大豆叶片光合速率与气孔导度、叶肉导度的关系

在田间条件下，研究１２个大豆品种两个生育时期的叶片光合速率（ＰＡ）、气孔导度（ｇｓ）、叶肉导度（ｇｍ）、气孔内ＣＯ２浓度（Ｃｉ）和蒸腾速率（ＴＲ）。结果表明，上述５个性状均有显著的品种间差异，并且鼓粒中后期明显大于开花前后。各性状的平均数在鼓粒中后期均极显著低于开花前后。ＰＡ与ｇｓ的关系，随生育期表现不同，在开花前后，可以配合成一条三次多项式曲线，并显示出一最大的ＰＡ值，而在鼓粒中后期则呈显著的线     

不同施肥条件下夏玉米光合对生理生态因子的响应

不同施肥水平下夏玉米光合对生理、生态因子的响应研究表明,施肥可以改善叶肉细胞的光合能力,使阻碍光合速率进一步提高的因素由非气孔限制逐渐转变为气孔限制,并可提高生育后期叶片的光合强度,延长高光合持续期,在日变化中表现为增加了叶片下午的光合强度.大田条件下,光合有效辐射(PAR)和气孔导度(S.)是影响光合速率(Pn)最主     

A partial root zone drying irrigation strategy for citrus—Effects on water use efficiency and fruit characteristics

In Australian irrigated citriculture, fruit yield and quality outcomes are not tightly related to levels of plant available water, which raises the possibility of using mild water stress applied to part of the root zone, i.e. partial root zone drying, to stimulate physiological mechanisms that reduce tree water use by changing the relationship between stomatal conductance and ambient evaporative conditions.The PRD technique alternates irrigation such that one side of the tree root zone is allowed to dry whilst the other side is irrigated. This significantly reduces the wetted soil volume at any point in time, whilst always maintaining a readily available water supply to part of the root zone. By adopting this irrigation strategy water use of mature Navel orange trees C. sinensis (L.) Osbeck was reduced and water use efficiency was increased. The technique did not induce excessive fruitlet drop and crop yield was unaffected. Both fruit size and juice percentage slightly decreased whereas total soluble solids percentage (TSS) and juice acid percentage increased. As water use was reduced and juice quality attributes were increased, this technique has obvious benefits for juice fruit production.PRD offers an advantage over conventional deficit irrigation strategies because it helps reduce water use by separating the biochemical signaling responses to water deficit in the dry part of the root zone from the physical effects of reduced stomatal conductance due to lower water availability, allowing developmental processes associated with plant growth to remain unperturbed. Irrigating a reduced root zone volume in this way reduces crop water requirement. However, it is also important to understand that this technique pushes the crop to its limits and should only be applied to well established healthy trees.When applying PRD irrigation, it is important that water is supplied with sufficient frequency and depth of wetting to meet the water needs of the whole plant.     

Water availability determines hydrological impact of tree belts in dryland cropping systems

Shallow groundwater can often develop when perennial ecosystems are replaced by annual agriculture. Returning trees to these landscapes is one option available to farmers to use more of the incident rainfall and stop the rising water table before it begins to affect production of the traditionally planted crops and pastures. This study examines the growth and water use of mallee (multi-stemmed) eucalypts in landscape positions with different water availability, integrated into an annual cropping and pasture farming system in the dryland agricultural zone of Western Australia. We found a ten-fold difference in biomass accumulation and a six-fold difference in rates of water use depending on water availability. Water use on a leaf area basis appeared to be independent of changes in water availability but transpiration efficiency in terms of grams of carbon fixed per litre of water transpired increased with increasing water availability. Thoughtful placement of trees in the landscape will minimize the area of land required to be planted to have the desired effect on the local hydrology, thus maximizing the amount of land on which the traditional annual crops and pastures can continue to be grown.     

Empirical and optimal stomatal controls on leaf and ecosystem level CO2 and H2O exchange rates

Linkage between the leaf-level stomatal conductance (g_s) response to environmental stimuli and canopy-level mass exchange processes remains an important research problem to be confronted. How various formulations of g_s influence canopy-scale mean scalar concentration and flux profiles of CO₂ and H₂O within the canopy and how to derive ‘effective’ properties of a ‘big-leaf’ that represents the eco-system mass exchange rates starting from leaf-level parameters were explored. Four widely used formulations for leaf-level g_s were combined with a leaf-level photosynthetic demand function, a layer-resolving light attenuation model, and a turbulent closure scheme for scalar fluxes within the canopy air space. The four g_s models were the widely used semi-empirical Ball-Berry approach, and its modification, and two solutions to the stomatal optimization theory for autonomous leaves. One of the two solutions to the optimization theory is based on a linearized CO₂-demand function while the other does not invoke such simplification. The four stomatal control models were then parameterized against the same shoot-scale gas exchange data collected in a Scots pine forest located at the SMEAR II-station in Hyytiälä, Southern Finland. The predicted CO₂ (F_c) and H₂O fluxes (F_e) and mean concentration profiles were compared against multi-level eddy-covariance measurements and mean scalar concentration data within and above the canopy. It was shown that F_c comparisons agreed to within 10% and F_e comparisons to within 25%. The optimality approach derived from a linearized photosynthetic demand function predicted the largest CO₂ uptake and transpiration rates when compared to eddy-covariance measurements and the other three models. Moreover, within each g_s model, the CO₂ fluxes were insensitive to g_s model parameter variability whereas the transpiration rate estimates were notably more affected. Vertical integration of the layer-averaged results as derived from each g_s model was carried out. The sensitivities of the up-scaled bulk canopy conductances were compared against the eddy-covariance derived canopy conductance counterpart. It was shown that canopy level g_s appear more sensitive to vapor-pressure deficit than shoot-level g_s.     

毛乌素沙地主要建群植物蒸腾耗水特性的研究

在植物生长旺季初期(7月份),采用LI-1600型气孔针对毛乌素沙地主要建群植物油蒿(Artemisia ordosica)、中间锦鸡儿(Caragana intermedia)、沙柳(Salix psammophyla)和旱柳(Salix matsudana)的蒸腾耗水进行了测定。结果表明:供试植物的蒸腾速率日动态曲线均为单峰型,无午休现象,其中固定沙地油蒿和半固定沙地油蒿的蒸腾速率在中午13∶00出现峰值。气孔扩散阻力是所有供试植物蒸腾速率的主要影响因子。对供试植物的蒸腾耗水进行的评估表明,不同植物的日最大蒸腾速率和日平均蒸腾速率大小为固定沙地油蒿>半固定沙地油蒿>沙柳>旱柳>中间锦鸡儿;植物单株月累计蒸腾耗水量大小为旱柳>沙柳>固定沙地油蒿>半固定沙地油蒿>中间锦鸡儿;植物种群单位面积单位时间内的蒸腾耗水量大小顺序为固定沙地油蒿>半固定沙地油蒿>沙柳>旱柳>中间锦鸡儿。     

Influence of Soil Water Regimes on VA Mycorrhiza IV. Effect on Root Growth and Water Relations of Sorghum bicolor

In a greenhouse trial, non-mycorrhizal and mycorrhizal plants of Sorghum bicolor were grown at three water regimes. The root length and root morphology of Sorghum bicolor was monitored in two soils during 34 days. From 29 days on, total root length of mycorrhizal sorghum was greater than of non-mycorrhizal sorghum in moderate and high water stress conditions. In soil A, at all water regimes a lower percentage of coarse roots and smaller root length per leaf area were found with mycorrhizal plants; in soil B, this was only the case in well watered conditions. In general, all root and water relation parameters were less affected by water stress when plants were mycorrhizal; this less sensitivity of mycorrhizal sorghum may increase the tolerance of the plant to drought. However, water relations of plants were indirectly enhanced by mycorrhiza via increased P uptake.     

冬小麦气孔与非气孔失水特性的基因型差异研究

以２年的冬小麦区域试验参试品系为材料，测定分析了离休叶片失水速率（ＲＷＬ），叶片蒸腾速率（ＴＲ）和叶片初始含水量（ＩＷＣ）。结果表明，ＲＷＬ、ＴＲＲ和ＩＷＣ都存在显著的基因型差异。品系间排序在不同次测定中有波动，但有基本稳定的趋势。不同试验区同一次ＲＷＬ的测定结果综合可比性较好，ＲＷＬ和ＩＷＣ趋向正态分布。ＲＷＬ和ＴＲＲ无相关关系，ＲＷＬ和ＩＷＣ有微弱的正相关趋势，３个性状与产量都不相关，根据此结果在同时选择较低的ＲＷＬ和ＴＲＲ方面进行了探讨。     

Physiological traits used in the breeding of new cultivars for water-scarce environments

A physiological understanding of plants’ responses to drought has often been sought on the pretext that this understanding will assist plant breeders develop higher yielding varieties for water-scarce environments. However, despite an extensive literature on plants’ response to drought there are few documented examples where a physiological understanding of drought has identified traits that limit yield under drought and where these have been used in successful crop improvement programs to enhance crop yields. This paper selects seven examples where a physiological understanding has resulted in more precise targeting of genetic variation and has resulted in higher yielding or more productive germplasm or varieties. The underlying features of these successes are then examined to identify the elements of success that may be used to further enhance yield improvement in dry environments. The conclusions are that all of these traits directly or indirectly transfer their effects to yield over long time scales by increasing either water-use (amount and pattern), water-use efficiency or partitioning of more biomass to grain.     

芋组培苗移栽驯化期的光合特性

 对芋组培苗在移栽驯化过程中的生理指标进行了测定, 结果表明: 其叶片叶绿素含量、表观量子产额、羧化效率、净光合速率随驯化时间的延长逐渐增加, 而蒸腾速率和气孔导度则呈下降趋势, 说明移栽驯化可以增强组培苗对环境的适应能力和自养能力。