Study of Diurnal Changes in Photosynthetic Rate and Quantum Efficiency of Grapevine Leaves and Their Utilization in Canopy Management

Photosynthetic rate and quatum efficiency of grapevine (Vitis vinifera L. cv. Sauvignon blanc) leaves were measured under the field with ample soil water supply, and in phytotron with ample supply of water and mineral nutrients, constant air humidity and CO2 concentration, and optimum air temperature, respectively. Under field conditions CO2 assimilation quantum efficiency of leaves reached its maximum in the morning, which was followed by continuous decrease and midday depression. The leaves intercepting more light energy in the morning showed a higher quantum efficiency. Those leaves subjected continuously to strong irradiance exhibited a more obvious and longer midday depression. Reduction of leaf light interception around midday could reduce midday depression. Shaded leaves had a higher quantum efficiency than leaves under direct sunlight. The diurnal changes in photosynthetic rate and quantum efficiency of leaves were shown to be closely related to the variations in mesophyll resistance to CO2. In phytotron experiments the photosynthetic quantum efficiency of leaves was reduced after a certain period of illumination not only at 1200 μmol · m-2 · s-1 PFD, higher than the saturating light of vine leaves (≈1000 μmol · m-2 · s-1), which was caused by "photoinhibition”, but also at 800 and 200μmol · m-2 · s-1, which was similar to "photoinhibition”. But photosynthetic quantum efficiency of leaves exposed continuously to a very weak PFD (100 μmol · m -2 · s-1) remained contant. The diurnal changes in mesophyll resistance to CO2 of vine leaves could be partly related to photoinhibition. It is considered that, under field conditions without soil water limitation, midday depression of vine leaf photosynthesis could be a result of an increase of the mesophyll resistance induced by multiple effects of strong light, high temperature and low humidity. A higher light interception by canopy plane in the morning may be advantageous to exploit higher photosynthetic potentiality of leaves, but a lower light interception in the middle of day may reduce midday depression. The north-south orientation plane can provide optimum light regime and improve photosynthetic environment in vineyards.     

铁皮石斛叶片光合作用的碳代谢途径

 利用LI-6400光合测定系统测定了不同天气条件下铁皮石斛（Dendrobium officinale）叶片24h CO2吸收的动态以及CO2吸收对光强和温度的响应。晴天的白天和夜间铁皮石斛都能吸收CO2,中午CO2吸收速率为负值, CO2的交换方式具景天酸代谢途径(CAM)的特点。阴雨天,只有白天吸收CO2,夜间表现为暗呼吸,光合作用碳代谢的途径为C3途径。在多云的天气条件下,白天吸收CO2,并持续至日落后。夜间21∶00仍有CO2吸收,23∶00以后至次日凌晨处于暗呼吸状态。在500 μmol·m-2·s-1光照件下,20℃出现最大CO2吸收值。在夜间,25℃时CO2的吸收速率最高。有光和无光条件下,低温或高温引起CO2吸收速率下降均为非气孔因素所致。晴天上午,铁皮石斛叶片的表观量子产额为0.035,光合补偿点为2.9μmol·m-2·s-1,饱和光强为500μmol·m-2·s-1,强光下出现光抑制现象。叶片受到强光预先照射后,即使光照减弱光抑制效应仍保持一段时间,致使光合补偿点升高,表观量子产额下降,相同光强下的CO2吸收效率降低。结果表明：铁皮石斛为兼性CAM植物,随着环境条件的变化,其光合作用在景天酸代谢途径(CAM)与C3途径间变化。     

热带雨林冠层树种绒毛番龙眼两种发育阶段叶片的光抑制

 通过测定西双版纳热带雨林冠层树种绒毛番龙眼(Pometia tomentosa)完全伸展嫩叶和成熟叶的叶片解剖、生理特征和雨季晴天自然条件下叶绿素a荧光以及午间强光对部分保护酶活性和膜脂过氧化作用的影响,探讨了两种不同发育阶段叶片光合作用的光抑制与强光和温度的关系。结果表明：绒毛番龙眼全展嫩叶和成熟叶表现出明显的解剖和生理特征差异。与全展嫩叶相比,成熟叶的叶片较厚、叶绿素含量高、气孔导度大、羧化效率高、最大净光合速率和光饱和点高,而气孔密度和保卫细胞长度没有显著差别。在雨季晴天自然条件下,午间最高光强可达2 200 μmol·m-2·s-1以上,最高叶温比气温高7～8 ℃,而成熟叶片的最高温度比全展嫩叶高1.5～2 ℃。上午随光强的增大,两种叶片的非光化学猝灭系数（NPQ）增大,PSⅡ原初光化学效率(Fv/Fm)、实际光化学效率［(Fm′_Fs)/Fm′］逐渐减小,在15∶30左右达最小。下午随着光强的减弱,Fv/Fm逐渐恢复,在傍晚基本恢复到清晨值。初始荧光(F0)在一天中变化很小。这表明绒毛番龙眼叶片光抑制是非辐射能量耗散增加引起的保护光合机构免受光破坏的保护性反应,而非光破坏。全展嫩叶比成熟叶有较低的光化学效率和非辐射耗散能力,对强光和高温处理的敏感性也较强,但在自然条件下一天中的光抑制程度与成熟叶没有显著差别。田间午间强光导致两种叶片的保护酶活性(超氧化物歧化酶,SOD;抗坏血酸过氧化物酶,APX)升高,而H2O2含量变化较小。其中,全展嫩叶的保护酶活性高,丙二醛(MDA)含量低。这表明自然条件下,与成熟叶相比,绒毛番龙眼全展嫩叶通过较低的光能利用效率、较低的叶温和高的保护酶活性减轻了强光高温的光抑制程度。     

冷锻炼对甜椒叶片光合作用及其低温光抑制的影响

以冷敏感植物甜椒 (CapsicumannuumL .)抗冷性不同的两个品种为试材 ,利用CIRAS 1光合测定系统和FMS2调制式荧光仪 ,在控温控光条件下分析比较了冷锻炼苗与未经锻炼苗的叶片光合特性、叶绿素荧光参数对温度的响应。结果表明 ,随着温度的降低 ,无论是否经过锻炼 ,低温主要通过抑制碳同化能力来影响光合作用 ,并使光能过剩 ,导致低温光抑制。提高环境CO2 浓度以增强暗反应对光能的利用 ,低温光抑制减轻。 5d的亚适温锻炼过程中甜椒叶片已发生一定程度的光抑制 ,但锻炼苗叶片能在低温下维持较高的光系统II光化学效率(ФPSII)、光化学猝灭系数 (qP)和光适应下光系统II最大光化学效率 (Fv′/Fm)值 ;冷锻炼提高了两品种低温下对光抑制的抗性 ,而且对抗冷品种的作用效果更明显     

10个秋菊品种的光合特性及净光合速率与部分生理生态因子的相关性分析

用CIRAS-2便携式光合测定系统测定了9月至10月10个秋菊[Dendranthema morifolium (Ramat.) Tvzel.]品种叶片的光合特征参数;在此基础上,对叶片光响应参数和CO2响应参数以及部分光合特征参数的日变化进行了比较分析;此外,还对净光合速率(Pn)与部分生理生态因子的相关性进行了分析.结果表明:10个秋菊品种的光补偿点(LCP)为92.83～167.37 μmol·m-2·s-1,光饱和点(LSP)为962.51～1 077.53 μmol·m-2·s-1,说明它们均为喜光植物;10个秋菊品种的CO2饱和点为1 060.46 ～1 485.48μmol·mol-1,CO2补偿点为77.62 ～ 133.16μmo1·mol-1,远大于一般的C3植物;各品种Pn的日变化呈典型的双峰型曲线,首峰(11～19μmol·m-2·s-1)出现在10:00左右,次峰出现在16:00左右,有明显的“午休”现象.相关分析结果表明:10个品种的Pn与气孔导度呈极显著正相关,与蒸腾速率呈显著或极显著正相关(品种‘关东新侠’、‘云龙凤舞’和‘日本黄’除外),与胞间CO2浓度呈显著或极显著负相关,与光合有效辐射强度和大气温度呈不显著正相关,与大气相对湿度和大气CO2浓度呈不显著负相关.早花品种‘太平的小鼓’和‘铜雀春深’具有较高的LSP以及较低的LCP和表观量子效率(AQY),对光照强度的适应范围较大,可栽培在光照较强的环境中;品种‘早粉盘’和‘檀香狮子’具有较高的LCP、AQY和LSP,对强光的利用能力较强;晚花品种‘关东新侠’、‘绿牡丹’和‘星光灿烂’具有较高的LCP和AQY以及较低的LSP,具有一定的耐阴能力,可种植在光照较弱的环境中.     

不同光照强度和温度对金钗石斛生长的影响

为了系统地研究不同光照强度下温度对金钗石斛(Dendrobium nobile)生长的影响,在金钗石斛分蘖期,于80μmol·m-2·s-1、160μmol·m-2·s-1、320μmol·m-2·s-1、640μmol·m-2·s-1的不同光强下,各设置5个温度(15℃、20℃、25℃、30℃、35℃)梯度对石斛进行处理。结果表明：石斛的生长与代谢随温度由低到高,表现出弱—强—弱的变化规律;80μmol·m-2·S-1光强下,石斛生长以25～30℃较为适宜;160μmol·m-2·s-1光强下则以20～25℃为适宜温度范围;320μmol·m-2·s-1与640μmol·m-2·s-1的中、强光照下,25℃处理石斛的生长优势尤为明显;不同光强下,石斛鲜重的增长大多以25℃处理更快,繁殖力则以20℃与25℃处理较高,各光强下的MDA含量随温度升高而先降后升,且均以25℃最低;可溶性蛋白质、可溶性总糖及叶绿素含量则表现出随温度由低到高而先增后减的趋势,其含量最高点均出现在25℃左右;净光合速率和叶绿素含量随光强和温度的变化趋势基本一致;各种光强下的暗呼吸速率均随温度升高而增大。因此,在不同的光照条件下,石斛生长的适宜温度均在25℃左右。光温处理引起石斛生理生化过程明显的相应变化表现出：高温和弱光照条件有利于石斛的株高增长,但不利于产量和质量提高;石斛的生长与MDA含量呈显著负相关(r80＝-0.9082、r160＝-0.9816、r320＝-0.8075、r640＝-0.8586),与可溶性糖含量呈一定正相关(r80＝0.7673、r160＝0.8892、r320＝0.8179、r640＝0.9278),并且石斛的生长与可溶性蛋白质含量、叶绿素含量、光合速率之间的变化趋势基本一致。     

杂交酸模叶片线粒体交替氧化酶呼吸途径在光破坏防御中的作用

以杂交酸模(Rumex K-1)为试材,研究了不同光强下线粒体交替氧化酶呼吸途径(AOX途径)对酸模叶片光破坏的防御作用.结果表明:在200 μmol·m-2·s-1弱光下,用水杨基羟肟酸抑制AOX途径后,Rumex K-1叶片的PSⅡ实际光化学效率、光合线性电子传递速率以及光合放氧速率均显著下降,非还原性QB反应中心显著升高,加重了叶片的光抑制,而活性氧清除机制上调,避免了活性氧的过量积累,部分缓解了Rumex K-1叶片的光抑制;在800 μmol·m-2·s-1强光下,AOX途径受抑,导致Rumex K-1叶片发生严重的光抑制,而此时活性氧清除机制的上调不足以缓解活性氧过量的积累.无论在强光还是弱光下,AOX途径在Rumex K-1叶片的光破坏防御过程中都起着重要作用,而且在强光下,AOX途径对叶片的光破坏防御作用是叶绿体内其他光破坏防御途径所不能代替的.     

Study on the Photosynthetic Characteristics of Eucommia ulmoides Leaves

A field study on the photosynthetic characteristics in Eucommia ulmoides Oliv. was conducted using a LI-6200 Portable Photosynthesis Analysis System as a measuring device and the modified half-leaf method. It was revealed that the light-saturating photosynthetic rate measured in leaves was in a range of 6~10 μmol CO2 · m-2 · s-1, and the lowest apparent quantum requirement was about 17. The CO2 compensation concentration of photosynthesis was a little more than 100μmol · mol-1 indicating that E. ulmoides was a C3 type plant. Besides stomatal limitation, photoinhibition of photosynthesis was a possible cause of the midday depression in photosynthetic rate. Only about 14 percent of the photosynthetic product was transported from the leaves during photosynthesis.     

Responses of Plant Dark Respiration to Doubled CO2 Concentration

Ten species of plants were grown at ambient (350μmol CO2·mol-1 air) and doubled (700 μmol CO2·mol-1 air) CO2 concentrations at ambient temperature and illumination in order to examine changes of dark respiration of whole seedlings or detached leaves. Effects of CO2 on dark respiration were determined by brief exposure ( ≤ 5 min) to corresponding CO2 concentration and temperatures ( 15,20,25,30 and 35 ℃ ) with infrared CO2 analyzer. The reductions in dark respiration on a weight base for leaves of East-Liaoning oak (Quercus liaotungensis Koidz. ) at 15,20 and 25 ℃ and of soybean ( Glycine max L. ) at 20,25,30 and 35 ℃ and for whole seedlings of three- tcoloured amaranth (Amaranthus tricolor L. ) at 15 and 20 ℃ and cucumber ( Cucumis sativus L. ) at 15 cE measured at elevated concentration relative to the ambient CO2 concentration were observed. No significant difference in respiration responded was observed to elevated or ambient CO2 concentrations at 15 ℃ in maize (Zea mays L. ) seedlings and alfalfa (Medicago sativa L. ) leaves, at 35 ℃ in East-Liaoning oak leaves and at 20,25 and 30 ℃ in three-coloured amaranth seedlings. However CO2 efflux in leaves of weeping willow (Salix babylonica L. ), simon poplar (Populus simonii Carr. ) and eucommia (Eucommia ulmoides Oliv. ) at 15,20,25,30 and 35 ℃, alfalfa at 20,25,30 and 35 ℃, East-Liaoning oak at 30 ℃, maize at 15 ℃, seedlings of common buckwheat (Fagotrytum esculentum Moench) at 15,20,25,30 and 35 ℃, cucumber and maize at 20,25,30 and 35 ℃ and three-coloured amaranth at 35 ℃ showed an increase at elevated in contrast to ambient CO2 concentration. In general, at lower temperatures (i. e. 15, 20 ℃ ) there was no significant difference between elevated and ambient CO2 concentration for dark respiration, while at higher temperatures (i. e. 30,35 ℃ ) elevated CO2 concentration positively stimulate clark respiretion. It has not yet been described that double CO2 concentration could enhance plant dark respiration at 30 and 35 ℃. Impacts of the characteristics in dark respiration on the future changes of vegetation and its mechanism were discussed.     

引种地被石竹光合特征与生理生态因子的关系

以上海地区引种的一年生地被石竹实生苗为材料,研究其苗高生长变化、生物量积累和分配、光合特性及其变化规律,并分析主要生理生态因子对其净光合速率的影响。结果表明:(1)3～6月份为地被石竹苗高生长速生期,生长量为年生长量的65.93%,实生苗各部分器官的生物量总体呈现上升的趋势;3～6月份苗木以地上部分生物量积累为主,其占总生物量的比例从46.89%升至65.60%,6月份以后地下部分生物量所占比例从34.40%升至53.11%。(2)地被石竹叶片净光合速率(Pn)日变化在春季和秋季呈单峰曲线型,而在夏季表现为双峰曲线,且具有典型的光合"午睡"现象。(3)影响光合变化的主要决定生理生态因子:春季为蒸腾速率和气温,夏季为气孔导度和大气CO2摩尔分数,秋季为胞间CO2摩尔分数和光合有效辐射;限制地被石竹Pn日变化生理生态因子:春季为胞间CO2摩尔分数和光合有效辐射,夏季为蒸腾速率和空气相对湿度,秋季为气孔导度和气温。(4)地被石竹具有较高水平的光补偿点(56.94μmol·m-2·s-1)和光饱和点(780.07μmol·m-2·s-1),应属于喜光植物。     

Photoinhibition of Photosynthesis Without Net Loss of D1 Protein in Wheat Leaves Under Field Conditions

To determine whether the net loss of D1 protein is the main cause of photoinhibition of photosynthesis in wheat leaves under field conditions in the absence of any environmental stress other than strong sunlight, the D1 protein content, photosynthetic evolution of oxygen and chlorophyll a fluorescence parameters were measured in field grown wheat leaves. After exposure to midday strong light for about 3 h, apparent photosynthetic quantum efficiency (Φ), Fv/Fm and Fo in wheat leaves declined, and these parameters recovered almost completely 1 h after transfer to the weak light of 30~40 ttmol photons · m-2 · s-1. No evident change in the D1 protein content was observed in the leaves after exposure to midday strong light for 3 h. After 3 hours exposure to strong light, the slow-relaxed fluorescence quenching in the leaves treated with streptomycin (SM) increased much more than that in the control leaves, but there was no effect SM on the recovery of Fv/Fm and F0; dithiothretol (DTT) treatment enhanced photoinhibition of photosynthesis and reduced the D1 protein content in the leaves after exposure to midday strong light. These results indicated that under field conditions with no environmental stress other than strong sunlight, photoinhibition of photosynthesis in wheat leaves was not due to the net loss of D1 protein, and it could be attributed mainly by the increased nonradiative energy dissipation.     

七子花苗期光合日进程及光响应

对七子花苗期光合日进程及光响应进行了研究,结果表明:(1)净光合速率的日进程曲线呈双峰型,胞间CO2浓度的日进程基本与净光合速率相反,中午胞间CO2浓度增高表明净光合速率午间降低主要受非气孔限制因素的影响。暗呼吸速率日进程呈单峰曲线,中午最高。光能利用效率以上午7∶00为最高,中午最低,以后又逐渐上升。(2)净光合速率最适温度为25～30℃,高光合有效辐射和高温下光抑制加剧。(3)29℃下饱和光强为890μmolm 2s 1,表观量子效率为0.0325,光补偿点为44μmolm 2s 1;随着光合有效辐射的增强,气孔阻力减小,但光合有效辐射过高,气孔阻力却有所上升。(4)在29℃的饱和光强下,羧化效率为0.0351,CO2补偿点为173μmolmol 1,低于或高于饱和光强,羧化效率下降,CO2补偿点升高。     

An Approach to a Function of Photorespiration in C3 Plants

Intact attached leaves of wheat were illuminated at 2000 μmol m-2·s-1 in CO2-free gas for 3 hours, inhibition percentage of photosynthesis in these leaves by illumination was related lo oxygen concentration in the gas. (1) The damage to the leaves became less gradually when oxygen concentration rose from 0 to 10%. (2) Almost no damage occurred between 10%–50% O2. (3) The damage appeared again when oxygen concentration exceeded 50%. The duration of CO2 outburst of wheat leaves in CO2-free gas containing 8%–11% O2 was 0nly about 15–30 min. However, no photoinhibition could be observed under this condition. Oxygen also could prevent isolated chloroplasts from the damage by strong light. No matter what concentration of oxygen in CO2-free gas was during photoinhibition treatment, the photodamaged site was always in PSⅡ. It is concluded from the results that the way in which photoinhibition was alleviated by oxygen seems not only to be photorespiration, but also the other unknown mechanisms waich may play more important part in it.     

Study on Leaf Anatomy and Photosynthesis of Cymbidium sinense

The leaf surface of Cymbidium sinense(Andr.) Willd was covered with cuticle and wax. The stomata were distributed in the dorsum of the leaf, the density being 100–130 mm-2 There was a stomatal cover on each stoma. The mesophyll was not differentiated into spongy tissue and palisade tissue. No chloroplast was observed in the vascular bundle sheath cells. The chloroplast in the mesophyll cells had well developed grana, with lightly stacked thylakoids and osmiophilic granules. The highest quantum yield of functional leaf was 0.082. The light compensation point of photosynthesis was about 5 μE·m-2·s-1, the light saturation point was about 200 μE·m-2·s-1. The photosynthetic ra,e of Cymbidium sinense was very low, generally 2.0–2.6 μmol CO2· m-2·s-1. The optimum temperature of photosynthesis of one-year-old leaf was 25℃. The photosynthe,ic rate of the three-year-old leaf declined with temperature rise. The ratio of chlorophyll a/b was about 2.7. The CO2 compensation point of photosynthesis was 105–220 ppm. All these data show that Cymbidium sinense belongs to the typical shade plants with low photosynthetic rate and high CO2 compensation point that explains that the growth of Cymbidium sinense is slow in nature.     

珠三角城市绿地CO2通量的环境响应特征

城市绿地的净生态系统CO2交换量(NEE)受多种环境因素控制,定量分析NEE的环境响应机制对评估绿地生态系统固碳效益、优化城市绿地布局有重要意义。本文应用2009、2010年位于东莞市植物园内的涡度相关CO2通量定位观测资料,分析了光合有效辐射(PAR)、土壤温度(Ts)、饱和水汽压差(VPD)、降水及周边不同下垫面类型对NEE的影响。结果表明:NEE绝对值随PAR的升高而增加,PAR超过光饱和点(约为1500μmol photons·m-2·s-1)后,NEE绝对值呈回落趋势;生态系统呼吸(Reco)随Ts升高而增加,在温度较低时,Reco对Ts的敏感性较强(10℃时,Lloyd-Taylor方程的Q10=1.8),随着温度升高,敏感性下降(30℃时,Q10=1.43);VPD通过影响植物气孔导度对CO2交换产生作用,相同温度下,随着VPD升高,气孔导度增大,呼吸释放与光合固定的CO2量均增加;降水能增加土壤湿度进而使Reco增大,25℃时,降水后的Reco比降水前增加15.8%;测站东北和西南方的绿地范围较大,当东北和西南部是主要贡献区时,NEE绝对值较大,表明增加城市绿地能有效提高城市固碳效益。     

Changes in Stomatal Conductance,Transpiration and Water Use Efficiency of Ten Species Experienced in High CO2 Concentrations in Biosphere 2

The stomotal conductance, transpiration and water use efficiency (WUE) were measured using a LI-6400 portable photosynthesis system for 5 tropical rain forest species and 5 desert species in Biosphere 2, USA. All the species have experienced in very high CO2 ( > 2 200 μmol• mol- 1 ) for more than 4.5 years. The results showed that the stomatal conductance and transpiration of rain forest species decreased from ( 127.4 ± 65.6) and (2.04 ± 0.61 ) mmol• m- 2•s- 1 to (61.3 + 30.5) and ( 1.54 ± 0.65 ) mmol• m-2• s -1 respectively, while WUE increased from (2.90 ± 0.55) to (8.45 ± 2.71) μmol CO2 •mmo1-1 H2O, with CO2 increasing from 350 – 400 to 700 – 820 μmol• mol-l. For the desert species, stomatal conductance and transpiration decreased from respectively (142.8±94.6) and (2.09±0.71) mmol•m-2•s-1 to (57.7±35.8) and (1.36±0.52) mmolm-2•s-l, but WUE increased from (4.69 ± 1.39) to (9.68 ± 1.61) μmol CO2•mmo1-1 H2O, with the CO2 increase from 320 - 400 to 820 – 850 μtmol• mol- 1. The stomatal conductance, transpiration and WUE were less influenced by light intensity under high CO2 than low CO2 concentrations. Most rain forest species reached their light saturation points at light intensity of 500 μmol• m-2•s-1, while desert species at 1 000 μmol•m-2•s-1. Among different species, the desert C3 tree, Nicotiana glauca Grah., had the highest decrease in stomatal conductance and transpiration and the highest increase in WUE, by 78%, 69% and 310% respectively. The enhancement of increasing CO2 to the stomatal, transpiration and WUE of species with different photosynthesis pathway and life forms in Biosphere 2 could be concluded as: C3 species > C4 species, and desert C3 species > rain forest C3 species.     

苋菜的光合特性

宽菜Amaranthus cruentus cv.生长在调控的温室条件。在光强0至800μmol.m~(-2)S~(-1),光合速率(PN,μmol.CO_2m~(-2)、s~(-1))随光强(PFD,μmol、m~(-2)、s~(-1))增高而增大,其关系为PN=56.82 PFD×10~(-3)—2.13。光补偿点为60μmol.m~(-2)、s~(-1)。叶片在1400 μmol.m~(-2)、s~(-1)达到光合光饱和点。在叶温35℃,叶片/空气水蒸汽压陡度20 m Pa、Pa~(-1)和外界CO_2浓度340μ1、1~(-1),光饱和光合速率为51.63±4.90μ mol.CO_2、m~(-2)、S~(-1)。在光强0至600μmol.m~(-2)、s~(-1),气孔传道率随光强增高而增大。光强高于600μmol.m~(-2)、s~(-1),气孔传道率变化较小。细胞间CO_2浓度为120μ1.1~(-1)由于细胞间CO_2浓度在光合速率——CO_2关系曲线的转折点,可能表明光合作用不受气孔限制。结果表明,苋菜适于高光强环境生长,在干旱条件下具有高的光合速率。     

二氧化氮对樟树幼苗生长及光合作用的影响

采用开顶式人工熏气装置,对1年生樟树幼苗进行了为期2个月不同体积分数NO₂(0.1、0.5和4.0 μl·L^-1)熏气试验,研究其对幼苗生长及光合作用的影响.结果表明:0.5和0.1 μl·L^-1 NO₂处理促进了樟树幼苗生长,而4.0 μl·L^-1 NO₂处理则抑制其生长.各处理樟树幼苗叶片净光合速率(P_n)日变化呈不对称的双峰型曲线,存在光合“午休”现象;在光合日进程中,0.5 μl·L^-1 NO₂处理使叶片P_n提高,最大值达8.542 μmol CO₂·m^-2s^-1,4.0 μl·L^-1NO₂处理的大多数时段使P_n降低,而0.1 μl·L^-1 NO₂处理对P_n的影响则依时段而不同;0.5和4.0 μl·L^-1 NO₂处理提高了叶片气孔导度(G_s)和胞间CO₂浓度(C_i)的最大值和最小值,0.1 μl·L^-1 NO₂处理提高了C_i的最大值和最小值,降低了G_s的最大值和最小值.熏气处理中、后期,0.5μl·L^-1 NO₂处理叶片的日均净光合速率显著高于其他处理.在熏气处理前期,0.5和4.0 μl·L^-1 NO₂处理使叶片最大PSⅡ的光能转换效率(F_v/F_m)显著下降;在熏气处理后期,4.0 μl·L^-1 NO₂处理的叶片F_v/F_m仍显著低于对照.     

Structure and Photosynthetic Characteristics of Awns of Wheat and Barley

The surface and the cross section of awns of wheat and barley were examined by scanning electron microscopy,ultrastructure of cells were observed under a transmisson electron microscope and the photosynthetic rates were measured with an oxygen, electrode and infra-red CO2 analyser. The main results were as follows :The cross section of wheat awn appeared to be acutely trianglular whereas that of barley awn was obtusely triangular. There were rows of stomota on either side of epidermis in both wheat and barley awns. Under the stomatic band there were green tissues. The green cells in the awn were differentiated from the parenchyma cells . The mature green cells possessed papillae which were rich in chloroplasts and mitochondria. The tamella system in chloroplasts was well developed and contained many starch grains. There were three vascular bundles in each awn. The sheath cells near the green tissues contained chloroplasts. The photosynthate in the green cells might pass through the sheath cells and companion cells to sieve elements. The highest photosynthetic rate of the awn was seen at the flowering stage ,reaching about 20 μmol CO2·m-2·s-1. The light compensation point was 70—80 μE·m-2· s-1. The light saturation point was about 1500 μE·m-2·s-1. The CO2 compensation point was 50—60 ppm and the CO2 saturation point was about 900ppm . The photosynthetic rate and stomatal conductance were easily effected by CO2 concentration, light intensity and the duration of illumination . There was a positive correlation between the photosynthetic rate and the chloro-phyll content in the awns. The CO2-releasing rate in photorespiration of awn was about 4–5 μmol CO2·m-2·s-1.     

西藏高原田间冬小麦旗叶光合作用研究

 西藏高原冬小麦旗叶光合速率日变化曲线为平坦或单峰型,没有明显“午睡”现象。净光合速率日最高值可与平原接近。光合日总量最高值出现在灌浆中期,其值比平原低4％～34％。净光合速率达20μmolCO2·m-2·s-1以上的环境因子组合是光合有效辐射光量子通量密度2000μmol·m-2·s-1以上,气温25～29℃,近地层大气CO2密度0.41mg·dm-3以上,0cm地温18～23℃、5cm地温15～19℃。这样的因子组合在高原同时满足的机率不高,由于CO2浓度与光温因子高值出现时间不同步,更由于CO2密度比内陆平原低1/3,严重制约了光合日总量值,高原冬小麦旗叶光合作用的特点是净光合速率日最高值可与平原接近,但光合日总量却明显低于平原。