河西地区几种中生植物的蒸腾和传导率与叶内外环境的关系

用LI-1600稳态气孔仪,测定了河西地区分布较广的五种木本植物的蒸腾和传导率及环境因子。只要光照不低于气孔开启所需的强度,植物蒸腾率最高点之前的高低变化与叶温上升的速率无关,而仅与每一时刻叶温高低密切相关。在种内,蒸腾率大致随叶的厚度和单位叶面积的栅栏组织表面积的增大而提高。但种间则无此相关性。同一样本叶的上下表面蒸腾率之比与其气孔数之比相对应,而种间则毫无关系。环境条件大致相同情况下,二白杨(Populus kansuensis)全天蒸腾量为78.2gH2O·dm-2,沙枣(Elaeagnus angustifolia)为40,4gH2O·dm-2。分别是箭杆杨(P.nigra var.thevestina)的2.5和1.3倍。同一灌溉条件下,梨光杏(Prunus armeniaca var.glabra)为26.7gH2O·dm-2,比毛杏(P.armeniaca var.ansu)高0.6倍。     

酸枣叶片结构可塑性对自然梯度干旱生境的适应特征

叶片是植物体暴露于环境中面积最大的器官,其最易感知环境变化而发生形态和结构上的改变。为探究植株叶片结构对不同生境的适应机理,研究以生长在烟台-石家庄-宁夏-新疆不同地域气候条件形成的自然梯度干旱环境中的酸枣为试验材料,应用植物显微技术研究酸枣叶片的结构的可塑性对不同自然梯度干旱环境的适应特征。结果表明:酸枣叶表皮着生有表皮毛,表皮细胞外覆有角质层与蜡质。叶肉为全栅型,栅栏组织发达,海绵组织退化,叶肉中有晶体及大量的分泌细胞。从烟台至新疆随生境梯度干旱加剧,酸枣叶片叶面积逐渐变小,叶片厚度依次增加,叶表皮角质层加厚,且上角质层厚度大于下角质层厚度;叶片上下表皮细胞长径及短径先增后降,栅栏组织总厚度和密度依次增大、层数减少,各层栅栏组织细胞的长径逐渐增加。叶脉薄壁细胞相对厚度逐渐减小,导管管径增大,晶体(草酸钙晶体)数增多。在梯度干旱环境中酸枣植株通过减小叶面积、提高栅栏组织密度、增加叶片及角质层厚度降低蒸腾作用,减少水分散失;通过增大导管管径提高水分利用率;通过增加晶体数量提高叶片机械性能,改变细胞的渗透势、提高吸水和保水能力。上述叶片结构的变化是酸枣植株长期对不同自然梯度干旱生境的适应特征。由此可知,叶片形态结构中叶面积、叶片厚度、角质层及叶肉组织(栅栏组织)随环境变化的可塑性较大。     

Plant responses to water stress: changes in growth,dry matter production,stomatal frequency and leaf anatomy

The responses of seedlings of three fast growing tree species,Eucalyptus hybrid(E. camaldulensis × E. teriticornis), Casuarina equisetifolia andMelia azedarach, to different levels of soil moisture in controlled glasshouse conditions were compared. The survival percentage, height of plants, number of leaves per plant, number of branches, fresh mass and dry mass of roots, stems, branches and leaves decreased in the three species with increasing water stress. Stomatal frequency and length of stomata inEucalyptus andMelia also decreased with increasing water stress. However, no significant difference was obtained in the width of stomata and the ratio of number of open stomata to total number of stomata per unit area. The leaf thickness decreased, but the thickness of palisade parenchyma increased with increasing water stress inEucalyptus hybrid andCasuarina. Leaf thickness ofMelia did not show any significant variation due to water stress.     

Changes in stomatal frequency, stomatal conductance and cuticle thickness during leaf expansion in the broad-leaved evergreen species, Eucalyptus regnans

Aspects of leaf anatomical and physiological development were investigated in the broad-leaved evergreen species, Eucalyptus regnans F.Muell. Newly emergent leaves were tagged in the field and measured for stomatal conductance while a subset was collected every 14 days for the measurement of stomata and cuticle over a 113-day period. Cuticle thickness increased during leaf expansion, the increase following a sigmoid curve. Stomatal frequency (no. mm⁻²) decreased from 56 to 113 days after leaf emergence. The frequency of both immature and intermediate developmental stages of stomata also decreased over this time, but the total number of stomata per leaf remained relatively constant. Stomatal conductance (g _s) of young expanding leaves increased during expansion, and was significantly linearly correlated with stomatal frequency (excluding immature stomata), and with cuticle thickness. The progressive increase in g _s in young developing leaves was contrary to the observed changes in structural characteristics (increased cuticle thickness and decreased stomatal frequency). This increase in g _s with development may be related to the progressive increase in number of mature stomata with larger apertures and, therefore, a higher total pore area in fully expanded leaves.     

Stomatal and hydraulic conductance in growing sugarcane: stomatal adjustment to water transport capacity*

Abstract Stomatal conductance per unit leaf area in well-irrigated field- and greenhouse-grown sugarcane increased with leaf area up to 0.2 m² plant ¹, then declined so that maximum transpiration per plant tended to saturate rather than increase linearly with further increase in leaf area. Conductance to liquid water transport exhibited parallel changes with plant size. This coordiantion of vapour phase and liquid phase conductances resulted in a balance between water loss and water transport capacity, maintaining leaf water status remarkably constant over a wide range of plant size and growing conditions. The changes in stomatal conductance were not related to plant or leaf age. Partial defoliation caused rapid increases in stomatal conductance, to re-establish the original relationship with remaining leaf area. Similarly, pruning of roots caused rapid reductions in stomatal conductance, which maintained or improved leaf water status. These results suggest that sugarcane stomata adjusted to the ratio of total hydraulic conductance to total transpiring leaf area. This could be mediated by root metabolites in the transpiration stream, whose delivery per unit leaf area would be a function of the relative magnitudes of root system size, transpiration rate and leaf area.     

Foliar uptake of Cd by pea (Pisum sativum) and sugar beet (Beta vulgaris)

Pea ( Pisum sativum L. cv. Fenomen) and sugar beet ( Beta vulgaris L. cv. Monohill) were cultivated in nutrient media without or with 10 μM CdCl₂. Leaves of the same size and stage of development, detached or still attached to the intact plants, were submerged into redistilled water containing 1 to 250 μM CdCl₂. The uptake experiments were run for 1 to 8 h at pH 3.6 and 5.1. Cuticular transpiration rate, density of leaf and density of stomata were also measured. Percentage of open stomata was studied at different pH.
Foliar uptake of Cd into the leaf is evident since Cd is transported from the exposed part of the pea leaves, through the petioles and into the stipules, and since the Cd concentration of the leaves increases with time and external Cd concentration. The foliar uptake depends on the permeability of the cuticular membrane, which is increased by a high intrinsic Cd level, which in turn enhances the foliar uptake of Cd in sugar beet. Higher cuticular permeability in pea than in sugar beet is shown by a 2.5 times higher cuticular transpiration rate and a 4 times lower density of leaf for pea, which causes a 7 times higher foliar uptake in pea than in sugar beet. Low pH decreases the net uptake of Cd, probably by an exchange reaction in the cutin and pectin of the cuticular membrane. Stomata are not directly involved in the Cd uptake, and the differences in the sum total of stomatal aperture area per unit leaf area is not related to differences in foliar uptake of Cd. Percentage of open stomata, calculated as average of both sides of the leaves, was not affected by changes in pH: but especially at high pH. proportionally more stomata were open on the adaxial than on the abaxial side.     

Early stomatal closure in waterlogged pea plants is mediated by abscisic acid in the absence of foliar water deficits

Abstract Soil waterlogging decreased leaf conductance (interpreted as stomatal closure) of vegetative pea plants (Pisuin sativum L. cv. ‘Sprite’) approximately 24 h after the start of flooding, i.e. from the beginning of the second 16 h-long photo-period. Both adaxial and abaxial surfaces of leaves of various ages and the stipules were affected. Stomatal closure was sustained for at least 3 d with no decrease in foliar hydration measured as water content per unit area, leaf water potential or leaf water saturation deficit. Instead, leaves became increasingly hydrated in association with slower transpiration. These changes in the waterlogged plants over 3 d were accompanied by up to 10-fold increases in the concentration of endogenous abscisic acid (ABA). Waterlogging also increased foliar hydration and ABA concentrations in the dark. Leaves detached from non-waterlogged plants and maintained in vials of water for up to 3 d behaved in a similar way to leaves on flooded plants, i.e. stomata closed in the absence of a water deficit but in association with increased ABA content. Applying ABA through the transpiration stream to freshly detached leaflets partially closed stomata within 15 min. The extractable concentrations of ABA associated with this closure were similar to those found in flooded plants. When an ABA-deficient ‘wilty’ mutant of pea was waterlogged, the extent of stomatal closure was less pronounced than that in ordinary non-mutant plants, and the associated increase in foliar ABA was correspondingly smaller. Similarly, waterlogging closed stomata of tomato plants within 24 h, but no such closure was seen in ‘flacca’, a corresponding ABA-deficient mutant. The results provide an example of stomatal closure brought about by stress in the root environment in the absence of water deficiency. The correlative factor operating between the roots and shoots appeared to be an inhibition of ABA transport out of the shoots of flooded plants, causing the hormone to accumulate in the leaves.     

盾叶秋海棠叶表皮气孔簇的发育及分布格局

气孔是植物控制气体交换和调节水分散失的门户。大部分高等植物气孔的分布格局是相邻气孔之间被一至多个表皮细胞所间隔。而在有限分布的几个科属的植物种中发现气孔成簇分布的现象 ,即由 2至多个紧密相邻的气孔器组成相对独立的单元 ,称为气孔簇 (stomatalcluster)。以中国原产的盾叶秋海棠 (BegoniapeltatifoliaLi)为研究对象 ,探讨了叶表皮气孔簇的发育机制及其分布格局。结果表明 :气孔发育初期 ,气孔拟分生组织的成簇 (相邻紧密 )排列可能是气孔簇形成的主要机制 ;气孔副卫细胞恢复分裂形成的卫星拟分生组织也对气孔簇的形成起一定的作用。把气孔簇和单个气孔视为一个气孔单元发现 ,盾叶秋海棠气孔单元密度 (单位面积中气孔单元数 )和气孔单元大小 (气孔单元所包含气孔数 )在叶片上呈有规律的分布 :前者由叶片中部向叶尖、叶缘逐圈增多 ,而后者逐圈减少。对这种分布格局的成因进行了讨论     

草原地区不同生态类型的植物生理特性的比较研究

比较研究了4种不同水分生态型植物在不同水分胁迫下的光合作用、叶片含水量和气孔阻力等生理指标的反应.结果表明,不同水分生态型植物抵御干旱的机制是不同的.中生植物主要是通过增加气孔阻力限制蒸腾失水,而旱生植物则依靠高浓度的细胞原生质减少水分的散失,后者保水效率远高于前者.植物从中生种到旱生种,生理特性亦显示出规律性的种间差异,叶片含水量和气孔阻力水平降低,而单位叶面积的净光合速率增加.     

草原地区不同生态类型的植物生理特性的比较研究

比较研究了４种不同水分生态型植物在不同水分胁迫下的光合作用、叶片含水量和气孔阻力等生理指标的反应。结果表明,不同水分生态型植物抵御干旱的机制是不同的。中生植物主要是通过增加气孔阻力限制蒸腾失水,而旱生植物则依靠高浓度的细胞原生质减少水分的散失,后者保水效率远高于前者。植物从中生种到旱生种,生理特性亦显示出规律性的种间差异,叶片含水量和气孔阻力水平降低,而单位叶面积的净光合速率增加。     

The effects of (2RS, 3RS)-1-(4-chlorophenyl)-4, 4-dimethyl-2-(1H-1,2,4 triazol-1-yl) pentan-3-ol (Paclobutrazol:PP333) and root pruning on the growth,water use and response to drought of Colt Cherry rootstocks

The effect of (2RS, 3RS)-1-(4-Chlorophenyl)-4, 4-dimethyl-2-(1H-1,2,4 triazol-1-yl) pentan-3-ol (PP333) on the growth and transpiration of normal and root pruned colt rootstocks was measured. PP333 reduced plant height, stem diameter increment, leaf number, area and weight and stem weight. Root pruning reduced root, leaf and stem weight, and plant height in control plants. PP333 reduced both total water use and transpiration per unit leaf area and increased stomatal resistance. In control plants root pruning also reduced total water use and increased stomatal resistance. 15 days after the beginning of the experiment half the plants in all treatments were allowed to dry out. The effects of drought, i.e. reduced transpiration, growth and leaf water potentials, were smaller in PP333 treated than in control plants.     

Identifying soybean lines differing in gas exchange sensitivity to humidity

The ratios of root length and root weight to leaf area differed within and between cultivars of soybean. Plants with low ratios of root length or weight to leaf area had leaf conductances and net photosynthetic rates more reduced by a given increase in the leaf to air water vapour pressure difference around a single leaf than plants with high ratios. Plant and root system conductances to water were estimated as transpiration rate per unit leaf area divided by the difference between substrate and leaf water potentials, and by the rate of water flow through pressurised root systems. These conductances were greater in plants with large, as compared with small, root systems per unit leaf area. Cultivar rankings in sensitivity of gas exchange to humidity were consistent in controlled environment chambers and in field tests.     

弱光下生长的葡萄叶片蒸腾速率和气孔结构的变化

 植物能够对生长环境产生生态适应性,这种适应性可从气孔导度、光合速率、水分利用效率等生态指标上反映出来。为了研究葡萄蒸腾特性对弱光环境的适应性变化,本试验以‘京玉’葡萄幼苗（Vitis vinefera cv. Jingyu）为试验材料,通过遮光处理（2个处理,分别遮光65%和85%）营造弱光环境,测定了在弱光环境下生长的葡萄叶片蒸腾速率、气孔导度、水分利用效率对光照强度的响应,同时用扫描电镜技术观察了气孔的发育。结果表明,弱光环境下生长的葡萄幼苗,叶片的水势较高,但水分利用效率较低,叶片蒸腾速率和气孔导度变化对光照强度的响应缓慢,而自然光下生长的葡萄叶片则反应较迅速。通过对气孔结构的研究发现,与自然光照环境下生长的植株相比,在弱光环境下生长的葡萄幼苗,叶片下表皮的气孔横轴变宽,大小气孔之间差异减少,气孔外突,表皮细胞变大甚至扭曲,角质层变薄。说明葡萄幼苗能够对弱光环境产生适应性变化,其蒸腾特性的变化与其气孔结构的变化相关,具有一致性。     

PHYSIOLOGICAL STUDIES ON THE VERTICILLIUM WILT DISEASE OF TOMATO

The water loss per unit leaf area of tomato plants was decreased after inoculation with Verticillium albo-atrum. When diseased plants began to wilt water loss temporarily increased, but then rapidly decreased to become less than that of healthy plants grown under conditions of adequate or restricted water supply.
The transpiration of excised leaves from plants grown with a restricted water supply was reduced, but not so severely as that of comparable leaves from infected plants. Water loss from leaves on infected plants was reduced irrespective of any blocking of the petiolar xylem.
The rate of water loss from turgid leaf disks on mannitol solutions, and the rate of water uptake of leaf disks on water was similar for disks cut from wilting or turgid leaves of diseased plants or healthy plants grown with an adequate or restricted water supply.
Disease or poor water supply reduced leaf growth but had no effect on the rate of leaf initiation. Although the density of stomata was higher on leaves of diseased plants the stomatal area was less than on healthy plants.
The resistance to water flow in diseased stems was high and was correlated with vessel blockage. About half the blocked vessels contained hyphae. The severity and localization of symptoms in inoculated plants growing on susceptible or resistant rootstocks was directly related to the extent of invasion by the pathogen and to vessel blockage.
Experiments on the wilting activity of cell-free filtrates from cultures of the pathogen in vitro indicated that it produced a stable substance, not an enzyme, that caused wilting in cut shoots by blocking the end of the stem. It is suggested that an increasing internal water shortage causes major symptoms of disease.     

Response of Cowpeas to Salinity and (2-Chloroethyl) trimethyl-ammonium Chloride (CCC)

Recent investigations have demonstrated that the growth retardant, (2-chloroethyl) trimethyl-ammonium chloride (CCC) inhibits several aspects of vegetative growth. In solution culture experiments, reduction in plant growth and dry matter production was confirmed in cowpeas, Vigna unguiculata L, (cv. Makueni II), when treated with CCC. The growth retardant had negligible effect on the rate of transpiration per unit leaf area although it slightly increased the relative water content of leaves. Stomatal opening was suppressed by CCC treatment but the number of stomata per unit leaf area was increased by the growth retardant. Variations in mineral element content (K, Ca, N and Na) of shoots are presented and discussed in relation to CCC treatment.     

Abscisic acid triggers whole-plant and fruit-specific mechanisms to increase fruit calcium uptake and prevent blossom end rot development in tomato fruit

Calcium (Ca) uptake into fruit and leaves is dependent on xylemic water movement, and hence presumably driven by transpiration and growth. High leaf transpiration is thought to restrict Ca movement to low-transpiring tomato fruit, which may increase fruit susceptibility to the Ca-deficiency disorder, blossom end rot (BER). The objective of this study was to analyse the effect of reduced leaf transpiration in abscisic acid (ABA)-treated plants on fruit and leaf Ca uptake and BER development. Tomato cultivars Ace 55 (Vf) and AB2 were grown in a greenhouse environment under Ca-deficit conditions and plants were treated weekly after pollination with water (control) or 500 mg l(-1) ABA. BER incidence was completely prevented in the ABA-treated plants and reached values of 30-45% in the water-treated controls. ABA-treated plants had higher stem water potential, lower leaf stomatal conductance, and lower whole-plant water loss than water-treated plants. ABA treatment increased total tissue and apoplastic water-soluble Ca concentrations in the fruit, and decreased Ca concentrations in leaves. In ABA-treated plants, fruit had a higher number of Safranin-O-stained xylem vessels at early stages of growth and development. ABA treatment reduced the phloem/xylem ratio of fruit sap uptake. The results indicate that ABA prevents BER development by increasing fruit Ca uptake, possibly by a combination of whole-plant and fruit-specific mechanisms.     

Gas exchange of a desert shrub (Zygophyllum dumosum Boiss.) under different soil moisture regimes during summer drought

The effects of soil water potential on photosynthesis and transpiration of whole Zygophyllum dumosum Boiss. shrubs were examined with a field IRGA system during a rainless summer. Daily photosynthesis and transpiration activities were not notably different on a unit phyllode area basis among shrubs at naturally differing soil water potentials. Irrigation of shrubs caused phyllodes to increase significantly in water content and new leaflets to appear. Leaflets had three times as many stomata per unit area (23000 stomata cm^-2) as phyllodes (7100 stomata cm^-2) but photosynthesis and transpiration rates were not measurably different between irrigated and non-irrigated shrubs on a unit area basis. This finding suggests that sufficient soil moisture will lead to increased carbon uptake of the entire shrub simply because the total area of photosynthesizing tissue increases. Gas exchange rates appear to be controlled solely by atmospheric conditions under the stresses of summer.     

Mechanisms of stomatal movement in response to air humidity,irradiance and xylem water potential

Turgor, and osmotic and water potentials of subsidiary cells, epidermal cells and mesophyll cells were measured with a pressure probe and a nanoliter osmometer in intact transpiring leaves of Tradescantia virginiana L. Xylem water potential was manipulated by changing air humidity, light, and water supply. In a transpiring leaf the water potential of mesophyll cells was lower, but turgor was higher, than in cells surrounding the stomatal cavity owing to the presence of a cuticle layer which covers the internal surface of subsidiary and guard cells. Cuticular transpiration from the outer leaf surface was negligibly small. When stomata closed in dry air, transpiration decreased despite an increasing vapor-pressure difference between leaf and air, and the water potential of subsidiary cells dropped to the level of the water potential in mesophyll cells. We suggest that the observed decrease of transpiration at increasing vapor-pressure difference can be attributed to a shortage of water supply to the guard cells from subsidiary cells, causing turgor to decrease in the former more than in the latter. The leafs internal cuticle appears to play a special role in channelling the internal water flow during a water shortage.Abbreviations and Symbols VPD Vapor-pressure difference between leaf and air - PFD photon flux density - water potential     

Leaf responses to iron nutrition and low cadmium in peanut: anatomical properties in relation to gas exchange

Aims

This study evaluated how iron nutrition affect leaf anatomical and photosynthetic responses to low cadmium and its accumulation in peanut plants.

Methods

Seedlings were treated with Cd (0 and 0.2 μM CdCl₂) and Fe (0, 10, 25, 50 or 100 μM EDTA-Na₂Fe) in hydroponic culture.

Results

Cadmium accumulation is highest in Fe-deficient plants, and dramatically decreased with increasing Fe supply. The biomass, gas exchange, and reflectance indices were highest at 25 μM Fe²⁺ treatments, indicating the concentration is favorable for the growth of peanut plants. Both Fe deficiency and Cd exposure impair photosynthesis and reduce reflectance indices. However, they show different effects on leaf anatomical traits. Fe deficiency induces more and smaller stomata in the leaf surface, but does not affect the inner structure. Low Cd results in a thicker lamina with smaller stomata, thicker palisade and spongy tissues, and lower palisade to spongy thickness ratio. The stomatal length and length/width ratio in the upper epidermis, spongy tissue thickness, and palisade to spongy thickness ratio were closely correlated with net photosynthetic rate, stomatal conductance, and transpiration rate.

Conclusions

Cd accumulation rather than Fe deficiency alters leaf anatomy that may increase water use efficiency but inhibit photosynthesis.     

Abnormal stomatal behavior in wilty mutants of tomato

An attempt was made to explain the excessive wilting tendency of 3 tomato mutants, notabilis, flacca, and sitiens. The control varieties in which these mutations were induced are Rheinlands Ruhm for flacca and sitiens and Lukullus for notabilis. Although all 3 mutants are alleles of separated loci, they seem to react similarly to water stress. The mutants wilt faster than the control plants when both are subjected to the same water stress. It was demonstrated by measurements of water loss from whole plants that all 3 mutants have much higher rates of transpiration than the control varieties, particularly at night. The extent of cuticular transpiration was compared in both kinds of plants by measuring the rate of water loss from detached drying leaves coated with vaseline on the lower surface. The difference in cuticular transpiration between the mutant and the control plants seems to be negligible. However, various facts point to stomata as the main factor responsible for the higher rates of water loss in the mutant plants. The stomata of the latter tend to open wider and to resist closure in darkness, in wilted leaves, and when treated with phenylmercuric acetate. Stomata of the 2 extreme mutants, sitiens and flacca, remain open even when the guard cells are plasmolyzed. The stomata of the mutants also are more frequent per unit of leaf surface and vary more in their size.