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1.
Summary Reduction of leaf photosynthesis due to water stress has been analyzed into various components and genetic variation in these components has been evaluated. Five potato cultivars were grown on nutrient solution in a conditioned glasshouse. Water stress was imposed by adding polyethylene glycol to the nutrient solution. Photosynthesis, transpiration and chlorophyll fluorescence were measured on intact leaves during the stress period and after recovery from the stress. Water stress reduced photosynthesis, initially as a consequence of stomatal closure, but after 3 days increasingly by inhibiting directly the photosynthetic capacity (mesophyll limitation). Stomatal closure correlated with the reduction in photosynthesis, but it was not the sole cause of this reduction because the internal CO2 concentration in the leaves was not affected by water stress, indicative of inhibitory factors other than stomatal ones. Chlorophyll fluorescence emission suggested that the Calvin cycle was inhibited, while quantum efficiency was not affected at 17°C. Increasing the temperature to 27°C reduced quantum efficiency but only in the stress environment. The recovery of young leaves after relief of the stress was associated with a lower stomatal conductance but a higher mesophyll conductance compared with the control, which caused a low internal CO2 concentration and probably invoked photo-inhibition and leaf damage. Cultivar differences in photosynthetic rate were highly significant under both optimal and stress conditions, and corresponded with differences in mesophyll conductance.  相似文献   

2.
Summary

To characterize the protection effect of silicon against excessive transpiration in rice plants (Oryza sativa L.), we investigated the factors responsible for transpiration, such as cuticular conductance (gc), leaf surface wax content (WC), and stomatal movement in response to environmental stimuli, using leaves of plants grown in nutrient solution with silicon (+Si) and without silicon (–Si). The rate of transpiration of whole plants (E) under field conditions was clearly reduced by application of silica. The gc of –Si leaves under precisely regulated conditions was 33% higher than that of +Si leaves, reflecting higher adaxial gc. Silicon has little effect on WC, a factor responsible for regulation of cuticular resistance to water flux in rice leaves. These results suggest that silicon is one of the main factors responsible for regulation of gc, but that its effect was not due to an increase in the WG. Leaf conductance (gl) of –Si leaves tended to decrease more slowly than that of +Si leaves over time after changes from high to low light intensity. Moreover, it was always higher over the entire duration of the experiment, irrespective of irradiation intensity. The gl of –Si leaves was higher at lower relative humidity (RH) and the initial response to a subsequent increase in RH was slower than that of +Si leaves. A comparison of gl and gc between +Si and –Si leaves showed that the higher gl of –Si leaves was due to higher stomatal conductance. These results indicated that the reduction in E by application of silica was mainly attributable to reduction in the rate of transpiration through stomatal pores.  相似文献   

3.
Abstract

The growth of crown and lateral roots emerged from the excised phytomers of pearl millet (Pennisetum typhoideum Rich.), barnyard millet (Echinochloa frumentacea Link.) and maize (Zea mays L.) was studied under normal and low osmotic potential conditions. The plants were grown in two solutions with osmotic potentials of –0.02 and –0.54 MPa for 6 days. The relative growth rate of the roots in total length (RGRL) , was not affected by osmotic stress in pearl and barnyard millets, but that in stressed maize was reduced to 64% of the control. Similarly, the relative growth rate of the roots in dry weight (RGRW), was not affected by osmotic stress in pearl and barnyard millets, but significantly reduced in maize. Osmotic stress increased the specific root length of the lateral roots in pearl and barnyard millets, but did not affect that of maize. The photosynthetic rate (Pr) in the two millets was decreased to ca. 60% of the control by the stress, and that in maize was reduced to 21%. Under the stress, Pr in the three species was limited mainly by low stomatal conductance, but no clear relationship was found between Pr and osmotic adjustment of the leaf. The relative water content of the leaf was lower in maize than in the two millets. The resistance to water flow through the phytomer (R) was significantly increased by osmotic stress in maize, but not significantly in the two millets. The mean root length (RL) was decreased by the stress in maize, but not in the two millets. The maintenance of RGRL in the two millets was associated with sustained R, RL and also with the maintenance of Pr and allocation of assimilates to roots.  相似文献   

4.
氮肥水平对限制灌溉下冬小麦旗叶光合性能及产量的影响   总被引：2，自引：0，他引：2  
为了解氮素营养供应与小麦节水效果的关系,以周麦22为材料,采取大田试验研究了不同氮肥水平对限制灌条件下冬小麦旗叶光合性能及产量的影响。结果发现,与正常灌水相比,限制灌溉降低了小麦旗叶叶绿素含量、净光合速率、气孔导度和蒸腾速率,提高了小麦旗叶胞间CO2浓度;限制灌溉条件下,与不施氮肥相比,增施氮肥能明显改善小麦旗叶光合性能。从产量来看,充分灌水有利于小麦产量提高,而限制灌溉条件下,灌水时期提前或增施氮肥能不同程度提高小麦产量。以上结果说明,增施一定量的氮肥能明显改善限制灌溉条件下冬小麦花后旗叶光合性能,提高小麦产量和水分利用效率。  相似文献   

5.
梯度干旱胁迫对水稻叶片光合和水分状况的影响   总被引：3，自引：0，他引：3  
采用温室营养液培养方式,通过添加0%、10%、20%、30%PEG6000模拟干旱胁迫,对水稻幼苗叶片的光合作用和水分状况进行比较分析。结果表明:1)在干旱胁迫下,水稻叶片的光合速率、气孔导度、叶肉导度、总导度和叶绿体内CO2浓度等都显著降低;2)在干旱胁迫条件下,限制光合作用的非气孔限制值并没有显著提高,而气孔限制值则大幅提高;与正常水分条件相比,扬稻6号和汕优63在30%PEG干旱胁迫下气孔限制值分别提高了42%和81%;3)光合速率与气孔导度、叶肉导度、总导度及叶绿体内CO2浓度呈正相关;4)在重度干旱胁迫下(20%和30%),叶片水势和含水量都显著下降,并且叶片水势与气孔导度、叶肉导度和总导度呈正相关。因此,气孔关闭导致的叶绿体内CO2浓度降低是限制光合作用的最主要因素,同时叶片水势的降低增加了叶片内CO2传输的阻力。  相似文献   

6.
Summary

The transpiration or photosynthesis decline curve of excised plant leaves has been used to predict water stress tolerance ability. This study analyzed the characteristics of the declining photosynthetic rate in excised leaves of sweet corn (Zea mays L.) plants after treatment with effective microorganisms (EM), a mixed culture of naturally occurring beneficial microorganisms, organic fertilizer (Bokashi) and chemical fertilizer. The net photosynthetic rates (P N) of intact leaves were measured using LI-6400 gas exchange system under 2000 μmol m?2 s?1 PPF. When P N reached the maximum (P max), the leaf was excised and P N was continuously monitored. A declining P N curve with time is obtained and modeled according to P N = [Pmax - P res (1 - βt)] e?α(t-τ) + P res (1 - βt), where t is the time elapsed after the leaf was excised; τ is the time point when the stomata begin to close; P res is the residual P N when stomatal closure completed; and α and β are constants related to stomatal and residual conductances respectively. Photosynthesis maintenance ability (PMA) is expressed as 1/(α+ β). Leaves of plants fertilized with organic materials and/or treated with EM showed a higher PMA and P N than the controls after the leaves were excised.  相似文献   

7.
Daily net canopy photosynthesis (Pn) of cocksfoot (Dactylis glomerata L.) was predicted for combinations of temperature, herbage nitrogen (N) concentration and water status from the integration of models of leaf photosynthesis of the light‐saturated photosynthetic rate (Pmax), photosynthetic efficiency (α) and the degree of curvature (θ) of leaf light‐response curves. The effect on Pn, maximum Pn (Pn max) and the optimum leaf area index (LAI at Pn max) was examined when any one of these factors was limiting. The ranges that gave the optimum values of Pn (Pn max = 30·8–33·5 g CO2m?2 d?1) for temperature (19–22°C) and N concentration (40–50 g N kg?1 DM) were smaller than those for net leaf photosynthesis. Also, Pn fell to 0 at a lower level of water stress (pre‐dawn leaf water potential, ψlp = ?12·5 bar) than for Pmax. The canopy photosynthesis model was then used to compare predicted and measured dry matter (DM) production for cocksfoot pastures grown under a diverse range of environmental conditions with field data from New Zealand and Argentina. To predict DM production leaf area index and leaf canopy angle were included from field measurements. The model explained about 0·85 of the variation in cocksfoot DM production for the range of 6·5–134 kg DM ha?1 d?1. The canopy model overestimated the DM production by 0·10 which indicates that a further Pmax function for leaves of different ages and a partitioning sub‐model may be needed to improve predictions of DM production.  相似文献   

8.
SGM对玉米发芽率及幼苗抗冷效果的影响   总被引：2，自引：1，他引：1  
试验以不同浓度的水杨酸(SA)和赤霉素(GA)复配剂(SGM)处理玉米种子,研究SGM对玉米发芽率及幼苗抗冷性的影响。结果表明,在低温(6.5～10℃)条件,SGM处理后能够提高玉米种子的发芽率,最高可达69.63%;叶片脯氨酸含量及SOD、POD、CAT酶的活性也有所增加,增幅最高分别为57.39%、42.62%、25.95%和16.63%,其中SOD>POD>CAT的活性。在低温条件下,SGM能够减缓膜脂过氧化物MDA的积累,降低幅度为2.72%～22.75%,达到了极显著水平,SGM处理可增强玉米幼苗的抗冷性。  相似文献   

9.
The physiological response to cutting in Italian ryegrass   总被引：1，自引：0，他引：1  
The kinetics of decline in net photosynthesis and transpiration after cutting was followed in a batch of Lolium multiflorum leaves at light saturation in an assimilation chamber where air temperature, leaf temperature, carbon dioxide concentration and water vapour concentration were controlled. After leaf excision the rates of photosynthesis and transpiration increased or remained the same for 1–2 min and then decreased sharply following a curve with two breaks of slope at 15 min and 30 min. To investigate stomatal behaviour, fragments of leaf tissue were removed, fixed by freezing in liquid nitrogen, then examined by scanning electron microscopy. The stomata were optically closed by 15 min after excision. The practical implications for field drying of Italian ryegrass are discussed.  相似文献   

10.
为给华北地区冬小麦节水栽培条件下氮肥合理运筹提供理论依据,以高产小麦品种周麦18为供试材料,在大田限水灌溉条件下,设置六个不同氮肥处理［各处理底施和追施氮量（底氮+追氮）分别为：0+0、120+0、120+60、120+120、120+180、120+240 kg·hm-2］,研究了限水灌溉条件下追氮水平对冬小麦旗叶光合特性及物质运转的影响。结果表明,施氮量120+60 kg·hm-2时,小麦产量最高,达到8 749 kg·hm-2。限水灌溉条件下追氮水平对冬小麦旗叶光合特性及物质运转有较明显的调控效应,总体表现为,在0～120 kg·hm-2范围内,随着追氮量的增加,旗叶净光合速率、气孔导度和叶绿素含量增大,胞间CO2浓度降低,延缓了旗叶的衰老进程,延长了光合功能期,有利于光合产物的积累,而过高的追氮量（180～240 kg·hm-2）并没有在更大程度上提高旗叶净光合速率和叶绿素含量以及降低胞间CO2浓度;适当追氮（60 kg·hm-2）虽然增加了花前贮藏物质和氮素的运转量,但运转率下降;过多的追施氮肥（120～240 kg·hm-2）会导致花前贮藏物质和氮素运转量、运转率及对籽粒的贡献率显著降低。在本试验条件下,最适的施氮处理为120+60 kg·hm-2。  相似文献   

11.
干旱胁迫对不同肥水类型小麦旗叶光合特性及产量的影响   总被引：8，自引：0，他引：8  
为给小麦抗旱育种和节水高产栽培提供理论和技术支持,在防雨旱棚池栽条件下研究了干旱胁迫对6个不同肥水类型小麦品种旗叶光合特性和产量的影响。结果表明,干旱胁迫条件下,小麦开花后旗叶的净光合速率、气孔导度、蒸腾速率、气孔限制值和单叶水分利用效率均呈下降趋势,而胞间CO2浓度有所升高。其中,水浇地品种烟农21、烟农24和济麦22净光合速率、气孔导度、蒸腾速率、气孔限制值和单叶水分利用效率较低且下降幅度大,而旱地品种青麦6号、济旱5034和鲁麦21的净光合速率、气孔导度、蒸腾速率、气孔限制值和单叶水分利用效率较高且下降较为缓慢,而胞间CO2浓度较低。青麦6号具有较高的抗旱指数,在干旱胁迫条件下能够保持较好的叶片结构和功能状况,是其获得高产的重要原因。  相似文献   

12.
《Plant Production Science》2013,16(2):118-127
Abstract

The whole-leaf photosynthetic rate in rice plants is controlled by various physiological processes. In a high-yielding indica rice variety, Habataki, the leaf photosynthetic rate (LPR) of the uppermost fully expanded leaves was approximately 130 to 140% of that in a japonica variety, Sasanishiki, from booting to the early ripening stage. We characterized the difference in the LPR between Habataki and Sasanishiki. Leaves of Habataki contained higher levels of nitrogen and, as a consequence, of Rubisco, and had higher stomatal conductance that was associated with higher hydraulic conductance from roots to leaves than those of Sasanishiki. These features were responsible for the higher LPR of Habataki. An analysis of chromosome segment substitution lines (CSSLs) in which chromosome segments from Habataki were substituted into the genetic background of Sasanishiki showed that three genetic regions on chromosomes 4, 5 and 11 were responsible for the increase in the LPR. Each of these regions was estimated to increase the LPR by 15 to 30%, and we showed that they were associated with higher activity of mesophyll photosynthesis due to higher leaf nitrogen content and greater stomatal conductance. Leaf nitrogen content and stomatal conductance may be useful parameters for further quantitative trait locus analysis of efficient photosynthesis in leaves.  相似文献   

13.
《Field Crops Research》1999,62(1):53-62
Maize was grown in the high-radiation arid summer environment of Davis, California, and its leaf photosynthetic rate was measured over diurnal courses on cloudless days with the leaf held perpendicular to the sunlight. On days of high atmospheric vapor pressure deficit (VPD), leaf photosynthesis reached a maximum in the late morning and then decreased gradually as the day progressed, though the soil was well irrigated. When CO2 concentration in the measurement chamber was raised to about 1000 μmol mol−1, photosynthesis was enhanced, but more in the afternoon than in the morning. As a result, rates measured at high CO2 in the morning and afternoon were essentially the same. There was also no difference in the curves of photosynthetic rate (A) versus intercellular CO2 concentration (Ci) for the morning and afternoon. Hence, photosynthetic capacity was similar for the two periods and there was no evidence of photoinhibition by the high photosynthetic photon flux density at noon. Further, Ci and photosynthetic rates A measured over a range of photon flux density were lower in the afternoon than in the morning. These results indicate that A at noon and early afternoon was more limited than in the morning by epidermal conductance (mostly stomatal). On a day of low VPD, however, midday depression in A and epidermal conductance were not evident for the well-irrigated plants. Without irrigation and with leaves at a lower midday water potential, midday reduction in conductance and A was much more marked, beginning late in the morning. Epidermal conductance of maize grown in the field in Davis is are not sensitive to VPD. Therefore, the midday reduction in conductance and A was more likely the result of low leaf water potential caused by high transpiration rates.  相似文献   

14.
Plants with limited transpiration rate (TR) under high vapor pressure deficit (VPD) offer the potential to conserve soil water and thus decrease the occurrence of soil water deficit. Genetic variability in TR response to VPD has been observed in the greenhouse for soybean (Glycine max (L.) Merr.) genotypes related to PI416937, but these differences have yet to be measured in the field. The objective of this study was to observe under field conditions leaf gas exchange properties of PI416937 in comparison to nine other genotypes to determine if it expressed limited TR at high VPD. Genotypic differences in stomatal conductance measurements (a proxy for TR) matched those obtained under controlled environment conditions. Genotypes varied from no stomatal response to VPD, to strong negative responses resulting in full stomata closure at ∼4 kPa. There was a greater proportional genetic variability in stomatal conductance in the field (75% at high VPD) than was observed in the greenhouse, but this variation was correlated with greenhouse TR. However, photosynthesis was considerably limited in genotypes that had a stomatal response to VPD. Although field differences in photosynthetic capacity among genotypes were not correlated with greenhouse measurements, there was sufficient genetic variation to allow the possibility of selection of high photosynthetic capacity to overcome about a 34% decrease in stomatal conductance. Thus, a targeted breeding program to combine the water conserving TR-VPD response with increased photosynthetic capacity has the potential to increase soybean yields in field water-deficit environments.  相似文献   

15.
为了解Wx基因对小麦光合作用的影响,对8个小麦Wx近等基因系的不同叶位叶片光合参数进行了测定和分析。结果表明,小麦叶片净光合速率、气孔导度、胞间CO2浓度和蒸腾速率在叶位和基因型间均有极显著差异,缺失单个Wx基因使叶片光合参数下降,且降幅表现为Wx-D1Wx-A1Wx-B1;胞间CO2浓度不影响光合作用,不同叶位叶片光合参数明显呈旗叶倒二叶倒三叶,但WxABD(糯小麦)光合参数在叶位间没有显著差异;Wild type和WxABD总体光合能力和产量相对较高。以上结果说明,Wx基因的缺失会引起叶片光合能力下降,不利于小麦产量形成。  相似文献   

16.
Summary

This study involved a comparison of two pear (Pyrus communis L. cv. Nijuseki) orchards in the South Nagano area that were managed according to either chemical farming (CF) or organic farming (OF) practices. Leaf-scorch was not observed in the pear orchard under OF but was severe under CF. Fruit yield was 62% higher for the pear orchard farmed organically. Photosynthetic capacity (P C) was 33% higher under OF. Leaf symplastic water fraction (z sym) and osmotic concentration (C FT) were higher for pear trees under OF than for those under CF. Both stomatal (a) and cuticular (b) transpiration were faster for excised pear leaves under CF and, as a consequence, the leaf water retention ability (WRA) of leaves under CF was lower than for those under OF. Results suggest that the higher yield of pear trees with organic farming management, compared with chemical farming, is attributed to high P C and that the absence of leaf-scorch is attributed to a high water retention ability that is associated with a high symplastic cell water fraction and high tissue osmotic concentration.  相似文献   

17.
Cowpea is a major food legume in Africa with relatively little information on N and C nutrition under field conditions in the continent. The aim of this study was to assess the relationship between leaf symbiotic N nutrition and photosynthetic carbon assimilation in cowpea genotypes grown under field conditions in the Guinea savanna of Ghana. The experiments were conducted in a randomized complete block design in Ghana, using 30 nodulated cowpea genotypes. Data collected from gas-exchange studies showed that genotypes with high photosynthetic rates expectedly exhibited greater stomatal conductance, high transpiration rates and increased water-use efficiency, leading to greater dry matter yield. In contrast, those with low photosynthetic rates revealed low stomatal conductance, low transpiration rates and low water-use efficiency. Quantification of symbiotic N in photosynthetic leaves indicated greater N2 fixation in genotypes with higher photosynthetic rates, leaf transpiration and better water-use efficiency. Furthermore, measurement of C in leaves also indicated greater accumulation in genotypes with higher symbiotic N yield and total N, clearly indicating a link between C and N metabolism in photosynthetic leaves. Additionally, measures of photosynthetic N-use efficiency showed that genotypes with high levels of C-fixed per unit leaf total N also exhibited greater C-fixed per unit leaf N-fixed. Data suggest that where symbiotic legumes derive a large proportion of their N from N2 fixation, photosynthetic C yield is much enhanced.  相似文献   

18.
高产水平下水肥耦合对小麦旗叶光合特性及产量的影响   总被引：6，自引：0，他引：6  
为了探讨黄淮麦区冬小麦的高产机理,在大田条件下设置不同梯度的水肥耦合模式,分析了高产水平下旗叶光合特性与籽粒产量的效应.结果表明,不同模式的水肥耦合对旗叶光合特性和籽粒产量的影响不同,总体表现为土壤水分的处理效应大于施氮量的效应.旗叶光合速率(Pn)和气孔导度(G5)均随着土壤水分的增加而升高,表现为W3(充足水分)＞W2(适宜水分)＞W1(自然降水),差异达显著水平.胞间CO2浓度(Ci)随着土壤水分的增加而降低;不同的氮肥处理,旗叶Pn和Gs随着施氮量的增加而升高,表现为N3(270 kg·hm-2)＞N2(195 kg·hm-2)＞N1(CK),Ci在不同水分条件下与施氮量的关系不尽相同.不同水肥耦合模式对水分利用效率的影响表现为W2＞W3＞W1,并以W2N2为最高,不同处理组合的籽粒产量亦以W2N2为最高.表明高产条件下W2N2水肥组合应是高产高效的运筹模式.  相似文献   

19.
灌水对黄淮海冬小麦叶片光合特性的影响   总被引：1，自引：0，他引：1  
为了解灌水对黄淮海地区冬小麦光合特性的影响,以周麦18、豫农202、豫麦49、郑麦366、矮抗58等5个黄淮海主栽冬小麦品种为材料,比较和分析了越冬水、越冬水+拔节水、越冬水+拔节水+灌浆水3个不同灌水处理下冬小麦开花后叶面积指数、旗叶叶绿素含量、光合参数及水分利用效率的特点。结果表明,随灌水次数减少,小麦灌浆期叶片光合功能衰退加快,叶面积指数和叶绿素含量下降,旗叶净光合速率、气孔导度和蒸腾速率减小,胞间二氧化碳浓度增加,光合作用受非气孔因素的限制增大,同时叶片水分利用效率增加。在不同灌水条件下,矮抗58和郑麦366叶片水分利用效率均较高,而周麦18、豫麦49和豫农202叶片水分利用效率均较低。  相似文献   

20.
《Field Crops Research》1999,62(1):35-52
A field study was conducted to investigate the effect of intermittent soil drying on resulting non-hydraulic and hydraulic root signals, leaf gas exchange, leaf growth, day of heading, leaf osmotic adjustment and yield of wheat grown in sand and loam soils in lysimeters. A 40-day-drought treatment was imposed when the flag leaf started to emerge and was terminated close to maturity. Soil water content and soil water potential of various soil layers were measured using the neutron moderation method and tensiometers, respectively. Soil drying in the top soil layers induced increase in both xylem and bulk-leaf abscisic acid (ABA) content and reduced the stomatal conductance and leaf growth even before a measurable change in leaf water potential could be detected in droughted plants when compared with fully watered plants. Further, heading and flowering occurred 4 days earlier in the droughted than in the well-watered plants before any loss in leaf water potential had occurred as compared with the fully watered plants. When more severe drought reduced the leaf water status, further accumulation of leaf ABA occurred and transpiration decreased in addition to gradual osmotic adjustment and senescence of older leaves. The osmotic adjustment sustained leaf turgor pressure during soil drying. At severe drought, the osmotic adjustment at full turgor in the flag leaves was 0.85 MPa. In sand, the kernel dry weight increased and as a result similar grain yield was obtained in both the treatments. In loam which had more water available than sand, no significant reduction in the final yield was induced by the drought. It is concluded that (1) non-hydraulic root signals caused early drought adaptation at mild water stress by reducing leaf growth and stomatal conductance and hastening of heading and flowering; (2) osmotic adjustment sustained turgor maintenance and hence the yield-forming processes during moderate and severe water stress.  相似文献   

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