Transfer of the Kosena Rfk1 gene,required in hybrid seed production,from oilseed rape to turnip rape

Radiant frost is a major abiotic stress, and one of the principal limiting factors for agricultural production worldwide, including Australia. Legumes, including field pea, faba bean, lentil and chickpea, are very sensitive to chilling and freezing temperatures, particularly at the flowering, early pod formation and seed filling stages. Radiant frost events occur when plants and soil absorb the sunlight during the day time and radiate heat during the night when the sky is clear and the air is still. Dense chilled air settles into the lowest areas of the canopy, where the most serious frost damage occurs. The cold air causes nucleation of the intracellular fluid in plant tissues and the subsequent rupturing of the plasma membrane. Among the cool season grain legume crops, chickpea, lentil and faba bean and field pea are the most susceptible to radiant frost injury during the reproductive stages. The more sensitive stages are flowering and podding. Frost at the reproductive stage results in flower abortion, poor pod set and impaired pod filling, leading to a drastic reduction in yield and quality. In contrast, in the UK and European countries, frost stress is related to the vegetative stages and, in particular, the effects of frost have been studied on cotyledon, uni/tri-foliolate leaf and seedling stages during the first few weeks of growth. Few winter genotypes have been identified as frost tolerant at vegetative stages. Vegetative frost tolerance is not related to reproductive frost tolerance, and hybrids from the vegetative frost-tolerant genotypes may not necessarily be tolerant at the reproductive stage. Tolerance to radiant frost has an inverse relationship with plant age. In the field, frost tolerance decreases from the vegetative stage to reproductive stage. Unlike wheat and barley, it is difficult to analyse and score frost damage in grain legume crops due to the presence of various phenophases on one plant at the reproductive stage. The extent of frost damage depends on the specific phenophases on a particular plant. However, current studies on genetic transformation of cold tolerant gene(s), membrane modifications, anti-freeze substances and ice nucleating or inhibiting agents provide useful information to improve our current understanding on frost damage and related mechanisms. The effects of frost damage on yield and grain quality illustrate the significance of this area of research. This review discusses the problem of radiant frost damage to cool season legumes in Australia and the associated research that has been carried out to combat this problem locally and worldwide. The available literature varies between species, specific climatic conditions and origin.     

Drought Priming at Vegetative Growth Stage Enhances Nitrogen‐Use Efficiency Under Post‐Anthesis Drought and Heat Stress in Wheat

To study the effects of early drought priming at 5th‐leaf stage on grain yield and nitrogen‐use efficiency in wheat (Triticum aestivum L.) under post‐anthesis drought and heat stress, wheat plants were first exposed to moderate drought stress (drought priming; that is, the leaf water potential reached ca. ?0.9 MP a) at the 5th‐leaf stage for 11 days, and leaf water relations and gas exchange rates, grain yield and yield components, and agronomic nitrogen‐use efficiency (ANUE ) of the primed and non‐primed plants under post‐anthesis drought and heat stress were investigated. Compared with the non‐primed plants, the drought‐primed plants possessed higher leaf water potential and chlorophyll content, and consequently a higher photosynthetic rate during post‐anthesis drought and heat stress. Drought priming also resulted in higher grain yield and ANUE in wheat under post‐anthesis drought and heat stress. Drought priming at vegetative stage improves carbon assimilation and ANUE under post‐anthesis drought and heat stress and their combination in wheat, which might be used as a field management tool to enhance stress tolerance of wheat crops to multiple abiotic stresses in a future drier and warmer climate.     

Alleviation of drought stress in maize by exogenous application of gibberellic acid and cytokinin

The study was conducted to investigate the ameliorative roles of GA₃ and CK on adverse effects of drought in maize. Drought stressed maize plants were applied with GA₃ and CK at 50, 100, and 150 mg L^?l as foliar spray at the vegetative and the reproductive stages. Plant height, internode length, stem diameter, leaf chlorophyll index, and dry matter production were significantly affected by drought. In most cases, GA₃ and CK significantly improved the depressed plant traits, but in varying degrees depending on the growth stage encountering hormones, and their types and concentrations. Both GA₃ and CK were found to be very effective in alleviating drought-imposed adverse effects on maize at the vegetative phase. Such alleviating effects varied depending on the concentration of the hormones. Application of CK at 150 mg L^?l was excellent resulting in a 106% yield advantage compared to drought stress and 79.9% increase relative to well-watered controls. Conversely, GA₃ at 50 mg L^?l performed well showing 78.8% increase in grain yield. However, both GA₃ and CK had very little effect on improving the depressed growth and yield attributes in maize at the reproductive phase. The relative yield advantages for the hormones were mainly attributed to improving the cob and seed-bearing capacity of drought-stressed maize plants.     

On the use of spectral reflectance indices to assess agro‐morphological traits of wheat plants grown under simulated saline field conditions

Successful breeding of plants for salinity stress tolerance requires realistic growing conditions and fast, non‐destructive evaluation techniques for phenotypic traits associated with salinity tolerance. In this study, we used subsurface water retention technique (SWRT) as a growing condition and spectral measurements as an evaluation method to assess different agro‐morphological traits of salt‐tolerant (Sakha 93) and salt‐sensitive (Sakha 61) wheat genotypes under three salinity levels (control, 60, and 120 mm NaCl). The effects of salinity on agro‐morphological traits were evaluated and related with forty‐five published vegetation‐ and water‐spectral reflectance indices (SRIs) taken at both the heading and grain milk growth stages for each salinity level, genotype, and growth stage. In general, the agro‐morphological traits gradually decreased as salinity levels increased; however, the reduction in these traits was more pronounced in Sakha 61 than in Sakha 93. The effect of salinity levels and their interaction with genotypes on the SRIs was only evident at the grain milk stage. The performance of the spectral reflectance indices depicted that the closest associations with agro‐morphological traits depended on salinity level, degree of salt tolerance of the genotypes, and growth stage. The SRI‐based vegetative indices correlated better with growth and yield of Sakha 93 than SRI‐based water indices and vice versa for Sakha 61. The SRI‐based vegetative and water indices are effective for assessment of agro‐morphological traits at early growth stages under high salinity level. The functional relationship between grain yield per hectare and the best SRIs was linear for the high salinity level and Sakha 61; however, the quadratic model was found to best fit this relationship for the control, moderate salinity level, and Sakha 93. The overall results indicate that the usefulness of the SRIs for assessment of traits associated with salinity tolerance is limited to salinity level and growth stage.     

Yield enhancement by short‐term imposition of severe water deficit in the vegetative growth stage of grain sorghum

Water deficit is generally thought to negatively impact crop yields, including grain sorghum (Sorghum bicolor L.), but a small body of literature reports changes in crop physiology and growth in plants with short‐term imposition of water deficit during vegetative development that could lead to increased yield. In a replicated and repeated pot experiment in which water deficit was imposed for 10‐day periods in grain sorghum plants that were otherwise well‐watered, we tested the hypothesis that relatively severe, short‐term water deficit imposed during early vegetative development could enhance grain sorghum yield. The results showed that severe water deficit (~30% of control ET) imposed during two vegetative periods enhanced grain yield compared to continuously well‐watered plants by 21% (p = .0356). Grain yield was correlated with average grain weight, grain number per head and shoot‐to‐root ratio. Yield enhancement was associated with a substantial shift in resource partitioning, as water deficit reduced root mass (p = .0032), stem/leaf mass (p < .0001) and total biomass (p = .0005), resulting in a 60% increase in harvest index. Imposition of water stress during vegetative growth in sorghum can increase grain yield.     

Lint Yield Compensatory Response to Main Stem Node Removal in Upland Cotton (Gossypium hirsutum)

Hail storm damage to the cotton (Gossypium hirsutum L.) plants can destroy vegetative and reproductive structures, modify canopy architecture and impact lint yield. Field studies were conducted at University of Arizona Maricopa Agricultural Center in 2011, 2012 and 2013 to examine cotton plant architecture changes and compensatory growth in response to removal treatments of uppermost nodes on main stem (terminal bud removal, 2 node removal and 4 node removal) as simulation of hail damage at the node 2, 4, 8, 12, 16 and 24 growth stages. Main stem node removal caused significant decrease in leaf area and biomass, especially at early growth stages. However, significant lint yield reduction only occurred by removing 2 nodes at the node 4 stage and removing 4 nodes at the node 8 stage in 2011, removing terminal bud at the node 12 stage in 2012 and removing terminal bud, 2 nodes and 4 nodes at the node 8 stage in 2013. The lint yield reduction did not exceed 13 % in all three growing seasons. Yield loss due to main stem node removal was mainly compensated by increased boll number on the vegetative branches at early growth stages and on fruiting branches at late growth stages. Yield compensation from vegetative branches increased with number of main stem nodes removed. This study suggests that the cotton crop has a strong compensatory ability to plant structure damage due to its indeterminate growth and longer growing season in the region.     

Late‐season photosynthetic rate and senescence were associated with grain yield in winter wheat of diverse origins

There is a lack of studies that have investigated grain yield, its components and photosynthesis in late stages of wheat growth, giving us insufficient understanding of how these factors interact to contribute to yield during this period. As a result, three field experiments were carried out examining 20 winter wheat genotypes of diverse origins under irrigated, terminal drought and dryland conditions in the southern Idaho. Our objective was to evaluate the interaction between post‐anthesis physiological traits, especially leaf‐level photosynthetic capacity, senescence and yield components on grain yield in different moisture regimes. Genotype differences were found in leaf‐level photosynthesis and senescence, canopy temperature depression, grain yield and yield components in each water regime. Grain yield was closely associated with traits related to grain numbers. In all three moisture regimes, positive correlations were observed between grain yield and photosynthesis that were dependent on the timing or physiological growth stage of the photosynthetic measurement: highly significant correlations were found in the mid‐ and late grain filling stages, but no correlations at anthesis. Consistent with these findings, flag leaf senescence at the late grain filling stage was negatively correlated with grain yield and photosynthetic rate (under terminal drought and dryland conditions). These findings provided evidence that grain yield was sink‐limited until the final stages of growth, at which time sustained photosynthesis and delayed senescence were critical in filling grain. Because the trends were consistent in moisture sufficient and deficient conditions, the results suggest that late‐season photosynthesis and delayed leaf senescence are driven by the size of the reproductive carbon sink, which was largely governed by factors affecting grain numbers.     

Role of 24‐Epibrassinolide in Wheat Production: Physiological Effects and Uptake

Brassinosteroids are plant steroid hormones important for plant growth and development. They include more then 70 compounds. Their physiological effect and possibilities of practical use are still being investigated. In this study, we evaluated the effects of exogenously applied 24‐epibrassinolide, one of the brassinosteroids, on the grain yield and grain chemical composition (carbohydrates, proteins, fats and minerals) of wheat. Moreover, we analysed the presence of brassinosteroids in newly formed wheat grains after exogenous plant treatment with 24‐epibrassinolide. Experiments were performed in a vegetation hall (plants cultivated in pots) and in the field. The tested regulator was applied via 48 h seed soaking (1 mg·dm^?3) or spraying plants at the heading stage (0.25 mg·dm^?3). 24‐epibrassinolide increased grain yield in plants growing in the field (by about 20 %), but not in plants cultivated in vegetation hall. Grain chemical composition was altered by 24‐epibrassinolide in wheat growing in the vegetation hall; the content of soluble sugars was higher while that of total fats and calcium was lowered, whereas the starch and soluble protein content was not affected. The effect of the hormone was in these cases dependent on the method of its application. As for plants cultivated in the field, the hormone impact on the amount of carbohydrates, proteins, fats and minerals contained in the grains was rather negligible. In wheat grains, the presence of brassinolide, castasterone and 24‐epicastasterone was found. 24‐Epibrassinolide applied exogenously to plants was not accumulated in newly formed grains. Additionally, significance of ethanol as a hormone solvent is discussed.     

开顶式气室对冬小麦的生长及产量的影响

开顶式气室（open-top chamber,OTC）通常是用来研究气候变化对农业生产的影响,为了探明开顶式气室内外冬小麦生长和产量的差异,分析了OTC内外气象因子（温度、相对湿度、饱和水汽压差和太阳辐射）的变化,测定了OTC内（CK组）和OTC外（AA组）冬小麦（扬麦13）在不同生育期的株高、叶面积、干物质、生长参数及产量指标。结果表明,OTC内温度、相对湿度和饱和水汽压差高于OTC外,而光合有效辐射低于OTC外。此外,OTC对冬小麦的株高、叶面积、生物量和产量都会造成不同程度的影响。与AA组相比,OTC对冬小麦的株高具有抑制作用,但是在生育后期对叶面积有促进作用。在冬小麦整个生育期,OTC对冬小麦叶干重、茎干重都表现出明显的负效应,但是对根干重具有促进作用。CK组穗的干物质累积低于AA组。OTC内的冬小麦穗重、单株粒数、单株粒重和千粒重都低于OTC外,导致OTC内冬小麦产量降低。     

Dry Matter Accumulation and Associated Changes in Biochemical Parameters during Wheat Grain Development

Field experiments were conducted in Rajkot, Gujarat, India comparing three cultivars of wheat, viz. Raj-1555, Lok-1 and Sonera, all differing in their grain yield. Apical grain of the seventh spikelet from the main spike was selected as a representative grain in each cultivar and analyzed at 4-day intervals from anthesis to maturity for dry matter, starch, sugars and protein content. The data for dry matter accumulation and starch content were fitted to a quadratic polynomial exponential which revealed a close correspondence between these two parameters. The absolute rates of starch and dry matter accumulation were highest in Lok-1 followed by Sonera and Raj-1555, respectively; however, the duration of the grain-filling observed from these curves was highest in Raj-1555. The maximum weight of the grain at harvest was in Lok-1 (80 mg) followed by Raj-1555 (71 mg) and Sonera (50 mg), respectively. Increase in the starch content coincided well with dry matter accumulation. Reducing and nonreducing sugars were high during early stage but declined with advances in growth up to almost middle of the grain growth; high levels were even found at later stages. Although protein increased with increasing grain growth in Raj-1555 and Sonera, no clear trend was observed in Lok-1 in relation to dry matter accumulation. The results are discussed in relation to the use of polynomial functions and the contribution of photosynthate supply from various plant parts in relation to grain growth and yield in wheat.     

A strategy of ideotype development for heat-tolerant wheat

Heat stress significantly limits yield in many wheat-growing areas globally including north-western NSW. While various traits linked to high-temperature tolerance have been identified, the combination of traits that optimize the heat tolerance of wheat has not been established in most environments. A total of 554 genotypes were evaluated in the field at different times of sowing in north-western NSW for three consecutive years to develop a heat-tolerant wheat ideotype for this environment. The later sown experiments were exposed to higher temperatures at the critical reproductive and grain-filling stages of development. The impact of high temperature was greatest at anthesis, and eventual grain yield was reduced by between 4% and 7% with every 1°C rise in average maximum temperature above the optimum of 25°C. High temperature reduced yield, plant height, grain weight and days to anthesis and maturity, and increased the percentage of screenings and grain protein content. Genotypes that produced higher yield under heat stress had shorter days to flowering and maturity, higher NDVI during grain filling, greater chlorophyll content at the milk stage of grain fill, taller plants, greater grain weight and number, and lower screenings compared with the benchmark cultivar Suntop. The genotype closest to the predicted heat-tolerant wheat ideotype identified from trait ranges had 79.6% similarity.     

Influence of Water Stress on Grain Yield and Vegetative Growth of Two Cultivars of Bean (Phaseolus vulgaris L.)

Lack of water during vegetative and/or reproductive growth stages is one of the most limiting factors for bean growth. The purpose of this study was to evaluate the effects of water stress applied during two phenological stages (flowering and pod filling) on growth, yield and yield components. Two genotypes of bean ( Phaseolus vulgaris L.) were used in this study, cv. Carioca, an indeterminate Brazilian landrace, and cv. Prince, a determinate cultivar grown in Europe. Carioca appears to be generally stress-tolerant while Prince is intolerant. Plants were grown in large plastic pots covered with a black plastic sheet to protect the soil from rain and evaporation. The water stress treatments were: control (well-watered plants), WSFS (water stress during flowering stage) and WSPFS (water stress during pod-filling stage). Water stress reduced yield and yield components at both flowering and pod-filling stages. The parameters affected were seed weight, number of seeds per plant and number of pods per plant. Number of seeds per pod and seed weight were not affected. No effects of water stress were detected on harvest index. Time to maturity was slightly prolonged, especially for WSFS. Water stress at both stages resulted in lower accumulated water loss compared to the control plants. Water stress during both phenological stages reduced other growth parameters, the number of trifoliate leaves, stem height, number of main branches and number of nodes on the main stem.     

The Relationship Between Sugar-Nitrogen Ratio and Reproductive Organs Abscission in Faba Bean (Vicia Faba L.)

The changes of soluble sugar and total nitrogen content of vegetative organs in faba bean, sugar-nitrogen ratio, abscission of reproductive organs and the relationship between sugar-nitrogen ratio and abscission probability were studied using the faba bean cultivar Xichang Dabai . Plants were field grown in 1986, 1988 and 1990. The lands were separated into high yield land, middling yield land and low yield land according to grain yield at maturing stage. The soluble sugar content in vegetative organs (leaf + stem) was greatest from branching to floral initiation stages and pod-set to filling grain stages, and distinctly decreased at the onset of bloom and maturing stages. The total N content was greatest at branching stage, and gradually decreased with growth. In general, the sugar and total N contents in high yield lands were greatest, followed by that in middling yield and low yield lands. The sugar-nitrogen ratio varied depending on the soluble sugar content.
Average yield on high yield lands, middling yield land and low yield land across 3 years were 5048.77 kg/ha, 3744.01 kg/ha and 2378.22 kg/ha, respectively. The total reproductive organs abscission exceeded 90 % of total flower buds. Abscission probability averaged across 3 yield lands and 3 years were 21.6 %, 84.0 % and 32.8 % in flower buds, flowers, and pods, respectively. Node 7–12 of canopy produced more flowers, and fewer flowers and pods were produced in the upper and lower regions. Photosynthate supply has been implicated in control of abscission. Faba bean reproductive organs abscission probability increased with the sugar-nitrogen ratio of vegetative organs decreasing. It seemed that the soluble sugar content influenced significantly the shedding rate during flowering and pod-growing stages.     

Growth Analysis in Relation to Pigeonpea Improvement

An attempt was made to assess possible constraints to higher production, with respect to partitioning of total dry matter to reproductive sinks in early pigeonpea. Growth, dry matter accumulation and yield components were determined in four diverse genotypes under four dates of sowing and different plant densities. Data on growth characteristics, dry matter accumulation (vegetative and reproductive) were obtained for three sowings, while the data on yield components were obtained for two dates of sowing. Growth analysis showed that the total dry matter was low upto 30 days after sowing and increased linearly upto 120 days. Coversely, LAD was high for the first 30 days and reduced at later stages of growth. The mean LAI of genotypes did not very much at initial stage of growth. However, it has given interesting picture during 70 to 90 days of growth. The higher biological yield and seed yield were attributable to high LAI and LAD coupled with thick stem, more effective branches, more pods per plant and larger raceme length. Harvest index was the maximum with increased plant populations in all sowings. Indeterminate varieties under high plant density and narrow row spacing (50 cm) developed a large leaf area and were presumably able to make better use of light. Growth and branching of individual plants were reduced at the higher plant population, but on per unit basis more dry matter was produced. It is suggested that breeding should be concentrated to improve an inability to accumulate adequate vegetative dry matter for the maintenance and filling of pods, may force the plant to continue vegetative production into the reproductive dry matter to support production of ultimate seed yield.     

缓释肥用量对夏谷光合特性、物质积累分配和产量性状的影响

旨在通过研究缓释肥用量对夏谷光合特性、物质积累分配和产量性状的影响，为夏谷高产栽培实践提供理论依据。以‘保谷21’为材料，在苗期、拔节期、抽穗期、灌浆期和成熟期，采用常规分析方法测定光合速率(Pn)、叶绿素含量(Chl)、叶面积指数(LAI)、群体干物重、生育后期植株营养器官干物质积累和转运特性、成熟期植株氮磷钾含量和单位面积氮磷钾累积量、植株性状、产量和收获指数。结果表明，在缓释肥底施用量0 kg/hm2(T1)、225 kg/hm2(T2)和450 kg/hm2(T3)处理中，各生育时期期叶片Pn 和Chl 均表现随施肥量增多而增高。随施肥数量增多，各生育时期LAI 和群体干物重增大，抽穗、成熟期植株叶片、叶鞘、茎秆干质量增加，且高施肥量处理上述营养器官干质量输出量增多，但处理间营养器官转运效率差异较小。高施肥量处理成熟期植株氮、磷和钾含量增加，养分累积量增多，穗部性状得到改善，产量显著提高。施用适量缓释肥能明显改善植株生长、发育和产量形成能力，这与植株在上述条件下养分吸收增强进而改善植株的光合碳同化能力密切相关。     

土壤水分胁迫对冬小麦生长的后效影响

为揭示土壤水分胁迫对冬小麦生长的后效影响及其规律,利用盆栽试验对供试冬小麦设置13种供水处理,测定作物株高、叶面积、冠干重及产量,研究水分胁迫对上述生理指标的后效影响。结果表明,中度水分胁迫对株高的后效影响大于重度水分胁迫,在重度水分胁迫下,除C5-A外,当前影响均大于后效影响;前期中度水分胁迫对叶面积的后效影响大于当前影响,后期则相反,重度水分胁迫对叶面积的当前影响大于后效影响;水分胁迫对冠重的后效影响大于当前影响;水分胁迫对冬小麦穗数的后效影响基本上表现为正效应,而对每穗粒数、千粒重、产量及WUE的后效影响则全部为负效应,拔节至孕穗阶段中度水分胁迫抽穗期复水的处理产量最高,达到对照的62%。不同程度、不同历时、不同生育阶段的水分胁迫,对作物生长均有后效应,并导致小麦减产。     

不同低温处理对小麦光合特性和产量性状的影响

为研究小麦在经受低温冻害后植株光合特性和产量性状变化规律,以‘周麦22’为研究对象,于拔节前期和拔节后期,分别设置-1℃、-3℃、-5℃、-7℃、-9℃温度梯度,低温处理4 h后,测定小麦光合特性和叶绿素SPAD值,并在收获后测量小麦植株性状变化。本研究结果表明,于拔节前期和后期,随温度的降低,小麦光合速率A,胞间CO2浓度Ci,叶片蒸腾速率E和气孔导度GH2O逐渐降低。但于拔节前期,-7℃处理较CK显著降低,且各低温梯度于7天后逐渐恢复正常。而于拔节后期,-5℃处理较CK显著降低,于各低温梯度于3天后逐渐恢复正常;在小麦拔节前期,温度低于-9℃时,SPAD值明显降低,而在拔节后期,温度低于-5℃时,SPAD开始显著降低;低温发生时间推迟,小蘖穗高降低,穗长缩短,粒数和千粒重则降低,而株高和单株成穗数增加。随温度的降低,小蘖穗高、株高降低和穗粒数显著降低。在发生低温冻害后,小麦生物产量和籽粒产量均显著降低。     

Evaluation of a semi‐controlled test as a selection tool for frost tolerance in durum wheat (Triticum durum)

Most durum wheat (Triticum durum) varieties possess only low winter hardiness due to their frost susceptibility. In North America and Central Europe, durum wheat is therefore typically sown in spring to circumvent the local winter conditions. However, the yield potential of durum in these regions could be much better exploited if durum varieties with increased frost tolerance were available, which could be sown in autumn. A factor limiting breeding for increased frost tolerance is the variation in the occurrence of frost stress across years. The ‘Weihenstephaner Auswinterungsanlage’ is a semi‐controlled test that exposes the plants to all weather conditions. Snow coverage of the plants, serving as frost protection, is prevented by the movable glass lid of the semi‐controlled test. In this study, different scorings for frost tolerance based on this semi‐controlled test were evaluated and compared with frost tolerance data in the field. Our results illustrate the potential of the ‘Weihenstephaner Auswinterungsanlage’ as an indirect selection tool for frost tolerance in durum breeding programmes, especially when regular frost tolerance data from the field are not available.     

Dry Matter and Nitrogen Distribution at Maturity of Three Rice (Oryza sativa L.) Cultivars Exposed to Ammonia at Two Growth Stages

A substantial proportion of ammonical fertilizers applied to lowland rice is lost as gaseous N from the soil–plant system. Besides various environmental factors, the low N use efficiency of flooded rice is also attributed to this factor. As atmospheric ammonia found in the leaf environment of the plants could also be responsible for differences in N use efficiency and fertilizer N losses from lowland rice, a greenhouse study was conducted on three rice cultivars varying in physio-morphological characteristics for their dry matter and nitrogen distribution to grains at maturity in response to ammonia (NH₃) exposure at tillering and anthesis growth stages. The results revealed that ammonia exposure of plants at two growth stages did not affect the total dry matter and total N yield of the rice cultivars at maturity; however, the grain yield and grain N yield were negatively effected by NH₃ exposure of the plants at anthesis. The variation observed in dry matter and N partitioning at maturity to grains/roots of the plants exposed to NH₃ at anthesis indicated that the growth stage of the plants at which they are exposed to NH₃ has an influence on N use efficiency of crop plants and subsequent vegetative as well as total N losses from the soil–plant system.