Interference between Redroot Pigweed (Amaranthus retroflexus L.) and Cotton (Gossypium hirsutum L.): Growth Analysis

Redroot pigweed is one of the injurious agricultural weeds on a worldwide basis. Understanding of its interference impact in crop field will provide useful information for weed control programs. The effects of redroot pigweed on cotton at densities of 0, 0.125, 0.25, 0.5, 1, 2, 4, and 8 plants m^-1 of row were evaluated in field experiments conducted in 2013 and 2014 at Institute of Cotton Research, CAAS in China. Redroot pigweed remained taller and thicker than cotton and heavily shaded cotton throughout the growing season. Both cotton height and stem diameter reduced with increasing redroot pigweed density. Moreover, the interference of redroot pigweed resulted in a delay in cotton maturity especially at the densities of 1 to 8 weed plants m^-1 of row, and cotton boll weight and seed numbers per boll were reduced. The relationship between redroot pigweed density and seed cotton yield was described by the hyperbolic decay regression model, which estimated that a density of 0.20–0.33 weed plant m^-1 of row would result in a 50% seed cotton yield loss from the maximum yield. Redroot pigweed seed production per plant or per square meter was indicated by logarithmic response. At a density of 1 plant m^-1 of cotton row, redroot pigweed produced about 626,000 seeds m^-2. Intraspecific competition resulted in density-dependent effects on weed biomass per plant, a range of 430–2,250 g dry weight by harvest. Redroot pigweed biomass ha^-1 tended to increase with increasing weed density as indicated by a logarithmic response. Fiber quality was not significantly influenced by weed density when analyzed over two years; however, the fiber length uniformity and micronaire were adversely affected at density of 1 weed plant m^-1 of row in 2014. The adverse impact of redroot pigweed on cotton growth and development identified in this study has indicated the need of effective redroot pigweed management.     

The effect of galls induced by the gall fly Procecidochares utilis on vegetative growth and reproductive potential of crofton weed, Ageratina adenophora

Reproductive potential and vegetative growth of Ageratina adenophora (Spreng.) K. & R. (crofton weed) were measured under ambient conditions to evaluate the efficacy of the gall fly, Procecidochares utilis Stone as a biocontrol agent for this weed. Galls induced by the fly resulted in the production of underdeveloped capitula and a reduction in the number of capitula and filled achenes per capitulum. Galling had no effect on subsequent germination of the seed produced. Where vegetative growth was concerned the effect of galling ranged from a temporary cessation of growth to death of stems above the gall. Although galling promoted production of side shoots, the dry mass of above-ground material was markedly reduced.     

Gibberellin A(4/7) and the Promotion of Flowering in Pinus radiata: Effects on Partitioning of Photoassimilate within the Bud during Primordia Diferentiation

Gibberellin A_4/7 mixture (GA_4/7), a highly effective promoter of early and enhanced flowering in the Pinaceae, caused a significant reallocation of dry matter and ¹⁴C-photosynthate within terminal buds of Pinus radiata D. Don within 8 days of hormone treatment. Treatment with GA_4/7 to terminal shoots of vigorous, potentially flowering mature grafted propagules reduced the flow of photoassimilated ¹⁴C and dry matter into the terminal bud as a whole, but significantly increased the dry matter and ¹⁴C allocated within the bud to developing long-shoot primordia (potential seed-cone buds). This was accomplished at the expense of the structural tissues, the apical dome region, and the vegetative branch buds. Although GA₃ caused a similar reallocation of dry matter within the terminal bud, it was significantly less effective than GA_4/7 thus appears to have, in addition to any nutrient diversion abilities, a distinct morphogenic function in sexual differentiation.     

Nutritional quality and yield of seedling alfalfa established with a barley companion crop and weeds

Alfalfa (Medicago sativa L.) was established with barley (Hordeum vulgare L.) and weeds to determine the effect of weed management treatments on yield and nutritional quality of alfalfa and companion crop and weeds. Alfalfa+barley and alfalfa+wild oat (Avena fatua L.) had much higher yields in August of the first year than alfalfa alone. Total yields for the first three harvests were similar for alfalfa established weed free, with broad leaf weeds, wild oat or green foxtail (Setaria viridis L.). Protein contents in forage from the August harvest were 228, 196, 117 and 181 g/kg dry matter (DM) in weed free alfalfa, alfalfa plus broadleaf weeds, alfalfa plus wild oat, and alfalfa plus green foxtail, respectively. Alfalfa+barley had higher total in vitro gas production than pure alfalfa, which is correlated with the digestibility of the forage. Total in vitro gas production indicated that alfalfa+barley+weeds had slightly lower digestibility than weed free alfalfa+barley. However, alfalfa with a high percentage of redroot pigweed (Amaranthus retroflexus L.), wild oat or green foxtail had similar or higher in vitro gas production than pure alfalfa. The results from this experiment support a previous economic study that indicated herbicide application for weed control in seedling alfalfa was not necessary.     

The impact of elevated CO2 on yield loss from a C3 and C4 weed in field-grown soybean

Soybean (Glycine max) was grown at ambient and enhanced carbon dioxide (CO₂, + 250 μL L^?1 above ambient) with and without the presence of a C3 weed (lambsquarters, Chenopodium album L.) and a C4 weed (redroot pigweed, Amaranthus retroflexus L.), in order to evaluate the impact of rising atmospheric carbon dioxide concentration [CO₂] on crop production losses due to weeds. Weeds of a given species were sown at a density of two per metre of row. A significant reduction in soybean seed yield was observed with either weed species relative to the weed‐free control at either [CO₂]. However, for lambsquarters the reduction in soybean seed yield relative to the weed‐free condition increased from 28 to 39% as CO₂ increased, with a 65% increase in the average dry weight of lambsquarters at enhanced [CO₂]. Conversely, for pigweed, soybean seed yield losses diminished with increasing [CO₂] from 45 to 30%, with no change in the average dry weight of pigweed. In a weed‐free environment, elevated [CO₂] resulted in a significant increase in vegetative dry weight and seed yield at maturity for soybean (33 and 24%, respectively) compared to the ambient CO₂ condition. Interestingly, the presence of either weed negated the ability of soybean to respond either vegetatively or reproductively to enhanced [CO₂]. Results from this experiment suggest: (i) that rising [CO₂] could alter current yield losses associated with competition from weeds; and (ii) that weed control will be crucial in realizing any potential increase in economic yield of agronomic crops such as soybean as atmospheric [CO₂] increases.     

Inhibitory effects of leachate from Eupatorium adenophorum on germination and growth of Amaranthus retroflexus and Chenopodium glaucum

Amaranthus retroflexus L. and Chenopodium glaucum L. are two widely distributed destructive weeds. Their strong adaptability and massive seed production make them the hardest weeds to deal with. This present study intended to investigate the effect of leachate from Eupatorium adenophorum on the growth of these weeds and explore the potential to develop an environmental friendly strategy to use the leachate to control the weeds. Seeds of A. retroflexus L. and C. glaucum L. were soaked in solutions containing 0%, 0.6%, 1.25%, 2.5%, and 5% leachate from E. adenophorum leaves. A. retroflexus and C. glaucum seedlings grown in pots were sprayed with leachate solutions in the same concentration range. The effects of these leachate solutions on membrane permeability and germination of seeds, and growth and physiological characteristics of the seedlings were investigated. The highest concentration of leachate (5%) caused significant damage to the cell membrane of seeds of both weed species, whereas lower concentrations (0.6%) promoted repair of the membrane system, as reflected by higher and lower than control in relative conductivity (RC), respectively. Different concentrations of leachate showed distinct allelopathic inhibitory effects on the two weed species; lower concentrations showed weak inhibitory or even positive effects, whereas higher concentrations showed stronger inhibitory effects. Higher concentrations of leachate (2.5% and 5%) delayed germination and significantly decreased the emergence rate of the seeds, survival rate, and dry matter accumulation of the seedlings. When treated by 5% leachate, the emergence date of A. retroflexus was delayed by 3.6 d, emergence rate of the seeds and survival rate was 69.1% and 70.6% of the control, respectively, seedling dry matter was 48.6% less than the control; In the case of C. glaucum, the emergence date was delayed by 2.7 d, emergence rate of the seeds and survival rate was 45.1% and 58.6% of the control, respectively, seedling dry matter was 44.7% less than the control. There were significant interactions among the different concentrations of leachate and the length of treatment period with respect to activities of antioxidant enzymes, malondialdehyde (MDA) contents, and chlorophyll contents. Seedlings treated with 0.6%, 1.25%, or 2.5% leachate solution for 24–72 h showed increased superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities. When seedlings were treated with leachate solutions for 96 h, antioxidant enzyme activities and chlorophyll content decreased in A. retroflexus, but only CAT activity decreased in C. glaucum. When seedlings of the two weed species were treated with 5% leachate solution, CAT activity and chlorophyll content decreased and MDA content gradually increased with longer treatment times (from 24 to 96 h). The two weed species showed different allelopathic responses to E. adenophorum; A. retroflexus was more sensitive than C. glaucum. Based on the investigation, it could be speculated that the delayed germination and low germination rate of the weeds after treatment by leachate could be due to the fact that leachate damaged the membrane system of the seeds. By delaying germination, lowering the germination rate of the weeds and inhibiting seedling growth, leachate from E. adenophorum could provide an effective way of controlling the weeds.     

Neighbouring crop diversity mediates the effect of Bt cotton on insect community and leaf damage in fields

Effects of large-scale cultivation of transgenic crops on agricultural biodiversity remain unclear, particularly in the context of complex ecological interactions between transgenic crops and other organisms. Here we conducted a comprehensive survey to investigate the number of species, population abundance, community evenness and dominance of insects and weeds as well as leaf damage to weeds in Bt and non-Bt cotton fields at 27 sites across northern China. The role of neighbouring crop diversity around cotton fields in controlling insects and weeds in the cotton fields was also assessed. In addition, we conducted a 3-year field experiment to verify the results of the survey. Weed diversity in Bt and non-Bt cotton fields was similar, but the species number and diversity indices of insects are significantly decreased in Bt fields aligning with reduced leaf damage to broadleaf plant species including cotton as well as crops in neighbouring plots. The leaf damage to Bt and non-Bt cotton negatively associates with the diversity of neighbouring crops in cotton fields. Our study demonstrates the neighbouring crop diversity mediates the effects of Bt crops on agricultural diversity in complex interactions among transgenic crops, in-field weed and insect communities, and neighbouring crops.

     

Establishment and Early Growth of Willow at Different Levels of Weed Competition and Nitrogen Fertilization

To evaluate the effects of weed competition and nitrogen fertilization on the early growth performance of willow, cuttings of the clone Tora (Salix schwerinii x S. viminalis) were planted in buckets together with model weeds (spring barley or white mustard) sown 15, 26, and 30 days after willow planting. The buckets were fertilized with 30 or 90 kg N ha^?1. Willow with weeds sown after 15 days produced less biomass and smaller leaf area and had a lower maximum shoot height compared to willow planted without weeds and willow with weeds sown after 26 or 30 days. Fertilization with 90 kg N ha^?1 gave higher willow biomass production in willow with weeds sown after 26 or 30 days. Type of model weed had no effect on willow performance. Weed biomass and maximum shoot height were higher in weeds planted without willows compared to the willow-weed mixtures. A high nitrogen level gave more weed biomass when planted without willows and in the willow-weed mixture with weeds sown after 15 days. We conclude that for the given high density of willow, competition from weeds emerging soon after willow planting had strong effect on early production. Furthermore, if there is a risk of weed infestation, fertilization should be delayed.     

Fitness costs associated with acetyl‐coenzyme A carboxylase mutations endowing herbicide resistance in American sloughgrass (Beckmannia syzigachne Steud.)

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Cover crops and compost prevent weed seed bank buildup in herbicide‐free wheat–potato rotations under conservation tillage

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Weed development in spring wheat after contrasting soil tillage and nitrogen management

Soil tillage and nitrogen (N) management effects on weed species composition were evaluated in 2013 and 2014 on a clayey soil after 5‐years of organic management at the Royal Agricultural University's Harnhill Manor Farm, UK. Three tillage systems – Conventional Tillage (CT), and High and Low Intensity Non‐inversion Tillage (HINiT & LINiT) – were compared at four N fertiliser rates of 0, 70, 140 and 210 kg N ha^?1. Broad‐spectrum herbicide was applied before soil operations across the site in both years. Previous organic management legacy of high weed biomass promoted greater weed prevalence in 2013 while 2‐years of herbicide inclusion reduced weed biomass. Contrasting weather conditions across the seasons affected weed incidence. In the 2014 wet season, early weed dry weight (DM) was higher under HINiT than CT and LINiT, while no differences were observed in the 2013 dry year. At midseason, weed DM was higher under HINiT than CT and LINiT in both years, which was related to higher DM of the dominant weeds Stellaria media (L.) Vill. and Sinapis arvensis L. Grass weed DM was higher under non‐inversion tillage than CT. N fertilisation increased midseason total weed DM and weed prevalence at harvest. Spring wheat yield was the highest under CT while LINiT produced 17% higher yields than HINiT. Despite higher but still tolerable weed prevalence under both non‐inversion tillage systems and with the application of N, weeds alone was not the only yield‐limiting factor. However, results show that CT is the most reliable option for weed control in changing weather, while N fertilisation rates needs to be considered.     

Evaluation of Pre-Emergence and Post-Emergence Herbicides for Weed Management in <i>Miscanthus sacchariflorus</i> and <i>Miscanthus sinensis</i>

Miscanthus, is a promising bioenergy crop, considered superior to other bioenergy crops because of its higher water and nutrient use efficiency, cold tolerance, and higher production of biomass. Broadleaf weeds and grass weeds, cause major problems in the Miscanthus field. A field experiment was conducted in 2018 and 2019, to assess the effects of pre-emergence (alachlor and napropamide) and post-emergence herbicides (nicosulfuron, dicamba, bentazon, and glufosinate ammonium) on broadleaf and grass weeds in M. sinensis and M. sacchariflorus fields. The weed control efficiency and phytotoxicity of pre- and post-emergence herbicides were evaluated at 30 days after treatment (DAT) and compared to those of the control plots. The results showed wide variations in the susceptibility of the weed species to the treated herbicides. Treatment with nicosulfuron 40 g.a.i.ha⁻¹ provided the most effective overall weed control (with 10% visual injury), without affecting the height and biomass of neither Miscanthus species in the field. Post-emergence herbicides such as glufosinate ammonium 400 g.a.i.ha⁻¹ and dicamba 482 g.a.i.ha⁻¹ were effective and inhibited the growth and density of the majority of weeds to a 100%; however, they showed significant phytotoxicity (toxicity scale of 1–10) to both species of Miscanthus. The application of glufosinate ammonium caused severe injuries to the foliar region (90% visual injury) of both Miscanthus sps. Comparatively, M. sinensis showed a slightly higher tolerance to the herbicides nicosulfuron, bentazon and napropamide with 10% visual injury at the recommended dose than M. sacchariflorus. The present study clearly showed that infestation of broadleaf and grass weeds in Miscanthus fields can cause significant damage to the growth and biomass of Miscanthus and applying pre-emergence and post-emergence herbicides effectively controls the high infestation of these weeds.     

Growth and NPK uptake of high-yielding cotton grown at different nitrogen levels in a permanent-plot experiment

Growth and N, P, K uptake of Acala SJ-2 cotton (Gossypium hirsutum) were investigated in an irrigated permanent-plot field (Typic chromoxerert) at Bet Dagan, Israel, under semi-arid conditions using different nitrogen levels: 0, 60, 120, 180 and 240 kg N ha⁻¹. The total dry matter accumulation at these levels was 9.0, 10.7, 15.1, 17.1 and 15.6 ton ha⁻¹, respectively. The uptake of N, P and K was 110, 144, 267, 322 and 301 kg N ha⁻¹∶31, 34, 46, 44 and 38 kg P ha⁻¹; and 120, 151, 208, 251 and 230 kg K ha⁻¹, respectively. Dry matter production, as well as N, P, K uptake by the cotton plants were greatly increased by raising the N application levels to 120 or 180 kg N ha⁻¹, but the pattern of accumulation and relative distribution of dry matter and NPK among plant organs were not considerably affected. Joint contribution from the Dept. of Soil Chemistry and Plant Nutrition, ARO, the Volcani Center, Bet Dagan, Israel (No. 1413-E, 1985 series)     

Wood properties of juvenile Pinus radiata growing in the presence and absence of competing understorey vegetation at a dryland site

Pinus radiata D. Don trees were grown in the presence and absence of the woody weed broom (Cytisus scoparius L.) on a dryland site for 2 years to determine the effects of competition from weeds on wood properties in juvenile trees. Wood property measurements made on cross-sections from the bark to the pith were scaled to convert results from distance to a time basis using sigmoidal equations fitted to monthly measurements of tree diameter. When averaged across the 2 years, the presence of the weeds significantly increased wood density (+11%), wall thickness (+6%) and modulus of elasticity (MOE_SS, +93%), and significantly reduced microfibril angle (MFA, –21%) and radial diameter (–8%). Radial growth rate was significantly correlated to wood density, and this relationship held across both treatment and age. At the seasonal scale, there was close correspondence between changes in MFA and growth rate. Ring width was significantly related to both MFA and MOE_SS at the annual scale. Although both of these relationships held across treatments, year significantly influenced the value of coefficients in the relationships. The results highlight the direct effects of the presence of weeds on wood properties and the need to consider silvicultural treatments appropriate for balancing gains in productivity with losses in wood quality for timber production.     

Global maximization of Jatropha oil production under semi‐arid conditions by balancing vegetative growth with reproductive capacity

Jatropha curcas L. is a drought tolerant crop that is globally cultivated under semi‐arid conditions as a biodiesel feedstock. Despite its great potential, however, many projects failed to reach commercially viable seed and oil yields. The aim of the study was to provide globally applicable solutions for maximization of Jatropha oil production under semi‐arid conditions. Under extremely low irrigation (10% of potential evapotranspiration; ETp), fruit production was very low and a surprisingly significant portion of the fruits delayed their maturity up to six months post‐bloom. Increasing irrigation to mid‐level (60% ETp) significantly elevated fruit production and speeded up the ripening rate, whereas further increasing irrigation to a higher level (90% ETp) decreased seed and oil yields, probably due to the increased investment in vegetative growth. Nevertheless, maximal seed and oil yields at 60% ETp remained far below targeted yields. Coupling irrigation at 60% ETp, with induction of vegetative arrest, by soil application of a commercial gibberellin synthesis inhibitor, brought forward the second bloom period by two months, reduced vegetative growth, promoted floral production and significantly enhanced reproductive capacity by more than doubling oil production. The results show that under semi‐arid conditions, commercially viable seed and oil yields of Jatropha can be achieved by carefully balancing vegetative growth with reproductive capacity through the combined application of optimal irrigation regimes and induced vegetative arrest.     

Ecology of invertebrate predators in a Coastal Plain stream

1. The spatial and temporal abundance patterns, production and feeding habits of invertebrate predators were determined in a sand-bottomed, headwater stream in Virginia, U.S.A. 2. Annual mean density and biomass of predators in debris dams were 3897 individuals m^?2 and 2.5 g dry mass m^?2, respectively, but only 711 individuals m^?2 and 0.2 gm^?2 on the sediment. Predator production was 8.36 gm^?2yr^?1 in debris dams compared to 1.52 gm^?2yr^?1 on the sediment. Annual predator production, weighted by habitat availability, was 1.73gm^?2yr^?1. 3. The predominant taxa in terms of production were the chironomids Thienemannimyia spp, complex, Ablabesmyia parajanta, Zavrelimyia sp., and the odonate Cordulegaster maculata. Chironomidae and Odonata together comprised 77% of the production of the predator guild. 4. Based on gut content analysis and calculations of the trophic basis of production, estimated predator production was supported mostly by Chironomidae (38%), detritus (20%), unidentifiable insects (14%), and Ephemeroptera (11%). Total food ingestion by predators was 9.8 gm^?2yr^?1, 63% of which was detritus and 37% of which was animal material on an areal basis. The predator guild consumed an estimated 94% of primary invertebrate consumer production on the channel surface of the stream.     

Water Deficit Enhanced Cotton Resistance to Spider Mite Herbivory

We investigated the responses of cotton (Gossypium hirsutumL.)to the combined effects of soil water deficit and two-spottedspider mite (Tetranychus urticaeKoch) infestation. Two mitetreatments (-M: uninfested, +M: artificially infested 83 d aftersowing), and two water regimes (+W: well watered, -W: waterstressed) were combined factorially in four treatments. Mitecolonies developed at similar rates in well-watered and water-stressedcrops. Despite the similar intensity of infestation, visualsymptoms of mite injury were more marked in well-watered hostplants (+M+W) than in their water-stressed counterparts (+M-W).Lint yield of unstressed controls (-M+W) was 175 g m^-2. In uninfestedcrops, water deficit reduced yield by 30%, mites reduced theyield of well-watered crops by 92%, and the combination of miteinfestation and water deficit reduced yield by 72% (water effect:P<0.01;mite and interaction effect:P<0.0001). Differences in yieldresponses to mites between well-watered and water-stressed cropswere mostly related to differences in reproductive partitioning.The interaction between mites and water deficit was also significantfor other crop variables including canopy temperature, leafwater potential, concentration of nitrogen in reproductive structuresand seed oil concentration. The magnitude and consistency ofthe interaction between both stresses indicates that, underour experimental conditions, mechanisms of adjustment to waterdeficit may have enhanced cotton resistance to mites. This isfurther supported by (a) an increase in specific leaf weightand a parallel increase in leaf penetration resistance due towater deficit; (b) a negative association between macroscopicsymptoms of mite injury and leaf penetration resistance; and(c) a choice test showing that adult female mites preferredto feed and oviposit on leaves from well-watered plants.Copyright1998 Annals of Botany Company Gossypium hirsutumL.;Tetranychus urticaeKoch; leaf water potential; leaf penetration resistance; canopy temperature; multiple stresses; specific leaf weight; radiation use efficiency; nitrogen concentration; reproductive allocation.     

Zinc efficiency of oilseed rape (t Brassica napus and t B. juncea) genotypes

Twenty five genotypes of oilseed rape (canola and mustard) were tested under varied supply of Zn (+Zn: 2 mg kg^–1 soil, -Zn: no Zn added) in two pot experiments in soil culture to determine the genotypic variation in tolerance to the Zn-deficient conditions, that is, to identify the Zn-efficient genotypes. On the basis of performance of genotypes in pot experiments, ten genotypes were tested in 1995 for their performance under varied supply of Zn (+Zn: 3.5 kg ha^–1, -Zn: no Zn added) on a Zn-deficient field in South Australia.Zn efficiency (ratio of shoot dry matter in -Zn to shoot dry matter in +Zn treatment and expressed in percentage) in pot Experiment 1 varied from 35% for 92-13 to 74% for Siren. Narendra, Dunkeld, Barossa, Oscar and Xinza 2 performed well under -Zn treatment. Zn efficiency in Experiment 2 varied from 32% for Wuyou 1 to 62% for Pusa Bold. Pusa Bold and CSIRO-1(mustard genotypes) were the most efficient in terms of dry matter production among all the oilseed rape genotypes tested. Root dry matter accumulation was significantly higher in Zn-efficient genotypes. Zn efficiency (ratio of seed yield in -Zn to seed yield in +Zn and expressed in percentage) in field experiment varied from 62% for Huashang 2 to 76% for Dunkeld. With few exceptions, the ranking of genotypes in pot and field experiments indicates similarity in their response to Zn deficiency. There looks to be genetic control over Zn concentration in tissues. Zn-efficient genotypes had lower Zn concentration in roots and higher Zn concentration in youngest fully opened leaf blades, indicating a better transport of Zn. This, together with a higher Zn uptake, appears to be the basis of expression of Zn efficiency.     

安徽沿江圩丘农区夏收作物田杂草群落分布规律的研究

作者创用了七级目测调查取样,进行数量分析的方法,对夏收作物田杂草群落进行分类研究,揭示了安徽沿江圩丘农区夏收作物田杂草群落的分布规律主要受土壤类型和轮作制度制约。看麦娘杂草群落分布于水稻土田,猪殃殃,野燕麦杂草群落分布于丘岗区旱地,卷耳、婆婆纳杂草群落分布于灰潮土旱地。首次提出综合草害指数,用以评定杂草群落类型中每种杂草的危害性,从而,提出了不同土壤类型和轮作制度的田块中恶性杂草的定量化指标与防除策略。     

Relationship between gibberellic acid and water amount in the cotton seed

The role of endogenous GA₃ and its application to seed development in two cotton genotypes Hybrid-6 (H-6) (big seeds) and Gujarat cotton 13 (G. Cot) (small seeds) was studied. Kernel and seed coat were subjected to growth analysis in terms of dry weight, water amount, and rates of dry matter accumulation and water uptake. H-6 kernel had manifold higher dry weight and water amount than G. Cot. Seed coat of both genotypes had similar dry weight at maturity, but the maximum rates of dry matter accumulation and water uptake were distinctly higher in H-6. According to growth analysis, development of seed kernel and coat was subdivided into four phases, i.e., cell division, cell elongation, dry matter accumulation and maturation. Endogenous GA₃ level was estimated in kernel and seed coat by indirect ELISA using antibodies raised against GA₃. GA₃ amount per seed components was higher in the seed kernel of H-6 than of G. Cot, except 33 and 36 days after anthesis in kernel. H-6 seed coat had the higher amount of GA₃ during cell division phase than that of G. Cot. Close correlation between in vivo GA₃ level and water amount was recorded in both seed components. With GA₃ or GA₃ + NAA treatments in ovule culture, higher promotion in dry weight, water amount and seed size was noted in G. Cot than in H-6 suggesting that G. Cot is more deficient in endogenous GA₃. The greatest stimulation of parameters studied was obtained in ovule culture with GA₃ + NAA. When GA₃ or GA₃ + NAA was applied, initial significant difference in water amount and seed size was nullified. Data presented in this study indicated that GA₃ regulates cell expansion through the water uptake by cotton seed.