Aims As a key element in plant tissue, nitrogen plays an important role in the growth and development of plants. Our objective is to determine (1) how both leaf nitrogen and its allocation between photosynthetic and non-photosynthetic systems have responded to an altitudinal gradient and (2) what role their response has played in the adaptation of Rumex dentatus to its changed environment along the altitudinal gradient.
Methods We measured foliar parameters of photosynthesis, diffusional conductance to CO₂, stable carbon isotope ratio (δ¹³C), nitrogen content and specific leaf area (SLA) of the forb R. dentatus in four sites with different altitudes (2350, 2700, 3150 and 3530 m) in the Wolong Reserve. One-way ANOVA was used to find the differences for all parameters among R. dentatus plants from different altitudes, and standardized major axis (SMA) was used to determine the relationships among some main parameters.
Important findings Leaf nitrogen content per area (N_area) increased as maximum photosynthetic capacity (A_max) increased with altitude in R. dentatus. Increased diffusional conductance also had a positive effect on increased photosynthetic capacity with altitude. These may be the result of adaptation of plants to a shortened leaf lifespan caused by low temperature at high altitude. Along with the altitudinal gradient, nitrogen and diffusional conductance of R. dentatus have an indirect effect on foliar δ¹³C through acting on the ratio of chloroplast partial pressure of CO₂ to ambient CO₂ partial pressure (P_c/P_a). Compared with diffusional conductance, nitrogen (or carboxylation capacity based on nitrogen) played a more important role in the process, in order to increase foliar δ¹³C with altitude. Rumex dentatus allocated more nitrogen to build defensive structural tissue with increased altitude. This is why SLA and photosynthetic nitrogen use efficiency (PNUE) decreased with altitude. In the photosynthetic system, more nitrogen was allocated to light-harvesting components in order that enhanced light resource was used preferably by R. dentatus, and then photosynthetic capacity was increased with altitude. Nitrogen and its allocation among systems (especially between photosynthetic and non-photosynthetic systems) are the keys to the adaptation and the response of R. dentatus to the gradient in altitude.

Aims The objective was to clarify the relationship between soil texture and characteristics of winter wheat cultivars in regard to nitrogen metabolism and utilization with different protein content. We planted the cultivars on three types of soil with different texture and looked for the optimum winter wheat cultivar under specific soil texture conditions.
Methods Field experiments using three winter wheat cultivars (‘ZM366’, ‘AK58’ and ‘ZM22’) with different protein content were carried out on soils of three textures, i.e. sandy, loam and clay soils, at the city of Huaxian, Henan Province, China during the 2011-2012 winter wheat growing season.
Important findings Soil texture greatly affected patterns of N metabolism and utilization efficiency. Glutamine synthetase (GS) activity and free amino acid content in the three varieties graphed as inverted “V”-shapes with different peak time depending on the soil texture. The peak of plants grown on sandy soil occurred 10 days earlier than plants on loam and clay soils. Moreover, on May 22 the GS activity and free amino acid content of plants grown on sandy soil was not detected. Cultivars grown on loam soil had the highest pre- and post-anthesis N accumulation (NA) of total plant, leaves, stems and grains, as well as nitrogen remobilization to grain (NR), grain yield and N use efficiency (NUE). Whereas, the highest N remobilization efficiency (NRE), contribution of N remobilized to grain nitrogen (NRC), N harvest index (NHI) and N physiological efficiency (NPE) appeared in the plants grown on sandy soil. Also, the NRC was 82.46%-95.84% and NR was about seven-fold higher than post-anthesis NA for plants on sandy soil. However, contribution of post-anthesis NA was higher for plants grown on loam soil and clay soil which were 36.6% and 29.2%, respectively. Among the three winter wheat cultivars planted on the same soil texture, ‘ZM366’ was the highest with GS activity, free amino acid content, grain yield, protein content, NUE and NPE on sandy soil. However, for loam soil, ‘AK58’ is the best, and ‘ZM22’ was the best on clay soil. Consequently, it is important to breed and cultivate winter wheat cultivars according to soil texture. We concluded that ‘ZM366’ is the most suitable cultivar for sandy soil, ‘AK58’ is the best for loam soil, and ‘ZM22’ is the best for clay soil, so as to obtain higher yield and high quality in winter wheat and improve NUE.

Aims Tree architecture refers to the overall shape and size of the woody plants, as well as the spatial arrangement of its components in response to changing light. Variation in tree architecture of overlapping species among successional stages can be used to indicate relationships between tree architecture and light availability, because confounding effects resulted from plant phylogenetics are excluded. Our objective was to examine how tree architecture varies among overlapping species in different successional stages.
Methods The study sites are located in Tiantong National Forest Park (29°52′ N, 121°39′ E), Nanshan Mountain (29°52′ N, 121°41′ E) and Beilun Forest Park (29°50′ N, 121°52′ E) in Zhejiang Province, China. We measured tree height, crown depth and area, stem basal diameter, leaf coverage and convergence, stretch direction of branch and crown exposure index for five overlapping species in four vertical layers among successional communities in three sites. Linear regression analysis was conducted to examine the quantitative relationship between tree architecture and crown exposure index.
Important findings With the forest succession, crown depth and area, leaf coverage and stem basal diameter increased gradually, but did not show significant differences between adjacent successional stages in some cases. The proportion of dispersed leaves increased, but the proportion of clumped leaves decreased. Among four vertical layers, crown exposure index decreased through forest succession. There were significant linear relationships between crown exposure index and each of eight tree architectural traits (p < 0.001). We conclude that variability in tree architecture among overlapping species through forest succession indicates a shifting pattern of plant functional groups from pioneer species to shade-tolerant species in evergreen broad-leaved forests. Light acclimatization is one of main factors driving variation in tree architecture.

Aims The relationship between biodiversity and ecosystem functioning has been a central issue in ecology. However, this relationship is poorly understood for the Stipa breviflora grassland, which is a major community type of desert steppe in Nei Mongol. With unpredictably fluctuating climate conditions, these desert steppe ecosystems are fragile and provide a unique opportunity to test our current understanding of the relationship between biodiversity and ecosystem functioning. This study has two objectives: (1) to examine if species diversity and functional group diversity affect ecosystem primary productivity in the desert steppe of Nei Mongol and (2) to explore how resource supply levels affect the relationship between diversity and productivity.
Methods Based on life forms, species were classified into five functional groups: shrub and semishrub, perennial bunchgrass, perennial rhizome grass, perennial forb, and annual and biennial. Species richness and functional group richness were used to represent species diversity and functional group diversity, respectively. Based on the dryness coefficient, 202 sites across the S. breviflora grassland in Nei Mongol were sampled, and divided into two resource supply levels: arid and semiarid zones. In order to tease out the effect of precipitation, partial regression analysis and partial correlation analysis were used for exploring the relationship of ecosystem primary productivity to species richness and functional group richness, respectively. According to the determination coefficient of regression analysis, the effect of resource supply levels on the diversity-productivity relationship was evaluated.
Important findings Species richness and ecosystem primary productivity were both positively and linearly correlated with precipitation, but no significant correlation was found between functional group richness and precipitation. Ecosystem primary productivity increased significantly with species richness, but not with functional group richness. Resource supply levels could affect the diversity-productivity relationship in that plant species diversity generally had a weaker effect on ecosystem primary productivity at the lower resource supply level and a stronger effect at the higher resource supply level.

Aims We aimed to detect the impact of soil factors on predicting the potential distribution of Phyllostachys edulis (bamboo) by comparing the prediction accuracy and the spatio-temporal pattern of potential habitat of P. edulis.
Methods Using IPCC (Intergovernmental Panel on Climate Change) climate change scenario datasets and FAO (Food and Agriculture Organization) Soil Map of the World, the potential distribution of P. edulis in China was predicted from 1981 to 2099 based on species distribution models, one-class Support Vector Machine (SVM). We used two groups of predictors: one included climate factors only, and the other had both climate factors and soil factors.
Important findings The SVM based on both predictor groups predicted the potential distribution of P. edulis, and the potential habitat expended and migrated northward with time. Factor importance analysis showed that the climate factors correlated with warm conditions played a driving role in the simulation of the potential habitat of P. edulis, while soil factors associated with soil texture and pH mainly impacted the simulation as limiting factors. However, the prediction using both climate and soil predictors performed with higher efficiency, and the intensity of the potential habitat expending and migrating was less than that of the group of climate factors only. The finding suggested that the soil factors significantly constrain the potential habitat of P. edulis, and soil constraint should be considered in predicting species distribution in future.

Aims The stamens of Glycyrrhiza species are diadelphous, with nine staminal filaments united at the base as a staminal sheath and separated in the upper portion of the staminal sheath. The arrayal shape of the nine stamens changes from two rows at an early stage to an inverted “V”-shaped arrangement at a later stage. Our objectives were to (1) describe development of the stamens in G. glabra (from the bud stage to full bloom) to determine differences in shape development, timing and position of stamens and (2) determine the functional role of long- and short-level stamens in the pollination processes and its adaptive significance.
Methods The development of stamens (measurement of the filament, anther, and style lengths at five developmental stages) and variability of timing and position of stamens were observed under a dissecting microscope. Scanning electron microscopy recorded pollen morphology. The vitality, quantity and chemical composition of pollen were counted and detected. In addition, the number of seeds following each pollination treatment and the pollinator behavior of insects on different stamen removal treatments were compared to examine differentiation of long- and short-level stamens.
Important findings There were differences between the long- and short-level stamens in filament length, anther size and shape early in development, but the differences disappeared when filaments elongated and mature pollen was released. The numbers of pollen grains and pollen vitality between the long- and short-level stamens were different later in development. However, no significant differences were observed in chemical composition of pollen and seed sets among different treatments. Emasculation of the long- and short-level stamens induced reductions in the visiting frequency, but the seed sets of emasculation were higher than without emasculation, which indicates that emasculation reduces the interference between stamens and stigma and improves the pollination rate. The arrayal shape of stamens changed from two rows early in time to an inverted “V”-shaped arrangement at a later stage and resulted in different quantity and vitality of pollen. This indicates that the flower of G. glabra uses fewer male resources to obtain the highest pollination efficiency and to improve male functionality.

Aims The photosynthetic-CO₂ response curve is an important tool for understanding the response of plants to CO₂. Common models of photosynthetic-CO₂ response curve can not calculate the max net photosynthetic rate accurately. In our study, we used a new model called the modified exponential model to simulate the relationship between net photosynthetic rate and CO₂ concentration of barley. We then compared the differences and accuracies with the modified rectangular hyperbola model, rectangular hyperbola model, nonrectangular hyperbola model and exponential model. Our objectives were to test the merit and precision of these models and provide reference for selecting the best models for the photosynthetic-CO₂ response curves of plants.
Methods The CO₂-response curves of Tibetan hulless barley were recorded with an infrared gas analyzer system (LI-6400). The measured data were used to simulate and test the precision of the models. Mean square error (MSE) and mean absolute error (MAE) were used to evaluate the precision of the models. Some predicted physiological parameters of the four models were compared with the measured values.
Important findings The photosynthetic-CO₂ response curves of barley were best described by the modified exponential model. The CO₂ saturation point and maximum net photosynthetic rate of barley obtained by the modified exponential model were 25.9 μmol CO₂∙m^-2∙s^-1 and 484 μmol∙mol^-1, respectively.

Aims Our objective was to investigate the physiological response of tea Chrysanthemum cultivars to salt stress in order to select salt-tolerant cultivars for use in saline soil.
Methods Stress physiological, biochemical and photosynthetic physiological parameters were measured for four tea Chrysanthemum cultivars, which were irrigated with nutrient solution adding different concentrations of NaCl (40, 80, 120, 160 and 200 mmol·L^-1) as treatment and without addition of NaCl as control.
Important findings Following the increase with the degree of NaCl stress, data of relative membrane permeability (Cond), malonic aldehyde (MDA), proline (Pro) and soluble sugar (SS) content were increased in leaves of different genotypes of tea Chrysanthemum, while superoxide dismutase (SOD) activity was initially increased and then decreased. Leaf chlorophyll (Chl) content of the ‘Fanbailu’ and ‘Yurenmian’ cultivars were initially increased then decreased, but continued to decline in the ‘Ruhe’ and ‘Huangchulong’ cultivars. Net photosynthetic rate (P_n), transpiration rate (T_r) and stomatal conductance (G_s) were significantly reduced, but the stomatal limitation value was first increased and then decreased following the increase of salt concentrations. Values of subordinate function were used to evaluate the salt tolerance among different tea Chrysanthemum cultivars. The salinity tolerance for those cultivars was ‘Ruhe’ > ‘Yurenmian’ > ‘Fanbailu’ > ‘Huangchulong’. Under NaCl stress, parameters for Chl, P_n, T_r and G_s were decreased less in ‘Yurenmian’ and ‘Ruhe’ than in the other two cultivars while parameters for MDA content and stomatal limitation value were increased less in ‘Yurenmian’ and ‘Ruhe’ than in the other two cultivars.

Aims Water is the most important limiting factor for plant growth in desert ecosystems. Our objective was to investigate the water sources of three co-existing desert plants and illustrate seasonal variation characteristics in southeastern Junggar Desert in China.
Methods We investigated three kinds of desert plants (Tamarix ramosissima, Nitraria sibirica and Reaumuria soongorica) in the same habitat and measured hydrogen and oxygen stable isotope ratio (δD and δ¹⁸O) values of their xylem water and potential water sources (precipitation, soil moisture and ground water). The IsoSource model was then used to calculate probable contributions of potential water sources to total plant water uptake.
Important findings The water sources of the three desert plants had obvious seasonal characteristics. Reaumuria soongorica and N. tangutorum obtained a high proportion of water from shallow soil water (0-100 cm) in spring. However, during the summer and autumn, R. soongorica tended to use deeper soil water, and N. tangutorum tended to use ground water. Tamarix ramosissima obtained 90% of its water from deep soil water and ground water, and there were no seasonal variations. The three kinds of plants had different water sources closely related to their water use strategies. This shows desert shrubs, through self-regulation, could tend to their optimal phenotypes and maximize water uptake.

Aims Our objectives were to: 1) examine fine root biomass, morphological characteristics and content of C and N of Alnus formosana in an A. formosana-Hemarthria compressa composite model in Danling, Sichuan Province, China, 2) examine the effects of fertilization on each order of fine roots, and 3) analyze the relationship between soil nutrients and fine root biomass, architecture and content of C and N.
Methods In September 2010, we established two subdistricts, eradicated weeds and planted H. compressa. We fertilized one subdistrict with N-P-K fertilizer in April, June, August and October and did not fertilize the other subdistrict. We excavated soil blocks of 20 cm × 20 cm × 10 cm (height) to sample intact fine root branches of at least the first branch orders. We dissected the intact root branches by orders and measured the diameter, specific root length, biomass, and C and N content of each order.
Important findings Fertilization reduced fine-root average diameter in soil surface and increased that in soil subsurface. In fine-root orders 1-5, specific root length increased as root order decreased. Fertilization significantly increased specific root length in fine-root orders 1-3 in soil surface and subsurface (p < 0.01). Fertilization reduced fine-root biomass in all soil layers and significantly reduced the ratio of fine-root biomass to total root biomass in orders 1-3 (p < 0.05), while fine root biomass increased in orders 4 and 5. The effect of fertilization on fine-root C content was not significant in all orders (p > 0.05). Soil surface total N content of fine roots of 1-5 orders was higher than that in subsurface. Fertilization significantly (p < 0.01) increased fine-root N content of order 1 fine roots in soil surface and orders 1 and 2 in the subsurface, but had no significant effects on orders 3-5 (p > 0.05).

Aims This paper explores soil types to suit the development of root system and improve the yield of peanut (Arachis hypogaea).
Methods We used the method of box-planted cultivation to study the effects of different soil textures, i.e., sandy, loam and clay soils, on the development and distribution of root system and yield of peanut.
Important findings Root dry matter weight of peanut in sandy and loam soils was higher significantly than in clay soil; however, in the later growth stage, the decrease of root dry matter weight of peanut in clay soil is relative slow compared with peanut in loam and sandy soil. In clay soil, the root system of peanut was mainly distributed in the shallow soil layer, but the decrease of root activity in the upper layers was much slower in the late growth period. Sandy soil was helpful for the root system of peanut to grow to the deeper soil layer, but the decrease of root activity in the surface layers was faster in the later growth period. The effects of loam soil on the spatial and temporal distribution of the development and activity of peanut roots were between sandy and clay soil. Sandy soil favored enlargement of the peanut pod, and the dry matter accumulation of peanut pod in sandy soil was earlier and faster, but the dry matter accumulation in the later growth period was less in sandy soil. In loam soil, the dry matter accumulation of peanut pod was mainly concentrated in middle and later periods, while clay soil was not suitable for the dry matter accumulation of peanut pod in the entire growth period. The pod yield, kernel yield and available pod number were largest in loam soil, second in sandy soil and lowest in clay soil. Results suggested that loam soil, with mid-levels of aeration and water and fertilizer conservation among the three soil textures, was most suitable for the growth and yield of peanut.

Leaf venation is the distribution and arrangement pattern of a leaf vein system. Earlier studies of leaf venation mainly focused on its taxonomic significance. In recent years, studies of leaf venation functional traits and their significance in plant water relations have been popular topics of plant ecological research. In this paper, we introduced an index system of leaf venation functional traits (including vein density, vein diameter, distance between veins and loopiness of veins). We also reviewed three aspects of leaf venation functional trait studies: relations between leaf venation functional traits and leaf vein system functions (i.e., water-nutrient-photosynthetic product transport, mechanical support and herbivore defense), positive and negative correlations between leaf venation functional traits and other leaf functional traits (e.g., leaf mass per area, leaf lifespan, leaf photosynthetic rate, leaf size and stomatal density), as well as relations between leaf venation functional traits and environmental factors (e.g., precipitation, temperature and light). In addition, leaf venation functional traits can be employed in studies of palaeoclimate reconstructions, watershed and urban transportation planning, as well as global change studies. Since leaf venation functional traits are products of both environmental factors and genetic factors, future leaf venation functional trait studies at molecular-leaf-plant-ecosystem scales are needed, and analyses of plant water relations between leaf venation functional traits and traits of other plant tissues or organs (i.e., stomata, wood and root) also need to be improved. All of these studies show promise in providing new insights into predicting responses of plants and ecosystems to global changes.