托里阿魏叶片蒸腾调节规律动力学测定方法探索

以新疆荒漠自然条件下生长的托里阿魏(Ferula krylovii)为材料, 用高灵敏度湿度等传感器配合特制叶室, 记录和模拟分析了整个大型复叶的蒸腾耗水和蒸腾调节的动力学特性, 并与光合仪和称重法测定的结果进行对比。结果显示, 用传感器配合特制叶室, 监测到植物在短时间(1-2分钟)内的快速蒸腾动态调节及其日变化特征和参数, 根据这些参数可以分析同等条件下温度、光照和湿度等因子对蒸腾作用影响的相关性, 从而更精确地分析自然和高湿度条件下叶片的蒸腾耗水动力学特性, 提供其它方法无法观测的气孔对湿度变化的快速调节细节。同时, 由于该方法能够测定大尺度样品, 减少了其它方法由于仅能测定叶片局部而造成的因选点位置不同导致的取样误差、因气体样品量小造成的系统误差以及小叶室夹可能造成的机械压力胁迫。该方法与其它传感器结合, 能够更全面地获取植物在不同环境条件下的蒸腾耗水调节机制的相关参数, 理论上也可以远程遥控和连续监测, 为分析植物对环境的适应能力及其机制提供更为详细的动态图景。     

低空气湿度下气孔运动的调控

植物气孔应答气候环境因子的机制,一直是植物抗逆生理研究领域的热点课题。空气湿度是主要的气候环境因子之一,人们很早就发现降低空气湿度能导致气孔开度变小,但到目前为止,对调控这一生物学过程的机制还知之甚少。本文概述近年来在植物气孔应答低空气湿度信号的运动规律、水被动反馈假说、水主动反馈假说、水力调节与代谢调节的关系等方面的进展,并基于进化学的理论,提出了水力调节和代谢调节的反向消长模式,以期解释大量物种气孔对低空气湿度的不同应答反应。     

云南干热河谷水库气候效应对车桑子幼苗生长发育的影响及其作用机制

干热河谷地区水电站建设对当地植被的潜在影响是一个值得关注的生态学问题。车桑子是当地植被灌木层的主要成分,开展水库气候效应对车桑子生长、发育影响的研究具有现实价值。以车桑子的实生幼苗为材料,将土壤含水量控制为13%、7%和1.5%,空气湿度控制为50%、65%和75%,从幼苗生长、构件发育、根系发育、生物量分配等方面研究了降水减少和大气湿度增加的气候效应对车桑子的影响,通过叶绿素含量、Fv/Fm、丙二醛(MDA)含量和叶片可溶性糖含量等指标,从光合系统特性、膜质过氧化和渗透调节3个方面研究了车桑子的受损与适应机制。结果表明,土壤干旱能够抑制车桑子幼苗高生长和根系发育的各项指标,并促进生物量向根系分配;当大气湿度增加时,幼苗高生长和根长虽呈增加趋势,但生物量积累、根系发育指标及RMR却具有单峰效应,显示空气湿度过高时对其生长发育具有抑制作用。综合而言,由于大气湿度增加能够部分补偿土壤的干旱效应,干热河谷区水库建设的气候效应不会对车桑子幼苗的生长和发育产生重要影响。结果还表明,土壤干旱和大气湿度变化对叶绿素含量无影响,土壤水分胁迫和空气湿度下降导致Fv/Fm显著下降,说明光合电子传递链受损是车桑子光合抑制的主要原因;土壤水分胁迫导致MDA含量升高,说明细胞膜质过氧化是车桑子幼苗受损的重要机制;而土壤干旱导致叶片可溶性糖含量升高,说明车桑子幼苗具有较好的渗透调节机制。研究结果对评估干热河谷区水电站建设对植被的影响具有参考价值。     

秦岭火地塘林区锐齿栎群落中6种植物光合特性研究

用Li-6400便携式光合测定系统测定了火地塘林区主要成林树种锐齿栎群落中6种植物的光合特性。结果表明：（1）从林冠层到草本层,光合有效辐射强度明显减弱,并且乔木层、灌木层和草本层之间的差异均达到了显著水平（P〈0．05）;（2）乔木层锐齿栎的光合速率日变化为“双峰”曲线,表现出明显的“午休”现象,而林下植物灌木层和草本层光合速率日变化整体上呈“单峰”曲线,无“午休”现象;（3）光饱和点和光补偿点均表现为乔木〉灌木〉草本。表明植物光合“午休”现象是由中午高光强、高气温和低湿度引起的。并非某些植物的特性．植物的光合特性与其生境特点相符。     

内蒙古半干旱草原区沙地植物群落光合特征的动态研究

沙蒿(Artemisia intramongolica)群落是半干旱草原地区沙地的重要植被类型,分别在植物的生长前期、中期、盛期和后期采用便携式光合测定仪和大型同化分析仪测定了沙蒿叶片和沙蒿群落的光合动态。单叶和群落的光合速率日进程类型随气候的不同而异,瞬时光合速率主要决定于光合有效辐射强度(PAR)。土壤干旱大大降低了单叶和群落的光合能力,晴天土壤湿润时气温和空气湿度控制着叶片的光合速率,午间大气湿度降低是光合午休的主要外因。叶片的蒸腾速率与气温呈显著线性相关,植物的光能和水分利用效率也主要取决于PAR和气温,随着PAR和气温的升高利用效率下降。沙蒿叶片光能利用效率在后期也能保持较高水平。沙蒿对土壤干旱和高温具有一定的适应性,在土壤湿润时能迅速提高光合速率,形成较大的生物量。但是沙蒿的蒸腾速率高,水分利用效率低。研究认为,沙蒿通过对土壤干旱和高温的忍耐机制而保持长时间较高的光能利用效率,并在土壤湿润时迅速提高光合能力和积累干物质来适应半干旱的沙地环境,而且依靠高蒸腾速率和强的水分吸收能力来竞争性抑制其他植物的生长。     

珍稀蕨类植物扇蕨光合速率与环境因子的关系

利用CO2光合测定仪分析了引种栽培的扇蕨叶片的光合补偿点和饱和光强,通过控制叶室的光合有效辐射、CO2浓度、温度和相对湿度,分析了叶片的羧化效率和CO2补偿点,并进行光合有效辐射、温度或相对湿度对光合速率影响的研究。扇蕨叶片光补偿点的光强为5.8μmol·m-2·s-1,饱和光强约为1000μmol·m-2·s-1。叶片的羧化效率为0.02665,CO2补偿点为66.1μmol·mol-1。叶片光合速率在20℃时达到最大值,最适温度为17～27℃。相对湿度20%～80%的试验范围内,叶片光合速率随湿度增加而增大,最适相对湿度条件在60%以上。     

土壤水分充足条件下羊草和大针茅光合速率午间降低的原因

本文研究了典型草原地带两个主要建群种,羊草和大针茅在没有土壤水分胁迫情况下的光合作用日进程,并分析了光合午间降低的原因。光合作用日进程为午前高峰型;午间,光合速率有所下降。光合午间降低的主要原因是大气湿度减小,引起叶片含水量和气孔传导率下降所致。午间温度和光强升高,导致光呼吸速率增大是次要原因。CO2浓度降低和光合产物积累对光合午间降低也起一定作用。而生物节律与光合午间降低没有关系。     

梭梭和多枝柽柳的枝干光合及其主要影响因子

荒漠植物长期演化过程中保留了枝干光合(Pg)的特性,枝干光合有效减少局部碳损失,且在维持植物正常生理代谢方面发挥重要作用.本研究以古尔班通古特沙漠南缘荒漠植物梭梭和多枝柽柳为对象,利用Li-Cor 6400便携式光合仪与特制叶室相结合监测枝干与叶片光合速率,同时辅以枝干/叶片功能性状(叶绿素含量、含水量、叶/枝面积、碳...     

半干旱黄土丘陵区五种植物的生理生态特征比较

通过测定陕北黄土丘陵区5种植物在旱季的光合速率、蒸腾速率和叶水势日变化,将植物划分为不同的水分生态适应类型.结果表明:柳枝稷的光合生理特征属于高光合、低蒸腾和高水分利用效率类型,其抗旱适应性特征属于高水势延迟脱水类型;苜蓿属于高光合高蒸腾低水分利用效率类型,耐旱性为高水势延迟脱水型;达乌里胡枝子属于低光合、低蒸腾、低水分利用效率类型,耐旱性为高水势延迟脱水型;白羊草属于高光合、蒸腾较高的水分利用效率中等型,耐旱性属于能忍耐脱水造成的低水势的一类.沙打旺属于高光合中等蒸腾速率中等水分利用效率类型,耐旱性为低水势延迟脱水型.     

光下无CO_2气体处理对叶片光合强度的影响

小麦等C_3植物的叶片在光下经无CO_2或低CO_2气体处理后,通入高CO_2气体,光合强度出现“升、降、升”的波动,而玉米等C_4植物无此现象。不同植物的光合波动幅度不同。强光、高CO_2、低O_2等能缩短第一次光合上升时间,增大光合下降幅度;而低CO_2、高O_2等则减少光合下降幅度。此现象与RuBP及ATP的含量变化有关。     

EFFECTS OF DESICCATION AND ILLUMINATION ON PHOTOSYNTHESIS AND PIGMENTATION OF AN EDAPHIC POPULATION OF TRENTEPOHLIA ODORATA (CHLOROPHYTA)1

The photosynthetic rates of Trentepohlia odorata (L.) Martius growing on wall surfaces in Singapore changed throughout the day with a maximum in midmorning and decreasing thereafter during the day. Optimum temperature for photosynthesis was 25° C. Different levels of air humidity also affected photosynthetic rates with low relative humidity reducing the rates and efficiency of photosynthesis. Our results suggested that T. odorata was able to maximize its rate of photosynthesis before photoinhibitory light levels were reached and that its growth might be dependent on high levels of atmospheric relative humidity, which may serve as a source of water supply for the alga.     

Photosynthesis at ambient and elevated humidity over a growing season in soybean

Daytime rates of net photosynthesis of upper canopy leaflets of soybeans were compared on 17 days for leaflets exposed to air at the ambient humidity and at a higher humidity. Leaflets at the higher humidity had higher rates of net photosynthesis on 16 of the 17 days. The daily total of net photosynthesis of leaflets at the higher humidity was on average 1.32 times that for leaflets at ambient humidity. A strong limitation of net photosynthesis by ambient humidity was found throughout the growing season.     

亚高温下不同空气湿度对番茄光合作用和物质积累的影响

为了研究亚高温下不同空气湿度对番茄植株光合作用及物质积累的影响,本试验利用人工气候室,在11:00—15:00平均温度为33℃的亚高温条件下,设置3个空气相对湿度处理,分别为70%～80%(高湿)、50%～60%(中湿)和不加湿的30%～40%(低湿)。结果表明:在处理25d时,高湿处理番茄叶片叶绿素含量、净光合速率显著高于低湿处理,而低湿处理果实空洞率比高湿处理高18.4%(P<0.05);在33℃亚高温条件下,70%～80%的相对湿度有利于光合作用的增强和果实品质的提高。     

Asymmetric patchy stomatal closure for the two surfaces of Xanthium strumarium L. leaves at low humidity

Images of chlorophyll fluorescence were used to demonstrate patchy stomatal closure at low humidities in leaves of well-watered Xanthium strumarium plants. The pattern and extent of patchy stomatal closure were shown to be different for the two surfaces of amphistomatous leaves by taking images of leaves with CO₂ available to only one leaf was exposed to low humidity, patchiness was more extensive on that surface. Gas-exchange experiments were also conducted to determine the apparent photosynthetic capacity of the mesophyll (photosynthesis rate at constant c_i when it was supplied with CO₂ through both surfaces or through each surface alone. These experiments showed declines in the apparent photosynthetic capacity of the mesophyll at low humidities that were consistent with patchy stomatal closure on one or both surfaces. The results suggest that patchy stomatal closure can be a factor in the steady-state reponses of stomata to humidity. In amphistomatous leaves this is further complicated by the fact that patches on one epidermis may not coincide with those of the other surface.     

4种针叶幼树的光合生理特性与大气湿度关系的研究

应用２２５ＭＫ３ＩＲＧＡ在室内控制的环境条件下测定研究了侧柏,樟子松,油松和杆等４种针叶幼树的净光合速率,暗呼吸强度,光补偿点与大气湿度的关系,研究结果证明,各种幼树的净光合速率均随大气湿度的降低而减弱,二者之间的关系可用ｙ＝ａ＋ｂｌｎｘ方程表达。其变化速率（ｂ）在树种间有明显差异,它可以反映出不同树种对大气干旱忍耐力即抗旱性的差异“ｂ＂值小的树种表明其抗旱性强。依此排列出的上述４种幼树的抗旱性强     

Plant response to atmospheric humidity

Abstract. Plants growing in environments differing in prevailing humidity exhibit variations in traits associated with regulation of water loss, particularly cuticular and stomatal properties. Expansive growth is also typically reduced by low humidity. Nevertheless, there is little evidence in plants for a specific sensor for humidity, analogous to the blue light or phytochrome photoreceptors. The detailed mechanism of the stomatal response to humidity remains unknown. Available data suggest mediation by fluxes of water vapour, with evaporation rate assuming the role of sensor. This implies that stomata respond to the driving force for diffusional water loss, leaf-air vapour pressure difference. Induction of metabolic stomatal response to humidity may involve signal metabolites, such as abscisic acid, that are present in the transpiration stream. These materials may accumulate in the vicinity of guard cells according to the magnitude and location of cuticular transpiration, both of which could change with humidity. Such a mechanism remains hypothetical, but is suggested to account for feedforward responses in which transpiration decreases with increasing evaporative demand, and for the apparent insensitivity of stomatal aperture in isolated epidermis to epidermal water status. Other responses of plants to humidity may involve similar indirect response mechanisms, in the absence of specific humidity sensors.     

Stomatal responses to humidity in air and helox

Abstract. Stomatal responses to humidity were studied in several species using normal air and a helium: oxygen mixture (79:21 v/v, with CO₂ and water vapour added), which we termed 'helox'. Since water vapour diffuses 2.33 times faster in helox than in air, it was possible to vary the water-vapour concentration difference between the leaf and the air at the leaf surface independently of the transpiration rate and vice versa. The CO₂ concentration at the evaporating surfaces ( c_i ), leaf temperature and photon flux density were kept constant throughout the experiments. The results of these experiments were consistent with a mechanism for Stomatal responses to humidity that is based on the rate of water loss from the leaf. Stomata apparently did not directly sense and respond to either the water vapour concentration at the leaf surface or the difference in water vapour concentration between the leaf interior and the leaf surface. In addition, stomatal responses that caused reductions in transpiration rate at low humidities were accompanied by decreases in photosynthesis at constant c_i , suggesting heterogeneous (patchy) stomatal closure.     

Spore Germination and Mycelial Growth of Streptomycetes at Different Humidity Levels

This study is the first to show the ability of streptomycetes to develop at a very low humidity level. All of the streptomycetes studied produced growth at low humidity (a_w 0.86 and 0.67). This capacity was most markedly pronounced in Streptomyces odorifer, whose spores were capable of germinating, and mycelial germs increased in length, at the air humidity a_w 0.50. The formation of lateral branches (mycelium branching) at this humidity was noted only in single S. odorifer germs and only after 72 h of incubation. Study of streptomycete growth on an agarized medium with different osmotic pressures, created by various glycerol concentrations in the medium, showed that, at a_w 0.67, the spores of all the streptomycetes studied germinate, producing mycelial germs but not microcolonies. The ecological significance of mycelial prokaryotes in soil microbial communities that develop and function under conditions of extremely low humidity is discussed.     

高温和低湿对干热河谷7个植被恢复树种光合参数的影响

采用人工气候室控制环境条件,研究了高温（30℃和40℃）对印楝（Azadirachta indica A．Juss．）、木豆[Cajanus cajan（Linn．）Huth]、赤桉（Eucalyptus camaldulensis Dehn．）、蓝桉（E．globulus Labillardiere）、柠檬桉（E．citriodoraHook．）、大叶相思（Acacia auriculiformis A．Cunn．）和麻风树（Jatropha curcas Linn．）7个干热河谷植被恢复树种幼苗叶片光合参数的影响,以及低湿条件对麻风树幼苗叶片光合参数的影响,并对高温及低湿条件下各树种叶片光合参数与叶片含水量的关系进行了探讨。结果表明：在高温条件下,供试树种叶片的净光合速率（Pn）和Fv／Fm值均随叶片含水量的提高逐渐增加,但在40℃条件下各树种的Pn以及刚nn值均明显降低,表明叶片含水量高有利于各树种叶片Pn和n／Fm的提高,而40℃高温则对其Pn和Fv／Frn有明显抑制作用。在非干旱条件下,高温对各树种幼苗的Pn、气孔导度（Gs）、胞间c0：浓度（ci）和蒸腾速率（Tr）均有不同程度影响。在40℃条件下,供试树种中印楝和赤桉幼苗的Pn降幅最小;大叶相思、蓝桉和木豆幼苗的Gs明显增加;各树种幼苗的ci均明显提高;除印楝外,其他6个树种幼苗的Tr明显加剧且叶片水分利用效率降低。在叶片含水量较高的状况下,供试7个树种中印楝和赤桉幼苗的FV／Fm值受高温的影响较小。在空气相对湿度20％的条件下,麻风树幼苗的Pn、Cs、ci及Tr均明显降低,且均随叶片含水量的提高而增加,表明叶片含水量下降是麻风树幼苗光合作用减弱的重要影响因素。研究结果表明：干热河谷地区的高温引起的植物光合限制以非气孔因素为主导;在供试的7个树种中,印楝和赤桉对干热河谷高温干旱生境的适应或忍耐能力较强。