亚低温与干旱胁迫对番茄植株水分传输和形态解剖结构的影响

为探讨亚低温和干旱对植株水分传输的影响机制,以番茄幼苗为试材,利用人工气候室设置常温(昼25 ℃/夜18 ℃)和亚低温(昼15 ℃/夜8 ℃)环境,采用盆栽进行正常灌水(75%～85%田间持水量)和干旱处理(55%～65%田间持水量),分析了温度和土壤水分对番茄植株水分传输、气孔和木质部导管形态解剖结构的影响。结果表明: 与常温正常灌水处理相比,干旱处理使番茄叶水势、蒸腾速率、气孔导度、水力导度、茎流速率、气孔长度和叶、茎、根导管直径显著减小,而使叶、茎、根导管细胞壁厚度和抗栓塞能力增强;亚低温处理下番茄叶水势、蒸腾速率、气孔导度、水力导度和叶、茎、根导管直径显著降低,但气孔变大,叶、根导管细胞壁厚度和叶、茎、根抗栓塞能力显著升高。亚低温条件下土壤水分状况对番茄叶水势、蒸腾速率、气孔导度、水力导度、气孔形态、叶、根导管结构均无显著影响。总之,干旱处理下番茄通过协同调控叶、茎、根结构使植株水分关系重新达到稳态;亚低温处理下番茄植株水分关系的调控主要通过改变叶和根导管结构实现,且受土壤水分状况的影响较小。     

几种作物的生理指标对土壤水分变动的阈值反应

 在生长盛期,谷子、高梁、冬小麦的气孔导度、叶水势和光合速率在一定土壤含水量范围内并不随着土壤含水量的降低而发生明显变化,只有当土壤含水量低于一定程度时,才随着土壤湿度的降低而减少,表现为对土壤水分有明显的阈值反应。不同作物此阈值下限存在差异,高粱在大于田间持水量42％～45％的根层土壤湿度条件下,气孔阻力和叶水势基本维持恒定;谷子的这个指标在50％左右,冬小麦在60％左右。而夏玉米在所试土壤湿度范围内(20％～30％土壤体积含水量),气孔阻力和叶水势基本维持不变,而光合作用随着土壤含水量的增高而出现增加趋势。表明在这4种作物中,只有玉米需要充足的水分供应才能维持其良好的生长发育,而高粱具有比其它3种作物更强的适应土壤水分变动能力,从而比其它作物更抗旱和耐旱。     

土壤含水量对麻疯树幼苗生长及其生理生化特征的影响

以麻疯树(Jatropha curcas L.)1年生盆栽幼苗为材料,通过设置3个土壤水分(分别为80%、50%和30%田间持水量(FC))处理,研究土壤含水量对麻疯树幼苗生长及生理生化指标的影响,探讨麻疯树的水分适应性。结果表明:随土壤含水量的降低,麻疯树的株高、生物量等均呈下降趋势,根重比、根冠比和比叶面积无显著变化;蒸腾速率和气孔导度显著降低,净光合速率和PSII的光能转换效率无明显变化;叶片色素含量显著升高。在80%FC下,丙二醛和过氧化氢含量、可溶性糖和游离脯氨酸含量、超氧化物歧化酶活性和抗坏血酸含量均呈现最大值。在本实验条件下:麻疯树作为一种抗旱性较强的树种,30%FC没有对其造成干旱胁迫;而从生理生化代谢方面看,80%FC不能为麻疯树生长提供最适宜的条件,主要体现在体内自由基积累、膜脂过氧化程度加重以及叶绿体色素含量的降低,但体内抗氧化防御系统的积极防御和渗透调节物质含量的增加缓解了水分过多对麻疯树造成的伤害,从而没有对净光合速率造成影响。因此,在当地土壤养分状况下,以30%-50%FC的土壤含水量栽培,更有利于麻疯树的生长。     

不同水分梯度下楸树苗期生长及光合特征比较

以1a生楸树根插苗为试验材料, 设置95%—100%FC、85%—90%FC、70%—75%FC、50%—55%FC等不同梯度的土壤含水量, 对生长旺季的光合特征及生长量进行测量, 研究苗期楸树对不同土壤水分含量的生长及光合特征响应。结果显示: 高土壤含水量(≧85%FC)和低土壤含水量(≦75%)地径和苗高生长量差异显著(P<0.05), 随着土壤含水量逐渐下降, 地径和苗高生长量、根重、茎重及根干比均呈下降趋势。光合特征比较发现, 上午净光合速率显著高于下午, 净光合速率的日变化主要直接受制于气孔因素; 85%—90%FC处理叶片的净光合日总量最大, 50%—55%FC处理叶片的净光合日总量最小。在所有光强梯度下, 高土壤水分含量处理(≧85%FC)的叶片净光合速率均明显较高, 尤其是85%—90%FC处理, 光利用能力和光合潜力都具有较大优势。从生长和光合特征综合分析结果可以看出, 四种处理中85%—90%FC处理最有优势和潜力, 是楸树苗期生长最为适宜的土壤含水量。     

山地枣树茎直径对不同生态因子的响应

以山地梨枣为试材,进行了枣树茎直径对土壤水势(WPs)、太阳辐射(Rs)、气温(Ta)、空气相对湿度(RH)等生态因子的响应试验研究。试验共设4个WPs区间的处理,连续测定枣树茎直径及不同生态因子的动态变化。结果表明:在果实膨大期,在-41—-390 kPa范围内,WPs越高的处理,其枣树茎直径(TD)越大;不同处理间枣树最大茎直径(MXTD)存在显著性差异,较高的WPs区间有利于茎直径的增加;MXTD是该期较为适宜的水分信息诊断指标。晴天时,茎直径日收缩幅度大;雨天白天时,茎直径基本处于同一水平,收缩不明显。TD与RH呈极显著正相关,与Ta呈极显著负相关关系,与Rs间无显著相关关系,RH与Ta是影响茎直径变化的最主要气象因子。综合考虑,枣树茎直径的微变化同时受到各种生态因子的影响,尤以RH、Ta、WPs的影响更为显著;WPs高时,WPs为影响茎直径变化的主要因子;WPs低时,RH成为影响茎直径变化的主要因子。     

土壤水分和磷营养对小麦根系生长生理特性的影响

采用小偃６号小麦品种,在模拟田间原状土容重的条件下土培,研究了土壤水分和磷营养对小麦根系生长生理特性的效应。结果表明：在土壤相对含水量为４０％─７０％范围内,土壤水分亏缺,小麦根系生长受到限制,根系比表面积（ＲＡ）、根呼吸速率（Ｒｐ）、根水势（Ｒψｗ）和叶片蒸腾强度（ＥＩ）明显降低,根系干物重（ＲＤＷ）减少;轻度干旱有利于根系的延伸生长;在土壤干旱条件下,磷营养可以提高根系ＲＡ,降低根系Ｒｐ,提高Ｒψｗ、增加叶面ＥＩ,促进根系延伸生长,扩大小麦根系对土壤深层水分的吸收和利用,进而促进地下部生长,提高ＲＤＷ。磷除作为一种营养物质促进作物根系生长发育外,在水分胁迫条件下,磷营养可明显改善植株体内的水分关系,增强对干旱缺水环境的适应能力,提高作物抗旱性。促进根系生长,提高水分利用的有效方法是根据土壤水分状况调节磷的用量。     

土壤因子对发光酶基因标记的荧光假单胞菌X16L2在小麦根圈定殖的影响

采用发光酶基因(luxAB)标记检测技术研究了根 盒土壤微宇宙(microcosm)中土壤灭菌、土壤含水量和土壤类型对荧光假单胞菌(Pseudonmonas fluorescens,简称Pf)Xl6L2在小麦根圈定殖的影响。研究结果表明,灭菌土壤中Pf·Xl6L2在小麦根圈的定殖水平较不灭菌土壤中的高。土壤类型对Pf·Xl6L2的定殖水平有较大影响,在黄棕壤中的定殖水平显著高于灰潮土中的。土壤含水量对定殖情况的影响与土壤类型有关 ,当土壤含水量为50%田间持水量(Field contents,简称FC)时,在黄棕壤中,Pf·Xl6L2主要定殖在种子下方4cm以内的根段上,但仍可散布至8cm处,而在灰潮土中,Pf·Xl6L2只能散布至种子下方4cm以内;在黄棕壤中,土壤含水量为60%FC和75%FC时,Pf·Xl6L2的定殖水平显著高于在50%FC条件下的,不但能散布至种子下方8cm处,而且定殖水平可达3.0×10.2cfu·g-1根,在灰潮土中,不同土壤含水量之间Pf·Xl6L2的定殖水平差异不大,但Pf·Xl6L2的散布范围不一,在60%FC和75%FC条件下,Pf·Xl6L2可散布至种子下方8cm处,而在50%FC下则不能。     

梨枣花果期耗水规律及其与茎直径变化的相关分析

设置4个水分处理,研究了4年生梨枣2010年及2011年花果期不同供水条件下土壤水分动态和耗水规律,分析了梨枣日耗水量与茎直径变化间的相关性,建立回归模型.结果表明:(1)2a内各处理梨枣耗水量随土壤供水量的增加而增大,其日耗水量最大值均出现在灌水后1周内;各处理果实膨大期日耗水强度大于开花坐果期.(2)2a内各处理茎直径日变化平均值(MTD)、茎直径日最大值(MXTD)均符合Logistic函数关系,MXTD与MTD在表征梨枣茎秆生长规律方面效果一致,各处理茎直径变化指标(MTD、MXTD)增长率因水分处理的不同而存在差异.(3)高水分(T1处理)条件下茎直径变化指标(MTD、MXTD、MDS(茎直径日最大收缩量)、DG(茎直径日生长量))在表征枣树耗水状况方面不敏感;在低水分(T4处理)条件下,日耗水量与茎直径日最大收缩量(MDS)相关系数较其他3个茎直径变化指标(MTD、MXTD、DG)高且达极显著水平,说明MDS能够更好的表征低水分处理的梨枣耗水规律.在此基础上建立耗水量与茎直径变化回归模型,为评价梨枣耗水状况提供依据.     

刺槐林水分生态研究

 本文以定位观测资料为基础,对晋西北黄土丘陵沟壑区人工刺槐林的水分生态特点进行了研究。结果表明,在年生长期中,刺槐林地水分条件严酷、土壤有效水分少。生长期刺槐的蒸腾强度为0.1140g·g-1·h-1±0.0586(平均值±标准差);蒸腾强度日变化与光照强度日变化的关系最为明显;与气温日变化的关系次之;但与相对湿度日变化的关系则不明显。生长期刺槐的水势为1.759-Mpa±0.457(平均值±标准差)。水势的日变化与气温日变化的关系最为明显,与相对湿度日变化的关系次之;而与光照强度日变化的关系最不明显。刺槐的蒸腾强度季节变化与土壤水分含量季节变化的关系不够显著;水势的季节变化与土壤水分含量季节变化的关系显著;但它们的季节变化与光照强度、气温和相对湿度季节变化的关系均不够显著。刺槐的蒸腾耗水量,林分总蒸散量分别占同期降水量的16.3%和68.0%,     

太行山南麓低山丘陵区栓皮栎直径变化及其与环境因子的关系

使用周长传感器(Circumference DC2)研究了太行山南麓低山丘陵上栓皮栎人工林树干直径的日变化及其影响因子.结果表明:在季节性干旱期间,栓皮栎树干的直径变化周期性明显,直径收缩与液流启动时间基本一致,直径最小值滞后于液流速率最大值3 ～4 h;栓皮栎直径日最大收缩量(MDS)呈现低-高-低的变化趋势,与累积液流通量和叶片水势日差值极显著相关,与土壤含水量呈显著的二次方程关系.MDS值受气象因子变化的影响,与温度日差值、蒸汽压亏缺日差值和相对湿度日差值显著相关,而与太阳辐射日差值的相关性不显著.连续降水后,土壤水分不再是栓皮栎直径变化的限制因子,MDS值与累积液流通量、叶片水势、土壤含水量和气象因子差值的相关性均不显著.季节性干旱期和雨季的土壤含水量和温度是影响树干直径日变化的主要因子.     

Biomass,anatomical changes and osmotic potential in Atriplex nummularia Lindl. cultivated in sodic saline soil under water stress

Atriplex nummularia exhibits excellent adaptability to environments with high salinity and low water availability. Accordingly, many studies have been conducted to identify the tolerance of the plant. We cultivated Atriplex in sodic saline soil under conditions of water stress in Northeast Brazil. The purpose of the study was to evaluate the growth characteristics and production of leaves, stems and roots of Atriplex under these conditions in order to identify anatomical changes in vesicular cells in leaf epidermis as well as to assess the osmotic potential of the soil solution and the leaves. The experiment was performed in a greenhouse where Atriplex was cultivated for 134 days in pots with sodic saline soil. The treatments comprised four moisture levels (35%, 55%, 75% and 95% of field capacity – FC). The height, diameter and dry mass of leaf, stem and root exhibited their highest values at levels of soil moisture that were 75% and 95% of FC. The high yields of dry biomass indicate the potential use of this halophyte for restoration of salt-affected soils. The vesicular cells were influenced by the soil moisture. The osmotic potential can serve as a good index for evaluating plant responses to water stress and salinity.     

Soil Water Stress and Photosynthesis in Cotton

An experiment was conducted in SPAR systems at Florence, S.C., to obtain a data set for use in the simulation of the effect of drying soil on photosynthetic rates in cotton. The plant water status was monitored using leaf water potential and stem diameter meaurements. Reductions were noted in apparent photosynthesis rates after only 5 days of soil drying, and as anticipated, there was uniform displacement of the diurnal cycle of leaf water potential, and corresponding decreases in transpiration and CO₂ uptake. The photosynthesis-light response curves indicated that an average two-fold reduction in photosynthesis rates occurred for solar radiation greater than 250 W/m². Stem diameter change (from a nonstress pre-sunrise value) and integrated stem stress were found to be good indicators of maximum daily plant water stress. The integrated stem stress gave a measure of the duration of the stress along with its magnitude. A simulation method for predicting leaf water potential from stem diameter measurements was used to show that the magnitude and duration of plant water stress increased uniformly during the experiment. This increase was representative of the decreased rates of photosynthesis measured. These data will be used in the simulation of cotton growth and yield.     

Water balance in the arborescent palm, Sabal palmetto. II. Transpiration and stem water storage

The contribution of stem water storage to the water balance of the arborescent palm, Sabal palmetto, was investigated using greenhouse studies, field measurements and a tree-cutting experiment. Water balance studies of greenhouse trees (1.5 to 3 m tall) were conducted in which transpiration was measured by weight loss, and changes in soil and stem water content by time-domain reflectometry. When the greenhouse plants were well-watered (soil moisture near saturation), water was withdrawn from the stem during periods of high transpiration and then replenished during the night so that the net transpirational water loss came primarily from the soil. As water was withheld, however, an increasing percentage of daily net transpirational water loss came from water stored in the stem. However, studies on palms growing in their natural environment indicated that during periods of high transpiration leaf water status was somewhat uncoupled from stem water stores. In a tree-cutting experiment, the maintenance of high relative water content of attached leaves was significantly correlated with stem volume/leaf area. Leaves of a 3-m tree remained green and fully hydrated for approximately 100d after it had been cut down, whereas those of a 1-m-tall plant turned brown within one week. The significance of stem water storage may be in buffering stem xylem potentials during periods of high transpiration and in contributing to leaf survival during extended period of low soil water availability.     

Effects of Chlorocholine Chloride and Water Regime on Growth, Yield, and Water Use of Spring Wheat

When CCC was applied as a spray to the leaves of Brassica oleraceaL. (Brussels sprout) grown in pots, plant height and mean internodelength were reduced. The effects appeared more slowly and wereless pronounced than those previously observed when CCC hadbeen applied to the soil; other differences were that root growthwas not inhibited, stem weight was only significantly reducedat the highest rate of application (2 per cent), and stomatalnumber per unit area of lower leaf epidermis was not affected.In common with soil applications, leaf thickness, stem diameter,and the percentage moisture contents of the leaves were allincreased by foliar applications.In a further experiment theprogress of wilting was observed in untreated plants and inplants treated with CCC applied either to the leaves or to thesoil. The rates of water loss and the moisture contents of theleaf laminae of the treated plants, after a period of wilting,were not significantly different from the controls. The treatedplants, however, looked less ‘wilted‘ for the changein angle of the leaf lamina to the stem was less and their leaveswere therefore held more upright.     

The Effects of Foliar Applications of (2-Chloroethyl)-trimethylammonium Chloride on Leaf Area and Dry Matter Production by the Brussels Sprout Plant

When CCC was applied as a spray to the leaves of Brassica oleraceaL. (Brussels sprout) grown in pots, plant height and mean internodelength were reduced. The effects appeared more slowly and wereless pronounced than those previously observed when CCC hadbeen applied to the soil; other differences were that root growthwas not inhibited, stem weight was only significantly reducedat the highest rate of application (2 per cent), and stomatalnumber per unit area of lower leaf epidermis was not affected.In common with soil applications, leaf thickness, stem diameter,and the percentage moisture contents of the leaves were allincreased by foliar applications.In a further experiment theprogress of wilting was observed in untreated plants and inplants treated with CCC applied either to the leaves or to thesoil. The rates of water loss and the moisture contents of theleaf laminae of the treated plants, after a period of wilting,were not significantly different from the controls. The treatedplants, however, looked less ‘wilted‘ for the changein angle of the leaf lamina to the stem was less and their leaveswere therefore held more upright.     

Biophysical properties and functional significance of stem water storage tissues in Neotropical savanna trees

Biophysical characteristics of sapwood and outer parenchyma water storage compartments were studied in stems of eight dominant Brazilian Cerrado tree species to assess the impact of differences in tissue capacitance on whole-plant water relations. The rate of decline in tissue water potential with relative water content (RWC) was greater in the outer parenchyma than in the sapwood for most of the species, resulting in tissue-and species-specific differences in capacitance. Sapwood capacitance on a tissue volume basis ranged from 40 to 160 kg m-3 MPa-1, whereas outer parenchyma capacitance ranged from 25 to only 60 kg m-3 MPa-1. In addition, osmotic potentials at full turgor and at the turgor loss point were more negative for the outer parenchyma compared with the sapwood, and the maximum bulk elastic modulus was higher for the outer parenchyma than for the sapwood. Sapwood capacitance decreased linearly with increasing sapwood density across species, but there was no significant correlation between outer parenchyma capacitance and tissue density. Midday leaf water potential, the total hydraulic conductance of the soil/leaf pathway and stomatal conductance to water vapour (gs) all increased with stem volumetric capacitance, or with the relative contribution of stored water to total daily transpiration. However, the difference between the pre-dawn water potential of non-transpiring leaves and the weighted average soil water potential, a measure of the water potential disequilibrium between the plant and soil, increased asymptotically with total stem capacitance across species, implying that overnight recharge of water storage compartments was incomplete in species with greater capacitance. Overall, stem capacitance contributes to homeostasis in the diurnal and seasonal water balance of Cerrado trees.     

Internal water balance of barley under soil moisture stress

Leaf water potential, leaf relative water content, and relative transpiration of barley were determined daily under greenhouse conditions at 3 growth stages: tillering to boot, boot to heading, and heading to maturity. The leaf moisture characteristic curve (relative water content versus leaf water potential) was the same for leaves of the same age growing in the same environment for the first 2 stages of growth, but shifted at the heading to maturity stage to higher leaf relative water content for a given leaf water potential. Growth chamber experiments showed that the leaf moisture characteristic curve was not the same for plants growing in different environments.

Relative transpiration data indicated that barley stomates closed at a water potential of about −22 bars at the 3 stages studied.

The water potential was measured for all the leaves on barley to determine the variation of water potential with leaf position. Leaf water potential increased basipetally with plant leaf position. In soil with a moisture content near field capacity a difference of about 16.5 bars was observed between the top and bottom leaves on the same plant, while in soil with a moisture content near the permanent wilting point the difference was only 5.6 bars between the same leaf positions.

     

古尔班通古特沙漠白梭梭枝干光合及其影响因素

植物枝干光合（P_g）固定其自身呼吸所释放的CO₂，有效减少植物向大气的CO₂排放量。以古尔班通古特沙漠优势木本植物白梭梭（Haloxylon persicum）为研究对象，利用LI-COR 6400便携式光合仪与特制光合叶室（P-Chamber）相结合，观测白梭梭叶片、不同径级枝干的光响应及光合日变化特征；同时监测环境因子（大气温湿度、光合有效辐射、土壤温度及含水量等）与叶片/枝干性状指标（叶绿素含量、含水量、干物质含量、碳/氮含量等），揭示叶片/枝干光合的主要影响因子；采用破坏性取样，量化个体水平上叶片与枝干的总表面积，阐明枝干光合对植株个体碳平衡的贡献。研究结果显示：（1）白梭梭叶片叶绿素含量是枝干叶绿素含量的12-16倍，各径级枝干叶绿素含量差异不显著；（2）枝干光饱和点低于叶片，枝干不同径级（由粗至细），暗呼吸速率和枝干光合逐渐减小；（3）光合有效辐射、土壤含水量和空气温湿度是影响叶片光合的主要因子，对枝干光合无显著影响；（4）枝干光合可以固定其自身呼吸产生CO₂的73%，最高可达90%，枝干光合固定CO₂约占个体水平固碳量的15.4%。研究结果表明，忽视枝干光合的贡献来预测未来气候变化背景下荒漠生态系统碳过程，可能存在根本性缺陷，并且在估算枝干呼吸时，需要考虑枝干是否存在光合作用，以提高枝干呼吸的准确性。     

Stem diameter in relation to plant water status

An instrument containing a linear variable differential transformer was constructed to obtain continuous, nondestructive measurements of both short term changes in stem diameter and long term growth. In cotton plants, stem diameter, leaf water potential, and leaf relative water content are all closely related to net radiation at the top of the canopy. Leaves from the east and west sides of a plant show slight, but consistent differences in diurnal water potential patterns.