Osmotic adjustment of sugar beets in response to soil salinity and its influence on stomatal conductance,growth and yield

Sugar beets were grown in tanks filled with loam and clay, and were irrigated with waters of three different levels of salinity. Osmotic adjustment was determined by analyzing the pressure-volume curves at three growth stages. Sugar beets showed osmotic adjustment in two ways: with their phenological development and towards salinity. Owing to the latter adjustment sugar beets are able to maintain the turgor potential at the same value for lower values of the leaf water potential, to maintain stomatal conductance and photosynthesis and finally their production under severe water stress.Salinity affected the pre-dawn leaf water potential, stomatal conductance and evapotranspiration on both soils, but leaf area and yield only on loam.Soil texture affected stomatal conductance, evapotranspiration, leaf area and yield. As the latter was about 35% lower on clay, whereas the evapotranspiration decreased 10 to 15%, the water use efficiency was about 25% lower on clay compared with loam.     

Response of tomatoes,a crop of indeterminate growth,to soil salinity

Tomatoes were grown in tanks filled with loam and clay, and were irrigated with waters of three different levels of salinity. Osmotic adjustment was determined by analysing the pressure–volume curves at four growth stages. Owing to the osmotic adjustment, tomatoes are able to maintain the turgor potential and the stomatal conductance at the same value for the lower values of the leaf-water potential. Salinity affected the pre-dawn leaf-water potential, stomatal conductance, evapotranspiration, leaf area and fruit yield on both soils. Soil texture only affected the fruit yield. The evapotranspiration showed a moderate decrease, owing to the small decrease in leaf area and the effect of osmotic adjustment on the stomatal conductance, whereas the fruit yield decreased strongly. The tomato plant apparently favours under saline conditions, the growth of foliage at the expense of fruit formation.     

Effects of frequency of irrigation and gypsum treatment on leaf water potential and leaf stomatal conductance of lucerne (Medicago sativa L.) grown on a heavy clay soil

Summary Concurrent diurnal measurements of water potential, osmotic potential and conductance were made on leaves of lucerne grown under weekly (W) and fortnightly (F) irrigation on gypsum-treated (G) and untreated soil (C). Measurements were made throughout the period of vegetative growth.Leaf water potentials were lower both at dawn and in the afternoon under fortnightly as compared to weekly irrigation. Gypsum application led to a slower decline in water potential under fortnightly irrigation, although the effect was small compared with more frequent irrigation. Stomatal conductance was reduced under treatments F_G and F_C during the later stages of vegetative growth, coinciding with leaf water potentials of less than c. –1.6 MPa.The relationship between leaf water potential and turgor potential changed with time such that positive turgor was maintained as leaf water potential declined. Turgor maintenance was achieved through a decrease in leaf osmotic potential. These data suggest that lucerne is capable of osmotic adjustment.Stomatal conductance declined rapidly below a leaf turgor potential of c. 0.1 MPa. It is hypothesised that osmotic adjustment enabled stomatal adjustment, which contributed to continued assimilation despite increasing soil moisture deficits.     

温室环境因子驱动甜瓜水分传输机理分析与模拟

利用人工气候室控制空气温度、相对湿度和光合有效辐射量,根据水量平衡法控制土壤含水率,按照四因素五水平的二次回归正交旋转组合设计,对甜瓜蒸腾量进行模拟,并探讨各因子调控水分传输的机制。基于Jarvis模型建立环境因素驱动的多元非线性气孔导度模型,结合水汽扩散原理建立蒸腾量模型,模型预测精度良好。探究因素交互作用及其耦合调控效应,结果表明:除相对湿度对蒸腾表现为抑制作用,土壤含水率、空气温度和光合有效辐射均对蒸腾具有促进作用;土壤含水率与空气温度的单因素效应相似,随因素水平增加,蒸腾量线性升高;光合有效辐射量驱动蒸腾的单因素效应为开口向下的二次函数,当因素水平超过阈值后,蒸腾量逐渐下降。环境因素在驱动和调控蒸腾过程中均存在密切耦合和反馈效应,土壤含水率与温度对蒸腾调控的耦合效应趋近于平滑曲面,蒸腾量随两因素水平的升高而升高,在试验水平内两因素对蒸腾表现为协同促进效应;空气相对湿度减弱了水汽扩散驱动力,进而抑制温度和土壤含水率对蒸腾的驱动作用,且这种抑制作用随相对湿度的升高而更明显。     

蓄水坑灌条件下不同灌水下限幼龄苹果树叶片光合特性研究

以3a生矮砧红富士为试验材料,采用LI-6400XT便携式光合仪,对蓄水坑灌条件下不同灌水下限(分别为田间持水率的50%、60%、70%)幼龄苹果树叶片光合特性进行研究,并通过通径分析与多元逐步回归分析量化各影响因子与净光合速率的关系。结果表明:蓄水坑灌条件下不同灌水下限叶片净光合速率、气孔导度、蒸腾速率、胞间CO2浓度变化规律基本一致。当土壤水分不足时,净光合速率主要受土壤含水率影响;当土壤水分充足时,净光合速率主要受光合有效辐射影响。气孔导度主要受光合有效辐射影响,地面灌溉条件下气孔导度对环境变化的响应更积极。蒸腾速率主要受土壤含水率和光合有效辐射的影响,土壤水分充足时,蒸腾速率对光合有效辐射的响应更敏感。相同条件下,土壤含水率越高蒸腾速率越大。     

Modelling of root ABA synthesis, stomatal conductance, transpiration and potato production under water saving irrigation regimes

Application of water saving irrigation strategies in agriculture has become increasingly important. Both modelling and experimental work are needed to gain more insights into the biological and physical mechanisms in the soil-plant system, which regulates water flow in the system and plays a central role in reducing crop transpiration. This paper presented a mechanistic model (Daisy) developed based on data obtained in the SAFIR project on measured leaf gas exchange and soil water dynamics in irrigated potato crops grown in a semi-field environment subjected to different irrigation regimes. Experimental data was compared to simulated results from the new enhanced Daisy model which include modelling 2D soil water flow, abscisic acid (ABA) signalling and its effect on stomatal conductance and hence on transpiration and assimilation, and finally crop yield. The results demonstrated that the enhanced Daisy model is capable of simulating the mechanisms underlying the water saving effects of the partial root-zone drying (PRD) irrigation as compared with the conventional full irrigation (FI). However the simulated effect on both crop yield and water use in this particular experiment was negligible indicating more experimental studies are necessary in order to improve on the model.     

Salinity and drought

Summary Water deficit (water stress — WS) and excess salt (salt stress — SS) evoke similar plant responses, yet clear differences have been observed. The effect of the two forms of stress applied consecutively to cotton (Gossypium hirsutum) and pepper (Capsicum annuum) was studied in a growth chamber (29/20°C day/night temperature, 50% RH, 12-h photoperiod) in 2.5-liter containers packed with a silt loam soil.Leaf water potential () under increasing WS [soil water potential decrease from –0.16 to –1.10 MPa] of transpiring cotton and pepper plants declined to lower levels than under equivalent SS. The decline of leaf solute potential ₀ on the other hand, was less under WS than under SS, resulting in reduced turgor potential ( _p ), in contrast with turgor maintenance under SS. Predawn turgor potential of WS plants was maintained at all levels of soil water potential. Transpiration, CO₂ assimilation and light period leaf extension rate were higher under low soil water potential produced by salinity than an equivalent value produced by water deficit.The more severe effect of WS was attributed to incomplete osmotic adjustment — the reduction in solute potential did not keep pace with the reduction in leaf water potential, and to increased root interface resistance in the dry soil.The leaf sap of cotton under WS had a higher proportion of sugars (65%) than electrolytes, compared to SS. When WS was converted to SS and plant solute potential decreased, electrolytes were taken up at the expense of a reduction in the sugar concentration. Water stress and salt stress may have an additive effect in depressing growth. But at equivalent levels, the relative magnitude of the effect of low soil matric potential (WS) on plant growth was twice as great as that of low soil solute potential (SS).     

Diurnal changes in the water relations and transpiration of a soybean crop simulated during the development of water deficits

Summary A new model for transpiration of a soybean crop is formulated and solved numerically: the model specifically includes the water stored in the plant. It describes the changes in the daily course of transpiration, stomatal behaviour, leaf water potential and leaf temperature as water deficits develop. The calculated values of leaf water potential (Fig. 3) and transpiration (Fig. 5) compared well with measured values observed during the development of water deficits in a soybean crop growing on a grey cracking clay soil.     

Water relations of drought-resistant and drought-sensitive wheat cultivars sprinkled with saline water

Summary Water potential, osmotic potential, turgor potential, and stomatal resistance were measured on leaves of a drought-sensitive (Ponca) and a drought-resistant (KanKing) cultivar of winter wheat (Triticum aestivum L.) treated with foliar applications of NaCl to determine the effect of salt on the water status of two cultivars varying in drought resistance. Plants were grown under controlled conditions in soil, which was watered or allowed to dry. Water potential of the soil was determined. Given an ample water supply, water potential and osmotic potential of leaves of both cultivars with NaCl were lower, and stomatal resistance was higher, than without NaCl. The combination of salt and drought killed both cultivars, but the turgor potential of the drought-sensitive cultivar with the two stresses reached zero before that of the drought-resistant cultivar. Under limited water supply, both cultivars with foliar applications of salt extracted more water from soil than they did with no salt, and the drought-resistant cultivar took up more water than did the drought-sensitive cultivar. The drought-resistant cultivar with foliar NaCl maintained a higher turgor potential and extracted more water from the drying soil than did the drought-sensitive cultivar with foliar NaCl, suggesting that the drought-resistant cultivar was also more salt tolerant.     

Water potential and turgor pressure as a selection basis for wind-grown winter wheat

Two varieties of winter wheat (Triticum aestivum L. em. Thell. ‘Ponca’ and ‘KanKing’), one considered drought sensitive (‘Ponca’) and one considered drought resistant (‘KanKing’), were grown from seed in pots of soil placed in wind or still air for 36 days to determine the effect of wind on water potentials, turgor pressure, and stomatal resistance of leaves. During the experiment, plants were well watered and soil was moist. In wind and still air, water potentials and turgor pressures of the drought sensitive wheat were higher, and stomatal resistances were lower, than those of the drought resistant wheat. Plants grown in wind had lower turgor pressures than plants grown in still air.The results showed that wind reduced turgor pressure and that measurements of water potential, turgor pressure, and stomatal resistance could be used to select varieties for windy areas.     

不同土壤对拉巴豆生长及光合特性的影响

土壤是影响植物生长的重要因子.选取重庆市典型和具有代表性的4种主要土壤为对象,以拉巴豆为试验材料,通过盆栽模拟试验,研究了不同土壤类型对拉巴豆生长、生理及光合特性的影响.结果表明:在微酸性和酸性的灰棕紫泥土壤上,拉巴豆生长、生理和净光合速率显著优于灰岩黄壤与碱性紫色土,其地上生物量是后者的2～3倍,估计与拉巴豆起源于热带和亚热带且长期适应酸性土壤有关;拉巴豆的生理及光合特性与其长势呈正相关,对于不同土壤类型和不同光合指标,其日变化曲线有所不同,但净光合速率、蒸腾速率和叶片气孔导度日变化均为单峰曲线,峰值均在10:30左右,微酸性紫色土的峰值最高,其次为酸性紫色土,最后为灰岩黄壤和碱性紫色土.     

Effect of salinity on water stress, growth, and yield of maize and sunflower

Maize and sunflower were grown in tanks filled with loam and clay, and were irrigated with water of three different levels of salinity. Predawn leaf-water potential and stomatal conductance were used as parameters for water stress. The predawn leaf-water potential of maize was higher than that of sunflower, but the effect of salinity and soil texture on the predawn leaf-water potential was the same for both crops. The stomatal conductance of sunflower was much higher and more severely affected by salinity and soil texture than the stomatal conductance of maize.

Although salinity had a more serious effect on the development of leaf area and canopy dry matter of sunflower, its effect on evapotranspiration and grain yield was the same for both crops. Soil texture had a stronger effect on the development of leaf area and canopy dry matter of sunflower, which also appeared in the evapotranspiration and grain yield, indicating that sunflower is more sensitive to drought than maize.     

玉米不同生育期水分胁迫指标

采用田间小区实验 ,通过对玉米不同生育期、不同土壤水分条件下叶水势、气孔导度、光合作用、植株蒸腾、生理生态状况及产量形成的观测试验 ,并在总结已有成果的基础上 ,分析研究了玉米不同生育阶段的水分胁迫指标阈值 ,提出了玉米不同生育阶段的水分胁迫指标 ,为节水灌溉与灌溉管理提供了科学、实用的依据。     

Overestimation of soybean crop transpiration by sap flow measurements under field conditions in Central Portugal

Direct measurements of the xylem sap flow by the stem heat balance technique can be a valuable aid for determining the irrigation demand of field crops. In the present study, soybean (Glycine max (L.) Merr.) sap flow was evaluated under well-watered and water-stressed conditions using Dynamax SGA10 sap flow gauges. Solar radiation was measured continuously throughout the growing season. Soil water content was measured before and after each irrigation. There was a close relationship between solar radiation and xylem sap flow. The water flux in the soybean stems responded realistically to changes in the soil water content. However, the absolute values of sap flow were highly questionable. Calculating crop transpiration from sap flow measurements, the results were up to 4 times as high as calculated transpiration from soil moisture data and simulated transpiration using the locally calibrated soybean crop growth model SOYGRO. A sensitivity analysis of the stem heat balance technique gave no indications of technique or input errors. The gauge design was possibly not appropriate for the outdoor installation on soybeans.     

Irrigation planning in cotton through simulation modeling

Experiments were undertaken at CCS Haryana Agricultural University Farm, Sirsa (India) to estimate the optimum irrigation schedule for cotton resulting in minimum percolation losses. The sprinkler line source technique was adopted for creating various irrigation regimes at different crop growth stages. The SWASALT (Simulation of Water And SALT) model after calibration and validation provided water balance components. The wa-ter management response indicators (WMRI's) such as transpiration efficiency E_t/(Irr + P), relative transpiration E_t/E_tp, evapotranspiration efficiency ET/(Irr + P), soil moisture storage change ΔW/W_int (deficit/excess) and percolation loss Perc/(Irr. + P) were evaluated using water balance components as estimated by the simulation study. Under limited water supply conditions, the optimum irrigation depth was found to be 57 mm at crop growth stages with pre-sowing and 1^st irrigation of 120 mm and 80 mm respectively for sandy clay loam underlain by sandy loam soil (Type I). The corresponding values of relative transpiration, transpiration efficiency and evapotranspiration efficiency were 0.65, 0.65 and 0.89 respectively. The crop yield varied linearly with increasing irrigation depth which was evident from increase in relative transpiration with increasing depth of water application. However, increased depth of irrigation resulted in less moisture utilisation from soil storage (20% depletion at 40 mm depth and 4.4% moisture built up at 100 mm depth). The extended simulation study for sandy soil underlain by loamy sand (Type II) indicated that two pre-sowing irrigations each 40 mm and subsequent irrigations of 40 mm at an interval of 20 days depending upon rainfall were optimum. This irrigation scenario resulted in zero percolation loss accompanied by 74% relative transpiration and 14 per cent soil moisture depletion. Received: 20 November 1995     

隔沟交替灌溉研究进展

隔沟交替灌溉是以通过改善作物根信号功能、光合作用、蒸腾作用和气孔导度等生理特性,进而提高作物产量为目的的一项高效节水灌溉技术。介绍了隔沟交替灌溉技术发展概况,系统阐述隔沟交替灌溉的作用机理,主要包括根系系统的吸收补偿功能、农田土壤水分消耗和水分利用效率变化3个方面,明确了该技术在作物栽培中的应用效果与发展前景。隔沟交替灌溉可显著提高作物产量和水分利用效率,在优质高产节水型农业生产中具有重要意义。      

北疆高产棉田水热平衡的初步研究

通过对高产棉田和普通棉田的生长状况、植物和土壤水分平衡与热量平衡的研究 ,提出在沙壤地的普通棉田 ,采用“轻灌勤灌”的灌溉方法 ,是改善棉田水热平衡 ,获得高产的有效技术措施     

Water use efficiency of narrow row cotton

Summary A field experiment was conducted on the west side of the San Joaquin Valley in California to determine water use, crop growth, yield and water use efficiency of Acala (SJ-2) cotton (Gossypium hirsutum L.) grown in 0.5 m spaced rows on a Panoche clay loam soil (Typic Torriorthents). Evapotranspiration was determined by water balance techniques utilizing neutron soil moisture measurements. All neutron measurements were made within a 3 m soil profile in 0.20 m increments. The measured evapotranspiration was compared to climatic estimates of potential evapotranspiration, and to calculations using a one-dimensional soil water balance model that separately computed soil water evaporation and plant transpiration. Crop growth was determined by weekly destructive plant sampling. Leaf area was determined along with dry matter components of leaves, stems, fruiting parts (flowers and squares) and bolls. Final yield was determined by machine harvesting (brush stripper) 720 m² from each plot. Lint yields and fiber quality were determined by sample ginning and fiber analysis at the U.S. Cotton Research Station at Shafter, California. Three irrigation regimes were established that resulted in an evapotranspiration range from a high deficit condition to full irrigation at the calculated atmospheric demand.The measured evapotranspiration of narrow row cotton under a full irrigation regime was 778 mm, 594 mm under a limited irrigation regime and 441 mm under a regime with no post-plant irrigation. The evapotranspiration from these irrigation treatments was accurately simulated by a water balance model. that used inputs of potential evapotranspiration, leaf area index, soil water holding capacity and root development.The average lint yield from narrow row cotton with a full irrigation regime was 1583 kg/ha, the average lint yield from a limited irrigation regime was 1423 kg/ha and the average lint yield from a treatment with no postplant irrigation (fully recharged soil profile at planting) was 601 kg/ha. The full irrigation regime resulted in a dry matter production of approximately 16 t/ha while the limited irrigated regime produce 11 t/ha and the no-postplant irrigation regime produced 7 t/ha of dry matter. The fiber quality results indicated significant (0.05 level) differences only in 50% span length and micronaire, with the 2.5% span length, uniformity index, elongation and strength indicating no difference.Cotton lint yield was found to be directly related to total evapotranspiration although the relationship was slightly non-linear while dry matter yield was found to be linearly related to evapotranspiration. Both lint and dry matter yield were found to have a linear relationship to estimated transpiration from the water balance model calculations.Contribution from the Unived States Department of Agriculture, Agricultural Research Service, Western Region and the University of California     

喷施乙烯利提高玉米幼苗抗旱机理研究

以室内盆栽玉米幼苗为材料,研究４００ｍｇ／Ｌ乙烯利（ＣＥＰＡ）提高玉米幼苗抗旱的机理。结果表明：干旱条件下,ＣＥＰＡ能显著提高玉米幼叶相对含水量（ＲＷＣ）,增强其渗透调节能力（ＯＡ）,并在一定程度上降低其膜相对透性（ＲＰ）。随干旱时间的延长,玉米幼叶的净光合速率（Ｐｎ）和气孔导度（Ｇｓ）皆下降,尤其在严重胁迫下,ＣＥＰＡ对维持叶片Ｐｎ有一定极积作用     

冬小麦叶片水势、气孔阻力、蒸腾速率与环境因素的关系

本文依据田间试验资料,分析了冬小麦叶片水势、气孔阻力和蒸腾速率在不同土壤基质势条件下的日变化规律,探讨了其与土壤基质势和天气条件(光照强度、净辐射、饱和差、气温)之间的关系,建立了叶片水势、气孔阻力、蒸腾速率与环境因素间的定量关系式。