Effect of Shading on Gas Exchange of Cotton Leaves Under Conditions of Different Soil Water Contents1

Effect of different shading levels (no-shading, 80% shading, and 40% shading) on photosynthetic and stomatal responses in cotton leaves were investigated under onditions of different soil water contents in summer midday. All cotton leaves exhibited similar basic responses to shading, including decreased netphotosynthetic rates, a tendency to decrease in transpiration rates, and increased stomatal conductance and intercellular CO2 concentration. The leaf conductance of 80% shaded and 40% shaded plants increased by 28% and 16.7% compared with no-shaded plants at high water, respectively, but the net photosynthetic rates of 80% shaded and 40% shaded plants declined by 50% and 14.73%, respectively. Results showed that combined effect of soil moisture and shading on photosynthetic and stomatal responses in cotton leaves was very remarkable.     

若干阔叶树树冠各层叶气孔密度及光照条件对气孔密度的影响

４０种阔叶树树冠的外、中、内层同龄叶中，均以外层叶的气孔密度最高，其次为中层叶，内层叶气孔密度最低。新银合欢和马尖相思幼苗在高光照强度下所形成的叶气孔密度最高，中等光照者次之，低光照者最低。在蓝光照射下形成的叶气孔密度最高，其次为红光照射者，自然漫射光下最低。这说明光照强度和光波长对气孔密度有深刻影响。     

Analysis of the variations in dry matter yield and resource use efficiency of maize under different rates of nitrogen,phosphorous and water supply

Abstract

Increasing resources use efficiency in intensive cultivation systems of maize (Zea mays L.) can play an important role in increasing the production and sustainability of agricultural systems. The objectives of the present study were to evaluate DM yield and the efficiency of inputs uses under different levels of water, nitrogen (N) and phosphorus (P) in maize. Therefore, three levels of irrigation including 80 (ETc₈₀), 100 (ETc₁₀₀) and 120% (ETc₁₂₀) of crop evapotranspiration were considered as the main plots, and the factorial combination of three levels of zero (N₀), 200 (N₂₀₀) and 400 (N₄₀₀) kg N ha^?1 with three levels of zero (P₀), 100(P₁₀₀) and 200 (P₂₀₀) kg P ha^?1 was considered as the sub plots. The results showed that increasing the consumption of water and P was led to the reduction of N and P utilization efficiency, while RUE increased. WUE was also increased in response to application of N and P, but decreased when ET_C increased. DM yield under ETc₈₀ treatment reduced by 11 and 12%, respectively, compared to ETc₁₀₀ and ETc₁₂₀ which was due to reduction of cumulative absorbed radiation (R_abs(cum)) and RUE. Under these conditions, changes of stomatal conductance (gs) had little effect on DM yield. It was also found that N limitation caused 11 and 20% reduction in DM yield compared to N₂₀₀ and N₄₀₀, respectively. This yield reduction was mainly the result of decrease in RUE. By decreasing R_abs(cum), P deficiency also reduced DM yield by 5 and 9%, respectively, relative to P₁₀₀ and P₂₀₀ treatments.     

Physiological Response of Multiple Contrasting Rice (Oryza sativa L.) Cultivars to Suboptimal Temperatures

The physiological response of multiple rice cultivars, eighteen initially and eight cultivars later on, to suboptimal temperatures (ST) conditions was investigated in laboratory and outdoor experimental conditions. Treatment with ST decreased growth in different extents according to the cultivar and affected the PSII performance, determined by chlorophyll fluorescence fast‐transient test, and stomatal conductance, regardless the experimental condition. Two groups of cultivars could be distinguished on the base of their growth and physiological parameters. The group of cultivars presenting higher growths displayed optimal JIP values, and higher instantaneous water use efficiency (WUE_i), due to a lower Gs under ST, unlike cultivars showing lower growth values, which presented worse JIP values and could not adjust their Gs and hence their WUE_i. In this work, we detected at least two cultivars with superior tolerance to ST than the cold tolerant referent Koshihikari. These cultivars could be used as parents or tolerance donors in breeding for new crop varieties. On other hand, positive and significant correlations between data obtained from laboratory and outdoor experiments suggest that laboratory measurements of most of the above mentioned parameters would be useful to predict the response of rice cultivars to ST outdoor.     

烟草气孔导度对光强的响应

气孔导度模型是评价植物叶片气孔调节的重要工具。为比较几种常用的气孔导度模型对烟草的适用性, 本研究采用Li-6400光合测定系统, 测定了大田条件下, 烟草叶片在控CO₂(390 μmol·mol^-1)和控温(20 ℃、25 ℃、30 ℃和35 ℃)情况下的气孔导度光响应曲线。以Ball-Berry模型(BB模型)、Leuning修正模型(BBL模型)、叶子飘和于强推导的机理模型(BBY模型), 对各温度下烟草的气孔导度进行拟合和比较, 将气孔导度模型与净光合速率的光响应修正模型进行耦合(耦合模型), 研究了烟草气孔导度的光响应特征, 并与Jarvis模型进行比较。拟合结果表明, 较之BB模型和BBL模型, BBY模型能更好地描述各温度下烟草气孔导度与净光合速率之间的关系。耦合模型和Jarvis模型都能较好地拟合烟草气孔导度对光强的响应曲线, 但耦合模型的拟合效果更好, 且可以直接估算最大气孔导度和对应的饱和光强, 同时可以研究最大气孔导度与最大净光合速率是否同步的问题。结果表明, 各温度下, 烟草最大气孔导度与最大净光合速率并不同步。20 ℃下气孔导度早于净光合速率达到最大值, 而其余温度下气孔导度晚于净光合速率达最大值。     

香港润楠属植物叶表皮形态及分类学意义

利用光学显微镜和扫描电镜观察了11种香港润楠属（Machilus Nees)植物叶表皮。在香港润楠属植物中，大多数种类的叶表皮均具有单细胞表皮毛，其气孔复合体均为平列型，保卫细胞两侧或一侧有1个副卫细胞；叶上表皮细胞的形态有较大的差异，主要有3种类型：垂周面平直、浅波状和深波状。叶表皮角质突起饰物的形态也有差异，根据表皮角质突起物的形态可划分出有2种类型。这些表皮特征有助于识别一些在外部形态较相近种类。     

Growth and Eco-Physiological Performance of Cotton Under Water Stress Conditions

A cotton cultivar Xinluzao 8 was grown under four levels of water stress treatments （normal irrigation, slight, mild and severe water stress） from the initial reproductive growth stage in Shihezi, Xinjiang, China, in 2002, to evaluate the growth and eco-physiological performances. Under water stress conditions, the transpiration ability decreased while the leaf temperature increased. Although the relative leaf water content decreased as water stress increased, the differences among the treatments were small, indicating that cotton has high ability in maintaining water in leaf. The stomatal density increased as water stress increased, while the maximum stomatal aperture reduced only in the severest stressed plants. The time of the maximum stomatal aperture was delayed in the mild and severe stressed plants. When severe stress occurred, the stomata were kept open until the transpiration decreased to nearly zero, suggesting that the stomata might not be the main factor in adjusting transpiration in cotton. Cotton plant has high adaptation ability to water stress conditions because of decrease in both stomatal conductance and hydraulic conductance from soil-to-leaf pathway. The actual quantum yield of photosystem Ⅱ （PS Ⅱ） decreased under water stress conditions, while the maximum quantum yield of PS Ⅱ did not vary among treatments, suggesting that PS II would not be damaged by water stress. The total dry weight reduced as water stress increased.     

Penman-Monteith模型模拟Venlo型温室黄瓜植株蒸腾

准确模拟温室作物蒸腾对于制定科学合理的灌溉制度及温室环境调控具有重要意义,该研究基于2017年秋冬季和2018年春夏季Venlo型温室黄瓜生育期内微气象数据、黄瓜生长发育指标和植株蒸腾,对Penman-Monteith(PM)模型中关键参数—冠层阻力和空气动力学阻力进行研究。通过分析黄瓜叶片孔阻力与温室内气象因子的响应关系,构建了由黄瓜有效叶面积指数及叶片孔阻力模拟冠层阻力的子模型;采用基于风速的Perrier对数法和基于温室对流类型的热传输系数法计算温室内低风速环境下的空气动力学阻力,并评价不同方法的适用性。结果表明:叶片孔阻力与太阳辐射呈指数关系(R~2=0.89),可通过观测温室内太阳辐射计算黄瓜叶片孔阻力;应用热传输系数法确定空气动力学阻力时,温室内对流类型绝大多数时间为混合对流;2种方法计算的温室内空气动力学阻力变化幅度均较小,Perrier对数法计算的春夏季和秋冬季空气动力学阻力平均值分别为388和383 s/m,热传输系数法计算的空气动力学阻力平均值分别为141和158 s/m;基于2种空气动力学阻力计算方法,PM模型模拟的植株蒸腾与实测值均具有较好的一致性,但采用Perrier对数法计算空气动力学阻力时,PM模型低估了植株蒸腾,春夏季和秋冬季拟合线斜率分别为0.87和0.91;而采用热传输系数法计算空气动力学阻力时,PM模型可更准确的模拟该地区温室黄瓜植株蒸腾,春夏季和秋冬季拟合线斜率分别为1.00和0.94,R~2分别为0.91和0.95,均方根误差分别为46.15和12.45 W/m~2。该研究结果为实现PM模型在Venlo型温室环境的准确应用提供了参考。     

Potassium deficiency impedes elevated carbon dioxide‐induced biomass enhancement in well watered or drought‐stressed bread wheat

Potassium (K) deficiency reduces photosynthesis and biomass production of crop plants and also renders them vulnerable to drought stress, whereas elevated carbon dioxide (CO₂) has a positive effect on photosynthesis and yield and ameliorates the adverse effects of drought stress. This study aimed to characterize the physiological responses of wheat (Triticum aestivum L.) stressed with K deficiency under elevated CO₂ and drought conditions. Increased biomass production caused by elevated CO₂ as a consequence of increased photosynthesis and water use efficiency was absent in young K‐deficient wheat plants. Shoot K concentration was negatively affected by elevated CO₂ particularly under K‐deficient conditions, whereas K content per plant was greatest in plants supplied with adequate K and adequate water. Specific leaf weight was increased as a consequence of carbohydrate accumulation in the source leaves of K‐deficient plants particularly under elevated CO₂ and drought stress. Potassium deficiency clearly impeded the impact of elevated CO₂ in both well watered as well as drought‐stressed plants. Adequate K fertilization is a prerequisite for efficient harvesting of atmospheric CO₂ through increased photosynthesis, decreased transpiration, and increased biomass production under changing atmospheric CO₂ and soil moisture conditions.     

土壤含水量对枣幼树生长及水分生理指标的影响

本试验研究了不同土壤相对含水量(30％-100％)对金丝小枣盆栽幼树生长、叶片组织含水量、蒸腾强度、气孔扩散阻力的影响。初步确定适宜金丝小枣生长的土壤相对含水量为70％。结果还表明,土壤水分严重亏缺时,叶片组织含水量减少,叶片气孔扩散阻力明显增大,蒸腾强度显著降低。气孔扩散阻力与蒸腾强度呈负相关。但当土壤相对含水量在较高范围内(50-100％)变化时,对叶片组织含水量、蒸腾强度和气孔扩散阻力影响不大。