Effect of Pre-Anthesis Drought Hardening on Post-Anthesis Physiological Characteristics,Yield and WUE in Winter Wheat

A drought event can cause yield loss or entire crops to fail. In order to study the effects of continuous drought on physiological characteristics, yield, and water use efficiency (WUE) of winter wheat (Triticum aestivum L.), the variety “Zhoumai 22” was grown in controlled water conditions of the pot-planted winter wheat under a mobile rainout shelter. Foot planting and safe wintering were used to evaluate, winter wheat under different drought conditions, including light, moderate and severe drought at the jointing, heading, and filling stages. The soil water content was controlled at 60–70%, 50–60%, or 40–50% of field capacity. Experimental trials included 3 pre-anthesis drought hardening, 3 three-stage continuous drought, and 1 test control conditions. Under drought stress conditions, winter wheat leaf water potential, soil plant analysis development (SPAD), photosynthesis parameters, and yield declined due to pre-anthesis drought hardening. And the degree of decline: continuous drought > pre-anthesis drought hardening. Changes in the post-anthesis photosynthetic capacity of winter wheat were mainly related to the pre-anthesis drought level, rather than post-anthesis rehydration. The threshold of non-stomata limiting factors caused by photosynthesis at the filling stage is 40–50%FC, while comprehensive yield and WUE affected, the yield in severe drought treatments was the most significant, B3C3 and B3C3G3 decreased by 55.68% and 55.88%, respectively. Pre-anthesis drought was the main reason for the decreased crop yield. Thus, severe drought should be avoided during planting, while pre-anthesis light drought is a suitable choice for water-saving and crop production, as proper pre-anthesis drought hardening (60–70% FC) is feasible and effective.     

Relationships of endogenous plant hormones to accumulation of grain protein and starch in winter wheat under different post-anthesis soil water statusses

Accumulation of protein and starch in grain is a key process determining grain yield and quality in wheat. Under drought or waterlogging, endogenous plant hormone levels will change and may have an impact on the yield and quality of wheat. In a greenhouse experiment, four winter wheat (Triticum aestivum L.) varieties differing in grain protein content, Heimai 76, Wanmai 38, Yangmai 10 and Yangmai 9, were subjected to drought (SRWC = 4550%, DR), waterlogging (WL) and moderate water supply (SRWC = 7580%, CK), beginning from 4 days post-anthesis (DPA) to maturity. On the 10 (grain enlargement stage) and 20 (grain filling stage) DPA, endogenous abscisic acid (ABA), gibberellins (GA₁₊₃), indole-3-acetic acid (IAA) and zeatin riboside (ZR) were determined in sink and source organs of wheat plants by enzyme linked immunosorbent assay (ELISA). The patterns of hormonal changes were similar in four varieties. The ABA levels were much higher under DR and WL than under CK. Compared with CK, GA₁₊₃ levels in whole-plant under DR and WL changed a little at 10 DPA, but markedly decreased under DR and WL at 20 DPA. Changes of endogenous IAA level under DR and WL exhibited a complicated pattern, depending on organs and growth stages. Particularly at the 20 DPA, the mean levels of IAA in roots, leaves and grains decreased significantly under DR and WL. In comparison with CK, ZR levels in all organs significantly decreased under DR and WL at both stages. The correlation analyses between yields and contents of starch and protein in grains and levels and ratios of four hormones in source and sink organs indicated that the changes in yield and content of grain starch and protein under DR and WL were associated with the reduced IAA, ZR and GA₁₊₃ levels and elevated ABA level in plants, especially in grains. It was proposed that the changed levels of endogenous hormones under post-anthesis DR and WL might indirectly affect protein and starch accumulation in grains by influencing the regulatory enzymes and processes.     

不同产量水平旱地冬小麦品种干物质累积和转移的差异分析

旱地小麦高产栽培中品种起着重要作用,研究不同产量水平旱地冬小麦品种干物质累积和转移的差异,对黄土高原旱区作物高产稳产有重要意义。以9个旱地冬小麦品种为材料,通过田间试验研究了不同产量水平旱地冬小麦品种的生物量、花前花后干物质累积量、干物质转移量、转移率及转移干物质对籽粒的贡献率、叶面积、SPAD值以及光合速率的差异。结果表明,不同小麦品种的生物量、花前花后干物质累积量、干物质转移量、转移率及转移干物质对籽粒的贡献率均存在明显差异。与不施肥相比,高、中、低3个产量水平小麦品种在低养分投入时,成熟期生物量分别提高29%,22%和6%,高水平时分别提高46%,39%和23%,高产品种的生物量及其对养分投入的敏感程度明显高于低产品种。不同品种的花后干物质累积量随养分投入水平提高而增加,但花前营养器官中储存物质的转移量、转移率和对籽粒的贡献率却明显随之下降。功能叶(旗叶)在灌浆期高、中、低3个产量水平品种的SPAD值在低养分投入条件下分别为20.7、17.5和13.7;高养分投入时,分别为35、26.1和16.8。高产品种西农88的光合速率为6.0μmolCO.2m-.2s-1),中产和低产品种的平均光合速率分别为4.3μmolCO.2m-.2s-1和4.0μmolCO.2m-.2s-1,高产品种功能叶(旗叶)在灌浆期能保持较高的SPAD值和光合速率,因而花后能生产较多的干物质,但其花前干物质转移量、转移率及转移干物质对籽粒的贡献率均没有明显优势。可见,花后较高的叶绿素水平、光合速率和干物质累积是旱地小麦品种高产的重要原因。选择优良品种,采取合理的栽培措施,特别是通过养分调控保持花后具较高的干物质累积量是西北旱地进一步提高冬小麦产量的重要途径。     

花前渍水预处理对花后渍水逆境下扬麦9号籽粒产量和品质的影响

以扬麦9号为材料,研究花前渍水预处理对花后渍水逆境下小麦籽粒产量和品质的影响。结果表明,与未进行渍水预处理相比,花前渍水预处理提高了小麦植株对花后渍害的抗性,生物产量、收获指数和千粒重显著提高,进而显著提高了籽粒产量;花前渍水预处理显著提高花后氮素积累量及其对籽粒氮素的贡献率,降低了花前贮藏氮素运转量及其对籽粒氮素的贡献率,进而引起籽粒球蛋白含量提高,但显著降低了清蛋白、醇溶蛋白、谷蛋白和全蛋白质含量、以及干湿面筋含量和沉降值;花前渍水预处理还提高了籽粒直链淀粉和总淀粉含量和降落值,降低了支/直链淀粉比,显著提高了面粉峰值粘度、低谷粘度、崩解值、最终粘度、回冷值和峰值时间,但对糊化温度无显著影响。     

Short-term effects of experimental warming and enhanced ultraviolet-B radiation on photosynthesis and antioxidant defense of <Emphasis Type="Italic">Picea asperata</Emphasis> seedlings

It is generally accepted that sucrose synthase (SuSy), ADP-glucose pyrophosphorylase (AGPase), soluble starch synthase (SSS), granule-bound starch synthases (GBSS) and starch branching enzyme (SBE) play a key role in starch synthesis in wheat grains. Starch synthesis in wheat grains is influenced by genotype and environment. However, what is not known is the degree of variation in enzyme activity during starch accumulation of wheat cultivars differing in kernel types. The present study was carried out to characterize the changing activities of key enzymes during grain filling in two kernel type winter wheat cultivars. Results showed that starch accumulation rate (SAR) and activities of SuSy, AGPase, SSS, GBSS and SBE in large kernel types were significantly higher than those in small kernel types. The soil water deficit experienced during the course of the experiment led to an increase at early grain-filling period and decrease during late grain-filling, respectively, in SAR and activities of key enzymes involved in starch synthesis, especially SuSy, AGPase, SSS, and SBE. Water deficit enhanced grain starch accumulation in small kernel types. It suggests that rainfed treatment increase physiological activities during early grain-filling and promote starch accumulation in small kernel types. The simulation with Richards’ equation showed that it was accumulation duration and SAR that determined the starch accumulation in large kernel types. Compared with small kernel types, plants of large kernel types maintained longer filling duration, higher SAR and greater activities of related enzymes during mid and late grain-filling. These observations suggest stronger sink activities in large kernel types at a later stage of development. Consequently, large kernel types have advantages over the small kernel types in terms of the amount of starch accumulation at mid and late stage, but are sensitive to water deficit.     

Physiological mechanisms contributing to the increased water-use efficiency in winter wheat under deficit irrigation

Deficit irrigation in winter wheat has been practiced in the areas with limited irrigation water resources. The objectives of this study were to (i) understand the physiological basis for determinations of grain yield and water-use efficiency in grain yield (WUE) under deficit irrigation; and (ii) investigate the effect of deficit irrigation on dry matter accumulation and remobilization of pre-anthesis carbon reserves during grain filling. A field experiment was conducted in the Southern High Plains of the USA and winter wheat (cv. TAM 202) was grown on Pullman clay loam soil (fine mixed thermic Torretic Paleustoll). Treatments consisted of rain-fed, deficit irrigation from jointing to the middle of grain filling, and full irrigation. The physiological measurements included leaf water potential, net photosynthetic rate (Pn), stomatal conductance (Gs), and leaf area index. The rain-fed treatment had the lowest seasonal evapotranspiration (ET), biomass, grain yield, harvest index (HI) and WUE as a result of moderate to severe water stress from jointing to grain filling. Irrigation application increased seasonal ET, and ET increased as irrigation frequency increased. The seasonal ET increased 20% in one-irrigation treatments between jointing and anthesis, 32-46% in two-irrigation treatments, and 67% in three- and full irrigation treatments. Plant biomass, grain yield, HI and WUE increased as the result of increased ET. The increased yield under irrigation was mainly contributed by the increased number of spikes, and seeds per square meter and per spike. Among the irrigation treatments, grain yield increased significantly but the WUE increased slightly as irrigation frequency increased. The increased WUE under deficit irrigation was contributed by increased HI. Water stress during grain filling reduced Pn and Gs, and accelerated leaf senescence. However, the water stress during grain filling induced remobilization of pre-anthesis carbon reserves to grains, and the remobilization of pre-anthesis carbon reserves significantly contributed to the increased grain yield and HI. The results of this study showed that deficit irrigation between jointing and anthesis significantly increased wheat yield and WUE through increasing both current photosynthesis and the remobilization of pre-anthesis carbon reserves.     

Relevance of physiological efficiency in wheat grain quality and the prospects of improvement

Released and pre-released bread wheat varieties evaluated in national wheat programme of India (503 genotypes) during 2005–14 under different environments were examined for the role of physiological parameters in grain quality. Genotypes with slow plant height growth but faster rate of grain filling enhanced protein content. Plants where growth in height and grain development was slow, grains were hard, provided proportionate vegetative growth phase is longer. Steady grain growth rate benefited gluten strength and gluten quality. Irrespective of total crop duration, longer reproductive phase was an effective indicator of higher flour recovery and test weight. Magnitude and significance of morphological attributes in grain quality was almost similar to that of physiological processes, therefore prospects of utilizing these field traits were examined to enhance grain properties. Early heading and longer grain filling was effective to increase test weight whereas delayed heading and shorter plant height enhanced protein content. Bold grains hampered grain hardness and delayed heading added more bran in the flour. Genotypes with poor grain bearing and quick grain ripening had lower sedimentation value. Instead of protein, it was wet gluten which expressed negative association with yield. To improvise gluten quality, extended reproductive phase but with less grain weight was helpful. Contribution of longer post-anthesis period was observed crucial in flour recovery. These useful simple field expressions can be deployed to uplift quality of wheat grains.     

不同酸度酸雨对小麦花后氮硫代谢和籽粒蛋白组分的影响

酸雨是中国重要的环境问题,为研究酸雨对小麦籽粒品质的可能影响,以小麦品种扬麦15和汶农17为材料开展盆栽试验,研究了不同酸度(pH2.5、p H4.0和p H5.6)酸雨对小麦花后氮硫代谢关键酶活性和籽粒蛋白质含量及组分的影响。结果显示:酸雨处理抑制叶片硝酸还原酶(NR)活性,提高了扬麦15整个灌浆期及汶农17灌浆中后期叶片谷氨酰胺合成酶(GS)活性,促进了叶片蛋白的降解,降低了叶片可溶性蛋白含量。不同酸度酸雨提高了成熟期籽粒中蛋白质含量,酸度越强,增加幅度越大,籽粒中各蛋白组分含量和大部分氨基酸含量也有明显提高。酸雨提高了扬麦15叶片丝氨酸乙酰转移酶(SAT)和O-乙酰丝氨酸硫裂解酶(OAS-TL)活性,但对汶农17硫代谢关键酶活性影响较小,酸雨处理还提高了籽粒中二硫键和含硫氨基酸含量。可见酸雨对小麦氮硫代谢有不同程度影响,进而影响了小麦籽粒蛋白质含量和组成,酸度越强影响越大,但不同品种对酸雨响应有一定差异。     

Comparison of the Drought Stress Responses of Tolerant and Sensitive Wheat Cultivars During Grain Filling: Changes in Flag Leaf Photosynthetic Activity,ABA Levels,and Grain Yield

Water status parameters, flag leaf photosynthetic activity, abscisic acid (ABA) levels, grain yield, and storage protein contents were investigated in two drought-tolerant (Triticum aestivum L. cv. MV Emese and cv. Plainsman V) and two drought-sensitive (cvs. GK élet and Cappelle Desprez) wheat genotypes subjected to soil water deficit during grain filling to characterize physiological traits related to yield. The leaf water potential decreased earlier and at a higher rate in the sensitive than in the tolerant cultivars. The net CO₂ assimilation rate (P _N) in flag leaves during water deficit did not display a strict correlation with the drought sensitivity of the genotypes. The photosynthetic activity terminated earliest in the tolerant cv. Emese, and the senescence of flag leaves lasted 7 days longer in the sensitive Cappelle Desprez. Soil drought did not induce characteristic differences between sensitive and tolerant cultivars in chlorophyll a fluorescence parameters of flag leaves during post-anthesis. Changes in the effective quantum yield of PSII (Φ_PSII) and the photochemical quenching (qP) depended on the genotypes and not on the sensitivity of cultivars. In contrast, the levels of ABA in the kernels displayed typical fluctuations in the tolerant and in the sensitive cultivars. Tolerant genotypes exhibited an early maximum in the grain ABA content during drought and the sensitive cultivars maintained high ABA levels in the later stages of grain filling. In contrast with other genotypes, the grain number per ear did not decrease in Plainsman and the gliadin/glutenin ratio was higher than in the control in Emese during drought stress. A possible causal relationship between high ABA levels in the kernels during late stages of grain filling and a decreased grain yield was found in the sensitive cultivars during drought stress.     

灌溉对干旱区冬小麦干物质积累、分配和产量的影响

为探明灌溉对干旱区冬小麦(Triticum aestivum)产量、水分利用效率(WUE)、干物质积累及分配等的影响, 以甘肃河西走廊冬小麦适宜种植品种‘临抗2号’为材料进行了研究。在冬季灌水180 mm的条件下, 生育期以灌水量和灌水次数等共设置5个处理, 分别为: 拔节期灌水量165 mm (W1)、拔节期灌水量120 mm +抽穗期灌水量105 mm (W2)、拔节期灌水量105 mm +抽穗期灌水量105 mm +灌浆期灌水量105 mm (W3)、拔节期灌水量75 mm +抽穗期灌水量75 mm +灌浆期灌水量75 mm (W4)、拔节期灌水量105 mm +抽穗期灌水量75 mm +灌浆期灌水量45 mm (W5)。结果表明: 随着生育期的推进, 土壤有效含水量(AWC)受灌水次数及灌水量影响更加明显; W3、W4处理的土壤各层AWC在灌浆期均较高; 叶面积指数(LAI)下降慢, 延缓了生育后期的衰老; 生育后期干物质积累增加, 提高了穗粒数、千粒重和籽粒产量。籽粒产量以W3处理最高, 但W4具有最高的WUE, 且籽粒产量与W3无显著差异, 但W4较灌溉总量相同的W2和W5以及灌水量最少的W1具有明显的指标优势。W1、W2、W5处理灌浆期各层土壤AWC均较低, 花后LAI下降快, 干物质积累减少, 灌浆持续期缩短, 穗粒数和千粒重减少, 最终表现为籽粒产量和WUE下降。灌浆期水分胁迫可促进花前储存碳库向籽粒的再转运, 并随着干旱胁迫的加重而提高, 对籽粒产量起补偿作用; 水分胁迫提高了灌浆速率, 但缩短了灌浆持续期。相关性分析表明, 灌浆持续期、有效灌浆持续期、有效灌浆期粒重增加值和最大籽粒灌浆速率出现时间与千粒重和籽粒产量均呈正相关。综合考虑, 拔节、抽穗及灌浆期各灌溉75 mm是高产高WUE的最佳灌水方案。     

黑龙港流域夏玉米产量提升限制因素

从产量构成因素及物质生产着手分析了黑龙港流域夏玉米产量进一步提高的限制因子.分析结果显示:穗数、穗粒数和千粒重均与产量显著相关,说明该地区夏玉米仍有继续增产的潜力;但在再高产过程中,单纯依靠穗数增加,产量增产幅度较小,应稳定在一定适宜的密度下,注重单位面积穗粒数和粒重的提高,但在穗数确定的情况下,穗粒数相对稳定,增加粒重成为再高产重要因素.因此,采取措施增强灌浆速率和延长灌浆时间是关键,即增强或稳定叶片在花后的有效光合能力.结果表明,增加叶片数量对产量贡献很小,而改善叶片质量、提高叶片功能,进而增加花后同化物合成至关重要.因此,茎秆和叶片的质量是再高产实现的关键技术突破点.同时,提高茎秆的花前物质转运比例也有助于提高于粒重,促进产量提升.在生产实践中,进一步挖掘产量必须搞清楚地上和地下两方面的关系,但目前对“根系-土壤”复合体的结构和功能研究相对较少.不合理耕作方式造成了土壤耕层太浅,严重影响了玉米根系生长发育,使生育后期吸收功能减弱,不利于产量形成.加之,吐丝前后阴雨寡照,造成穗粒数形成决定期的“源”不足,同时也限制了灌浆速率,提前播期,躲避灾害天气或推迟收获时期,延长灌浆时间等逆境栽培措施就显得尤为重要.     

强筋与弱筋小麦籽粒蛋白质组分与加工品质对灌浆期弱光的响应

选用强筋小麦品种济麦20和弱筋小麦品种山农1391,在大田试验条件下,分别于籽粒灌浆前期(花后6—9 d)、中期(花后16—19 d)和后期(花后26—29 d)对小麦进行弱光照处理,研究了籽粒产量、蛋白质组分及加工品质的变化。灌浆期弱光显著降低小麦籽粒产量,灌浆中期对济麦20和灌浆后期对山农1391的产量降幅最大。弱光处理后,籽粒氮素积累量及氮素收获指数减少。但弱光使籽粒蛋白质含量显著升高,其中灌浆中期弱光升幅最大,原因可能是由于其粒重降低造成的。弱光对可溶性谷蛋白无显著影响,但增加不溶性谷蛋白含量,使谷蛋白聚合指数显著升高,面团形成时间和稳定时间亦升高,籽粒灌浆中、后期弱光对上述指标的影响较前期大。灌浆期短暂的弱光照对改善强筋小麦粉质仪参数有利,但使弱筋小麦变劣;并均伴随籽粒产量的显著降低这一不利影响。     

Interactions between polyamines and ethylene during grain filling in wheat grown under water deficit conditions

This study was to test the hypothesis that polyamines (PAs) and ethylene may be involved in mediating the effect of water deficit on grain filling. Two wheat cultivars, drought-tolerant Shannong16 (SN16) and drought-sensitive Jimai22 (JM22), were used and subjected to well-watered and severe water deficit (SD) during grain filling. SD reduced the weight of superior and inferior grains, by 7.38 and 23.54 % in JM22, 13.8 and 2.2 % in SN16, respectively. Higher free-spermidine (Spd) and free-spermine (Spm) concentration and lower free-putrescine (Put) concentration, ethylene evolution rate (EER) and 1-aminocylopropane-1-carboxylic acid (ACC) concentration were found in superior grains than those in inferior ones. Opposite to the variations of Spd and Spm concentration, ACC, Put concentration and EER were significantly increased under SD. The percentage variation of PAs and ACC differed with cultivars and grain types. ACC concentration of superior and inferior grains under SD increased significantly at 21 days post-anthesis, by 90 and 164 % in JM22, 65 and 13.2 % in SN16, respectively. The equivalent value of Put concentration was 1.04 and 7.9 % in JM22, 34.4 and 10.3 % in SN16. Spd concentration of superior grains showed a higher decrease than that of inferior ones in both cultivars, while Spm exhibited an opposite trend between both grain types. These percentage variations were highly consistent with the differed responses of weight of both grain types to SD in JM22 and SN16. Grain filling rate was negatively correlated with EER and ACC concentration, while positively correlated with Spd and Spm concentration as well as the ratio of Spd or Spm to ACC. Exogenous Spd or aminoethoxyvinylglycine (an inhibitor of ethylene synthesis by inhibiting ACC synthesis) obviously reduced ACC concentration and EER and increased Spd and Spm concentration, while exogenous ethephon (an ethylene-releasing agent) or methylglyoxal-bis (an inhibitor of Spd and Spm synthesis) showed the opposite effects. The results suggested that it would be good for wheat to have the physiological traits of higher Spd and Spm, as well as a higher Spd/ACC or Spm/ACC, under SD.     

Root growth and water uptake in winter wheat under deficit irrigation

Root growth is critical for crops to use soil water under water-limited conditions. A field study was conducted to investigate the effect of available soil water on root and shoot growth, and root water uptake in winter wheat (Triticum aestivum L.) under deficit irrigation in a semi-arid environment. Treatments consisted of rainfed, deficit irrigation at different developmental stages, and adequate irrigation. The rainfed plots had the lowest shoot dry weight because available soil water decreased rapidly from booting to late grain filling. For the deficit-irrigation treatments, crops that received irrigation at jointing and booting had higher shoot dry weight than those that received irrigation at anthesis and middle grain filling. Rapid root growth occurred in both rainfed and irrigated crops from floral initiation to anthesis, and maximum rooting depth occurred by booting. Root length density and dry weight decreased after anthesis. From floral initiation to booting, root length density and growth rate were higher in rainfed than in irrigated crops. However, root length density and growth rate were lower in rainfed than in irrigated crops from booting to anthesis. As a result, the difference in root length density between rainfed and irrigated treatments was small during grain filling. The root growth and water use below 1.4 m were limited by a caliche (45% CaCO₃) layer at about 1.4 m profile. The mean water uptake rate decreased as available soil water decreased. During grain filling, root water uptake was higher from the irrigated crops than from the rainfed. Irrigation from jointing to anthesis increased seasonal evapotranspiration, grain yield, harvest index and water-use efficiency based on yield (WUE), but did not affect water-use efficiency based on aboveground biomass. There was no significant difference in WUE among irrigation treatments except one-irrigation at middle grain filling. Due to a relatively deep root system in rainfed crops, the higher grain yield and WUE in irrigated crops compared to rainfed crops was not a result of rooting depth or root length density, but increased harvest index, and higher water uptake rate during grain filling.     

高温下干旱和渍水对冬小麦花后旗叶光合特性和物质转运的影响

以蛋白质含量不同的两个冬小麦品种扬麦9号和豫麦34为材料,研究了不同温度和水分条件下小麦花后旗叶光合特性的变化、营养器官花前贮藏干物质和氮素转运特征及其与籽粒产量和品质形成的关系.结果表明,高温及干旱和渍水均明显降低了旗叶光合速率和叶绿素含量（SPAD值）,但高温下干旱和渍水对光合作用的影响加重.小麦营养器官花前贮藏干物质、氮素转运量和转运率在适温下表现为干旱>对照>渍水,高温下则表现为对照>干旱>渍水.适温下花后同化物积累量表现为对照>渍水>干旱,高温下则表现为对照>干旱>渍水.花后氮素积累量在适温和高温下均表现为对照>渍水>干旱.籽粒淀粉含量以适温适宜水分处理最高,高温渍水下最低;蛋白质含量以高温干旱下最高,适温渍水下最低.温度和水分逆境下小麦粒质量和淀粉含量的降低与花后较低的光合能力及干物质积累有关,而蛋白质含量则与花前贮藏氮素的转运量和转运率有关.     

花后干旱和渍水对不同品质类型小麦籽粒品质形成的影响

 防雨池栽条件下研究了花后干旱和渍水胁迫对两个不同品质类型小麦（Triticum aestivum）品种籽粒产量和品质形成的影响。结果表明,花后渍水和干旱处理明显降低了小麦籽粒产量和蛋白质产量。在整个灌浆期内干旱处理明显提高了籽粒蛋白质和醇溶蛋白含量,而渍水处理降低了籽粒蛋白质及其组分的积累量。籽粒总淀粉和直链淀粉含量以渍水处理最高,而支链淀粉以对照最高。干旱处理提高了籽粒干、湿面筋含量、沉降值和降落值,而渍水处理降低了上述品质指标。试验表明干旱和渍水胁迫对小麦籽粒蛋白质与淀粉的含量和组分及面粉品质等均有不同程度的影响,从而改变了不同品质类型小麦的籽粒品质。     

Contributions of root uptake and remobilization to grain zinc accumulation in wheat depending on post-anthesis zinc availability and nitrogen nutrition

Background and aims

Whether root Zn uptake during grain filling or remobilization from pre-anthesis Zn stores contributes more to grain Zn in wheat is subject to an on-going debate. This study investigated the effects of N nutrition and post-anthesis Zn availability on the relative importance of these sources.

Methods

Durum wheat plants were grown in nutrient solution containing adequate Zn (0.5?μM) and three different N levels (0.5; 1.5; 4.5?mM). One third of the plants were harvested when they reached anthesis. One half of the remaining plants were grown to maturity with adequate Zn, whereas the Zn supply to the other half was discontinued at anthesis. Roots, straw and grains were harvested separately and analyzed for Zn and N.

Results

Depending on the N supply, Zn remobilization from pre-anthesis sources provided almost all of grain Zn when the Zn supply was withheld at anthesis; otherwise up to 100?% of grain Zn could be accounted for by Zn taken up post-anthesis. By promoting tillering and grain yield and extending the grain filling, higher N supply favored the contribution of Zn uptake to grain Zn accumulation.

Conclusion

Remobilization is critical for grain Zn accumulation when Zn availability is restricted during grain filling. However, where root uptake can continue, concurrent Zn uptake during grain development, favored by higher N supply, overshadows net remobilization.     

Hormonal changes in the grains of rice subjected to water stress during grain filling

Lodging-resistant rice (Oryza sativa) cultivars usually show slow grain filling when nitrogen is applied in large amounts. This study investigated the possibility that a hormonal change may mediate the effect of water deficit that enhances whole plant senescence and speeds up grain filling. Two rice cultivars showing high lodging resistance and slow grain filling were field grown and applied with either normal or high amount nitrogen (HN) at heading. Well-watered and water-stressed (WS) treatments were imposed 9 days post anthesis to maturity. Results showed that WS increased partitioning of fixed (14)CO(2) into grains, accelerated the grain filling rate but shortened the grain filling period, whereas the HN did the opposite way. Cytokinin (zeatin + zeatin riboside) and indole-3-acetic acid contents in the grains transiently increased at early filling stage and WS treatments hastened their declines at the late grain filling stage. Gibberellins (GAs; GA(1) + GA(4)) in the grains were also high at early grain filling but HN enhanced, whereas WS substantially reduced, its accumulation. Opposite to GAs, abscisic acid (ABA) in the grains was low at early grain filling but WS remarkably enhanced its accumulation. The peak values of ABA were significantly correlated with the maximum grain filling rates (r = 0.92**, P < 0.01) and the partitioning of fixed (14)C into grains (r = 0.95**, P < 0.01). Exogenously applied ABA on pot-grown HN rice showed similar results as those by WS. Results suggest that an altered hormonal balance in rice grains by water stress during grain filling, especially a decrease in GAs and an increase in ABA, enhances the remobilization of prestored carbon to the grains and accelerates the grain filling rate.     

Effects of Soil Drought and Atmospheric Humidity on Yield,Gas Exchange,and Stable Carbon Isotope Composition of Barley

The combined effects of water status, vapour pressure deficit (VPD), and elevated temperature from heading to maturity were studied in barley. Plants growing at high VPD, either under well-watered or water deficit conditions, had higher grain yield and grain filling rate than plants growing at low VPD. By contrast, water stress decreased grain yield and individual grain dry matter at any VPD. Water regime and to a lesser extent VPD affected ¹³C of plant parts sampled at mid-grain filling and maturity. The differences between treatments were maximal in mature grains, where high VPD increased ¹³C for both water regimes. However, the total amount of water used by the plant during grain filling did not change as response to a higher VPD whereas transpiration efficiency (TE) decreased. The net photosynthetic rate (P _N) of the flag leaves decreased significantly under water stress at both VPD regimes. However, P _N of the ears was higher at high VPD than at low VPD, and did not decrease as response to water stress. The higher correlation of grain yield with P _N of the ear compared with that of the flag leaf support the role of ear as the main photosynthetic organ during grain filling under water deficit and high VPD. The deleterious effects of combined moderately high temperature and drought on yield were attenuated at high VPD.