decrease in the ratio of root respiration C and exudation C to total C consumption, which was very different from other treatments/cultivars. The ratio of the sum of root respiration C and exudation C to total C consumption was 53%, 52% and 83% respectively for W, M and S treatments in L cultivars, and 58%, 49% and 55% in D cultivars. The lowest ratio occurred in the M treatment for both cultivars, and this ratio was far lower in D cultivars than in L for the S treatment. Grain yields were similar for both cultivars, but a little higher in L than in D under wet conditions. The ratio of grain yields of individual treatments to the mean yield of the three treatments was 1.34, 1.14 and 0.53 for W, M and S treatments in L cultivars, and 1.04, 1.06 and 0.90 in the three treatments of D cultivars. This suggests a higher stability of grain yields in D than in L cultivars. The decrease in daily C consumption of roots and the relative stabilization of daily photosynthetic rates accounted for the higher water use efficiency and relatively high grain yields under conditions of medium soil moisture.

CHANGES IN THE ENDOGENOUS PHYTOHORMONE CONTENT OF THE SUPER-XEROPHYTIC SHRUBLET, POTANINIA MONGOLICA, DURING FISSURATE GROWTH
HOU Yan-Wei, WANG Ying-Chun, YANG Chi
Chin J Plan Ecolo. 2004, 28 (2):  198-203.  doi:10.17521/cjpe.2004.0029
Abstract ( 2047 )   PDF (231KB) ( 924 )
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Potaninia mongolica is an archaic, single-species genus plant and is a member of the Rosaceae family. It is well adapted to drought environments. P. mongolica reproduces primarily by vegetative means, but it also can reproduce sexually. This species has two modes of vegetative reproduction: one is that the branches drop and grow new vegetal body and the other is by fissurate growth. Many other xerophilous plants in the Inner Mongolia West Erdos region share the same characteristic of fissurate growth, which is an adaptive strategy to drought environments. Correlated studies of fissurate growth are few, and this is the first report on the changes of the endogenous phytohormone content during fissurate growth.We determined the content of ABA, IAA, GA3, ZR in tissues of P. mongolica in different states of fissurate growth using ELISA (Enzyme-Linked Immunosorbent Assay), to relate changes of phytohormone content to changes during fissurate growth.The results are as follows: 1) in the four states measured, ABA content was the lowest in the leaf and the fissurate part during the fissurated state and highest in the root. Compared with other endogenous phytohormones, ABA content was the highest. 2) before fissuration, IAA accumulated greatly in the fissurate part, especially during the transitional state, and IAA content was the highest in the fissurate part. 3) during fissurate growth, changes in GA3 content followed that of the IAA content. 4) ZR content was also the highest in the fissurate part before fissuration. During fissurate growth, ZR content carried from the root to the fissurate part and the leaf decreased gradually, and, during the transitional state, the percent of ZR carried from the root to the fissurate part was higher; these were 19.44% and 20%. 5) IAA, GA3, and ZR mutually regulated and promoted the growth and splitting of the cells in the fissurate part, and the accumulation of ABA in P. mongolica roots was an adaptive response to its droughty environment.

THE EFFECTS OF GAP SIZE AND WITHIN GAP POSITION ON THE SURVIVAL AND GROWTH OF NATURALLY REGENERATED ABIES GEORGEI SEEDLINGS
LIU Qing
Chin J Plan Ecolo. 2004, 28 (2):  204-209.  doi:10.17521/cjpe.2004.0030
Abstract ( 2204 )   PDF (315KB) ( 1020 )
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The survival and growth of Abies georgei seedlings growing in forest canopy gaps was investigated over a 4-year period on the Baima Snow Mountain in northwest Yunnan Province, China. Of the total gaps surveyed in A. georgei forests, 45% were small (gap area <50 m2), 35% were medium sized (50-100 m2) and 20% were large (>100 m2) gaps. Seedling growth rates, survivorship, abundance and size were measured and compared among the three different sized gaps and under the closed forest canopy and within gaps according to their position (north, south and center) in each gap. The seedlings all originated from natural seed rain. The results showed that there were significant differences in the size and number of seedlings among the different sized gaps and understorey. There were 1.5 times more seedlings in larger gaps than in smaller ones and very few seedlings (0.5 ind.·10 m-2) were found in the understory. The survival of A. georgei seedlings within gaps tended to increase from south to north positions within the larger gaps, whereas survivorship did not vary within the small and medium sized gaps. Seedling size, in terms of both height and basal diameter, in the different sized gaps was as follows: medium > small > large > understorey. Relative growth rates showed a similar pattern. The average annual growth in height was (7.8±0.5) cm in medium gaps. Furthermore, size and annual relative height growth of seedlings did not differ significantly among positions within the medium and small gaps, but seedling height peaked in the southern position of large gaps and declined towards the center and north edges. Seedling establishment was greater in gaps than under the closed-canopy. Due to adaptation to light conditions, relative growth rates of seedlings were greatest in medium sized gaps but were relatively low in regions of the large gaps that had greater exposure to direct solar radiation as well as in small gaps that were shaded and received little direct solar radiation. Finally, based on observed changes in survival and growth of seedlings over four growing seasons, the author suggests that medium sized forest canopy gaps provide the best habitat for regeneration of A. georgei seedlings.

THE ROLE OF ANTS IN SEED DISPERSAL OF GLOBBA LANCANGENSIS AND THE SPATIAL DISTRIBUTION OF ITS SEEDLINGS
CHEN Fan, CHEN Jin, LIU Zhi-Qiu, ZHANG Ling, LIU Yong, BAI Zhi-Lin
Chin J Plan Ecolo. 2004, 28 (2):  210-217.  doi:10.17521/cjpe.2004.0031
Abstract ( 2097 )   PDF (328KB) ( 927 )
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Seed dispersal is a key process determining the spatial pattern of plant populations. Myrmecochory is a term referring to a plant-ant mutualism in which ants disperse plant seeds while using the nutritionally valuable elaiosomes as food. In this study, our goal was to understand how ants affect seed dispersal and seedling distribution patterns of a myrmecochorous plant, Globba lancangensis. G. lancangensis is a small perennial herb of Zingiberaceae mainly distributed in southwest Yunnan Province. It propagates primarily by seeds but also by a small number of bulbils. There are 31.2±2.13 (Mean±SE, n=32) seeds in each fruit. The seeds are 2-3 mm in length and bear a white-colored elaiosome. We conducted an observational study on the seed dispersal of G. lancangensis in October 2002 in its natural habitat in Xishuangbanna, Yunnan Province of China (21°59′ N, 100°16′ E; 1 180 m asl; annual mean temperature, 18.3 ℃; annual mean rainfall, 1 339 mm). A total of ten species of ants were identified that transported the seeds of G. lancangensis and their activities were recorded. The mean dispersal distance of seeds was （0.47±0.03） m (n=216), ranging from 0.01 m to 3.35 m. Odontoponera transversa, Pheidole sp. and Pachycondyla luteipes were the most important seed dispersing ant species, occurring 61%, 50% and 28% of the time, respectively, with mean dispersal distances of (0.60±0.09) m, (0.20±0.01) m and (0.32±0.05) m, respectively. As a whole, ants promoted a decrease in the degree of aggregation of G. lancangensis seeds. Ants of Pheidole sp. collected a total of 43% of the seeds of G. lancangensis but consumed most of the seeds collected, suggesting that Pheidole sp. is a seed harvester ant　O. transversa did not remove seeds with artificially removed elaiosomes and appeared to be the most sensitive ant species to seed elaiosomes. Overall, O. transversa made the most significant contribution to seed dispersal, as demonstrated by the highest visiting frequency (61%) and the greatest mean dispersal distance (0.60±0.09) m of all ants. These results imply that a tight mutualism exists between O. transversa and G. lancangensis. To understand whether ants influence the spatial pattern of seedlings, we compared the spatial distribution of seedlings of G. lancangensis in its natural habitat with that of two other species in the Globba genus, G. barthei and G. racemosa; the latter two species propagate mainly by bulbils which are dispersed by abiotic means. Nine 25 m×25 m plots, three plots for each species, were established and the location of every Globba seedling inside the plots was recorded. The mean distance to the nearest neighbor of G. lancangensis was significantly higher than both G. barthei ((36.8±1.45) cm vs. (29.8±2.70) cm, Mean±SE; t73,33=2.11, p=0.037) and G. racemosa ((36.8±1.45) cm vs. (28.7±3.16) cm, t73,31=2.33, p=0.022). We used Z-values to describe the degree of aggregation of the populations of the three species. The Z-value of G. lancangensis (-1.70±0.19, Mean±SE) was significantly larger than the Z-value of both G. barthei (-2.58±0.37, t73,33=2.36, p=0.020) and G. racemosa (-3.28±0.53, t73,31=3.54, p=0.001), indicating that G. lancangensis was significantly less aggregated. These results suggest that ants make a significant contribution to dispersing G. lancangensis seedlings by increasing the distance to its nearest neighbor and decreasing the degree of aggregation in its natural habitat.

THE ROLE OF ECTOMYCORRHIZAL FUNGAL HYPHAL LINKS IN PHOSPHORUS TRANSFER BETWEEN LARIX KAEMPFERI SEEDLINGS AND PLANT GROWTH
LI Fang, XU Bing, FENG Gu, PAN Jia-Rong, LI Xiao-Lin
Chin J Plan Ecolo. 2004, 28 (2):  218-224.  doi:10.17521/cjpe.2004.0032
Abstract ( 2140 )
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A COMPARATIVE STUDY OF SEED WEIGHT OF 69 PLANT SPECIES IN HORQIN SANDYLAND, CHINA
LIU Zhi-Min, LI Rong-Ping, LI Xue-Hua, LUO Yong-Ming,WANG Hong-Mei, JIANG De-Ming, NAN Yin-Hao
Chin J Plan Ecolo. 2004, 28 (2):  225-230.  doi:10.17521/cjpe.2004.0033
Abstract ( 2337 )   PDF (238KB) ( 1516 )
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Previous studies have shown that seed mass is related to dispersal distance, seed longevity, establishment success and fecundity. Many ecologists have employed seed weight as a trait to classify plant functional types; however, few studies of this kind have been conducted in China. Horqin Sandyland, located in the semiarid agropastoral zone of northern China, has undergone severe desertification during the past decades. Formation of active dunes, degradation of natural vegetation, and loss of biodiversity are the primary issues of environmental concern. At present, no comparative studies on the regenerative strategies of the constituent plant species have been conducted, and basic information necessary for vegetation restoration activities is lacking. We conducted a comparative study on the seed weight of 69 species in Horqin Sandyland to better understand regeneration strategies of these species for purposes of improving vegetation management and restoration.Seeds were collected at the Wulanaodu region (119°39′-120°02′ E, 42°29′-43°06′ N, 480 m a.s.l.). The climate there is semiarid with a mean annual precipitation of ca. 340 mm and a mean annual temperature of 6.3 ℃. At present, 90% of the total land has been desertified and 70% of the meadow has become saline and sodic. Psammophile-dominated vegetation is well developed. Plant diaspores are usually referred to as seeds, even though many of them are in fact fruits. We analyzed data on seeds and indehiscent, single-seeded fruit. The air-dried weight of 100 diaspores was measured for each plant. Most grasses caryopses were measured with the persistent lemmas and awns with which they are normally dispersed. The achenes of Compositae were measured with pappus and seeds and those of Cynanchum sibiricum, Metaplexis japonica and Apocynum venetum were also measured with hairs. Fruits of Xanthium sibiricum, Lappula myosotis and Bassia dasyphylla were measured with thorn and hook.The results showed that species could be divided into four groups with regard to the weight of diaspores as fruits (<0.1 mg, 0.1-0.999 9 mg, 1-9.999 9 mg, 10-99.999 9 mg). The fruits of Artemisia scoparia (0.051　7 mg) and Typha minima (0.068　2 mg) were the lightest, and those of Xanthium sibiricum were the heaviest. Species could be divided into 3 groups with regard to the weight of diasporas: 0.1-0.999 9 mg; 1-9.999 9 mg; and 10-99.999 9 mg. Seeds of Portulaca oleracea (0.151　4 mg) were the lightest, while the seeds of Sophora flavescens (46.781　6 mg) were the heaviest. Small seeds and a persistent soil seed bank might be responsible for the extensive distribution of such species as Artemisia scoparia, Portulaca oleracea, Adenophora tetraphylla, Kochia sieversiana, Lysimachia barystachys, Chenopodium glaucum, Salsola ruthenica, Cuscuta chinensis, Artemisia sieversiana, Setaria viridis, and Arundinella hirta. The pioneering species that establish on sand dunes such as Agriphyllum squarrosum, Artemisia halodendron, A. wudanica, Setaria viridis and Bassia dasyphylla had medium or high diaspore weight, or had mechanisms to protect diaspores from being carried away by the wind.

BASIC CHARACTERISTICS OF SUBMERGED PLANT COMMUNITIES INVADED BY CABOMBA CAROLINIANA AND ITS HABITAT IN CHINA
YU Ming-Jian, DING Bing-Yang, YU Jian, JIN Xiao-Feng, ZHOU Hong, YE Wan-Hui
Chin J Plan Ecolo. 2004, 28 (2):  231-239.  doi:10.17521/cjpe.2004.0034
Abstract ( 2275 )   PDF (481KB) ( 1047 )
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Cabomba caroliniana (common names: Cabomba, Fanwort) is a submerged plant from the USA and South America that was introduced into China in the 1980s as an aquarium plant for its beautiful and finely dissected submerged foliage. Cabomba is now distributed

CHANGES IN PLANT SPECIES DIVERSITY AND PRODUCTIVITY ALONG AN ELEVATION GRADIENT IN AN ALPINE MEADOW
WANG Chang-Ting, WANG Qi-Ji, LONG Rui-Jun, JING Zeng-Chun, SHI Hui-Lan
Chin J Plan Ecolo. 2004, 28 (2):  240-245.  doi:10.17521/cjpe.2004.0035
Abstract ( 2415 )   PDF (259KB) ( 1278 )
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Understanding the relationship between biodiversity and ecosystem function is central to the Global Change and Terrestrial Ecosystem (GCTE) project as well as to ecosystem ecology in general. Productivity and nutrient maintenance, both critical ecosystem functions, can be measured in relation to species diversity to test how ecosystem functions are affected by species diversity. We studied changes in species diversity and productivity along elevational gradients in alpine meadow grasslands to assess the influence of changing species diversity on productivity.The results show a significant unimodal pattern of species diversity across the elevation gradient with species diversity highest at mid-elevations. Maximum species diversity occurred at intermediate levels of productivity and species richness. Above-ground biomass decreased with increasing elevation and below-ground biomass was greatest at low and high elevations and lowest at mid-elevations. Below-ground biomass varied during the growing season and vertically within the soil profile: maximum underground biomass occurred at the beginning and end of plant growing and was distributed primarily in the top 0-10 cm of soil.

THE BIOMASS OF PHRAGMITES AUSTRALIS AND ITS INFLUENCING FACTORS IN WULIANGSUHAI
DUAN Xiao-Nan, WANG Xiao-Ke, OUYANG Zhi-Yun, MIAO Hong, GUO Ran
Chin J Plan Ecolo. 2004, 28 (2):  246-251.  doi:10.17521/cjpe.2004.0036
Abstract ( 2266 )   PDF (274KB) ( 1606 )
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There is an increasing need to understand the importance of ecosystem services provided by wetlands, including nutrient storage, water quality improvement, soil organic matter enhancement and biodiversity protection. Phragamites australis (common reed) is a dominant plant in many aquatic ecosystems and plays a critical ecosystem service role in wetlands. However, few studies have focused on common reed communities, especially concerning its characteristics in eutrophic wetlands in western China.To investigate the relationship between the biomass of P. australis and the physical and chemical characteristics of water and soil (water depth, N and P water and sediment concentrations, soil organic mater and N and P content of plants), a field study was conducted in September 2002 in Wuliangsuhai, Inner Mongolia where eutrophication is a very serious problem in this arid climate. We randomly selected 15 sampling sites and determined the reed biomass with harvest method in 1 m×1 m plots. To eliminate the effects of different aged stands on biomass, we chose uniform plots of two-year old reed stands. The reed height, culm diameter and the number of shoots were measured and soil, water and plant (leave, stem, rhizome, root) were sampled, and the N and P content analyzed. The results showed that the reed biomass was as high as 1.73-3.00　kg·m2 with a below-ground to above-ground biomass ratio ranging from 1.1-2.1. Many factors influenced reed biomass, but water-depth was the most important factor. Above-ground and above-water biomass increased and the ratio of below- to above- ground biomass decreased with water depth. Water-depth effected reed biomass by changing the morphology and structure of the reed community, such as reed height, culm diameter, density, and biomass allocation. There was a significant correlation between reed biomass and water N concentrations. The nitrogen to phosphorus ratio ranged from 7.59-12.21 (< 14) indicating that N limited the reed growth at the community level. Reed biomass was not correlated with water P concentrations. Soil organic matter did not influence reed biomass because the soil was primarily consisted of mineral and organic sediment with little reed litter that releases phytotoxic acids. To investigate the combined effect of the physical and chemical characteristics of water and soil on reed biomass, an equation was developed which indicated that the reed biomass of Wuliangsuhai was mainly influenced by water depth and N concentrations of the water.

STUDY ON NUMERIC DYNAMICS OF NATURAL POPULATIONS OF THE ENDANGERED SPECIES DISANTHUS CERCIDIFOLIUS VAR. LONGIPES
XIAO Yi-An, HE Ping, LI Xiao-Hong, DENG Hong-Ping
Chin J Plan Ecolo. 2004, 28 (2):  252-257.  doi:10.17521/cjpe.2004.0037
Abstract ( 2171 )   PDF (209KB) ( 1195 )
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Disanthus cercidifolius var. longipes is an endangered plant species which is only distributed in Jinggang Mountain, Junfeng Mountain and Guanshan, Jiangxi Province,Longquan, Zhejiang Province, and Mangshan, Hunan Province, China. At present, its population is small and decreasing. In order to better understand its decline, we studied the population dynamics of this species using static life tables, fecundity schedules, Leslie matrices and time sequence analysis based on an in-depth investigation of age structure, seed production and seed germination rate. The results are as follows: Net reproductive rate (R0), intrinsic rate of increase (rm) and finite ratio fineries (λ) are 0.833　7, -0.004　7 and 0.995　3, respectively. Values of the separameters (R0<1, rm<0, λ<1) indicated that the population is decreasing. The Leslie matrix model predicted that over the next 50 years the number of populations would decrease from 227 1 to 764, i.e., only 30% will remain. The results of the time sequence analysis agreed with the Leslie matirix model prediction. The key threats to this species are most likely deforestation and habitat fragmentation.

EFFECT OF INSERTING CORNSTALK IN BARE ALKALI-SALINE PATCHES ON SURVIVAL RATE OF CHLORIS VIRGATA AND SUAEDA CORNICULATA
HE Nian-Peng, WU Ling, ZHOU Dao-Wei
Chin J Plan Ecolo. 2004, 28 (2):  258-263.  doi:10.17521/cjpe.2004.0038
Abstract ( 2187 )   PDF (280KB) ( 874 )
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The Song-nen grassland in China, where Leymus chinensis is the dominant plant, ordinarily belongs to meadow grassland, but now there exists a mass of degraded alkali-saline grassland, with secondary bare alkali-saline patches in a regressive succession, caused by irrational exploitation in past years. It is an imperative and difficult task for scientists and grassland managers to improve or ameliorate these secondary bare alkali-saline patches. There have been extensive studies of the eco-physiological properties of many salt-tolerant plants and the property of soil in the Song-nen grassland. Many scientists and managers consider that the too high content of soluble saline ion in soil is the dominant cause, which made the natural restoration process of secondary bare alkali-saline patches so slow, and have brought forward some effective measures to improve them. However, relatively little is known about the survival rate of some salt-tolerant plants in secondary bare alkali-saline patches under natural conditions. It is a very important factor to the improvement of these bare patches and will to some extent influence the improving effect in practice. So, determining the survival rate of these salt-tolerant plants in natural conditions will help to find an economic and operable way to restore these secondary alkali-saline bare patches. We have investigated the growing dynamics of two salt-tolerant plants (Suaeda corniculata and Chloris virgata) in secondary bare alkali-saline patches in natural conditions through seeding experiments. Moreover, we have also inspected whether some simple experimental treatments can enhance the survival rate of plants in natural conditions through inserting cornstalks in secondary bare alkali-saline patches and seeding. Finally, based on our results and previous work, we have discussed the potential causes, which made their natural restoration process so slow in natural conditions, and ways of optimizing ecological restoration patterns. The results show that Suaeda corniculata is able to grow in the secondary bare alkali-saline patches in natural condition without any auxiliary utilities, and its ultimate survival rate arrives at 61.2%±16.5% in fall; the survival rate of Chloris virgata is very low, and its ultimate survival rate is only 5.7%±6.1%. The mortality rate of the two plants is comparably high in their initial growth period. The treatment of inserting cornstalks significantly enhances the survival rate of Suaeda corniculata and Chloris virgata, and their ultimate survival rates are 74.8%±18.4% ant 43.1%±20.8% respectively. More importantly, they both can reproduce successfully and provide the necessary seeds for subsequent natural succession in these bare patches. The soil seed bank is the template of plant restoration and influences the restoration speed and direction on these secondary bare alkali-saline patches. Natural restoration should be accelerated if there exist substantive seeds of salt-tolerant plants, such as seeds of Suaeda corniculata. Therefore, lack of propagulum in soil (including seeds and other propagulum) should be another important restricting factor, besides the too high content of soluble saline ion in soil, which made their natural restoration process so slow in natural conditions. The experiment shows that it is possible to boost the survival rate of these salt-tolerant plants in secondary bare alkali-saline patches in natural condition, if we take some effective measures. Then, based on these properties of the secondary bare alkali-saline patches, we have put forward a new ecological restoration pattern to accelerate their natural restoration, i.e., rationally integrating the ecological theories into ecological engineering and making the best of local seed resources and local specific climate to improve secondary bare alkali-saline patches. Restoration of these secondary bare alkali-saline patches looks promising, especially where the area of these secondary bare patches is relatively small and their distribution is patchy in Song-nen grassland.

FOG CHARACTERISTICS IN A TROPICAL SEASONAL RAIN FOREST IN XISHUANGBANNA, SOUTHWEST CHINA
LIU Wen-Jie, ZHANG Yi-Ping, LI Hong-Mei, DUAN Wen-Ping
Chin J Plan Ecolo. 2004, 28 (2):  264-270.  doi:10.17521/cjpe.2004.0039
Abstract ( 2027 )   PDF (306KB) ( 1006 )
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Fog frequency and duration were measured between November 1998 and February 2003 in a seasonal rain forest in Xishuangbanna, Southwest China. The amount of fog and dew precipitation was measured daily using twelve bottle-funnel collectors set in a random pattern on the forest floor. Related microclimatic variables including air temperature, relative humidity, wind speed, solar radiation and rainfall were recorded by a meteorological observation system mounted on a 72 m tall meteorological tower in the study site. At night the fog occurred first at the top layer of the canopy, and then a thick fog penetrated the understory. Before fog occurred, the air temperature was greater at 0.5 m above the canopy than on the canopy surface but was lower after fog occurred. The number of fog days was much higher inside the rain forest (258 days/year) than in open areas (188 days/year). Fog frequency in the rain forest was 90% during the foggy season (November-February), slightly lower (78.7%) in the dry-hot season (March-April), and lowest (55.4%) in the rainy season (May-October). The number of fog days in each season was negatively correlated with the amount of rainfall. The onset of fog occurred on average at 2 300 and lifted at 1 100 hours during the foggy season. During the dry-hot season and rainy season, the fog occurred 0.7 and 2.3 hours later and lifted 0.8 and 2.2 hours earlier, respectively. Meanwhile, there was a negative correlation between the time of fog occurrence and lift. Average fog duration per day during the foggy season was 12.2 hours, and was 1.2 and 1.6 times longer than average fog duration of the dry-hot and rainy season, respectively. During the study period, the absolute amount of mean annual fog and dew precipitation was (89.4±13.5) mm (mean±SD), which was 4.9%±1.7% of the annual precipitation. Of the total annual amount of fog and dew precipitation, 85.9%±6.6% was collected during the foggy season and dry-hot season. The results suggest that fog, which both condenses water vapor into available precipitation in the forest and buffers temperature changes, plays an important role in the hydrology of the forest, especially during the foggy and dry-hot seasons. Therefore, horizontal precipitation (fog interception) needs to be included in calculations of the water balance in this forest. These results also demonstrate the importance of understanding the impacts of climate factors, and have important implications for ecologists and hydrologists interested in fog-inundated ecosystems.

BRIEF REVIEW OF FIG-POLLINATOR COEVOLUTION AND FICUS CLASSIFICATION
YAO Jin-Yan, ZHAO Nan-Xian, CHEN Yi-Zhu
Chin J Plan Ecolo. 2004, 28 (2):  271-277.  doi:10.17521/cjpe.2004.0040
Abstract ( 2309 )   PDF (250KB) ( 1625 )
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Ficus is the keystone plant in tropical forests, and it also occurs in subtropical and even temperate areas. More than 700 species in the genus Ficus (Moraceae: Ficus) and their species-specific pollinator, the fig wasp, (Chalcidoidae: Agaonidae) has been discovered. The interactions between them, which have become an obligate mutualist relationship, have a very long evolutionary history. Pollen dispersal in figs is completely dependent on fig wasps, which enter the syconium where viable seeds are produced. Fig pollinators are uniquely dependent on the fig for the completion of their life cycle. Each fig species attracts its own species of fig wasp by emitting specific volatile compounds during their receptive period and these wasps lay their eggs in the developing ovary of the host fig species. As ovipositing female wasps simultaneously carry pollen from other syconia and pollinate figs actively or passively, they show peculiar morphological and behavioral adaptations to figs and a life cycle highly synchronous with fig inflorescence. Such specialization and interactions make diversity in species, genetics, morphology and behavior in pollinators and their host plants an exciting example for studying interspecific coevolution. Although fig-pollinator symbiosis is now widely regarded as a model system of plant-insect coevolved mutualism, little is known about the history and process of their interactions. Current experiments and observations have suggested the fig/fig wasp obligate mutualism (this is not a complete sentence but I am not sure what the author is trying to say here). However, present fig and fig wasp classifications, which are based on morphological characteristics and their interactions, are still incomplete and controversial. This short review summarized the knowledge and questions on coevolved mutualism, the molecular phylogeny of fig/fig pollinator symbionts and the traditional classification of Ficus. Studies on the interactions between fig/fig pollinator and re-classification of Ficus in China based on molecular phylogeny were also discussed. Research on the phylogeny of about 100 species of fig trees, which mainly occur in tropical and subtropical areas in China, has just started and only a few reports on fig pollination biology and ecology exist. Much work should be done to make a thorough study of both symbiotic partners. Though systematic classification of Ficus is the basis of the coevolutionary study, application of molecular phylogeny is also necessary and feasible, which will promote further research and understanding of plant-insect coevolution in China.

ON THE ORIGIN AND DEVELOPMENT OF ECOLOGICAL PLANT PHYSIOLOGY
JIANG Gao-Ming
Chin J Plan Ecolo. 2004, 28 (2):  278-284.  doi:10.17521/cjpe.2004.0041
Abstract ( 2824 )   PDF (216KB) ( 2005 )
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The origin and development of ecological plant physiology is discussed. An important subject of plant ecology, ecological plant physiology probes the mechanisms of an ecological phenomenon through physiological theory and technology. According to the available historical information, A. F. W. Schimper, a German sophist, can be regarded as the father of this subject. However, the person who suggested that ecological plant physiology be treated as an independent field of ecology was W. D. Billings. Professor W. Larcher has contributed greatly to the promulgation of the subject throughout the world. In China, the modern development of ecological plant physiology was due to Professor T. T. Li. However, the translation and promulgation of Larcher's works was done by Professor B. Li, who popularized this subject in the ecological field of China. Nowadays, the study of ecological plant physiology has expanded rapidly both overseas and in China, largely owing to the fact that it can explain ecological processes on the basis of eco-physiological mechanisms and help guide the sustainable use of natural resources. For Chinese researchers, hot topics such as the response of plants to environmental stresses that grow on the Tibetan Plateau, the response of plants to CO2 enriched environments, and plant responses to restoration efforts of human degraded ecosystems should be of particular interest.

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