西双版纳地区附生与非附生植物叶片角质层对水分的透性研究

为了探讨雾水对西双版纳地区不同类型植物的生态学效应,干季于20℃及30℃下用自制的设备测定了西双版纳地区4种附生和4种非附生植物叶片上表皮水分进出角质层的透性,比较研究了不同类型植物叶片通过角质层蒸腾失水速率(P_T)、叶片通过角质层吸水速率(P_A)以及吸水与失水速率的比值(R=P_A/P_T)高低,及其与生活方式的关系。结果表明,附生植物的R值都高于非附生植物且大于1,说明附生植物通过叶片吸收的水分大于蒸腾失水,雾水对于附生植物具有更重要的生态学意义;P_T和P_A在不同植物间有显著差异,这可能与不同植物的角质层化学成分和物理结构不同有关,对其适应各自生活方式及多雾环境有重要意义。除附生植物贝母兰(Coelogyne occultata)和掌唇兰(Staurochilus dawsonianus)以及非附生植物大叶藤黄(Garcinia xanthochymus)外,30℃下其余植物的P_T和P_A都显著高于20℃的,说明温...     

叶片相对含水量的活体测定

植物叶片相对含水量(RWC)是植物组织水分状况的重要指标,对抗旱育种的选择具有特殊的意义;但叶片相对含水量的常规测量方法繁冗费时,大量样品的测定很难得到满意的结果。本文采用一种简便、尤适于田间活体测定的方法——β射线衰减法,测定了棉花、玉米叶片的相对含水量及其昼夜变化,得到了较好结果。     

不同叶位大豆叶片细胞壁弹性调节与抗旱性关系

干旱条件下,不同叶位的大豆叶片的弹性调节表现出明显差异：初生叶和顶端幼叶（顶叶）不存在弹性调节,而第一、第三、第五复叶均存在弹性调节,弹性调节能力的大小依次为第五复叶＞第三复叶＞第一复叶;各叶位叶片的水势值（ψｗ）干旱时均下降,但降低值无明显差异;各叶片的相对含水量（ＲＷＣ）干旱时的变化为：初生叶和顶叶的下降值较大,三种复叶的下降值较小,其顺序为：第一复叶＞第三复叶＞第五复叶。细胞壁弹性调节的存在增强了植物的抗旱性,弹性调节能力的大小与抗旱能力的大小成正比。     

不同叶位大豆叶片细胞壁弹性调节与抗旱性关系

干旱条件下,不同叶位的大豆叶片的弹性调节表现出明显差异：初生叶和顶端幼叶(顶叶)不存在弹性调节,而第一、第三、第五复叶均存在弹性调节,弹性调节能力的大小依次为第五复叶>第三复叶>第一复叶;各叶位叶片的水势值(ψw)干旱时均下降,但降低值无明显差异;各叶片的相对含水量(RWC)干旱时的变化为：初生叶和顶叶的下降值较大,三种复叶的下降值较小,其顺序为：第一复叶>第三复叶>第五复叶。细胞壁弹性调节的存在增强了植物的抗旱性,弹性调节能力的大小与抗旱能力的大小成正比。     

亚热带常绿阔叶林冠层附生植物叶片形态结构及生理功能特征的适应性研究

以南亚热带常绿阔叶林林冠层不同部位的4种附生植物:瓜子金(Dischidia chinensis Champ.ex Benth.)、蔓九节(Psychotria serpens L.)、白背瓜馥木(Fissistigma glaucescens (Hance) Merr.)和山萎(Piper hancei Maxim.)为研究对象,比较其叶片解剖结构和光合、蒸腾等生理特性,探讨附生植物叶片形态结构、生理生态功能对冠层不同部位水、热和光资源的适应以及叶片形态结构与生理生态功能的联系.结果表明:着生在冠层上部的两种附生植物瓜子金和蔓九节叶片小而厚(厚度分别为3558±63 μm和217.1±33.1 μm),气孔面积小(分别为185.7±3.7 μm2和225 4±5.2 μm2)且覆盖角质膜,有利于降低蒸腾速率(两者分别为0.17±0.02 mmol H2O和0.34±0.05 mmol H2O),提高水分利用效率WUE(分别为11.35±0.87 μmol CO2/mmolH2O和7.88±1.31 μmol COJmmol H2O),更适应冠层顶部高温、低湿、强光照的生境.这些结构特征却不利于气体交换,会致使瓜子金和蔓九节的光合作用降低(二者最大净光合速率Pmax分别为2.2±0.1 μmol CO2 ·m-2·s-1和3.2±0 4 μmol CO2·m-2·s-1).冠层中下部的白背瓜馥木和山蒌叶片相对较薄(厚度分别为90.8±9.9 μm和114 9±18.2 μm),气孔面积较大(分别为260.6±6.3 μm2和362.5±8.7 μm2),叶肉细胞分化明显,海绵组织排列松散,有利于提高对弱光的利用,增强光合能力(二者Pmax分别为9.5±1.3 μmol CO2·m-2·s-1和7.1±0.8 μmol CO2·m-2·s-1,是瓜子金和蔓九节Pmax的3～4倍),更适应冠层中下部低温、高湿、弱光照环境.这些结构同时会导致白背瓜馥木和山蒌蒸腾速率提高(两者分别为0.67±0.10 mmol H2O和0.74 +0.13 mmol H2O),WUE下降(分别为4.4±1.01μmol CO2/mmol H2O和3.4±0.9 μmol CO2/mmol H2O,仅为瓜子金和蔓九节WUE的30％ -48％).这表明着生在林冠层不同部位的附生植物叶片形态结构特征随着光合有效辐射、温度、湿度等微环境因子的变化表现出显著的差异,并致使各自的生理生态功能发生了相应的适应,是植物适应环境条件的重要表现.     

不同甘蔗品种叶片气孔对水分胁迫的响应

干旱是甘蔗面临最主要的环境胁迫之一,为了解不同甘蔗品种在干旱胁迫时的气孔响应,该研究以F172、GT21、YT93/159和 YL6四个抗旱性有显著差异的甘蔗品种为材料,采用桶栽,在伸长期进行四种不同程度的干旱胁迫(不浇水)处理：土壤持水量在①65％~70％为轻度干旱;②45％~50％为中度干旱;③25％~30％为重度干旱;④以土壤含水量为75％为对照(CK).检测不同品种不同处理甘蔗的叶片相对持水量变化,并利用扫描电镜技术观察甘蔗叶片下表皮气孔特性.结果表明：在干旱胁迫下,四个甘蔗品种叶片气孔导度急剧下降,重度干旱时耐旱性强的 F172和 GT21的气孔导度低于耐旱性弱的 YT93/159和 YL6的;复水后3 d,F172和 GT21的气孔导度上升至82．07和88．85 mmol·m-2·s-1,而 YT93/159和 YL6的仅有18．88和33．08 mmol·m-2·s-1.干旱还导致气孔下陷、闭合,气孔器的长、宽明显减小,且品种间气孔器长度变化差异显著;干旱胁迫下气孔密度增大,尤以耐旱性最强的 F172在重度干旱时达到显著差异.重度干旱时 F172与GT21的气孔闭合百分比是 YT93/159和 YL6近3~4倍.在水分胁迫下,叶片相对含水量降低,但 F172和GT21在重度干旱时仍可以保持相对较高的含水量,其它两个品种相对较低,尤以 YT93/159的最低.在复水后叶片含水量都有所恢复.这些研究结果表明不同甘蔗品种抗旱能力与叶片气孔特性和含水量密切相关.     

云南石林喀斯特地区半湿润常绿阔叶林附生植物的初步研究

对云南石林喀斯特山地原生植被——半湿润常绿阔叶林中附生植物的组成、生物量以及附生植物持水量等进行研究,结果表明该区森林林木附生植物种类相对较少,只有8科9种附生维管束植物和5种苔藓植物,而林内岩石表面则有石附生维管束植物16科17种,苔藓植物3种,两种不同生境附生植物的相似性系数为0.5。相同取样面积(400cm2)条件下,岩石表面附生植物平均生物量(11.7g)比林木表面(4.9g)的高。附生植物一次持水量为自身干重的5.5~9.7倍。     

北京山区干旱胁迫下侧柏叶片水分吸收策略

干旱与半干旱地区,水分是限制树木生长的重要影响因子。由于降水稀缺且分配不均,叶片吸收水分是此地区树木吸收和利用小量级降水和凝结水的主要方式。北京山区处于易旱少雨的生态脆弱地带,森林植被经常遭受干旱胁迫,所以对该地区的森林系统而言,叶片直接吸收利用截留的降雨是干旱时期树木获得水分的重要途径。基于野外对比控制试验和室内盆栽模拟试验,选取北京山区的主要造林树种侧柏为研究对象,进行利用天然降雨与模拟降雨试验,研究降雨前后侧柏叶片吸水特征,探究侧柏在干旱环境下如何通过叶片吸水缓解干旱胁迫。结果表明：当侧柏长期处于干旱胁迫状态时,叶片可以利用降雨,从中获益用来缓解树木的干旱胁迫状态;叶片的吸水能力与降雨强度呈正相关关系,与土壤含水率呈负相关关系;重度干旱下侧柏植株在降雨强度为15 mm/h时叶片吸水现象最明显,叶水势变化最大为(1.18±0.17) MPa,叶片含水率变化最大为(8.47±1.00)mg/cm~2;当土壤水率高于20.8%时,基本不发生叶片吸水现象。试验结果说明在干旱地区叶片吸水是树木除根系吸水外的重要水分来源方式,并且对干旱地区有效利用短缺水资源,减轻植物水分亏缺具有重要意义。     

干旱胁迫条件下6种喀斯特主要造林树种苗木叶片水势及吸水潜能变化

水势是反映植物水分亏缺或水分状况的一个直接指标,可用来确定植物受干旱胁迫的程度和抗旱能力高低。本文研究了6种喀斯特造林树种苗木在干旱胁迫条件下叶片水势及其吸水潜能的变化。结果表明：（1）随着胁迫强度的增加,6种树种不同生长时期,其叶片水势均表现出下降趋势,且不同干旱胁迫强度之间差异显著（p<0.002）。在干旱胁迫下,所有树种叶片水势均以生长旺期的下降幅度最大,生长末期次之,生长初期最小。在生长旺期,6个树种叶片水势最低值分别比对照下降了2.21 Mpa、2.14 Mpa、3.57 Mpa、2.89Mpa、4.02Mpa和3.07Mpa。（2）侧柏苗木在生长初期轻度干旱条件下,其叶片水势胁迫指数只有0.150;在中度干旱胁迫条件下,其胁迫指数增加到0.559;在重度干旱胁迫条件下,达0.716,叶片水势下降超过70%。香樟苗木在生长初期轻度干旱胁迫条件下,其叶片水势胁迫指数就已达0.603,叶片水势下降超过了60%;在中度和重度干旱胁迫条件下,其水势胁迫指数相差不大。其它树种苗木的胁迫指数亦有与侧柏或香樟相似的变化趋势。（3）6个树种苗木在干旱胁迫条件下平均叶片水势与土壤水势差值大小排序为,生长初期：刺槐（1.261Mpa）>香樟（0.850 Mpa）>滇柏（0.846 Mpa）>侧柏（0.568 Mpa）>构树（0.524 Mpa）>杜英（0.219 Mpa）;生长旺期：香樟（2.994 Mpa）>刺槐（2.68 Mpa）>侧柏（2.028 Mpa）>滇柏（2.008 Mpa）>杜英（1.824 Mpa）>构树（1.543 Mpa）;生长末期：刺槐（0.692 Mpa）>构树（0.687 Mpa）>滇柏（0.653 Mpa）>侧柏（0.354 Mpa）>香樟（0.338 Mpa）>杜英（0.262 Mpa）。（4）干旱胁迫复水24h后,不同生长阶段苗木叶片水势恢复指数随干旱胁迫强度的增加而逐渐减小。叶片水势恢复度按生长时期排序为：生长末期>生长旺期>生长初期。（5）利用隶属函数累加法将6个树种苗木的吸水潜能大小可排序为：侧柏>滇柏>刺槐>香樟>构树>杜英。     

西双版纳热带雨林和热带山地常绿阔叶林附生苔藓的组成与多样性格局

为探讨西双版纳热带雨林和热带山地常绿阔叶林附生苔藓的组成、多样性格局及其维持机制,该文对两种植被的树干附生苔藓植物进行了调查与分析.所选择的样地位于西双版纳勐腊县,每种植被类型选择10个20 m×20 m的样方,每个样方选择约10棵样树.结果表明:(1)本调查共记录到附生苔藓20科39属60种,其中热带雨林附生苔藓有1...     

Xylem acoustic emissions and water relations of Calluna vulgaris L. at two climatological regions of Britain

The acoustic emission rate (as a result of xylem cavitation), stem water content, stomatal conductance, and leaf water potential of heather (Calluna vulgaris L. Hull) were compared over a period of 18 months at two contrasting sites in Britain. The sites were Thursely Common in south-east England, and Flanders Moss in central Scotland (average rainfall of 600 mm per year and 1500 mm per year, respectively). In the first year of study (1992) the natural difference between the sites was amplified by a severe drought affecting south-east England. The relative water content of the xylem (RWC) did not differ between the sites, and did not fluctuate seasonally, despite the drought at Thursely. Acoustic emissions were detected at both sites, but the incidence was low. The same range of foliage water potential and stomatal conductance was found at both sites. The leaf area to sapwood area ratio at the dry site was half that at the wet site, and it is suggested that this adjustment of the transpiring area relative to the water conducting area facilitates the close physiological state of the plants at the two sites. The possible occurrence of aerial refilling and freezing induced xylem cavitation is also discussed.     

Hydraulic conductance and water potential gradients in squash leaves showing mycorrhiza-induced increases in stomatal conductance

Stomatal conductance (g _s) and transpiration rates vary widely across plant species. Leaf hydraulic conductance (k _leaf) tends to change with g _s, to maintain hydraulic homeostasis and prevent wide and potentially harmful fluctuations in transpiration-induced water potential gradients across the leaf (ΔΨ _leaf). Because arbuscular mycorrhizal (AM) symbiosis often increases g _s in the plant host, we tested whether the symbiosis affects leaf hydraulic homeostasis. Specifically, we tested whether k _leaf changes with g _s to maintain ΔΨ _leaf or whether ΔΨ _leaf differs when g _s differs in AM and non-AM plants. Colonization of squash plants with Glomus intraradices resulted in increased g _s relative to non-AM controls, by an average of 27% under amply watered, unstressed conditions. Stomatal conductance was similar in AM and non-AM plants with exposure to NaCl stress. Across all AM and NaCl treatments, k _leaf did change in synchrony with g _s (positive correlation of g _s and k _leaf), corroborating leaf tendency toward hydraulic homeostasis under varying rates of transpirational water loss. However, k _leaf did not increase in AM plants to compensate for the higher g _s of unstressed AM plants relative to non-AM plants. Consequently, ΔΨ _leaf did tend to be higher in AM leaves. A trend toward slightly higher ΔΨ _leaf has been observed recently in more highly evolved plant taxa having higher productivity. Higher ΔΨ _leaf in leaves of mycorrhizal plants would therefore be consistent with the higher rates of gas exchange that often accompany mycorrhizal symbiosis and that are presumed to be necessary to supply the carbon needs of the fungal symbiont.     

短期干旱对水稻叶水势、光合作用及干物质分配的影响

采用盆栽水分试验,研究了不同生育期短期干旱处理对水稻叶水势、光合作用和干物质分配的影响．结果表明,干旱胁迫后,水稻叶水势低于对照,午后叶水势回升缓慢。凌晨叶水势随土壤含水量的降低而降低,表现为阈值反应。叶片净光合速率与凌晨叶水势密切相关,低于凌晨叶水势临界值,水稻叶片净光合速率急剧下降在水稻抽穗期和灌浆期叶片净光合速率显著下降的凌晨叶水势临界值为-1.04和-1．13MPa,对应的土壤含水量阈值分别为饱和含水量的61.0％和50．9％,土壤水势分别为-0．133和-0．240MPa干旱胁迫下单叶净光合速率的日变化规律表现为：胁迫较轻时,单叶净光合速率在正午附近出现低谷;胁迫严重时,净光合速率全天低于对照,且不及对照的一半。短期干旱后,水稻叶、根、穗的分配指数均降低,茎鞘的分配指数升高。本研究可为水稻节水灌溉管理和水分限制下水稻的生长模拟提供生理基础和理论依据。     

小麦冠层反射光谱与植株水分状况的关系

研究了不同土壤水、氮条件下小麦冠层光谱反射特征与叶片和植株水分状况的相关性．结果表明,在小麦主要生育期,冠层叶片含水率与460～510、610～680和1480～1500nm波段范围内的光谱反射率有较高的相关性,植株含水率与810～870nm波段范围内的光谱反射率密切相关．在整个生长期内,小麦冠层叶片含水率与460～1500nm波段范围内的光谱反射率均有良好相关性,植株含水率与560～1480nm波段范围内光谱反射率的相关性均达到极显著水平．冠层叶片(CL)、上层叶(UL)和下层叶片(LL)含水率与光谱指数的相关程度为CL>LL>UL．冠层叶片和植株含水率与比值指(R(610,560))和光谱指数(R(610,560)／ND(810,610))呈极显著线性负相关,与归一化指数((R810-R610)／(R810+R610))呈极显著线性正相关．其中,用光谱指数(R(610,560)／ND(810,610))监测不同生育期小麦冠层叶片和植株含水率的效果最好。     

Effect of PEG-6000 imposed drought stress on RNA content,relative water content (RWC), and chlorophyll content in peanut leaves and roots

Drought, one of the environmental stresses, plays crucial role in reduction in plant production on majority of agricultural fields of world, In order to evaluate drought stress on RNA content Relative water content (RWC), and chlorophyll content, Water deficit was induced by Polyethylene glycol (PEG) in peanut (Arachis hypogaea), accession number ICGV 91114. In this current study we evaluate RNA content and Relative water content (RWC) both in leaves and roots and chlorophyll content in leaf. The present study was undertaken with the aim to investigate the effect of water deficit imposed by PEG-6000, 40 old day seedlings were treated with varying concentrations of polyethylene glycol-6000 (PEG-6000; w/v-5%, 10%, 15% & 20%) for 24 h. The results showed that RNA content and Relative water content (RWC) content was significantly reduced in both leaves and roots with increased concentration of PEG, In leaves, a concentration dependent decline in chlorophyll content with increasing concentration of polyethylene glycol-6000 (PEG-6000). Reduction in chlorophyll ‘a’ level was to a greater extent than the chlorophyll ‘b’. Thus, this attributes can be used as screening tool for drought tolerance in peanut.     

Fog in the California redwood forest: ecosystem inputs and use by plants

Fog has been viewed as an important source of moisture in many coastal ecosystems, yet its importance for the plants which inhabit these ecosystems is virtually unknown. Here, I report the results of a 3-year investigation of fog inputs and the use of fog water by plants inhabiting the heavily fog inundated coastal redwood (Sequoia sempervirens) forests of northern California. During the study period, 34%, on average, of the annual hydrologic input was from fog drip off the redwood trees themselves (interception input). When trees were absent, the average annual input from fog was only 17%, demonstrating that the trees significantly influence the magnitude of fog water input to the ecosystem. Stable hydrogen and oxygen isotope analyses of water from fog, rain, soil water, and xylem water extracted from the dominant plant species were used to characterize the water sources used by the plants. An isotopic mixing model was employed to then quantify how much fog water each plant used each month during the 3-year study. In summer, when fog was most frequent, ～19% of the water within S.sempervirens, and ～66% of the water within the understory plants came from fog after it had dripped from tree foliage into the soil; for S.sempervirens, this fog water input comprised 13–45% of its annual transpiration. For all plants, there was a significant reliance on fog as a water source, especially in summer when rainfall was absent. Dependence on fog as a moisture source was highest in the year when rainfall was lowest but fog inputs normal. Interestingly, during the mild El Niño year of 1993, when the ratio of rainfall to fog water input was significantly higher and fog inputs were lower, both the proportion and coefficient of variation in how much fog water was used by plants increased. An explanation for this is that while fog inputs were lower than normal in this El Niño year, they came at a time when plant demand for water was highest (summer). Therefore, proportional use of fog water by plants increased. The results presented suggest that fog, as a meteorological factor, plays an important role in the water relations of the plants and in the hydrology of the forest. These results demonstrate the importance of understanding the impacts of climatic factors and their oscillations on the biota. The results have important implications for ecologists, hydrologists, and forest managers interested in fog-inundated ecosystems and the plants which inhabit them.     

土壤含水量与苹果叶片水分利用效率的关系

以盆栽苹果幼树为试材研究了土壤相对含水量与叶片水分利用效率（WUE）的关系,探讨了引起WUE变化的原因,结果表明,土壤相对含水量（SWC）52.0％时WUE最高。SEC从77.2%降至52.0％时,气孔导度下降,并使蒸腾速率（Tr）的于净光合速率（Pn）的降幅而导致WUE升高;SEC从52.0％降至20.1%时,WUE降低的根本原因在于羧化效率下降使Pn大为降低 水后WUE回升,但至复水第7天仍低于对照,土壤渍水当天WUE下降,第3天回升至对照水平,之后随渍水期延长WUE逐渐降低,淹水第6天羧化效率开始下降。     

Plant-water relations in wheat as influenced by root pruning

Summary A greenhouse study in which 24, 54 and 71 per cent roots of wheat (Triticum aestivum L.) were pruned on the 73rd day from the date of planting (anthesis stage) showed that during a 7-day period following root pruning, total transpiration and leaf water potential were significantly lower (P=0.05) and the stomatal resistance was significantly higher (P=0.05) where 54 and 71 per cent roots were pruned, as compared to no root pruning or 24 per cent root pruning. The leaf relative water content, however, showed no significant differences. Thus about one-fourth root sytem could be reduced without adversely affecting the plant-water status.     

三角叶滨藜根吸水特点与其抗盐性的关系

采用压力室和冰点渗透压计测定了三角叶滨藜在不同浓度NaCl的根系环境溶液中根木质部的压力势和伤流液的渗透势,并利用原子吸收分光光度计测定了植株和伤流液以及环境溶液中Na 含量。结果表明:随着根环境溶液NaCl浓度的增加,三角叶滨藜植株和木质部伤流液中Na 含量虽呈上升趋势,但根系的过滤系数和体内Na 相对累积量逐渐降低,说明三角叶滨藜根细胞对盐分有很强的过滤作用;木质部伤流液的渗透势随着环境溶液渗透势的降低而降低,但根木质部溶液的水势则逐渐高出根外环境溶液的渗透势;表明三角叶滨藜能够利用较低的木质部负压来抵抗根外溶液的低渗透势而反渗透吸水,并利用根细胞对盐分的过滤作用来避免从环境摄取过量的盐分。