Root restriction-induced limitation to photosynthesis in tomato (Lycopersicon esculentum Mill.) leaves

Root restriction often depresses photosynthetic capacity and the mechanism for this reduction, however, remains unclear. To identify the mechanism by which root restriction affects the photosynthetic characteristics, tomato (Lycopersicon esculentum Mill.) seedlings were subjected to root restriction stress with or without supplemental aeration to the nutrient solution. With the development of the root restriction stress, CO₂ assimilation rate was decreased only in confined plants without supplemental aeration. There were also significant decreases in leaf water potential, stomatal conductance (g_s), intercellular CO₂ concentration (C_i), and increases in the stomatal limitation (l) and the xylem sap ABA concentration. Meanwhile, the maximum carboxylation rate of Rubisco (V_cmax) and the capacity for ribulose-1,5-bisphosphate regeneration (J_max) also decreased, followed by substantial reductions in the quantum yield of PSII electron transport (Φ_PSII). Additionally, root restriction resulted in accumulation of carbohydrates in various plant tissues irrespective of aeration conditions. It is likely that root restriction-induced depression of photosynthesis was mimicked by water stress.     

柃木苗期光合特性研究

运用美国Li-COR公司制造的Li-6400便携式光合作用测定系统,研究柃木Eurya muricata苗期的光合特性.结果表明,柃木叶片净光合速率(Pn)的日变化曲线呈双峰型,有"光合午休"现象,第1个峰值出现在9:00左右,净光合速率(CO2)达到7.35 μmol·m-2·s-1;第2个峰值出现在16:00,净光合速率为2.64 μmol·m-2·s-1.柃木叶片CO2补偿点为53.8 μmol·mol-1,饱和点为1 621.4 μmol·mol-1.柃木叶片光补偿点为42 μmol·m-2·s-1,饱和点为1 000 μmol·m-2·s-1左右.图5参11     

不同水分条件下不同抗旱基因型小麦的产量及旗叶光合特性比较

在不同水分条件下,对不同抗旱基因型小麦的产量及旗叶光合特性进行了比较研究。结果表明：在干旱胁迫条件下,洛旱2号的产量显著高于温麦6号,水处理条件下2个品种的光合速率、蒸腾速率、气孔导度和胞间CO2浓度均高于旱处理;在干旱胁迫条件下,洛旱2号的光合速率、蒸腾速率和气孔导度下降幅度均小于温麦6号。     

毛乌素沙地主要建群植物蒸腾耗水特性的研究

在植物生长旺季初期(7月份),采用LI-1600型气孔针对毛乌素沙地主要建群植物油蒿(Artemisia ordosica)、中间锦鸡儿(Caragana intermedia)、沙柳(Salix psammophyla)和旱柳(Salix matsudana)的蒸腾耗水进行了测定。结果表明:供试植物的蒸腾速率日动态曲线均为单峰型,无午休现象,其中固定沙地油蒿和半固定沙地油蒿的蒸腾速率在中午13∶00出现峰值。气孔扩散阻力是所有供试植物蒸腾速率的主要影响因子。对供试植物的蒸腾耗水进行的评估表明,不同植物的日最大蒸腾速率和日平均蒸腾速率大小为固定沙地油蒿>半固定沙地油蒿>沙柳>旱柳>中间锦鸡儿;植物单株月累计蒸腾耗水量大小为旱柳>沙柳>固定沙地油蒿>半固定沙地油蒿>中间锦鸡儿;植物种群单位面积单位时间内的蒸腾耗水量大小顺序为固定沙地油蒿>半固定沙地油蒿>沙柳>旱柳>中间锦鸡儿。     

Regulated deficit irrigation in potted Dianthus plants: Effects of severe and moderate water stress on growth and physiological responses

The purpose of this study was to analyze the physiological and morphological response of carnation plants to different levels of irrigation and to evaluate regulated deficit irrigation as a possible technique for saving water through the application of controlled drought stress. Carnations, Dianthus caryophyllus L. cultivar, were pot-grown in an unheated greenhouse and submitted to two experiments. In the first experiment, the plants were exposed to three irrigation treatments: (control); 70% of the control (moderate deficit irrigation, MDI) and 35% of the control (severe deficit irrigation, SDI). In the second experiment, the plants were submitted to a control treatment, deficit irrigation (DI, 50% of the control) and regulated deficit irrigation (RDI). After 15 weeks, MDI plants showed a slightly reduced total dry weight, plant height and leaf area, while SDI had clearly reduced all the plant size parameters. RDI plants had similar leaf area and total dry weight to the control treatment during the blooming phase. MDI did not affect the number of flowers and no great differences in the colour parameters were observed. RDI plants had higher flower dry weight, while plant quality was affected by the SDI (lower number of shoots and flowers, lower relative chlorophyll content). Leaf osmotic potential decreased with deficit irrigation, but more markedly in SDI, which induced higher values of leaf pressure. Stomatal conductance (g_s) decreased in drought conditions more than the photosynthetic rate (P_n). Osmotic adjustment of 0.3 MPa accompanied by decreases in elasticity in response to drought resulted in turgor less at lower leaf water potentials and prevented turgor loss during drought periods.     

聚-γ-谷氨酸对小白菜生长和光合作用的影响

采用水培方法研究了聚-γ-谷氨酸对小白菜地上部生长、叶片叶绿素含量、光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)和蒸腾速率(Tr)的影响。结果表明,随着养分含量的降低,聚-γ-谷氨酸处理小白菜较对照叶片Pn、Gs、Tr和Ci均有提高;在90%养分含量下施加聚-γ-谷氨酸显著提高了叶片中叶绿素a的含量;在70%～100%养分含量范围内,小白菜地上部产量较对照均有所提高,说明聚-γ-谷氨酸可通过降低气孔限制值、增加叶绿素含量和提高吸收光强的能力,从而促进小白菜对光能的捕获及其转化,提高其光能利用效率。     

大豆叶片光合速率与气孔导度、叶肉导度的关系

在田间条件下，研究１２个大豆品种两个生育时期的叶片光合速率（ＰＡ）、气孔导度（ｇｓ）、叶肉导度（ｇｍ）、气孔内ＣＯ２浓度（Ｃｉ）和蒸腾速率（ＴＲ）。结果表明，上述５个性状均有显著的品种间差异，并且鼓粒中后期明显大于开花前后。各性状的平均数在鼓粒中后期均极显著低于开花前后。ＰＡ与ｇｓ的关系，随生育期表现不同，在开花前后，可以配合成一条三次多项式曲线，并显示出一最大的ＰＡ值，而在鼓粒中后期则呈显著的线     

Microsprinkler Irrigation Influences Clementine Fruit Quality,Leaf Temperature and Physiology

Abstract

The effect on leaf physiology and fruit quality, of two irrigation schedules, daily and twice a week irrigation (control), were tested on ‘SRA 63’ Clementine (Citrus reticulata Blanco) during 2002 and 2003. Micrometeorological data revealed a higher impact of everyday irrigation on air and leaf temperature compared with the control. While in 2002 daily irrigation treatment reduced air temperature up to 3.4°C with respect to the control, in 2003 the cooling effect was greater, with reductions of air temperature up to 9°C as compared with the control. In 2002, gas-exchange related parameters were influenced little by daily undertree microsprinkler irrigation, on the contrary, in 2003 net photosynthetic rates were significantly increased by daily irrigation with respect to the control.     

基于夏玉米叶片气孔导度提升的冠层导度估算模型

叶片气孔导度模拟及其向冠层导度的尺度提升是实现蒸散发尺度转换的基础,对农业水资源高效利用与评价意义重大。本文依据夏玉米叶片气孔导度和冠层导度实测值,在建立叶片气孔导度估算模型基础上,构建冠层导度估算模型。结果表明,夏玉米叶片气孔导度每日在10:00－14:00之间达到峰值,其日变化趋势与光合有效辐射的一致性较好,较大的饱和水汽压差对夏玉米叶片气孔导度具有一定的限制作用。根据光合有效辐射和饱和水汽压差建立的叶片气孔导度估算模型能较好反映当地夏玉米叶片气孔导度对主要环境因子的响应过程,以光合有效辐射作为尺度转换因子构建的冠层导度估算模型可较好实现从叶片气孔导度向冠层导度的尺度转换提升。     

Influence of Exogenous Glycine Betaine on Gas Exchange and Biomass Production in Sunflower (Helianthus annuus L.) under Water Limited Conditions

This study investigated whether the exogenous application of glycine betaine (GB) could alleviate the adverse effects of water deficit on sunflower. Two sunflower lines, Gulshan-98 and Suncross, were subjected to water deficit at the vegetative or the reproductive stages of plant growth. Three levels (0, 50 and 100 mmol l⁻¹) of GB were applied as a pre-sowing seed treatment or as a foliar spray at the time of initiation of water deficit at the vegetative or reproductive stages. Foliar application of GB at the time of initiation of water deficit treatments showed a marginal increase in shoot biomass in drought-stressed plants. Exogenously supplied GB as a foliar spray also showed a positive role in reducing the effects of water deficit on net CO₂ assimilation rate, transpiration rate and sub-stomatal CO₂ concentration in both sunflower lines. Pre-sowing seed treatment with GB had no effects on the above-mentioned physiological and growth attributes in both normally irrigated and drought-stressed plants. Taken together, foliar application of GB increased net CO₂ assimilation rate which in turn showed a slight increase in growth of water-stressed plants but this increase was not related to stomatal regulation.