Effects of Repeated Cycles of Dehydrationrehydration on Gas Exchange and Water Use Efficiency of Seedlings \=

该文研究了多重复干旱循环对１年生北美短叶松和黑云杉苗木的气体交换速率及水分利用效率的影响．结果表明,多重复干旱循环对它们的气体交换（Ｃｓ,Ｐｎ,Ｔｒ）有显著影响（Ｐ＜０．５）,而对其水分利用效率（ＷＵＥ）影响不大（Ｐ＞０．１）．尽管北美短叶松的气孔对轻度干旱胁迫不如黑云杉敏感,但是它对中度及严重干旱胁迫的敏感程度却高于黑云杉．在轻度及中度干旱胁迫下,北美短叶松的光合作用主要受非气孔因素的影响,而黑云杉则主要受气孔因素的影响．解除干旱胁迫后,黑云杉的气孔敏感性、光合能力及水分利用效率的恢复都要比北美短叶松更快．轻度的干旱胁迫锻炼可以帮助北美短叶松在更严重的干旱胁迫下保持固有而强劲的耐旱能力．然而,通过多重复干旱循环锻炼后,黑云杉在改善耐旱能力的强度方面大于北美短叶松．     

四个生长季高浓度CO_2处理长白松的气孔响应(英文)

在长白山站以开顶箱方式对4 年生长白松连续4 个生长季进行CO2 处理,包括700 和500 μmolmol-1 高浓度CO2,以及接受空气CO2的对照箱和不扣箱的裸露地条件(约350 μmolmol-1 CO2),通过测定气孔导度(gs),ci/ca比及气孔数量等指标评价气孔对高浓度CO2的响应。气孔导度及ci/ca比的转换实验表明,在各自生长CO2下和在相同测定CO2 下进行比较时,生长在高浓度CO2 下植株的气孔导度要高于空气CO2 下对照组植株的气孔导度(除700 μmol mol-1 CO2 下的植株在生长CO2 浓度下及在350 μmol mol-1 CO2 下测定时的气孔导度低于裸地植株外)。在各自生长CO2浓度下测定时,高浓度CO2下植株的ci/ca比低于对照组植株,但在相同测定CO2浓度下比较时,却是高浓度CO2下植株的ci/ca高于对照组植株的ci/ca比。高浓度CO2下植株与对照组植株在每单位长度气孔数量上无明显差异,但高浓度CO2通过降低气孔线数使长白松当年生针叶的总气孔数量降低,并且改变了气孔在针叶上、下表面的分配模式。表4 参18。     

Effect of salinity on water stress, growth, and yield of maize and sunflower

Maize and sunflower were grown in tanks filled with loam and clay, and were irrigated with water of three different levels of salinity. Predawn leaf-water potential and stomatal conductance were used as parameters for water stress. The predawn leaf-water potential of maize was higher than that of sunflower, but the effect of salinity and soil texture on the predawn leaf-water potential was the same for both crops. The stomatal conductance of sunflower was much higher and more severely affected by salinity and soil texture than the stomatal conductance of maize.

Although salinity had a more serious effect on the development of leaf area and canopy dry matter of sunflower, its effect on evapotranspiration and grain yield was the same for both crops. Soil texture had a stronger effect on the development of leaf area and canopy dry matter of sunflower, which also appeared in the evapotranspiration and grain yield, indicating that sunflower is more sensitive to drought than maize.     

New approach for olive trees irrigation scheduling using trunk diameter sensors

Trunk diameter fluctuations (TDFs) have been suggested as an irrigation-scheduling tool for several fruit trees, but the works in olive trees has not obtained successful results with any of the indicators (maximum daily shrinkage (MDS) and trunk growth rate (TGR)) that are calculated from the daily TDF curves. No studies of olive trees have ever used reference trees to reduce the influence of the environment, as in work for other fruit trees. In this work, we compare different continuous and discrete water status measurements in a drought cycle. We suggest the calculation of a new and related indicator (DTGR), the difference between the TGR of stressed trees, and the TGR of reference trees. Negative DTGR values always indicate water stress conditions. The current work describes the variations of this new indicator (DTGR) in relation to water stress, and compares DTRG to the midday stem water potential, maximum leaf conductance and to the MDS. The midday stem water potential and the maximum leaf conductance describe the stress cycle clearer than the trunk diameter fluctuation indicators. No significant differences were found in the values of MDS between stressed and reference trees. On the other hand, the DTGR pattern values were near that of the stem water potential, though positive values were recorded in some dates during the water stress cycle. These variations indicate that DTGR is not a cumulative water stress indicators, as is water potential. Therefore, according to our data, water potential is a better indicator than the TDF parameters when no deficit irrigation scheduling is performed in olive trees. DTGR seems to be a good indicator of water stress from a threshold value around −1.4 MPa in olive trees. In addition, higher variability of DTGR than stem water potential may also be reduced with the increase in the number of sensors.     

8种野生葱属植物的叶形态特征及其分类学意义研究

【目的】比较8种野生葱属植物的叶形态特征,为其分类学研究和生态适应性机制分析提供依据。【方法】以分布于新疆不同生境的8种野生葱属植物齿丝山韭、实葶葱、新疆蒜、健蒜、多籽蒜、奇台蒜、喀纳斯蒜和乌鲁木齐蒜为研究对象,采用田间观测和树胶制片法,测定其叶片数量、长度、宽度等指标,观察其解剖结构异同;通过相关性分析和聚类分析,研究叶片表皮性状之间的关系以及性状的分类学意义。【结果】8种葱属植物的叶形态和微形态存在差异,实葶葱和齿丝山韭叶直立,其余呈不同程度倒伏;实葶葱叶圆柱形,其余叶均为条形;实葶葱叶表面被蜡粉,其余均为光滑;实葶葱叶表皮细胞矩形,其余均为菱形;实葶葱垂周壁直线型,其余均为弧线形。8种植物叶片均为双面气孔型,气孔椭圆形,保卫细胞肾形,无副卫细胞,保卫细胞不同程度下陷。基于叶表皮结构性状的聚类分析结果显示,供试8种材料分为3类,齿丝山韭和实葶葱分别聚为一类,其余6种聚为一类。【结论】叶形态、表皮细胞形状、垂周壁形状、表皮细胞密度和气孔指数大小可为种的界定提供重要的形态分类学依据,具有分类学意义。叶片上表皮细胞比下表皮细胞可以提供更为全面的微形态特征。新疆8种野生葱属植物的叶片形态和微形态结构均呈现一定的抗旱和抗寒特征。     

水分胁迫对番茄幼苗生理特性的影响

为了探讨番茄苗期生理特性在水分胁迫胁迫下的响应,试验设置充分灌溉的对照(T)和轻度(T1)、中度(T2)、重度(T3)水分胁迫处理.在试验开始的第5,10,15和20 d,测定各处理番茄幼苗的叶绿素荧光参数、气孔特征及抗氧化酶等指标.与对照相比,不同程度水分胁迫条件下,随胁迫程度的增大,各处理番茄幼苗的PSⅡ光化学效率(Fv/Fm)、光化学淬灭(qP)及电子传递速率(ETR)均有所下降,且由大到小基本表现为T,T1,T2,T3;处理T1,T2和T3的气孔密度、长度及宽度均有所减小,重度水分胁迫条件下,气孔关闭;叶片中的超氧化物歧化酶、过氧化物酶及过氧化氢酶活性随着水分胁迫的加重而增加.轻度水分胁迫番茄幼苗各生理指标与对照差异较小,故可在番茄苗期进行50%~60%田间持水量的参考灌溉制度.     

Growth and Physiological Performance of Aerobic and Lowland Rice as Affected by Water Stress at Selected Growth Stages

Aerobic rice technology is still new in Malaysia, and information regarding MARDI Aerob 1 (MA1), the first local aerobic rice variety, is still lacking. Therefore, comparative studies were carried out to determine the physiological performance of aerobic rice variety MA1 and lowland rice variety MR253 under water stress given at the panicle initiation, flowering and ripening stages. This experiment was arranged in a randomized complete block design. Stomatal conductance (g_s), chlorophyll a fluorescence (F_v/F_m), leaf relative water content (leaf RWC), and soil moisture content (SMC) as well as yield component parameters such as panicle number, grain yield and 100-grain weight were measured. Results revealed that g_s and leaf RWC for both varieties decreased with depletion of SMC. The correlation study between the physiological parameters and SMC indicated that F_v/F_m was not affected by water stress, regardless of varieties. The yield components (panicle number, grain yield and 100-grain weight) for both varieties greatly decreased when water stress was imposed at the panicle initiation stage. This study showed that the panicle initiation period was the most sensitive stage to water stress that contributed to a substantial reduction in yield for both varieties. Under the aerobic condition (control), MR253 produced higher panicle number, 100-grain weight and yield than MA1. Although MR253 is bred for lowland, it is well adapted to aerobic condition.     

Charcoal production through selective logging leads to degradation of dry woodlands:a case study from Mutomo District,Kenya

Provision of woodfuel is an important ecosystem service of dry forests and woodlands.However,charcoal production through selective logging of preferred hardwood species has the potential to alter the physiognomic composition of the residual or re-growth woodlands and may lead to their deterioration and degradation.This study,conducted through forest inventory in Mutomo District in Kenya,assessed the impact of charcoal production on unprotected dry woodlands in terms of tree density,targeted species basal area,species richness,evenness and Shannon diversity.The parameters of the disturbed woodlands were evaluated for significant differences with those of the neighbouring protected Tsavo East National Park,which served as a reference for an ecologically undisturbed ecosystem.By evaluating a consequence of tree harvesting for charcoal production,this study confirmed the overall significant differences between the protected and unprotected woodlands in all the tested parameters.To confirm if the differences in the land-covers of the woodlands had any influence on their degradation,all mentioned parameters were compared between the four differentiated classes and their respective control plots in the protected areas.At the "land-cover level",the statistically significant difference in the basal area of tree species preferred for charcoal production between the protected and unprotected open trees confirms that the class with a high density of large mature trees is the prime target of charcoal producers.In addition,there seems to be a general trend of lower values of tree species richness,evenness and Shannon diversity for the unprotected woodlands subjected to charcoal production.On the other hand,the disturbed woodlands display the potential to recover through their comparably high saplings density.The findings make an important contribution to the discourse on the impact of charcoal production in dry woodlands,a topic that is highly controversial among researchers.     

Trade-offs between water-use related traits,yield components and mineral nutrition of wheat under Free-Air CO2 Enrichment (FACE)

This study investigated trade-offs between parameters determining water use efficiency of wheat under elevated CO₂ in contrasting growing seasons and a semi-arid environment. We also evaluated whether previously reported negative relationships between nutrient content and transpiration efficiency among wheat genotypes will be maintained under elevated CO₂ conditions. Two cultivars of wheat (Triticum aestivum L.), Scout and Yitpi, purportedly differing in water use efficiency related traits (e.g. transpiration efficiency) but with common genetic backgrounds were studied in a high yielding, high rainfall (2013), and in a low yielding, very dry growing season (2014) under Free-Air CO₂ Enrichment (FACE, CO₂ concentration of approximately 550 μmol mol⁻¹) and ambient (approximately 390 μmol mol⁻¹) CO₂. Gas exchange measurements were collected diurnally between stem elongation and anthesis. Aboveground biomass and nutrient content (sum of Ca, K, S, P, Cu, Fe, Zn, Mn and Mg) were determined at anthesis. Yield, yield components and harvest index were measured at physiological maturity. Cultivar Scout showed transiently greater transpiration efficiency (measured by gas exchange) over cultivar Yitpi under both ambient and elevated CO₂ conditions, mainly expressed in the high yielding but not in the low yielding season. Nutrient content was on average 13% greater for the lower transpiration efficiency cultivar Yitpi than the cultivar with higher transpiration efficiency (Scout) in the high yielding season across both CO₂ concentrations. Elevated CO₂ stimulated grain yield to a greater extent in the high yielding season than in the low yielding season where increased aboveground biomass earlier in the season did not translate into fertile tillers in cultivar Yitpi. Yield increased 27 and 33% in the high yielding and 0 and 19% in the low yielding season for cultivars Yitpi and Scout, respectively. Intraspecific variation in CO₂ responsiveness related mechanisms of grain yield were observed. These results suggest CO₂-driven trade-offs between traits governing water use efficiency are related to both growing season and intraspecific variations, and under very dry finishes, the trade-offs may even reverse. The negative relationship between nutrient content and transpiration efficiency among wheat genotypes will be maintained under elevated CO₂ conditions.     

黄瓜气孔导度、水力导度的环境响应及其调控蒸腾效应

以营养生长期温室黄瓜为研究对象,通过四元二次正交旋转组合设计,分析稳态流条件下土壤相对含水率、空气温度、空气湿度和光合有效辐射对气孔导度、土壤植物系统总水力导度的影响及其调控蒸腾效应。结果表明,4个环境因子对气孔导度、总水力导度均有正效应,对其影响最大的环境因子分别是空气湿度、空气温度;土壤相对含水率与光合有效辐射、空气温度与空气湿度对气孔导度和总水力导度存在明显的交互作用;空气湿度对气孔导度、总水力导度的单因子效应为开口向上的抛物线函数,其他环境因子的单因子效应皆趋近于线性递增函数;各因子的边际效应分析表明,空气湿度是气孔导度的主要调控途径,除光合有效辐射外,其他因子均可有效调控总水力导度。采用通径分析方法研究了环境因子、气孔导度、总水力导度调控蒸腾效应,结果表明,空气温度、光合有效辐射和气孔导度均主要通过增强总水力导度对蒸腾作用产生间接正效应,其次是对蒸腾作用的直接正效应;土壤相对含水率主要通过增强总水力导度和气孔导度对蒸腾作用产生间接正效应;空气湿度的直接影响为负效应,但其主要影响途径为通过增强总水力导度和气孔导度对蒸腾作用的正效应;气孔导度与总水力导度响应环境因子变化并相互作用,协同调控蒸腾作用。