Improving Drought Tolerance by Exogenous Application of Glycinebetaine and Salicylic Acid in Sunflower

Water shortage is a severe threat to the sustainability of crop production. Exogenous application of glycinebetaine (GB) and salicylic acid (SA) has been found very effective in reducing the adverse affects of drought stress. This study was conducted to examine the possible role of exogenous GB and SA application in improving the yield of hybrid sunflower (Helianthus annuus L.) under different irrigation regimes. There were three levels of irrigation, viz. control (normal irrigations), water stress at vegetative stage (irrigation missing at vegetative stage) and water stress at flowering stage (irrigation missing at flowering stage). GB and SA were applied exogenously at 100 and 0.724 mm , respectively, each at the vegetative and at the flowering stage. Control plants did not receive application of GB and SA. Water stress reduced the head diameter, number of achene, 1000‐achene weight, achene yield and oil yield. Nevertheless, exogenous GB and SA application significantly improved these attributes under water stress. However, drought stress increased the free leaf proline and GB, and were further increased by exogenous application of GB and SA. However, exogenous GB application at the flowering stage was more effective than other treatments. Oil contents were also reduced under water stress; however, GB and SA application could not ameliorate the negative effect of water stress on achene oil contents. The effects of water stress and foliar application of GB were more pronounced when applied at the flowering stage than at the vegetative stage. Moreover, exogenous GB application was only beneficial under stress conditions.     

Breaking Uniculm Growth Habit of Spring Cereals at High Latitudes by Crop Management. II. Tillering, Grain yield and Yield Components

Long days at high latitudes inhibit tillering of cereals and hence seeding rates of 500–700 seeds m⁻² are commonly used for spring wheat, barley and oats in Finland. Costs could be reduced by using a lower seeding rate in combination with crop management to produce more head-bearing tillers m⁻². This study was designed to assess possibilities of breaking the uniculm growth habit of spring cereals by (1) lowering the seeding rate from 600 to 300 seeds m⁻² and (2) manipulating tiller growth with early mechanical treatments to the crop (rolling, cutting) or chemical applications (foliar urea, CCC and GA). A low seeding rate and early application of foliar CCC at high latitudes, under good moisture conditions prior to heading, promoted 20% more head-bearing tillers and 6% higher grain yield than standard management practices. However, cultivars differed in their response to CCC. The advantageous effects of CCC at a low seeding rate were attributed to increase, over the controls, in contribution of head-bearing tillers to grain yield in wheat (cultivar Heta ), but more grains per head in oats (cultivar Veli ). Varietal recommendations for use of low seeding rate in combination with early CCC spraying should be examined further.     

Foliar Application of Glycinebetaine and Salicylic Acid Improves Growth,Yield and Water Productivity of Hybrid Sunflower Planted by Different Sowing Methods

Improved planting methods and foliar application of glycinebetaine (GB) and salicylic acid (SA) can improve the water productivity in field crops under limited water supply conditions. A 2‐year field study was conducted to evaluate the possible role of different planting methods and foliar applications of GB and SA in improving the yield, quality and water productivity of hybrid sunflower (Helianthus annuus L.). The crop was planted by flat sowing (75 cm spaced rows) and ridge sowing (75 cm spaced ridges), with GB and SA applied exogenously at 100 and 0.724 mm , respectively, at both budding and flowering stages, while control plots received distilled water. Ridge sowing, rather than flat sowing, improved the biological yield, oil yield, leaf area index (LAI), crop growth rate (CGR), plant height, water‐use efficiency and final achene yield during both the years. Foliar applications of GB and SA at both the stages improved the achene yield, although foliar application of GB at flowering was the most effective. Neither the planting methods nor the foliar application of GB and SA altered the achene oil contents during both the years. Foliar application of GB and SA increased the free proline content of the leaf and GB contents at flowering but reduced the achene protein contents, whereas planting method had no effect on these attributes across the years. Of the foliar applied chemicals, GB was more effective in improving sunflower growth and yield and water productivity than SA. To conclude, ridge sowing coupled with foliar application of GB at flowering stage could be beneficial for achieving maximum yields of hybrid sunflower under relatively water limited conditions in the field.     

Interactive Effects of Sudden and Gradual Drought Stress and Foliar‐applied Glycinebetaine on Growth,Water Relations,Osmolyte Accumulation and Antioxidant Defence System in Two Maize Cultivars Differing in Drought Tolerance

Influence of sudden and gradual drought stress (DS) and foliar‐applied glycinebetaine (GB) on growth, water relations, osmolyte accumulation and antioxidant defence system were investigated in the plants of two maize (Zea mays L.) cultivars, that is, drought‐tolerant Shaandan 9 (S₉) and drought‐sensitive Shaandan 911 (S₉₁₁). Sudden DS caused less accumulation of GB and free proline, but a more accumulation of malondialdehyde (MDA), which resulted in a greater reduction in leaf relative water content (RWC) and dry matter (DM) in both cultivars compared with the gradual DS. Exogenous GB application caused a rise in DM, RWC, contents of GB and free proline as well as the activities of SOD, CAT and POD along with a decline in MDA content to various extent in both cultivars under both types of DS. A more pronounced effectiveness of GB application was observed in S₉₁₁ than that in S₉ under the same type of DS. It seemed that the more serious damage of DS was on maize plants, and the better positive role of GB was observed in terms of mitigating the adverse effects of DS. From this study, it was possible to propose that hardening for drought resistance by gradual DS treatment and GB application are effective to make plants robust to thrive under water‐deficit conditions.     

Effects of an Early Application of Sulphur or Etephon as Foliar Spray on the Growth and Yield of Spring Barley in a Mediterranean Environment

Leaf area development, biomass production and yield of four spring barley varieties grown in a Mediterranean environment (southern Spain) in response to an early application of foliar sulphur or etephon have been studied. Both sulphur and etephon produced similar results compared to the control. Thus, whereas the maximum leaf area index on untreated plots was reached at the beginning of shooting, the growth of foliar area in the treated ones was extended until anthesis and its decline during maturity was similarly retarded. This led to a significant improvement in the biomass at anthesis (which was closely correlated with grain yield) as well as in the leaf area duration during grain filling. These effects were principally due to variations in the number of leaves per plant, caused by a higher tiller production in the treated plants and not by an increase in the number of leaves per tiller or by leaf size.
An application of sulphur or etephon at tillering increases grain yield by raising both the number of ears per plant and per plot, without modifying the number of grains per ear or 1000-grain weight. The similarity between the effects of sulphur and etephon may be due to the fact that sulphur absorbed by the leaves results in an increase in methyonine, the biological precursor or ethylene. The positive correlation between biomass at anthesis and number of ears over grain yield suggests that sink capacity and source activity are closely related and both simultaneously limited by the environment.     

Effect of Water Stress on Physiological Attributes and their Relationship with Growth and Yield of Wheat Cultivars at Different Stages

The effects of water stress on physiological attributes of drought‐sensitive (Kalyansona) and drought‐tolerant (C‐306) wheat cultivars were studied in a pot experiment. Water stress was imposed by withholding irrigation at boot and anthesis stages. Leaf water potential, leaf osmotic potential and leaf turgor potential (measured with pressure chamber and osmometer), as well as leaf diffusive resistance, leaf transpiration rate and leaf‐to‐air transpiration gradient (measured with a steady‐state porometer) were measured diurnally. Growth and yield parameters were recorded after harvesting of the crop. Triplicate data were analysed using a completely randomized design and correlations amongst these parameters were computed. Water stress was found to reduce diurnal leaf water potential and leaf osmotic potential in both the genotypes but leaf osmotic potential was significantly higher in the drought‐tolerant cultivar C‐306 than in the drought‐sensitive cultivar Kalyansona. Positive turgor was recorded in both the genotypes under water stress and non‐stress conditions. Water‐stressed plants showed significantly lower turgor potential than control plants. In diurnal observations, water‐stressed plants exhibited significantly higher leaf diffusive resistance in both genotypes at both stages. The diffusive resistance of C‐306 was predominantly higher than that of Kalyansona. Water stress decreased leaf transpiration rate at both stages but the reduction was higher at the anthesis stage. The leaf‐to‐air temperature gradient was much higher in C‐306 than in Kalyansona at the boot stage but at the anthesis stage genotypic variation was non‐significant. The capacity to maintain cooler foliage was lower at the anthesis stage than at the boot stage in both the cultivars. Shoot dry weight, number of grains, test weight, grain yield, biological yield and harvest index decreased to a greater extent when water stress was imposed at the anthesis stage, while imposition of water stress at the boot stage caused a greater reduction in plant height and number of tillers. Similarly, water stress caused a smaller reduction in growth, yield and yield attributes in C‐306 than in Kalyansona. In general, the correlation coefficient of grain and biological yield with water potential and its components was positive and highly significant. Similarly, turgor potential was also correlated positively and significantly with grain yield at both the stages, but with biological yield it was significant only at the anthesis stage. A negative and significant correlation was obtained for diffusive resistance and leaf‐to‐air temperature gradient with grain yield at the boot and anthesis stages. The rate of transpiration was also positively and significantly correlated to grain and biological yields at both the stages. Amongst the yield attributes, number of leaves and number of tillers were positively correlated at the anthesis stage, whereas leaf area and shoot dry weight were significantly correlated with grain and biological yields at both the stages.     

Effects of Temporary Water Stress After Anthesis on Grain Yield and Yield Components in Different Tiller Categories of Two Spring Wheat Varieties

Water stress might limit grain yields of cereals under humid conditions. The objective of this study was to investigate the effect of a temporary water shortage at three different stages after anthesis on the grain yield and yield components of different tiller categories in two spring wheat varieties. A pot experiment with controlled water supply and rain shelters was conducted in 1984 and 1985 in Kiel, N. W. Germany. The water stress (pF 2.9 to 3.4) was imposed either between anthesis to early milk development of the caryopsis (WS1) (EC 65 to EC 72 according to Z adoks scale), early milk development to late milk development of the caryopsis (WS2) (EC 72 to EC 77) and late milk development to maturity (WS3) (EC 77 to EC 92). The control had a constant water supply throughout the growing season of between pF 2.2 to 2.5.
The water stress treatment WS1 significantly reduced the single plant yield by 10 % (1984) and 15 % (1985) in one variety (Selpek), whereas the other variety was unaffected. The response of both varieties to the two later treatments was smaller and insignificant.
In the first year the yield decrease in the variety Selpek after the WS1 treatment was mainly caused by a lower number of ears per plant compared with the untreated control (WS0). In the second year (1985) additionally a lower grain weight of the second category shoots caused by a reduction of the number of kernels per ear contributed to the decrease of the single plant yield. The yield component thousand grain weight could not compensate for the reduction in the number of kernels per ear.     

不同时期干旱胁迫对甘薯内源激素的影响及其与块根产量的关系

在人工控水条件下, 以抗旱品种济薯21和不抗旱品种济紫薯1号为试验材料, 设置全生育期干旱胁迫(DS)、发根分枝期干旱胁迫(DS1)、蔓薯并长期干旱胁迫(DS2)、快速膨大期干旱胁迫(DS3) 4个处理, 全生育期正常灌水(WW)为对照, 研究其对甘薯内源激素及块根产量的影响。结果表明, 与对照相比, 2个品种不同年份的所有干旱胁迫处理的鲜薯和薯干产量均显著下降。其中, DS薯干产量减产幅度最大, 济薯21和济紫薯1号3年平均分别减产44.62%和56.21%; 其次是DS1, 减产32.03%和44.03%; 再次是DS2, 减产30.41%和39.39%; DS3的减产幅度最小, 为13.66%和17.88%。抗旱品种济薯21的减产幅度小于不抗旱品种济紫薯1号。干旱胁迫抑制了甘薯地上部生长及块根的形成和膨大, 两个品种的单株叶片数、蔓长、地上部干重、地下部干重和块根淀粉率, 与对照相比, 各时期均表现为, DS的减少幅度最大, 其次是DS1和DS2, DS3的减少幅度最小。不同时期干旱胁迫均引起叶片和块根中GA、IAA和ZR含量下降, ABA含量上升。地上部干重与叶片GA、IAA和ZR含量呈显著正相关, 与ABA含量呈显著负相关; 地下部干重与块根GA、IAA和ZR含量呈显著正相关, 与ABA含量呈显著负相关。总之, 不同时期干旱胁迫均导致甘薯产量下降, 且胁迫时间越早, 对甘薯内源激素和块根产量的影响越大, 发根分枝期是甘薯对水分最敏感的时期。     

氮素水平对杂交棉氮素吸收、生物量积累及产量的影响

在滴灌条件下,采用单因素随机区组设计,研究了不同氮素水平(0、135、270、405、540 kg·hm-2)对杂交棉生物量、氮素吸收及产量的影响。结果表明:杂交棉生物量、吸氮量和产量随氮素水平的增加而增加,至施氮量为405 kg·hm-2时达最高值,分别较不施氮水平提高了49.93%,75.43%和82.24%;氮素水平对杂交棉蕾、花、铃生物量积累和氮素吸收的影响大于茎和叶;氮素的增加还显著提高了杂交棉的生物量积累速率、氮素吸收速率以及单株铃数和铃重。本试验中270 kg·hm-2的施氮量可初步满足杂交棉获得高产的需要,施氮量过大不利于产量的提高。本研究条件下杂交棉获得最高产量的氮肥适宜用量为386.5～388.4 kg·hm-2。     

Drought Stress Effects on Seed Yield, Yield Attributes, Growth, Cell Membrane Stability and Gas Exchange of Synthesized Brassica napus L.

Drought stress effects on leaf gas exchange, cell membrane stability, seed yield and yield attributes of synthesized Brassica napus L. cv. Bangla kale and Bangla cabbage were compared. Drought stress treatments were imposed at early vegetative, late vegetative and flowering stages by withholding watering. Bangla cabbage produced greater pods/plant, larger seed size, greater total dry matter/plant, seeds/pot, and 17% greater yield than Bangla kale. The seed yield in plants stressed at early vegetative, late vegetative and flowering stages were 59, 74, 88% lower respectively, than watered plants. Drought stress reduced leaf photosynthesis by 67 to 97%. Bangla cabbage had 68% greater photosynthesis and 56% greater stomatal conductance than Bangla kale under stress at flowering stage. Leaf temperature was 1 to 2°C higher in stressed plants than watered plants. The cell membrane stability (CMS) increased up to 83% at flowering stage under stress compared to 21% under watered conditions. Although Bangla cabbage had high seed yield, yield attributes and photosynthesis under stressed conditions at flowering stage, its CMS values were lower than those of Bangla kale.     

播种期对农牧交错带莜麦生长发育和产量形成的影响

为了探索播种期对莜麦生长发育和产量形成的影响,为农牧交错带莜麦适期播种和高产栽培提供依据,此研究采用随机区组排列设计,通过两年的分期播种实验,研究播种期对莜麦生育期、形态指标和产量形成的影响。结果表明：播种期对莜麦生育期、株高和单株叶面积影响显著,中播和晚播莜麦的株高和单株叶面积均高于早播。随着播期推迟,莜麦营养生长期缩短,温度是主要原因,生殖生长期延长,降水是主要原因,生育期总天数缩短,莜麦生殖生长阶段在整个生育期中所占比例增加。播期处理对莜麦单株分蘖数、穗数和千粒重影响达显著水平。两年试验中,中播（5月18日）产量平均可达107.7 g/m2,均高于早播（5月8日）和晚播（5月28日）。建议农牧交错带地区莜麦适宜播期安排在5月18日左右。     

氮素对滨海盐土棉花产量、品质及生物量的影响

为研究不同施氮量对滨海盐土花后棉株生物量、生物量累积特征及其与产量、品质的关系,于2010年和2012年在江苏滨海盐土设置了氮肥水平试验。结果表明:在0~600 kg·hm-2范围内施氮量越大棉株总生物量累积越多,而皮棉产量2010年和2012年分别在施氮375 kg·hm-2和300 kg·hm-2时达到最大;成铃数在施氮300~375 kg·hm-2范围内达到最大;铃重和衣分随施氮量增加而增加,达到最大值后(≥300 kg·hm-2)差异不显著。在300~375 kg·hm-2施氮量范围内纤维比强度最高;高氮有利于上部、顶部果枝纤维长度、比强度、伸长率的提高和马克隆值的优化,但显著降低中下部果枝棉纤维比强度,导致中部纤维马克隆值变劣、下部果枝纤维伸长率下降,说明高氮对中下部果枝棉纤维品质的形成利弊各半,适量高氮可提高上部及顶部果枝产量、品质。在滨海盐土条件下,利于产量、品质及氮素利用效率提高的适宜施氮量为375 kg·hm-2。     

减磷加炭对北疆春小麦磷素利用及产量的影响

本试验探讨不同施肥模式对小麦磷素积累与转运及产量的影响,为合理减磷加炭、提高磷肥利用率提供理论参考。本试验磷肥（P₂O₅）设4个水平,生物炭设3个水平。比较不同施肥模式下小麦磷素积累分配、磷素利用率、产量与磷肥利用率等指标的差异。结果表明：在减量施磷15%(102 kg/hm²)配施生物炭22.5 t/hm²(P3B2)处理下各指标综合效果最好,在该处理下春小麦干物质量最高,为4.07 g/株,较对照增加8.24%,该处理下植株磷含量增加,且主要分配在穗部,较对照增加6.21%;茎部磷素转移在磷肥配施低炭时增幅最高,磷肥配施高量生物炭时增幅最低;叶部磷素转移在磷肥与生物炭配施时对植株叶部磷素的影响大于单施磷肥。本试验条件下,施磷102 kg/hm²同时施加生物炭22.5 t/hm²对提高茎、叶对籽粒的贡献率有明显的促进作用,提升了磷素利用效率与磷素生理效率,并且达到最好的增产效果,为北疆灌区磷肥减施增效提供理论依据。     

花后高温胁迫下氮肥追施后移对小麦产量及旗叶生理特性的影响

为探明施用氮肥与减缓小麦花后高温伤害的关系并阐明其生理机制,于2011-2012年和2012-2013年连续两个生长季,选用小麦品种山农16和济麦22,在增温棚中进行花后11~15 d的高温胁迫处理,比较了氮肥全作基肥(T0)、1/2基肥+1/2拔节期追肥(T1)、1/2基肥+1/2孕穗期追肥(T2) 3种施氮方案下的产量、产量构成因素、旗叶光合特性及部分酶的活性。在高温胁迫下,T2方案较T0和T1显著增加籽粒千粒重和产量,提高旗叶谷氨酰胺合成酶(GS)活性,增加旗叶气孔导度和光合速率,提高旗叶过氧化氢酶(CAT)和过氧化物酶(POD)活性,促进花前营养器官干物质向籽粒转运,增加开花后积累的干物质对籽粒的贡献率。两个品种结果基本一致。综合两年结果可以看出,T2处理显著优于T0和T1处理,T2处理能显著缓解高温胁迫的伤害,提高籽粒产量。     

长江流域直播冬油菜氮磷钾硼肥施用效果

冬油菜直播种植的推广应用对提高我国油菜籽总产量和保障食用油安全有重要意义。2009-2010年度在长江流域6个冬油菜主产省布置36个大田试验,研究当前生产条件下我国直播冬油菜的氮磷钾硼肥施用效果和肥料利用率,比较农民习惯施肥与推荐施肥的差异,并与移栽油菜施肥效果进行对比,以探讨直播冬油菜的施肥管理措施。结果显示,在推荐施肥量和施肥方法条件下,氮磷钾硼肥配合施用(NPKB)处理直播冬油菜的油菜籽产量和产值平均分别为2001 kghm^–2和8205元hm^–2,显著高于农民习惯施肥(FFP)处理,施用效果为N > P > B > K。NPKB配合施用显著促进直播冬油菜的养分吸收,N、P、K累积量分别为104.2、20.4和160.2 kg hm^–2。NPKB配施条件下,直播冬油菜的氮、磷、钾肥表观利用率平均分别为35.8%、22.3%和45.9%,明显高于农民习惯施肥的20.8%、7.2%和28.0%。说明合理施肥对直播冬油菜生产有重要作用,现阶段应积极推行氮磷钾硼肥配施技术,并根据生长发育特点和养分吸收规律调整肥料的施用时期和比例。     

Comparison of Salt and Drought‐Stress Effects on Maize Growth and Yield Formation with Regard to Acid Invertase Activity in the Kernels

The long‐term effects of salt stress (11 dS m^?1) and drought stress (35 % WHC) were investigated for two maize genotypes, focusing on the relation between metabolic changes around the time of pollination and the impact on yield determinants at maturity. The relatively salt‐resistant hybrid Pioneer 3906 and the relatively drought‐resistant hybrid Fabregas were compared. The experiments were conducted in large plastic containers in a vegetation hall in two consecutive years (2011 and 2012). Plant height and leaf area were significantly reduced under both stress conditions. The transpiration rate was only slightly reduced under drought stress; but under salt stress, a significant reduction occurred 40–53 days after sowing. As a significant increase in sucrose concentrations was observed in the salt‐treated maize kernels 2 days after pollination, the availability of assimilates was not limiting and the plants could afford to save water by reduced stomatal opening. Although under both stress conditions the soluble acid invertase activity was reduced 2 days after pollination, concomitantly, an increase in hexose concentrations was observed. Thus, in these experiments, the delivery of hexoses by acid invertase activity did not limit kernel development. Differences in grain yield at maturity between salt and drought stress were most likely caused by salt‐specific effects (Na⁺ toxicity), Fabregas being more affected than Pioneer 3906.     

砂姜黑土区秸秆还田与肥料配施对夏玉米生育和产量的影响

为探索在苏北平原砂姜黑土区推广小麦秸秆还田技术,以‘苏玉23’为材料,通过设置小麦秸秆不还田、小麦秸秆还田和有机肥、常规肥配施等5种处理方式,研究了其对玉米出苗、茎秆形态、干物质积累分配和产量及其构成因素的影响。结果表明：小麦秸秆不还田+不施肥料(T0)对玉米出苗质量、植株生长发育、干物质积累分配、穗部性状和产量及其构成因素均造成不利影响。小麦秸秆还田+肥料配施处理(T2、T3、T4)能显著改善当季玉米的出苗质量和幼苗素质,有利于植株的正常发育。与对照化肥处理相比,小麦秸秆还田+常规施肥(T2)虽能改善玉米出苗质量和茎秆形态,但对玉米穗部特征和产量有不利影响。T2处理缩短穗长,降低千粒重6.7%,导致减产8.4%;而小麦秸秆还田+有机肥配施或优化施肥处理(T3、T4)均有促进作用,出苗素质显著提高,其中以小麦秸秆还田+优化施肥处理(T4)效果最显著。与对照(T1)相比,T4处理的穗粒数和千粒重分别增加24.0%和6.7%,增产5.8%。播种后15天,T4处理的出苗率达到77.9%,比对照增加4.9%,出苗均匀度提高14.4%,为玉米增产提供了保障。可见,砂姜黑土区小麦秸秆还田能改善当季玉米的出苗质量、促进玉米植株的生长发育,有利于干物质向籽粒转移,配施有机肥和优化施肥能显著提高玉米产量,其中以优化施肥效果更佳。     

Effect of Temperature Hardening on Growth, Carbohydrate and Protein Levels in Three Grain Crops

The effect of seedling pretreatment at different temperature levels and periods of exposure on growth, pigments, carbohydrates and proteins was studied in three grain crops; sorghum, wheat and barley at different stages of growth. Greater shoot-dry weights were obtained in sorghum with exposure for 15 hrs at 40 °C in the flowering, in wheat for 2 hrs at 10 and 40 °C in the fruiting and in barley for 15 hrs at 0 °C in the flowering stage. Increased root-dry weights were achieved by wheat with exposure for 4 and 15 hrs at all levels even at 0 °C in the flowering and for 15 hrs at 40 °C in the fruiting stage. Chl_a and Chl_b were more responsive in sorghum to higher temperature pretreatments than either wheat or barley. In sorghum the temperature extremes (0 and 50 °C) had resulted in a substantial reduction of Chl_a, and Chl_b in the fruiting stage. Lower and higher temperature-pretreatments had resulted in total available carbohydrate reduction in shoot and root of sorghum and wheat at the early stage, but the reverse was true later in flowering. In contrast, lower and higher temperature pretreatments had increased shoot-protein in sorghum and wheat in the vegetative and in sorghum in the flowering stage. Root-protein was more responsive to low temperature-pretreatments in sorghum and barley during the fruiting stage.     

Effects of Irrigation at Different Growth Stages on Vegetative Growth of Mung Bean, Vigna Radiata (L.) Wilczek, in Dry and Intermediate Zones of Sri Lanka

Mung bean crops in the subhumid zones of Sri Lanka experience significant drought periods. The objective of this study was to quantify the growth response of mung bean to irrigation at different phenological stages and thereby determine the optimum irrigation regime to maximize growth. Four field experiments were conducted at two sites in 1995 and 1996. The crop duration of mung bean was divided into three stages: vegetative (from germination to appearance of first flower), flowering (from appearance of first flower to 75 % pod initiation) and pod-filling (from 75 % pod initiation to maturity). Eight treatments were devised to represent all possible combinations of irrigation at the three stages. Maximum leaf area index (ranging from 0.6 to 2.6 across treatments) and total leaf area duration were increased significantly by irrigation during the vegetative stage. Specific leaf weight decreased and maximum total crop biomass (150–400 g m⁻²) increased with the number of stages irrigated. Irrigation decreased the absolute root biomass and increased the shoot:root ratio. It is concluded that, in this agroclimatic zone of Sri Lanka, irrigation of mung bean during the vegetative stage is critical for maximizing leaf area. However, biomass production can be maximized by increasing the number of stages irrigated irrespective of irrigation at any specific stage.