田间小麦叶片光合作用“午睡”现象的研究

小麦叶片的光合作用有明显的“午睡”(即“中午降低”现象)。 光合作用的“中午降低”只是在较小的程度上与大气CO_2浓度下降有关,而与中午前后颇低的空气相对湿度和较高的温度引起的饱和差的增加有很大的关系。通过增加空气湿度(伴随降温)缩小饱和差,不仅消除了小麦叶片的“午睡”现象,而且显著地提高了净光合作用速率。 提出了一个解释光合作用“午睡”机理的图解。     

松嫩平原西部林网生态场中玉米光合生态研究

东北松嫩平原林网生态场(Ecofield)中主要气候因子对玉米(Zea mays)光合作用影响的研究表明：在整个生长季中,玉米的瞬时光合速率与气温、光强正相关;日光合量则与空气温、湿度正相关。林网中部和东部(10—20H,H为1树高)玉米的光合日进程基本无午休现象,仅两侧主林带附近(1H、5H、25H)仍有午休;与此相应,日光合量也以中、东部高于两侧,这是由于林网中部的气温和湿度高于两侧。通过综合分析,发现午间空气湿度低是造成光合午休的主要原因,在东北松嫩平原,空气温、湿度是制约玉米光合作用主要的气候因子,其中气温是主导因子;光照不是限制因子。防护林可提高林网中的空气温、湿度,从而提高玉米的生产力。     

田间大豆光合午休原因的综合研究

本研究利用主成分分析构造同归模型,利用典型相关分析等方法,对自变量的重要程度进行排序,确定了光合午休的主要原因是气孔因素限制所致.光抑光合也是一个值得注意的因素,但不是主要因素.空气相对湿度、叶片与大气间水汽压差是诱发气孔限制的重要因素.当空气相对湿度较为适中时,叶温的影响较小,在空气相对湿度变坏的情况下,叶温才对光合午休有重要影响.     

西藏高原地区引种的大田西瓜的一些光合特性（简报）

引种到西藏高原地区的大田西瓜,其叶片光合作用的光补偿点约为250μmol@m-2@s-1,光饱和点约为860μmol@m-2@s-1.开花初期(6月)的净光合速率(Pn)日变化为单峰曲线,未出现"光合午休”现象.故认为,因雨季造成的土壤水分充足可能是这一地区大田西瓜不产生光合午休的主要原因.大田西瓜的水分利用效率在上午900和1100时较高,是蒸腾作用较低的结果.     

小麦叶片日光合高值持续时间基因型差异的初步研究

首次把“日高值光合作用持续时间”作为重要的光合特性进行了基因型比较研究,研究了不同基因型小麦开花期旗叶光合速率的日变化和日光合量的变化,提出了“日光合高值持续时间”的概念。结果表明：日光合高值持续时间和日光合量在基因型间存在显着差异．所有基因型都存在不同程度午休现象,矮秆、大穗基因型午休现象较轻,有利于日高值光合持续时间。日光合高值持续时间长,日光合量大,有利于干物质生产。     

植物光效生态学研究 Ⅰ.小麦光合作用午休的原因

本文报道了用小麦作材料,从作物生理生态特性方面研究了小麦光合作用午休的原因。试验结果证明:在中午前后,小麦叶片气孔开关数目与光合作用午休密切相关;大部分小麦光合作用午休与生物节律无关;中午遮光后,光合作用加强和生物学产量提高,说明光合产物的累积是形成光合作用午休的重要因素之一。     

陕西渭北旱塬土壤—植物—大气连续体中水分运转规律的研究──Ⅴ．田间冬小麦土壤—叶片途径水运转阻力研究

采用Ｍｉｓｈｉｏ和Ｙｏｋｏｉ（１９９１）的方法,在水分运转阻力短期内（如几个小时）恒定不变的假设下,研究了田间冬小麦土壤—叶片途径水分运转阻力．结果表明,一天中,当气孔没有“午休”现象或“午休”现象不明显时,冬小麦土壤—叶片途径水分运转阻力在白天保持恒定,到夜晚则明显增大;当气孔“午休”现象较明显时,冬小麦土壤—叶片途径水分运转阻力在气孔“午休”期间和夜晚明显增大,其余时间基本保持恒定．夜间和气孔“午休”期间阻力增大的原因不确定．土壤干旱条件下冬小麦土壤—叶片途径水运转阻力显著大于土壤湿润条件下,表明水运转阻力与植物抗旱性有关．土壤干旱条件下施肥处理冬小麦土壤—叶片途径水运转阻力显著大于不施肥处理,而土壤湿润条件下显著小于不施肥处理,表明施肥对植物具有调节作用,使之更好地适应干旱环境．     

浅谈光合作用在农业生产上的应用

从以下８个方面对植物的光合作用在农业生产上的应用进行了概述,利用间作套种;增施二氧化碳”气肥”;延长光合作用时间;培育高光效作物品种;选育有利于光合作用进行了株型;避免或减轻农作物“午休”期间的影响;合理应用生长调节物质;利用不同色光改善光合产物品质。     

高寒矮嵩草草甸群落光合作用的“午休”现象

自然条件下,植物光合作用的日变化在全晴天多数表现为"午休"型。然而,长期以来,许多人认为在青藏高原的广大地区,植物的光合作用井不存在"午休"现象,并认为这是高原植物的光合生理特性（黄庆榴等1962,苏梯之和潘锦珊1981,张树源1988）。这到底是不是一种普遍现象？是高原独特自然环境条件决定的,还是高原植物本身具有的生理特性？为了进一步探讨这些问题,我们从1990年起,应用红外CO。分析技术在高寒矮嵩草草甸进行了群落光合作用气体代谢的研究,发现矮嵩草草甸的群落光合作用表现出一定程度的"午休",并对其形成机理进行了初步…     

不同穗型小麦品种旗叶光合作用日变化的研究

在大田条件下,对多穗型小麦品种豫麦49和大穗型小麦品种周麦13的旗叶净光合速率（Pn)及基影响因素,包括叶温（T1）、光合有效辐射（PAR）、蒸腾速率（Tr)、气孔导度（C）、细胞间隙CO2浓度（Ci)等日变化的测定结果表明,开花期2品种都存在光合“午休”现象,豫麦49Pn日变化呈双峰曲线,峰值出现在10：00和14：00,周麦13Pn日变化为单峰曲线,峰值在10：00。相关分析表明,开花期的温度和光照对豫麦49旗叶光合已造成一定程度的影响,此期的光温条件较有利于周麦13旗叶的光合作用。灌浆中期2品种均表现出一降不起型的严重“午休”现象,在强光、高温下,豫麦49旗叶Pn比周麦13降低明显。     

城市遮阴环境变化对大叶黄杨光合过程的影响

城市遮阴与自然生态系统遮阴环境不同,它由城市中的建筑、基础设施等人工构筑物所产生,并对植物光合过程产生影响。采用Li-6400便携式光合作用测定系统对北京市不同建筑遮阴环境下的生态因子特征及大叶黄杨光合参数特性进行了现场实验对比观测与分析。研究显示:(1)城市建筑或基础设施布局或格局变化导致建筑遮阴环境光、温等生态因子的差异性变化,主要体现在光合有效辐射(PAR)在时间分布及强度上的显著差异。(2)遮阴改变大叶黄杨的光合参数,日净光合速率曲线为不规则单峰型,由遮阴进入太阳直射时,净光合速率(Pn)明显升高,随遮阴程度加重峰值时间有后延现象,完全遮阴时净光合速率最低。(3)大叶黄杨叶片在有一定时间太阳直射的中度遮阴(2.3h和5.5h)下适应性良好,日均净光合速率、光补偿点(LCP)、光合能力(P_nmax)、叶面积(LA)、比叶重(LMA)没有显著差异,植物主要通过光合色素含量及组成的改变来适应太阳直射时间变短(2.3h)的遮阴环境。(4)遮阴改变植物的光暗适应策略,没有阳光直射的重度遮阴下,大叶黄杨通过其光合、形态、光合色素等多方面的改变来适应遮阴环境,建筑重度遮阴严重影响植物光合过程。探讨了不同程度建筑遮阴对植物光合作用的影响及植物的适应机制,为基于提高其生态服务功能的树种配置和城市规划提供科学依据。     

6种热带雨林木本植物幼苗光合诱导的研究

 在晴天上午适宜条件下,测定了生长在模拟林下光环境中的6种热带雨林木本植物幼苗的光合特性和光合诱导特征。6种植物分别为先锋树种大穗野桐(Mallotus macrostachys),冠层树种绒毛番龙眼(Pometia tomentosa)、玉蕊(Barringtonia pendala)、望天树(Shorea chinensis)、滇南插柚紫(Linociera insignis)和林下灌木睫毛粗叶木(Lasianthus hookeri)。研究结果表明：暗处理3 h的叶片经连续饱和强光照射后,6种植物的净光合速率呈s形到双曲线形。6种植物达到90%最大净光合速率的时间为4.4～12.5 min,这与所报道的其它热带雨林中一些阴生植物的诱导速率相近。大穗野桐和睫毛粗叶木的诱导速率最快,达到50%和90%最大净光合速率的时间为其它4种冠层植物幼苗的1/2至1/3。诱导过程中,最大气孔导度对强光的响应明显滞后于净光合速率。充分诱导的叶片在黑暗中20 min后,6种植物的诱导状态都较高。其中,大穗野桐的诱导状态消失相对较快,这可能与其气孔导度和羧化能力的快速降低有关。玉蕊诱导状态的消失主要与生化限制有关,因为此时它的气孔导度仍维持相对较高的值。而睫毛粗叶木较高的气孔导度和羧化能力的维持导致了很高的诱导状态。林下植物这种对强光的快速反应和黑暗中高的维持状态对有效利用光斑具有重要的意义,这与其一生中在林下生长和更新的特点是一致的。     

Studies on Characteristics of Photosynthetic Ecology in Leymus chinensis

This paper deals with light-photosynthesis curve, temperature-photosynthesis curve, diurnal changes of photosynthesis, and effects of water content and nitrogen in soil on photosynthetic characteristics of leaves of Leymus chinensis. The results obtained are as follows: 1. Light-photosynthesis curve of Leymus chinensis approximates to a hyperbola below light saturation point, and the influence of light intensity on photosynthesis is expressed by light intensity coefficient of photosynthesis. When Leymus chinensis was grown in a good water condition, its light intensity coefficient was 1.33 mg CO2· dm-2· h-1 · klx-1 at 5 klx light intensity, and light saturation point was 50 klx, and net photosynthetic rate at light saturation condition was about 31 mgCO2 · dm-2 · h-1. Temperature-photosynthesis curve of Leymus chinensis was a parabola, and optimum temperature of photosynthesis was 26–29 ℃. CO2 compensation point of Leymus chinensis was about 35 ppm. According to aforesaid characteristics of photosynthetic ecology, Leymus chinensis is a sun plant of C3 type. 2. The curve of diurnal changes of photosyn thesis in Leymus chinensis shows as a two-peak type in typical steppe, when water content of soil is about 14%. Major ecological factor which caused midday depressing photosynthesis in Leymus chinensis is atmospheric humidity. 3. The photosynthetic characteristics of Leymus chinensis, especially the leaf area and aerial biomass are closely related with water and nitrogen in soil. Irrigation has greater influence on photosynthetic production as compared with fertilization. The efficiency of increasing production is more notable, combining the measures of irrigation with fertilization. Leymus chinensis may be regarded as a eurytopic xerophyte according to the relationship between some photosynthetic characteristics and soil water. 4. Compared photosynthetic rate with leaf area in Leymus chinensis, the influence of the leaf area change on photosynthetic production is greater and is more remarkable during arid conditions. Therefore, irrigation and fertilization during dry season are effective measures to develop photosynthetic organ and to raise aerial biomass of Leymus chinensis rapidly.     

Ecological consequences of photomovement and photobleaching in the marine flagellate Cryptomonas maculata

Abstract The marine flagellate Cryptomonas maculata is bleached and eventually killed by exposure to even moderate white-light fluence rates. Bleaching affects all of its photosynthetic pigments and the kinetics depend on the fluence rate of the radiation the organisms are exposed to. Nitrogen-deficient cells which show a reduced pigment concentration and impaired photosynthetic efficiency tolerate bleaching white-light exposure far better than the normally colored cells. In their natural environment the organisms escape this situation by a pronounced negative phototaxis at fluence rates above 3.6 klx (= 15 W.m⁻²), while they show positive phototaxis at lower fluence rates. In nitrogen-deficient cells, however, though being less prone to photobleaching, negative phototaxis commences even at a fluence rate of about 830 lx (= 3.5 W.m⁻²). The ecological consequences of the remarkable light sensitivity and the phototactic orientation are being discussed.     

不同淹水条件下河竹叶片光合生理特性的变化

为阐明淹水条件下河竹( Phyllostachys rivalis H. R. Zhao)叶片的光合生理特性,设置对照组( CK,正常供水)及中度淹水(T1,水面高出基质表面5 cm)和重度淹水(T2,水面高出基质表面10 cm)处理组,对持续淹水360 d内2年生河竹幼苗叶片的光合气体交换参数、光响应曲线、光合特征参数、资源利用效率参数、光合色素含量及比值的变化进行了分析;在此基础上,探讨了河竹对淹水环境的适应性。结果表明：随淹水时间延长,2个处理组的多数光合生理参数呈“升高—降低—升高”的变化趋势,且多数参数在淹水90 d时达到峰值、在淹水270 d时达到谷值;T1组的各项光合生理参数总体上高于T2组。淹水30~180 d,与CK组相比,2个处理组的净光合速率( Pn)、蒸腾速率( Tr)、气孔导度( Gs)、胞间CO2浓度( Ci)和叶面饱和水汽压亏缺( Vpdl)总体上降低,表观量子效率( AQY)显著降低;气孔限制值(Ls)升高,而光饱和点(LSP)和光补偿点(LCP)显著升高;T1组的最大净光合速率(Pmax)略降低,而T2组的Pmax值则显著降低;但2个处理组的水分利用效率( WUE)、表观CO2利用效率( CUE)和表观光能利用效率(LUE)却无明显变化。淹水270和360 d,与CK组相比,2个处理组的Pn、Tr、Gs、Ls和Vpdl值降低,Pmax、LSP、LCP、WUE、CUE和LUE值显著降低,仅Ci值升高;T1组的AQY值略降低,而T2组的AQY值则显著降低。2个处理组的光响应曲线变化趋势与CK组相似,但随淹水时间延长,2个处理组的Pn值变幅不同,其中T1组的Pn值总体上高于T2组。淹水30和90 d,与CK组相比,T1组的叶绿素b( Chlb)和总叶绿素( Chl)含量总体上显著升高,而T2组的Chlb和Chl含量总体上显著降低;2个处理组的叶绿素a(Chla)和类胡萝卜素(Car)含量以及Chla/Chlb和Chl/Car值也显著降低。淹水180~360 d,仅2个处理组的Chla/Chlb值显著升高,而其他光合色素含量及比值总体上显著降低。综合分析结果显示：河竹叶片Pn值在淹水前期和中期下降的主要原因为气孔限制,而在淹水后期下降的主要原因为非气孔限制。河竹对淹水环境有较强耐受性,并对长期淹水有一定的适应性;此外,中度淹水条件下河竹叶片的光能转化效率、对光辐射的利用范围和对光变化的适应能力均高于重度淹水条件。     

Light and the correlation of chloroplast development and coupling of phosphorylation to electron transport

Coupling of phosphorylation to electron transport was examined by measuring the photosynthetic control ratio for broken wheat plastids isolated from seedlings at different greening stages. The photosynthetic control ratio progressively increased during greening and tight coupling was noted after granal stacking and thylakoid elongation. ADP impaired nonphosphorylating (state 2) electron transport rates of plastids at extremely early stages of greening and interfered with photosynthetic control measurements. Partially developed plastids exhibited low nonphosphorylating electron flow rates but did not exhibit high phosphorylating or uncoupled electron transport rates to the same extent as nearly developed plastids. Prolamellar body dispersal, primary thylakoid production, and the development of photosynthetic control were stimulated equally by 48 minutes of low irradiance, in cycles of 2 minutes every 2 hours, or by 9 hours of continuous light of moderate irradiance. Wheat plastids that greened for 6 hours in continuous light of moderate intensity did not exhibit photosynthetic control or much differentiation beyond the etioplast stage. It is concluded that plastid differentiation and the development of photosynthetic control early in greening under continuous light were limited by developmental time (dark time) rather than by either light intensity or duration.     

Light-Induced Adaptive Responses under Greenhouse and Controlled Conditions in the Fern Pteris cretica var. ouvrardii

The photosynthetic capabilities of the fern Pteris cretica var. ouvrardii were analysed by means of the light response curves of CO₂ exchange. In control growth conditions (greenhouse, low-light: 20–32 W m^?2); photosynthesis was shown to be saturated for low irradiance (20–25 W m^?2); the saturating photosynthetic rate, very low as compared to higher plants, was due to an extremely high intracellular resistance. When irradiance during the photosynthesis measurement was higher than 60–80 W m^?2, a constant decline of net CO₂ exchange as a function of time was observed. When irradiance during growth was enhanced, whether in greenhouse (20–250 W m^?2) or controlled (62 W m^?2) conditions, the first fronds that had developed in the new condition from the crosier stage exhibited decreased net maximal photosynthesis and a decreased efficiency in low light, but saturating irradiance was unmodified. However, the fronds whose entire differentiation (from meristem) occurred under these moderate irradiances (plants defoliated of all fronds and crosiers at the time of transfer), possessed more efficient photosynthetic characteristics than control plants. Pteris is able to grow under extreme shade conditions (4–8 W m^?2); light saturating photosynthesis and efficiency are higher under extreme shade than under control conditions. These adaptive characteristics indicate that Pteris is a well-adapted shade species.     

Aboveground biomass allocation patterns within Mediterranean sub-shrubs: A quantitative analysis of seasonal dimorphism

The monthly patterns of aboveground biomass allocation were studied in the branches of six Mediterranean sub-shrubs with different leaf phenology. Four of them were seasonally dimorphic species, and the remaining two were a winter deciduous and a cushion plant with photosynthetic stems. By the analysis of these species we aimed to identify different aboveground biomass allocation patterns within seasonally dimorphic species and to understand the role of seasonal dimorphism as a strategy to avoid the main stresses of mediterranean climate: summer drought and winter cold. The biomass allocation to the different living and photosynthetic fractions of 3-year-old branches was studied monthly for a minimum of 13 months per species. Leaf area (LA, mm²) and leaf mass per area (LMA, mg cm⁻²) measurements were used to characterize the diverse types of leaves of each species. Standing dead and senescent tissues accounted for a great percentage of the branch biomass of seasonally dimorphic species both during summer and winter. Different patterns of photosynthetic biomass allocation were found within the seasonally dimorphic species analysed. These patterns ranged from the moderate photosynthetic biomass oscillation of Salvia lavandulifolia to the almost deciduousness of Lepidium subulatum, and they were achieved by keeping alive, drying out or shedding different types of branches and leaves throughout the year. The formation of stress tolerant leaves and the reduction in the amount of photosynthetic biomass responded both to the occurrence of summer drought and winter cold. These results demonstrate that seasonal dimorphism is a flexible ecological strategy, as it comprises very different leaf phenologies and enables plants to escape both summer drought and winter cold.     

Complementary ecophysiological strategies combine to facilitate survival in the hostile conditions of a deep chlorophyll maximum

In the deep, cooler layers of clear, nutrient-poor, stratified water bodies, phytoplankton often accumulate to form a thin band or "deep chlorophyll maximum" (DCM) of ecological importance. Under such conditions, these photosynthetic microorganisms may be close to their physiological compensation points and to the boundaries of their ecological tolerance. To grow and survive any resulting energy limitation, DCM species are thought to exhibit highly specialised or flexible acclimation strategies. In this study, we investigated several of the adaptable ecophysiological strategies potentially employed by one such species, Chlamydomonas acidophila: a motile, unicellular, phytoplanktonic flagellate that often dominates the DCM in stratified, acidic lakes. Physiological and behavioural responses were measured in laboratory experiments and were subsequently related to field observations. Results showed moderate light compensation points for photosynthesis and growth at 22°C, relatively low maintenance costs, a behavioural preference for low to moderate light, and a decreased compensation point for photosynthesis at 8°C. Even though this flagellated alga exhibited a physiologically mediated diel vertical migration in the field, migrating upwards slightly during the day, the ambient light reaching the DCM was below compensation points, and so calculations of daily net photosynthetic gain showed that survival by purely autotrophic means was not possible. Results suggested that strategies such as low-light acclimation, small-scale directed movements towards light, a capacity for mixotrophic growth, acclimation to low temperature, in situ exposure to low O(2), high CO(2) and high P concentrations, and an avoidance of predation, could combine to help overcome this energetic dilemma and explain the occurrence of the DCM. Therefore, corroborating the deceptive ecophysiological complexity of this and similar organisms, only a suite of complementary strategies can facilitate the survival of C. acidophila in this DCM.     

Combined effects of elevated CO<Subscript>2</Subscript> concentration and drought stress on photosynthetic performance and leaf structure of cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.) seedlings

Drought stress is one of the main environmental factors limiting plant growth and productivity of many crops. Elevated carbon dioxide concentration (eCO₂) can ameliorate, mitigate, or compensate for the negative impact of drought on plant growth and enable plants to remain turgid and functional for a longer period. In order to investigate the combined effects of eCO₂ and drought stress on photosynthetic performance and leaf structures, we analyzed photosynthetic characteristics and structure and ultrastructure of cucumber leaves. The decline in net photosynthetic rate under moderate drought stress occurred due to stomatal limitation alone, while under severe drought stress, it was the result of stomatal and nonstomatal limitations. Conversely, eCO₂ improved photosynthetic performance under moderate drought stress, increased the lengths of the palisade cells and the number of chloroplasts per palisade cell under severe drought stress, and significantly increased the grana thickness under moderate drought stress. Additionally, eCO₂ significantly decreased stomatal density, stomatal widths and stomatal aperture on the abaxial surface of leaves under moderate drought stress. In conclusion, eCO₂ can alleviate the negative effects of drought stress by improving the drought resistance of cucumber seedlings through stomatal modifications and leaf structure.