不同遗传背景下杂交籼稻功能叶与产量构成因素的相关性

为明确水稻功能叶与产量构成因素间的相关性,以不同遗传背景下籼稻的10个不育系和16个恢复系为亲本,按照NCII设计配制两套双列杂交组合,对水稻12个功能叶性状与8个产量性状构成因素进行了相关分析,结果表明：3片功能叶叶长与叶面积、剑叶宽、倒2叶宽等性状之间均存在极显著正相关,功能叶夹角之间也存在极显著正相关,但不同遗传背景对夹角性状与9个形态性状之间的相关性则存在明显差异,在第1套组合中,其相关系数均为负值,且相关均不显著;而第2套组合则相反。8个产量构成因素中,单株穗数与平均穗长、着粒密度、穗实粒数以及穗着粒数之间存在极显著负相关,平均穗长与穗着粒数、结实率与单株产量呈显著或极显著正相关,遗传背景对产量组成上有较大影响,在第1套组合中单株产量主要由结实率、单株穗数以及穗实粒数等性状决定,而在第2套中则主要由穗实粒数和结实率等性状决定。在功能叶与产量构成因素的相关中,叶长、叶面积、剑叶宽、倒2叶宽与着粒密度、穗实粒数以及穗着粒教等3个性状之间存在显著或极显著正相关。12个水稻功能叶性状与8个产量构成因素之间的主成分分析表明,在不同的遗传背景下,产量构成因素均主要受叶面积和叶夹角影响,两种不同遗传背景中其累积贡献率分别为69．8％和84．0％。     

Effect of Defoliation During the Early Vegetative Phase and at Silking on Growth of Maize (Zea mays L.)

Two experiments were conducted in the glasshouse and in thefield to evaluate the effect of leaf loss on development, drymatter accumulation and yield of maize. In the glasshouse, defoliationtreatments were imposed on maize after 3 weeks of planting.Removing 2 or 3 leaves every 2 weeks affected plant height,days to tassel, root and shoot yield. The plant diameter androot:shoot ratio were not affected by defoliation. In the field experiment, six defoliation treatments were imposed7 days after 50 per cent silking. Defoliation of all leaveswas the most severe treatment on cob d. wt, dry matter accumulationin grains, weight of 100 test grains and yield. The effect ofremoving all leaves above the ear was not significantly differentfrom that of removing all leaves below the ear. The effect ofremoving half of the leaves above the ear was not differentfrom the control. Zea mays, vegetative growth, dry matter accumulation, yield, defoliation     

Effects of Nitrogen Fertilizer on Growth and Yield of Spring Wheat

Nine amounts of nitrogen fertilizer, ranging from 0 to 200 kgN ha^–1, were applied to spring wheat cv. Kleiber in the3 years 1972-1974. In 1972 grain dry weight with 125 kg N ha^–1or more was 100 g m^–2 (23 per cent) greater than withoutnitrogen. Grain yield was unaffected by nitrogen in the otheryears. Leaf area at and after anthesis was increased throughoutthe range of nitrogen tested, most in 1972 and least in 1973.Consequently, the addition of 200 kg N ha^–1 decreasedthe amount of grain produced per unit of leaf area by approximately25 per cent in all years. The dry weight of leaves and stems at anthesis and maturitywas increased by nitrogen in all years, similarly to leaf area.However, the change in stem dry weight between anthesis andmaturity was not affected by nitrogen; stems increased in dryweight for about 20 days after anthesis and then decreased tovalues similar to those at anthesis. The uptake of CO₂ per unit area of flag leaf or second leaf(leaf below the flag leaf) was slightly decreased by nitrogenwhen the increase in leaf area caused by nitrogen appreciablydecreased the light intensity at the surface of these leaves.In spite of such decreases the CO₂ absorbed by flag and secondleaves per unit area of land was always increased by nitrogen,and relatively more than was grain yield. It is suggested that increases in respiratory loss of CO₂ withincreasing nitrogen fertilizer may explain why nitrogen increasedvegetative growth and leaf area relatively more than grain yield.     

Genotypic variation in partitioning of dry matter and manganese between source and sink organs of rice under manganese stress

Key message

Genetic variability in dry matter and manganese partitioning between source and sink organs was the key mechanism for Mn efficient rice genotypes to cope with Mn stress.

Abstract

Considerable differences exist among cereal genotypes to cope manganese (Mn) deficiency, but the underlying mechanisms are poorly understood. Minimal information regarding partitioning and/or remobilization of dry matter and Mn between source and sink organs exists in rice genotypes differing in Mn efficiency. The present study was aimed to assess the growth dynamics in terms of dry matter and Mn remobilization in the whole plant (leaves and tillers as source and panicles and grains as sink) during the grain development in diverse rice genotypes. The efficient genotypes accumulated higher dry matter than inefficient genotypes under low Mn level. The translocation index i.e., uptake in grain/total uptake was 0.11 in efficient genotype (PR 116) and 0.04 in inefficient genotypes (PR 111). The efficient genotype had higher grain Mn utilization efficiency of 0.71 in comparison to 0.48 of inefficient genotype indicating that in efficient genotype, Mn in grain produces more dry matter than inefficient genotypes. The efficient genotypes also had higher flag leaf area and nitrate reductase activity. The source of efficient genotypes contributed to a greater extent to developing sink but further mobilization to grain was hindered by panicle. The panicle of inefficient genotypes had higher per cent of Mn uptake than efficient genotypes indicating that Mn was least mobilized from panicle to grain in inefficient genotypes. The lower per cent uptake of Mn in efficient genotypes indicated that Mn was mobilized from panicle to developing grain and this led to higher Mn translocation index in grain of efficient genotypes. The uptake partitioning revealed that source of all genotypes mobilized the Mn towards the sink to almost same extent but it was the panicle where highest per cent uptake per plant was in inefficient genotypes and lowest in efficient genotypes. The lowest per cent uptake in panicle of efficient genotypes revealed that it supported developing grain to have highest translocation index.     

水稻SL基因调控水稻的粒形

水稻产量和稻米品质的提高是水稻研究的中心问题。水稻产量主要取决于单株穗数、每穗粒数和粒重;粒重作为一个非常重要的产量性状,由粒长、粒宽和粒厚所决定。影响粒重和粒形的基因多为数量性状基因,精细定位并克隆到的较少。本研究中,我们克隆到一个影响粒形的基因SL,超表达（SL-OE）转基因植株表现出粒长增加、粒宽减小、叶宽减小的表型;同时,SL-RNAi的转基因植株呈现出粒长缩短、叶宽增加的表型。颖壳表面细胞在超表达转基因植株中伸长,而在RNAi转基因植株中缩短。叶片横向细胞数目在转基因植株中发生变化,推测乩基因可能与细胞分裂相关。SL-OE转基因植株中G嗽因被明显上调,说明盟基因可能通过调节GW2的表达对水稻粒宽造成影响。另外,观基因影响稻米的品质。     

Damage loss assessment and control of the cereal leaf beetle (Coleoptera: Chrysomelidae) in winter wheat

Cereal leaf beetle, Oulema melanopus (L.), invaded northern Alabama and Georgia more than a decade ago and since has become an economic pest of winter wheat and other cereal crops in the southeastern United States. A series of trials was conducted beginning in 1995 to determine optimal rate and timing of applications of selected foliar insecticides for managing cereal leaf beetle in soft red winter wheat. These trials, cage studies with larvae, and a manual defoliation experiment were used to provide information on cereal leafbeetle yield loss relationships and to develop economic decision rules for cereal leaf beetle in soft red winter wheat. Malathion, methomyl, carbaryl, and spinosad effectively controlled larval infestations when treatments were applied after most eggs had hatched. Encapsulated endotoxin of Bacillus thuringiensis, methyl parathion, and disulfoton applied at the lowest labeled rates were not effective treatments. Organophosphate insecticides generally were not effective when applied before most eggs had hatched. The most effective treatments were the low rates of lambda cyhalothrin when applied early while adults were still laying eggs and before or near 50% egg hatch. These early applications applied at or before spike emergence virtually eliminated cereal leaf beetle injury. The manual defoliation study demonstrated that defoliation before spike emergence has greater impact on grain yield and yield components than defoliation after spike emergence. Furthermore, flag leaf defoliation causes more damage than injury to lower leaves. Grain test weight and kernel weight were not affected by larval injury in most trials. Regression of larval numbers and yield losses calculated a yield loss of 12.65% or 459 kg/ha per larva per stem, which at current application costs suggested an economic threshold of 0.4 larvae per stem during the spike emergence to anthesis stages.     

Prediction of relative efficiency of some selection indices used in winter wheat

Separate selection indices were constructed for various combinations of selective characters, in which together with components of economic yield also four separate subcharacters, yield prerequisites were used, namely: flag leaf area, length of the flag leaf, angle of the second leaf (from the top) and length of plant at heading time. Maximum genetic advance in weight of grains per plant (yield) from selections may be expected in selection indices in which three economic yield components together with flag leaf area or angle of the second leaf were used. When as criteria for selection the flag leaf area together with yield components were used, selection indices with six different sets of economic weights for yield and weight of one grain were also computed. For the ratio of economic values 1∶1, the total expected advance was the highest, but separate advance in yield was approximately only 57% in comparing with selection made according to yield as complex character. For the ratio of economic values 1∶0·03 to 1∶0 the expected genetic advances in yield were about 22 and 24 per cent higher in comparing with selections according to yield. It may be expected that yield improvment will not be acquired by means of a great number of small, inferior grains.     

The Influence of Leaf Removal upon the Development of the Grain of Winter Wheat

The paper describes the effects on grain development of theremoval of half the flag leaf, the entire flag leaf and allthe leaves from selected main shoots of a field crop of wheat,cultivar Maris Ranger, 7 days after anthesis. None of the treatmentsreduced grain weights in the 14 days following defoliation.Even in the next 14 days only the more severe defoliations reducedgrain weight, with the most severe treatment causing the greatestreduction. Ultimately the rate of grain growth in plants onwhich only a half of the flag leaf had been removed also fellbehind that of the controls. Final grain yields were in theorder, control plants, > plants with half the flag leaf removed,> the entire flag leaf removed, > all the leaves removed.The significance of these results in interpreting the factorslimiting grain growth in wheat is discussed.     

Influence of reproductive organs on plant senescence in rice and wheat

The chlorophyll and protein contents of the flag, second and third leaves gradually decreased during the reproductive development of rice (Oryza sativa L. cv. Rasi) and wheat (Triticum aestivum L. cv. Sonalika) plants, whereas proline accumulation increased up to the grain maturation stage and slightly decreased thereafter. In rice plant, the rate of decrease in chlorophyll and protein and increase in proline level were higher in the flag leaf than in the second leaf. It was opposite in wheat plant. The export of [³²P]-phosphate from leaves to grains gradually increased reaching a maximal stage at the grain development stage, and then declined. The export of this radioisotope was greater in rice than in wheat. Removal of panicle at the anthesis and grainfilling stages delayed leaf senescence of rice plant, while in wheat the ponicle removal at any stage did not have a marked effect on delaying leaf senescence. The contents of chlorophyll and protein of glumes were higher in wheat than in rice. The variation of such source-sink relationship might be one of the possible reasons for the above effect on leaf senescence.     

Comparison of phosphorus mobilization during monocarpic senescence in rice cultivars with sequential and non-sequential leaf senescence

The senescence pattern of the three uppermost leaves of four rice (Oryza sativa L.) cultivars viz. Ratna, Jaya, Masuri and Kalojira was analysed in terms of decline of chlorophyll and by measuring [³²P]-phosphate retention and export from leaf to grains during the reproductive development. With the advancement of reproductive development, the cultivars Masuri and Kalojira showed a sequential mode of senescence, but the cultivars Ratna and Jaya showed a non-sequential mode of leaf senescence where the flag leaf senesced earlier than the older second leaf. Foliar spraying with benzyladenine (0.5 mM) significantly delayed, and abscisic acid (0.1 mM) accelerated, leaf senescence. In untreated control plants, the second leaf had the highest export of labelled phosphate among the leaves at the grain formation stage (0–7 days) in Masuri and Kalojira. This was compensated by the flag leaf at the grain development stage (7–14 days), whereas export of [³²P]-phosphate was highest from the flag leaf of Ratna and Jaya at the grain development stage. Compared with the control, benzyladenine treatment caused higher retention of [³²P]-phosphate in the leaves and also export to the grains, but abscisic acid treatment gave lower retention and export of [³²P]-phosphate to the grains. The amount of [³²P]-phosphate export from a mother to a daughter shoot developed in the axil of the second leaf of plants with the panicle removed, was less than that to panicles remaining on control plants of all cultivars. When the panicle had been excised, the greatest export of [³²P]-phosphate took place from the second leaf to the daughter shoot in all cultivars. Excision of the panicle delayed leaf senescence as compared with intact controls and maintained an age-related leaf senescence pattern in all the four cultivars. The results presented here demonstrate that mobilization of phosphorus from leaf to grains, regardless of cultivar or age and position of the leaf, correlates well with the senescence of that leaf.     

Effects of elevated carbon dioxide and ozone on the growth and yield of spring wheat (Triticum aestivum L.)

Spring wheat cv. Minaret was grown under three carbon dioxide(CO₂) and two ozone (O₃) concentrations from seedling emergenceto maturity in open-top chambers. Under elevated CO₂ concentrations,the green leaf area index of the main shoot was increased, largelydue to an increase in green leaf area duration. Biomass increasedlinearly in response to increasing CO₂ (ambient, 550 and 680ppm). At anthesis, stem and ear dry weights and plant heightwere increased by up to 174%, 5% and 9 cm, respectively, andbiomass at maturity was 23% greater in the 680 ppm treatmentas compared to the ambient control. Grain numbers per spikeletand per ear were increased by 0.2 and 5 grains, respectively,and this, coupled with a higher number of ears bearing tillers,increased grain yield by up to 33%. Exposure to a 7 h daily mean O₃ concentration of 60 ppb inducedpremature leaf senescence during early vegetative growth (leaves1–7) under ambient CO₂ concentrations. Damage to the mainshoot and possible seedling mortality during the first 3 weeksof exposure altered canopy structure and increased the proportionof tillers 1 and 2 which survived to produce ears at maturitywas increased; as a result, grain yield was not significantlyaffected. In contrast to the older leaves, the flag leaf (leaf8) sustained no visible O₃ damage, and mean grain yield perear was not affected. Interactions between elevated CO₂ andO₃ influenced the severity of visible leaf damage (leaves 1–7),with elevated CO₂ apparently protecting against O₃-induced prematuresenescence during early vegetative growth. The data suggestthat the flag leaf of Minaret, a major source of assimilateduring grain fill, may be relatively insensitive to O₃ exposure.Possible mechanisms involved in damage and/or recovery are discussed. Key words: Carbon dioxide, ozone, spring wheat (cv. Minaret), leaf damage, tiller, yield     

Grain Yield in Pearl Millet in Relation to Source Size and Proximity to Sink

Two pearl millet [Pennisetum glaucum (L.) R. Br. emend. Stuntz] hybrids GHB-30 and MH-179 were given defoliation treatments prior to anthesis comprising zero leaf to intact control. Keeping or removing even flag leaf only significantly altered the grain yield. With increasing leaf area (leaf numbers) the grain yield also significantly increased. Test mass showed more or less a similar trend. The leaves in the upper portion (nearer to sink) showed a greater contribution to the grain yield than the lower ones (away from sink). However, the highest leaf efficiency in terms of contribution per unit leaf area and the contribution by the whole leaf to the grain yield was recorded by 4^th and 3^rd leaf, respectively. The stem (covered with petioles) contributed to the extent of around 12 %. The existing leaves compensated to some extent for the defoliated ones.     

Effect of Defoliation on the Growth and Yield of Wheat

The effect of removal of the fifth (L₁), fifth and sixth (L₂) and fifth, sixth and seventh leaves (L₃) from the main shoot and of similar number of leaves from the primary and secondary tillers, on the growth and yield of two varieties of wheat, was investigated. The plants were grown in pots under natural conditions. Defoliation did not affect tillering, ear number, and number of spikelets per ear. The area of the last 3 leaves was reduced only in L₃. Defoliation reduced the growth of stem up to the flag leaf stage but thereafter there was a remarkable recovery in increase in height and dry weight. The grain yield of the main shoot was affected relatively more than that of the primary and secondary tillers by defoliation. The grain yield per plant was reduced by 5 per cent in L₁, and L₂ and by 11 per cent in L₃. The bearing of these observations on productivity per unit area is indicated and it is suggested that a plant with two fewer leaves per shoot may suffer less from mutual shading of leaves and hence prove more efficient in a dense community.     

Dwarfing genes and cell dimensions in different organs of wheat

A field experiment was conducted under non-limiting water and nutritional conditions with three near-isogenic lines of spring wheat (dwarf, DD; semi-dwarf, SD and standard height, SH) to study the impact of the GA-insensitive alleles Rht1 and Rht2, at the cellular level, on the growth of different vegetative organs and of the pericarp of grains. Cell length and width of blades of different leaves (3, 7 and flag leaf), the flag-leaf sheath and the penultimate internode as well as the pericarp of basal grains from central spikelets of the spike were evaluated. With the exception of the flag leaf, dwarfing genes produced a significant reduction in cell length in all the different vegetative organs analysed. There was no effect on the number of cells nor their width. Therefore, in vegetative organs, the effects of these alleles appeared to be exclusively due to a reduction in cell length. It would appear that dwarfing genes act on cell elongation without affecting cell division.The Rht alleles did not modify cell length nor width in the pericarp. Grain weight was different between the lines and these differences were associated with grain volume at the beginning of linear grain growth. Thus, they reduced the size of individual grains by reducing the total number of cells in the pericarp.It appears that Rht alleles reduced the final sizes of vegetative organs (such as internodes and leaves) and of tissues (pericarp) associated with reproductive structures (grains), but the modes of action in these different organs were different.Keywords: Cell dimensions, plant height, Rht alleles, Triticum aestivum/wheat.      

The Developmental Anatomy of Leaves in Lolium temulentum

Measurements of the epidermal cells in Lolium temulentum andassessments of cell number indicate that differences in bladewidth are due mostly to variations in cell number, whereas changesin blade and sheath length result mainly from differences incell length. A marked increase in length of the flag-leaf aheath,however, was related to an increase in cell number. Considerable changes in the relative proportions of leaf bladeand sheath were observed in the flag leaf, and the leaves immediatelypreceding it, associated with inflorescence initiation. As oneconsequence of this the area of the flag leaf, the largest onthe shoot, is virtually constant under different environmentalcondi-tions. It is suggested that this aspect of correlateddevelopment is related to the nutrition of the panicle, sincein annual grasses such as the cereals the flag leaf may be responsiblefor producing up to 30 per cent. of the starch in the grain.     

Effect of spikelet removal on the whole plant senescence of rice

The rice (Oryza sativa L.) cultivar IET 1444 showed a nonsequential mode of senescence as evident from the decline in chlorophyll and protein of the flag and second leaves at the senescent stage. Removal of 50,75 and 100 % spikelets from the panicle of rice plant or emasculation of the panicle by hot water treatment induced the development of secondary branch from the axil of second leaf but 25 % removal had no effect. Similarly, removal of 75 and 100 per cent spikelets from the panicle of secondary branch induced tertiary branch development, while 25 and 50 per cent removal had no such effect. Similar treatments on tertiary branch had no effect on further branch production. The pattern of leaf senescence of the untreated (control) main tiller, secondary and tertiary branches was identical, i. e. nonsequential, which could be changed into the sequential type only by the development of additional sinks (i. e. side branch). The leaf area and the seed number of secondary and tertiary branches were gradually reduced and reached a critical value in the tertiary branch. The removal of spikelets or emasculation delayed leaf senescence of the main tiller and the secondary and tertiary branches. Also the longevity of the whole plant could be increased by 40 d i. e., up to the senescence of the tertiary branch. Both leaves and reproductive parts control side branch production, which, in turn, controls the longevity of the whole rice plant.     

The Contribution of Different Organs to Grain Weight in Upland and Swamp Rice

The contribution of dry matter was significantly greater inthe ears of Dima than that of Kindinga. The flag-leaf lamina,flag-leaf sheath and peduncle, lower leaves and stem of Kindingamade greater contribution of dry matter in the grain at harvestthan those of Dima. On the average of the two varieties 23 percent. of the dry matter in the grain at harvest originated fromphotosynthesis in the ears; 60 per cent. came from photosynthesisin the flag-leaf lamina and sheath and peduncle and 17 per cent.from parts of the shoot below the flag leaf.     

Much Improved Water Use Efficiency of Rice under Non-Flooded Mulching Cultivation

Water shortage is increasingly limiting the luxury use of water in rice cultivation. In this study, non-flooded mulching cultivation of rice only consumed a fraction of the water that was needed for traditional flooded cultivation and largely maintained the grain yield. We also investigated the growth and development of rice plants and examined grain yield formation when rice was subjected to non-flooded mulching cultivation. One indica hybrid rice combination was grown in a field experiment and three cultivation methods, traditional flooding （TF）, non-flooded straw mulching cultivation （SM） and non-flooded plastic mulching cultivation （PM）, were conducted during the whole season. Grain yield showed that there was no significant difference between SM and TF rice, but the grain yield of SM cultivation was significantly higher than that of PM. The tiller numbers were inhibited in the early stage under non-flooded mulching cultivation, but the situation was reversed at the later period. Both SM and PM rice reduced dry matter accumulation of shoot, but increased root dry weight, enhanced the remobilization of assimilates from stems to grains and increased the harvest index. During the middle and later grain filling period, mulched plants showed a faster decrease in chlorophyll concentrations, photosynthetic rates of flag leaves and root activity than TF rice, indicating that non-flooded mulching cultivation enhanced plant senescence. In comparison, SM treatment produced higher grain yield and, more dry matter accumulation and panicle numbers than the PM treatment. The overall results suggest that high yield of non-flooded mulching cultivation of rice can be achieved with much improved irrigaUonal water use efficiency.     

Mechanism of monocarpic senescence in rice

During grain formation stage (90 to 110 days), the youngest flag leaf of rice (Oryza sativa L. cv. Jaya) remained metabolically most active (as indicated by cellular constituents and enzyme activities) and the third leaf the least active. At the grain development stage (110 to 120 days) the above pattern of age-related senescence of the flag leaf completely changed and it senesced at a faster rate than the second leaf which remained metabolically active even up to grain maturation time (120 to 130 days), when both the flag and the third leaf partially senesced. Removal of any leaf temporarily arrested senescence of the remaining attached leaves, that of flag leaf did not hasten senescence of the second leaf, while that of either the second or the third accelerated senescence of the flag. Removal of the inflorescence after emergence or foliar treatment of intact plant with kinetin equally delayed senescence and produced an age-related, sequential mode of senescence or leaves. Both translocation and retention of ³²P by the flag leaf were maximum at the time of grain formation and that by the second leaf was maintained even up to grain maturation time. The induction of senescence of the flag leaf was preceded by a plentiful transport of ³²P to the grains. Kinetin treatment decreased the transport of ³²P, prolonged its duration, and almost equally involved all of the leaves in this process. The pattern of senescence of isolated leaf tips was similar to that of attached leaves. The level of endogenous abscisic acid-like substance(s) maintained a close linearity with the senescence behavior of the leaves of intact and defruited plants during aging, and the rise in abscisic acid in the flag leaf was also preceded by higher ³²P transport to the grains.     

Photosynthesis and transpiration of the flag leaf in four spring-wheat cultivars

Co₂ exchange and transpiration rates of the flag leaves of four spring wheat (Triticum aestivum L.) cultivars, namely Glenlea, Neepawa, Opal and Kolibri, were compared using infra-red gas-analysis technique. The plants were grown in a controlled environment under an 18-h photoperiod, with day and night temperatures of 20 and 15° C, respectively. The time course of the CO₂-exchange rate (CER) of the flag leaf differed among cultivars. CER began to decrease rapidly some 2 weeks after ear emergence in Glenlea, Neepawa and Kolibri, but only after 4 weeks in Opal. The decline in CER of Glenlea, Neepawa and Opal was continuous throughout the period of grain development whereas in Kolibri CER was maintained at a constant level between the 4th and 6th weeks after ear emergence. The transpiration rates of the flag leaves of the 4 cultivars did not change markedly until 6–7 weeks after ear emergence, indicating that the reduction in CER was not primarily a response to increased stomatal resistance to the diffusion of CO₂. Removing the ear of the main shoot of intact plants failed to depress CER of the subtending flag leaf until 5 weeks after ear removal. Removing the ears of all the tillers of plants in which all but 3 tillers had been removed at ear emergence did not depress CER until 4 weeks after ear emergence, but removal of the ear of the main shoot of plants where all the tillers had been removed at ear emergence reduced the CER of the flag leaf 2 weeks after ear removal. Removal of tillers at ear emergence had a marked effect on the time course of CER and transpiration rates of the flag leaf. Both CER and transpiration rates of a 4-tiller plant were maintained at a higher level throughout ear development as compared to those of a one-tiller plant. The transpiration rate of the flag leaf of Glenlea increased during the later part of the life of the leaf even for one-tiller plants with no ear, indicating that such a stomatal response may be part of the normal course of leaf aging and not a response to a feedback stimulus from the ear.