We studied the breeding system and pollination ecology of Meconopsis integrifolia (Papaveraceae), which is an alpine herb, for two consecutive years.

Five plots (plot 1, 4452 m a.s.l; plot 2, 4215 m a.s.l; plot 3, 4081 m a.s.l; plot 4, 3841 m a.s.l; plot 5, 3681 m a.s.l) were established along an altitudinal gradient in the Balang Mountain. Flower longevity, stigma height and the highest stamen were measured and recorded. The stigma receptivity and pollen viability were tested by the Benzidine-H₂O₂ method and the TTC method, respectively. The breeding system was tested by experimental approaches, and flower visitors were observed over the life span of the flower. The temperatures of the flower and environment were also recorded. Important findings Flower longevity was greater in plots 1 and 2 than in plots 3, 4 and 5. The stigmas were higher than the anthers at the beginning of anthesis, and the distance between stigmas and the anthers then gradually decreased with the progress of flowing. The stigmas and anthers came into contact when the corolla wilted in 65% of the flowers sampled, indicating an incomplete herkogamy. The stigmas became receptive before the dehiscence of anthers (protogyny). Under natural conditions, stigma receptivity lasted for 8 d and pollen viability lasted for 2 d. Hand-pollination experiments indicated that M. integrifolia was self-compatible and did not exhibit apomixis. Seed set was significantly increased after a supplemental hand-pollination, suggesting the pollen-limitation of reproduction. The pollinators in plots 1 and 2 were flies, and in plots 3, 4 and 5 flies and Thripidae spp. We observed that flies moved and transferred pollen between plants, and that both flies and Thripidae spp. moved within flowers, the latter resulted in “facilitated selfing”. About 65% of the plants sampled set seed by autonomous self-pollination. There was a significant difference in the visiting frequency of flies between plots, with plot 1 being the lowest and plot 2 the highest. Pollen limitations were evident across all plots due to lack of sufficient outcrossing pollinators. Two different selfing mechanisms, unexplored here, may provide a partial compensation for the natural reproduction of this alpine species in the arid, alpine habitats. M. integrifolia could attract pollinators by providing a warm shelter.

Log is an important pool of carbon (C) and nutrients in alpine forest ecosystems. Changes in log quality with decay could reveal the process of C and nutrient release during log decomposition. However, little information is available on this. Therefore, this study aims to understand the changes in log quality during log decaying.

Changes in C, nitrogen (N), phosphorus (P), lignin and cellulose concentrations were investigated in the heartwood, sapwood and bark of fir (Abies faxoniana) logs at five (I-V) decay stages in an alpine forest in western Sichuan, China. The stoichiometry of C:N:P and the ratios of lignin:N, lignin:P, cellulose:N, and cellulose:P were also calculated.

C content in bark increased from the stage I to stage III of decay and then significantly decreased, but in the heartwood and sapwood it decreased from the stage I through stage V, especially at stages IV and V. N content increased from the stage I through stage V regardless of the log components. P content in sapwood also showed tended to increase from the stage I through stage V, but P content in heartwood and bark decreased following an increase tendency. In comparison with sapwood and heartwood, bark had the lowest C:N:P stoichiometry at the same decay stages. Percentage of the labile to total C (F_m) also inferred that bark was the most decomposable component. The higher C:N:P stoichiometry in sapwood was observed in logs of the stages I and II, but higher F_m in heartwood was detected from the stage III to stage V. Critical values of C:N in sapwood and bark and C:P in heartwood, sapwood and bark were negatively correlated with the initial N and P concentrations, respectively. Cellulose concentration decreased from the stage I to stage V regardless of log components, and among different components followed the order of heartwood > sapwood > bark at corresponding decay stages. In contrast, lignin concentration increased from the stage I to stage V regardless of log components, and among different components followed the order of bark > sapwood > heartwood at corresponding decay stages. Cellulose degraded faster than lignin regardless of log components, and the ratio of lignin:cellulose increased significantly at the advanced decay stages. Moreover, bark showed a relatively higher lignin:cellulose ratio compared with sapwood and heartwood. In addition, statistical analysis suggested that the degradation of lignin and cellulose in logs would be affected by N concentration. Bark decay was limited by N at early decay stages but by P at all decay stages, and the decay of heartwood and sapwood was limited by both N and P based on ecological stoichiometry theory.

Variations in leaf characteristics can reflect plant acclimation to environments. We aimed to examine the relationship between leaf traits of Melica przewalskyi and slope aspect.

In alpine grassland of Qilian Mountains, Gansu Province, China, 80 plots were sampled at intervals of 20 m along eight aspects. Latitude, longitude and altitude of each plot were recorded by GPS. At each plot, 10 individuals of M. przewalskyi were random selected and harvested for measurements of leaf mass, leaf area, and leaf volume. A digital elevation model (DEM) was constructed to extract elevation, aspect, and slope for each plot by ArcGIS. The 80 plots were divided into groups of north, east, west and south aspect. Values for leaf traits were log-transformed. the standardized major axis (SMA) estimation method, was used to examine the covariation among leaf traits.

Leaf area and leaf volume decreased significantly as aspect turns from north to east, from east to west, and from west to south, but not so for leaf mass, suggesting that leaf thickness increased as slope aspect changes, and thus led to the smaller and thicker leaves on the south-facing slope than that on north-facing slope. A clear allometric relationship between leaf mass and leaf area was found only on the south-facing slope where increase in leaf mass was greater than that in leaf area. While on other slope aspects, an isometric relationships between them was observed. The allometric relationship between leaf mass and leaf volume was found on all four aspects, with the growing speed of leaf volume greater than that of leaf mass, and a rising SMA slope. We can conclude that variations in leaf traits of M. przewalskyi with slope aspect could reflect plant acclimation.

Plant functional traits have been widely used to study the responses of plant to environmental change. Cleistogenes squarrosa is an important C₄ species in Nei Mongol grassland. How its functional traits would respond to varied nitrogen and water conditions have rarely been studied. Our subject was to examine the responses of the whole-plant traits and leaf morphological and physiological traits to nitrogen addition and drought in this species.

We conducted a pot experiment with a gradient of N addition (0, 10.5, 35.0, and 56.0 g·m^-2·a^-1) and water treatments (natural precipitation vs. 70% of mean monthly precipitation) in 2013. The whole-plant traits (e.g., root depth and stem-leaf biomass ratio), leaf morphological (e.g., leaf area and specific leaf area) and physiological traits (e.g., photosynthetic rate, water use efficiency, and leaf N content) were investigated.

N addition had a significant effect on the whole-plant traits in C. squarrosa. The effects of N addition, water treatments, and an interaction between N addition and water treatments on leaf morphological and physiological traits were highly significant in most cases. The patterns of functional traits in response to N addition differed between plants under natural precipitation and with reduced mean monthly precipitation. Root depth, stem biomass, and stem-leaf biomass ratio were increased in treatments with low and intermediate N additions under reduced precipitation, but not changed under natural precipitation. Specific leaf area increased along the N addition gradient under drought, but did not change under natural precipitation. High N addition stimulated photosynthetic rate and transpiration rate and increased water use efficiency under natural precipitation, but had no effect on under reduced precipitation. Leaf N content on area basis increased slightly with the increases in N addition under natural precipitation, but decreased significantly under reduced precipitation. N addition influenced mainly the leaf morphological and physiological traits under natural precipitation and the whole-plant traits and leaf morphological traits under reduced precipitation. In conclusion, our results indicate that the functional traits in C. squarrosa respond to N addition and the patterns of responses differ under different water conditions, reflecting the adaptation to changes in N and water availability.

Research on how competition between invasive and native plants responds to simulated warming can provide insights into the trends and mechanisms of plant invasion, and profoundly helps to screen ecological substitutes under future climates. Our objective was to explore the effects of simulated warming on competition between an invasive species Alternanthera philoxeroides and a native plant Sambucus chinensis.

An experiment was conducted from May to December 2013 with the same five competition scenarios being arranged for under both warming and non-warming environments. Simulated warming was created by using infrared heater. Competition scenarios included non-competition (one plant per pot), intraspecific competition (two plants of the same species per pot) and interspecific competition (one plant for each species per pot). Biomass and root morphological variables were investigated of the plants under different warming and competition treatments.

(1) The average air temperature of the simulated warming environment was 0.47 °C higher than that of the non-warming environment, but the relative air humidity was decreased by 1.87% by the simulated warming. (2) Compared with the non-competition scenario, the values of all variables in A. philoxeroides under interspecific competition were significantly lower except the root/shoot ratio, which had no significant difference between the non-competition and interspecific competition scenarios. Root/shoot ratio, the biomass ratio of fine root to total root, relative root length and relative root surface area in S. chinensis did not show significant differences among the three competition scenarios; whereas other variables in S. chinensis decreased significantly following a pattern of non-competition > interspecific competition > intraspecific competition. (3) The effect of warming was not significant under any of the three competition scenarios in A. philoxeroides, but it varied with competition scenarios in S. chinensis. The warming treatment significantly decreased the total biomass and root biomass in S. chinensis under non-competition and interspecific competition scenarios, but it increased the values of the two variables in S. chinensis under the intraspecific competition scenario. (4) The relative crowding coefficient for S. chinensis decreased with warming, reflecting the sensitivity of the species to warming; whereas A. philoxeroides had some adaptability to warming. Therefore, S. chinensis can be a potential ecological substitute for A. philoxeroides under moderate shade in terrestrial habitat.

Our objective was to explore the effect of growth stage on leaf C:N:P stoichiometry in dominant species of a monsoon broad-leaved evergreen forest in Pu’er, Yunnan Province.

We collected leaves from six dominant species (i.e. Castanopsis hystrix, C. echidnocarpa, Lithocarpus fenestratus, L. truncatus, Schima wallichii and Anneslea fragrans) at different growth stages from seedlings to mature trees. The leaf N, P and C contents were measured. The effects of species, growth stage and their interaction on leaf C, N and P contents and stoichiometry were analyzed by Repeated-Measure ANOVA in SPSS 19.0.

The ranges of leaf N, P and C contents and mass ratios of C:N, N:P and C:P in the six species across different growth stages were 7.90-17.72 mg·g^-1, 0.34-1.39 mg·g^-1, 458.48-516.87 mg·g^-1, 28.04- 65.70, 11.41-63.50 and 355.23-1878.17, respectively. The coefficient of variation (CV) for N:P mass ratio ranged between 19.19%-91.65%, with an average of 36.46%; CV for C:P varied between 15.99%-91.60%, with an average of 34.80%; whilst CV for C varied between 1.61%-5.89%, with an average of 3.12%. Factorial analysis of the variation for each variable, with growth stage and species as independent factors, showed that leaf N and C contents and the mass ratios of leaf C:N, N:P and C:P were mainly determined by growth stage, while leaf P content was mainly determined by an interaction between growth stage and species.

Phosphorus mining wasteland is a very special kind of degraded ecosystems, where vegetation and landscape are severely damaged. Our objective was to select plants suitable for phytoremediation of phosphorus-rich soils in mining wasteland.

We conducted pot experiments to investigate phosphorus uptake and accumulation capacity in Helianthus annuus, Sorghum sudanense and Cucurbita moschata grown in soils with different levels of phosphorus supply. The phosphorus concentrations applied are 0, 100, 300, 500 and 700 mg·kg^-1. Phosphorus concentration, phosphorus accumulation, bioaccumulation and translation coefficient of the plants were measured for three growth periods (4 weeks, 7 weeks, 10 weeks), respectively.

Over the same growth period, phosphorus concentration in shoots of the three plant species increased with increasing phosphorus supplies, with the maximum of 9.67 g·kg^-1 in H. annuus, 4.86 g·kg^-1 in S. sudanense, and 6.32 g·kg^-1 in C. moschata. Under the same phosphorus treatments, phosphorus concentration significantly increased with growth time in shoots of H. annuus, decreased in shoots of S. sudanense, and did not significantly change in shoots of C. moschata. The aboveground total phosphorus accumulation in the three plant species all reached highest values when grown for 10 weeks in soils supplied with 700 mg·kg^-1 phosphorus, amounting to 217.83 mg·plant^-1 in H. annuus, 93.92 mg·plant^-1 in S. sudanense, 135.82 mg·plant^-1 in C. moschata, respectively. The bioaccumulation and translation coefficients in both H. annuus and S. sudanense exceeded 1.00 under each treatment. The peak values of the two coefficients were 11.39 and 4.09 for H. annuus. In conclusion, the phosphorus uptake and accumulation capacity of the tested plant species were in the order of H. annuus > C. moschata > S. sudanense, and H. annuus can be a possible candidate for phytoremediation of phosphorus mining wastelands.

Achnatherum sibiricum plants were infected by fungal endophytes Neotyphodium and Epichloëand high infection rates have been found in our experimental field. Our objective was to determine the effects of Neotyphodium and Epichloë on growth and physiological characteristics in A. sibiricum.

In a field experiment, we measured plant growth and physiological characteristics of A. sibiricum with a LI-6400 portable photosynthesis system and determined the contents of carbon (C%) and nitrogen (N%) and other physiological variables in 2011 and 2012. Achnatherum sibiricum plants were successfully infected with Neotyphodium and Epichloë.

Neotyphodium infection had a significant positive effect on both leaf length and plant height in A. sibiricum, whereas Epichloë infection had a significant negative effect on the two variables. Maximum net photosynthetic rate was significantly higher in the endophyte-free plants than in plants infected by Neotyphodium and Epichloë; whilst Neotyphodium infected plants had significantly higher maximum net photosynthetic rate than Epichloë infected plants. Moreover, Neotyphodium infection significantly increased stomatal limitation and water use efficiency (WUE) of the host grass. Epichloë infection had a negative effect on photosynthetic variables except intercellular CO₂ concentration in the first year. Neotyphodium infection resulted in greater accumulation of soluble sugars in host plants than Epichloë infection and endophyte-free treatment. The N% in Epichloë infected plant was significantly higher than in Neotyphodium infected plants in both years and in endophyte-free plants in the second year.

Soil salinity is a major limiting factor for plant establishment, development and productivity in arid environment. This study was conducted to determine the responses and adaptation of xylem hydraulic conductivity to salt stress in Populus euphratica in order to understand the mechanisms of stress resistance and restoration strategy of this species.

The responses and adaptation of hydraulic conductivity to different levels of salt stress (NaCl concentrations of 0, 0.05, 0.15 and 0.30 mol·L^-1) were investigated in P. euphratica seedlings. The testing plants were subjected to salt stresses for three months, and the stomatal conductance of leaves, hydraulic conductivity and vulnerability to cavitation of roots and stem xylem, anatomical structure of xylem vessels and root morphology and distribution were measured. The resulting data were analyzed to determine the relationships of salt stress with root uptake, hydraulic conductivity of xylem and foliar transpiration by using ANOVA, LSD and Pearson correlations.

The roots of P. euphratica seedlings were more responsive to salt stress than stem and leaves. Root length and root tips were significantly inhibited by the salt stresses imposed. Under the salt stress, root hydraulic conductivity was significantly reduced and root xylem was more vulnerable to cavitation. The responses of stem xylem conductivity to salt stresses varied with the level of salt stress. Under a mild (0.05 mol·L^-1 NaCl) and moderate (0.15 mol·L^-1 NaCl) salt stress, Populus euphratica seedlings adjusted hydraulic conductivity in stem xylem by increasing the wall thickness of conduit and between conduits as well the wall mechanical strength to maintain norm growth. Under a severe salt stress (0.30 mol·L^-1 NaCl), hydraulic conductivity and safety and efficacy of water transportation of stem xylem in P. euphratica seedlings significantly decreased accompanied by reduced stomatal conductance of leaves, which eventually inhibited the plant growth.

The invasion of Spartina alterniflora has imposed significant influences on structure and functioning of coastal saltmarshes. The Spartina marsh has been found to contain relatively higher sulfur content than the adjacent native Phragmites marsh. This research is aimed to investigate if sulfur helps with S. alterniflora in competition over Phragmites australis.

Seedlings of S. alterniflora and P. australis were grown in an imitated mesocosm on the campus of Nanjing University. Three common salts of the sea water, Na₂SO₄, Na₂S and NaCl were respectively added to the cultural medium. Light response curves of the plants before and during the four days of treatments were obtained by measuring gas exchange with varying light levels. Maximum quantum yield of photosynthesis II (PSII) and light induction curves were also measured by chlorophyll fluorescence analysis.

Among the three salts, Na₂S caused the greatest difference in the response of photosynthesis between S. alterniflora and P. australis, and Na₂SO₄ had the least effect. The Na₂S treatment significantly increased net photosynthetic rate (P_n) and light saturation point (I_sat) in S. alterniflora, but decreased P_n in P. australis. The NaCl treatment also increased P_n in S. alterniflora to a less degree and decreased P_n in P. australis. The Na₂SO₄ treatment had little effect on P_n in both S. alterniflora and P. australis. The non-photochemical quenching (NPQ) in P. australis were promoted by all three salts, whereas it was only affected by Na₂S and NaCl in S. alterniflora. Our results suggest that S. alterniflora has significantly greater tolerance to sulfate and sulfide than P. australis. Therefore, sulfuric compounds and especially sulfide in saltmarsh environments might benefit the competition of S. alterniflora over P. australis, which could contribute to the formation of the mono-specific vegetation of the invasive S. alterniflora.

In order to further understand the inner mechanism of plant respiration and the relationship between respiration and photosynthesis of plant under light, our objective was to reveal the relationship between cyanide-resistant respiration and photosynthesis in bean (Phaseolus vulgaris) leaves under light.

By exposing the dark-grown leaves to light for 10 h, changes in total respiration (V_t), the cyanide-resistant respiration (V_alt), photosynthetic O₂ evolution, and photosynthetic CO₂ fixation, and the effects of inhibitor of the cyanide-resistant respiration on photosynthesis were measured and analyzed. We also measured and analyzed changes in the ratio of cyanide-resistant respiration, total respiration, and photosynthetic CO₂ fixation when leaves in the dark were exposed to a brief period (10 min) of light. Important findings After exposing the dark-grown leaves to light for 10 h, V_t, V_alt, and the value of V_alt/V_t all increased. During the process, time-course analysis after the onset of illumination demonstrated that the induction of the cyanide-resistant respiration in light was prior to the formations of the photosynthetic O₂ evolution and CO₂ fixation. This observation indicates that the induction of the cyanide-resistant respiration by light is independent of photosynthesis. The dark-grown leaves pretreated with 1 mmol·L^-1 salicylhydroxamic acid (SHAM; the inhibitor of the cyanide-resistant respiration) were exposed to illumination for 10 h, and SHAM did not result in apparent modification of the photosynthetic O₂ evolution and CO₂ fixation in the leaves when exposed to light. This observation also showed that there was no direct linkage between photosynthesis and the cyanide-resistant respiration when the dark-grown leaves were exposed to light. In addition, under the condition of darkness, 10 min of light illumination obviously increased the value of V_alt/V_t but did not significantly affect the level of photosynthetic CO₂ fixation.

indicate that the induction of the cyanide-resistant respiration by light may be independent of photosynthesis. Light should have a direct influence on induction of the cyanide-resistant respiration.