花后干旱和渍水对冬小麦光合特性和物质运转的影响

在温室盆栽条件下，以黑小麦76、皖麦38、扬麦10号、扬麦9号4个蛋白质含量不同的冬小麦(Triticum aestivum L.) 基因型为材料，研究了花后土壤干旱（Soil relative water content, SRWC=45%～50%）、渍水和适宜水分条件（SRWC=75%～80%）下，小麦旗叶净光合速率和叶绿素含量的动态变化，营养器官花前贮藏同化物再运转，花后同     

Yield and Agronomic Characters of Tropical Maize (Zea mays L.) Cultivars under Different Irrigation Regimes

Drought spells are unpredictable under tropical conditions and can occur at every growth stage of the maize plants. Little is known about the reactions of tropical maize cultivars to water shortage. A set of Thai cultivars was examined in the field during the dry season. Three stress situations were imposed: prolonged stress throughout the growing season, pre- and post-anthesis stress. Pre-anthesis water stress delayed flowering and especially the data of silking. Thus, the anthesis-silking interval was wider. Prolonged water stress decreased grain yield mainly due to a low number of kernels and/or thousand kernel weight (TKW). Post-anthesis stress mainly reduced TKW grain set per ear. Relief from pre-anthesis stress increased grain yield by a grater number of kernels and higher TKW as compared to prolonged stress. Genotypic differences were high for the anthesis-silking interval following pre-anthesis stress. Low yielding, early but generally drought-stable cultivars existed as well as cultivars which were generally high yielding even under water stress because of a good residual yield. Some cultivars were resistant to pre-anthesis stress but not to post-anthesis stress and vice versa. It can be concluded that ample genotypic variability exists for adaptation to varying situations of pre-and post-anthesis stress within tropical maize cultivars.     

不同穗型小麦花后物质运转及产量对氮肥的响应

在大田条件下,以多穗型小麦‘烟农19’和大穗型小麦‘兰考矮早8’两个不同穗型的冬小麦为材料,研究了不同施氮量及氮肥基追比例对小麦营养器官花前贮藏同化物再运转,花后同化物输入籽粒量,产量及产量构成因素的影响。结果表明,氮肥水平在225~300 kg/hm2范围内,多穗型小麦‘烟农19’和大穗型麦‘兰考矮早8’籽粒产量的形成均以花后绿色器官光合同化为主,其次才是花前积累干物质的再动员分配。大穗型品种‘兰考矮早8’籽粒产量的形成较多穗型品种‘烟农19’更依赖于花后绿色器官同化,积累干物质再运转分配只占籽粒产量的15%左右。两种穗型品种小麦花前贮存物质再动员分配对籽粒产量的贡献都随着氮肥后移而降低。随着施氮量的增加,运转物质对籽粒产量的贡献率呈降低趋势。综合物质运转和产量表现,‘烟农19’施氮量300 kg/hm2,基追比例5:5时较适宜;‘兰考矮早8’施氮量262.5 kg/hm2,氮肥基追比例7:3时较适宜。     

施氮量对冬小麦灌浆期光合产物积累、转运及分配的影响

采用花前¹⁴C-同位素标记旗叶的方法, 研究了盆栽条件下不同施氮量对两种穗型冬小麦品种光合产物转运及¹⁴C同化物积累、分配的影响。结果表明, 冬小麦成熟期¹⁴C-同化物主要分配在茎鞘中, 其分配率为44.31%~60.96%; 其次在籽粒中, 分配率为31.81%~40.67%; 其中大穗型品种兰考矮早八茎鞘、叶片中的分配率高于多穗型品种豫麦49-198, 表明成熟时大穗型品种有更多的同化物滞留在茎鞘和叶片中。施氮量对¹⁴C-同化物分配率有影响, 在施氮量36 g m^-2处理的茎鞘中分配率下降, 而籽粒中的分配率增加, 表明增施氮肥促进花前同化物向籽粒中分配。随着籽粒灌浆进程, 光合产物在营养器官中的分配率逐渐下降, 在籽粒中的分配率逐渐增加, 表明营养器官的同化物逐渐向籽粒转运。小麦籽粒的同化物有34.94%来自花前贮藏物质的转运, 65.06%来自开花后同化量, 但不同品种、不同氮素水平处理之间有较大差异。施氮量36 g m^-2处理的花前转运量、转运率、花前贮藏物质对籽粒贡献率均下降, 但花后同化量、对籽粒贡献率以及单穗粒重均增加; 其中兰考矮早八和豫麦49-198的花后贡献率分别为77.84%和56.29%, 表明兰考矮早八花后同化量对籽粒的贡献大于豫麦49-198。两品种籽粒产量均表现为施氮量36 g m^-2处理高于18 g m^-2处理, 并且大穗型品种的增产幅度大于多穗型品种, 表明增施氮肥对不同冬小麦品种的增产效应存在差异。     

How do timing,duration, and intensity of drought stress affect the agronomic performance of winter rye?

Winter rye (Secale cereale L.) will be especially affected by drought induced yield losses in Central and Eastern Europe in the future because it is predominantly cultivated on low-fertile soils with a poor water-holding capacity. In order to examine the performance of winter rye under different drought conditions, field experiments were carried out during the years 2011, 2012, and 2013 near Braunschweig, Germany. Two sets of genotypes were tested under severe, mild, pre-anthesis, and post-anthesis drought stress in rain-out shelters as well as under rainfed and well-watered conditions. The grain, straw, and total above ground biomass yields, harvest index, grain yield components, leaf area index (LAI), and phenological characteristics were examined, as well as phenotypic correlations between grain yield and further characteristics. Drought induced grain yield reduction ranged from 14 to 57%, while straw yield and harvest index were lesser affected by drought than the grain yield. Under drought conditions, fully ripe was reached up to twelve days earlier than under non water-limited conditions. Pre-anthesis drought mainly reduced spikes m⁻² and kernels spike⁻¹ while drought during grain filling reduced the 1000-kernel weight (TKW) only. The grain yield was positively associated with straw yield, spikes m⁻², and kernels spike⁻¹ under water limited conditions while the TWK was only positively associated with grain yield under drought during grain filling. Consequently, high pre-anthesis biomass as well as high numbers of spikes m⁻² and kernels spike⁻¹ are especially important for obtaining high grain yields under water-limited conditions. Focusing on these traits is, therefore, recommendable for developing drought tolerant rye genotypes.     

亏缺灌溉下小麦水分利用效率与光合产物积累运转的相关研究

在大田栽培条件下,以小麦旱地品种晋麦47和西峰20、水旱兼用型品种石家庄8号和水地品种4185为材料,分别进行0水(T0)、一水(T1)和二水灌溉(T2)处理(每次灌水量60mm),研究了光合速率、叶面积指数、干物质积累与分配、根系分布、耗水量、产量因子与水分利用效率(WUE)的关系。结果表明,在拔节前不灌溉,拔节到开花期亏缺灌溉,促进干物质积累和深根发育。随着灌溉水的增加,耗水量显著增加,产量和WUE与耗水量呈二次曲线关系。T0处理显著减少了干物质积累和成穗数,产量、经济系数(HI)和WUE最低。T1和T2产量的提高主要是增加了穗数和穗粒数。灌浆期水分亏缺降低了光合速率(Pn)和气孔导度(Gs),加速了功能叶片的衰老,但诱导了花前储存碳库的再转运,显著提高了HI和产量。因此,在拔节和开花期亏缺灌溉促进根系生长,提高了土壤水分的利用效率。而产量和产量WUE的提高主要是由于增加了灌浆期叶片的Pn和光合功能持续期,促进花前储存碳库的再转运,显著提高了HI。     

亏缺灌溉下小麦水分利用效率与光合产物积累运转的相关研究

在大田栽培条件下,以小麦旱地品种晋麦47和西峰20、水旱兼用型品种石家庄8号和水地品种4185为材料,分别进行0水（T0）、一水（T1）和二水灌溉（T2）处理（每次灌水量60 mm）,研究了光合速率、叶面积指数、干物质积累与分配、根系分布、耗水量、产量因子与水分利用效率（WUE）的关系。结果表明,在拔节前不灌溉,拔节到开花期亏缺灌溉,促进干物质积累和深根发育。随着灌溉水的增加,耗水量显著增加,产量和WUE与耗水量呈二次曲线关系。T0处理显著减少了干物质积累和成穗数,产量、经济系数（HI）和WUE最低。T1和T2产量的提高主要是增加了穗数和穗粒数。灌浆期水分亏缺降低了光合速率（P_n）和气孔导度（G_s）,加速了功能叶片的衰老,但诱导了花前储存碳库的再转运,显著提高了HI和产量。因此,在拔节和开花期亏缺灌溉促进根系生长,提高了土壤水分的利用效率。而产量和产量WUE的提高主要是由于增加了灌浆期叶片的P_n和光合功能持续期,促进花前储存碳库的再转运,显著提高了HI。     

The importance of the period immediately preceding anthesis for grain weight determination in wheat

Although individual grain weight is an important source of variation forgrain yield, there is still poor understanding of the causes determining finalgrain weight. Almost all studies conducted for understanding thedeterminants of grain weight have been focused on the post-anthesis period.However, there is important evidence that pre-anthesis conditions couldalso modify final grain weight. Three experiments including different sowingdates, genotypes and temperature regimes between booting and anthesis,were carried out in Argentina and Mexico to analyse the effect oftemperature and associated traits during the pre- and post-anthesis periodson grain weight under field conditions. In these experiments final grainweight could not be explained by average or maximum temperature duringthe post-anthesis period. However, average temperature between bootingand anthesis was closely related to the observed grain weight differences,probably as a consequence of the effects of this factor on carpel growth.Differences in grain weight between genotypes and grain position weresuccessfully explained by differences in carpel weight at anthesis. Theseresults suggest that our knowledge to determine grain weight could improveif the immediately pre-anthesis period conditions were taken into account.     

Genetic variation for dry matter and nitrogen accumulation and translocation in two-rowed spring barley II. Nitrogen translocation

An understanding of the partition between pre-anthesis and post-anthesis N uptake and their contribution to total grain N and protein content in spring two-rowed barley (Hordeum vulgare spp. distichum L.) is important to achieve additional breeding progress for both fodder and malting barley. N translocation from the vegetative tissues at anthesis to the kernel, N translocation efficiency, and N harvest index (NHI) were studied in field experiments during 4 years (1995–1998). Plants were harvested at anthesis and maturity and divided into leaf+culm, chaff and grain. Significant cultivar differences in N translocation, N translocation efficiency and NHI were determined. Across cultivars, the highest N translocation was in a favorable year (93 kg ha⁻¹) and the lowest in a year with poor growing conditions (40 kg ha⁻¹). Cultivar differences in N translocation were related to dry matter and pre-anthesis N accumulation (R²>0.70). N translocation efficiency varied more among the cultivars (0.27–0.66) than years (0.47–0.52). Post-anthesis N uptake was negatively correlated (P<0.01) with N translocation. NHI ranged among the cultivars from 0.49 to 0.73 and among the years from 0.57 to 0.74. The cultivars Arapiles, Schooner, Cantala, Kaskade and Pek stored in the grain more than 70% and Hiproly less than 50% of above-ground N at maturity. Translocated N participated with 85, 56, 42, and 61% in grain N in 1995, 1996, 1997, and 1998, respectively. The ratio of translocated N to grain N could be an indicator of growing conditions; a higher ratio indicates good growing conditions over the entire growth period, a lower ratio indicates poor conditions during pre-anthesis, and a medium ratio indicates some temperature and water deviations from the long-term average. Straw N concentration was in significant positive (P<0.01) correlation with N translocation and translocation efficiency. Straw N concentration adequately represents N efficiency utilization for synthesis of grain protein, and because it saves time and money compared to N harvest index determination, it can be used for the testing of breeding materials for the development of new barley cultivars.     

Genetic variation for dry matter and nitrogen accumulation and translocation in two-rowed spring barley: I. Dry matter translocation

A 4-year field study was carried out to determine dry matter and nitrogen accumulation until anthesis and at grain filling period and dry matter translocation and utilization in grain filling of barley. Twenty two-rowed spring barley (Hordeum vulgare ssp. distichum L.) cultivars originated from different countries (Yugoslavia, Germany, Australia, the Czeck Republic, Netherlands, France and USA) were grown during 1995–1998 on a non-calcareous chernozem soil near Novi Sad (45° 20′N, 15° 51′E, 86 m asl). Dry matter and nitrogen accumulation depended on the cultivar and year. In a year with favorable weather conditions, 58% of dry matter was accumulated during pre-anthesis, while in a year with less favorable weather the amount was 48%. In the favorable year 91% and in unfavorable year 65% of nitrogen was accumulated until anthesis. The results indicated that the greater amount of dry matter and nitrogen accumulated before anthesis. Dry matter translocation efficiency depended on the cultivar and ranged from 3 to 16.4%, while the contribution of pre-anthesis assimilates to kernel varied from 4 to 24.2%. Cultivars that have been developed for the growing conditions of the area where the experimental site was located, i.e. adapted ones, did not use pre-anthesis dry matter for grain filling. High positive correlations (P<0.01) were found between biomass at anthesis and biological yield, dry matter translocation efficiency, contribution of translocated dry matter to grain yield, and total plant nitrogen at maturity. Accumulated nitrogen at anthesis was positively correlated (P<0.01) with growing degree–days until anthesis, dry matter at anthesis and dry matter translocation parameters. Heritability for the investigated characters was rather high, over 0.60.     

Phosphorus use efficiency in tall, semi-dwarf and dwarf near-isogenic lines of spring wheat

The impact of the Rht dwarfing genes on P utilization efficiency (PUTE = grain dry matter per kg P in above-ground biomass), total P uptake (Pt) and related traits was studied in the varietal backgrounds of two tall wheat cultivars, Maringa and Nainari 60. Four sets of near-isogenic lines carrying different combinations of the alleles Rht-B1b, Rht-D1b and Rht-B1c for gibberellin-insensitive dwarfism in the hexaploid wheat (Triticum aestivum L.) were compared with tall controls in two field trials under conditions of adequate nutrient supply and irrigation in Northwest Mexico. The yield-increasing effect of the dwarfing genes Rht-D1b and Rht-B1b led to improved PUTE in Maringa and total P uptake in both cultivars. Also, the double dwarf line of Maringa had larger grain yields and P uptake compared to the tall control. The Rht-B1c genotypes showed low PUTE, thick roots and high P concentration in vegetative biomass indicating a surplus of assimilates and P, which could not be translocated into the grains. A similar problem could be observed in Nainari 60 with Rht-B1b and Rht-D1b, which produced the largest grain dry matter with the lowest P concentrations in grains although they showed high P accumulation in straw. Most of the net P uptake occurred before anthesis. P absorption after anthesis was more critical for the dwarf genotypes. For double dwarfs and Rht-B1c, respectively, only 3% and 21% of the total accumulated P at maturity was absorbed at post-anthesis. The grain P of the dwarf lines came more from P accumulated at pre-anthesis and translocated from the vegetative biomass into the grain. The pre-anthesis P accumulation was positively correlated with spikes per m² (r = 0.91), whereas post-anthesis P accumulation correlated better with grains per spike(r = 0.72), and thousand kernel weight (r = 0.51). P uptake efficiency played a secondary role under these non-P-limiting conditions, and differences in root length density were only slightly affected by Rht-genes. This revised version was published online in July 2006 with corrections to the Cover Date.     

吐丝期干旱胁迫对玉米生理特性和物质生产的影响

以玉米品种郑单958 (抗旱性强)和陕单902 (抗旱性弱)为材料,采用抗旱池栽控水试验,研究了叶片光合特性、保护酶活性以及干物质转运对吐丝期干旱胁迫的响应。结果表明,在吐丝期干旱胁迫下2个品种产量分别降低39.10%和44.87%;叶片净光合速率(P_n)和气孔导度(G_s)显著下降,胞间CO₂浓度(C_i)先升后降。PSII最大光化学效率(F_v/F_m)、实际量子产额(Φ_PSII)、光化学猝灭(q_P)降低,非光化学猝灭(q_N)升高;抗氧化酶(SOD、POD和CAT)活性先升高后降低,而丙二醛(MDA)含量一直升高。说明吐丝期干旱胁迫增加了花前营养器官贮藏同化物转运量(率)及其对籽粒转运的贡献率;但郑单958受干旱影响程度小于陕单902。说明抗旱品种郑单958具高抗氧化酶活性清除活性氧,使得膜脂过氧化程度轻,维持较高的光化学效率,延长叶片光合功能期,促进花前营养器官贮藏同化物转运量对籽粒的贡献率。这可能是其在干旱胁迫下仍能获得较高产量的重要原因之一。     

施肥对春青稞干物质积累、分配及产量的影响

为研究施肥对青稞干物质积累、分配及产量的调节作用,以‘藏青27’、‘QTB13’和‘QTB25’为试验材料,比较分析不同施肥处理下干物质积累、分配及产量的变化规律。结果表明：增加施肥量促进青稞分蘖期—成熟期的干物质积累及开花期和成熟期干物质向营养器官和籽粒的分配,提高了花前营养器官贮藏同化物转运量及对籽粒贡献率,降低了花后同化物输入籽粒量对籽粒贡献率。‘QTB13’和‘QTB25’在F₂条件下,更有利于干物质积累及向营养器官和穗部的分配,花后同化物输入籽粒量最大,产量也最大。‘藏青27’在F₃条件下,更有利于干物质积累及向营养器官和穗部的分配,花后同化物输入籽粒量和对籽粒贡献率最大,产量也最大。说明合理施肥有利于青稞干物质积累分配及产量提高。     

开花期干旱胁迫对鲜食糯玉米产量和品质的影响

为探明开花期(抽雄吐丝期)干旱胁迫对鲜食糯玉米(吐丝后23 d采收)产量和品质的影响, 以苏玉糯5号和渝糯7号为试材, 采用负水头供水控水盆栽装置控制土壤含水量, 设置开花期正常供水(土壤相对含水量80%)和干旱胁迫(土壤相对含水量60%) 2个处理, 研究干旱胁迫对鲜食糯玉米产量(鲜果穗和鲜籽粒)、籽粒组分、糊化和热力学特性的影响。结果表明, 开花期干旱胁迫减少籽粒数量、降低籽粒重量、缩小籽粒体积, 导致鲜果穗和鲜籽粒产量损失。开花期干旱胁迫下鲜食期籽粒淀粉含量升高, 但对于蛋白质含量渝糯7号降低, 苏玉糯5号变化不显著。蛋白质组分中, 对球蛋白含量影响不显著, 清蛋白、谷蛋白和醇溶蛋白均显著降低。开花期干旱胁迫显著降低淀粉粒平均粒径。碘结合力2015年度显著下降, 2014年度受干旱影响不显著。开花期干旱胁迫下籽粒峰值黏度、谷值黏度和终值黏度在苏玉糯5号中降低, 在渝糯7号中升高。开花期干旱胁迫下两品种峰值温度降低, 回生热焓值和回生值升高, 而热焓值仅渝糯7号在2014年度升高。总之, 开花期干旱降低糯玉米鲜果穗和鲜籽粒产量, 增加籽粒淀粉含量, 降低籽粒蛋白质含量、淀粉粒径和支链淀粉中长链比例, 进而使籽粒回生增加, 但糊化黏度两品种表现不同(渝糯7号升高, 苏玉糯5号下降)。     

用单片段代换系研究水稻产量和籽粒充实对花后不同土壤干旱的响应

以介入巴西陆稻IAPAR9抗性基因片段的单片段代换系(single segment substitution line, SSSL)和受体亲本华粳籼74为材料,设置正常灌水(CK)、中度干旱胁迫(MD)、重度干旱胁迫(SD) 3种土壤水分处理,分析SSSL和受体亲本籽粒灌浆特征、蔗糖及淀粉代谢中相关酶活性动态,探讨了水稻籽粒充实和产量对花后干旱胁迫响应的生理机制。结果表明,与受体亲本相比,携带抗旱基因的SSSL在MD和SD处理下其耐旱性的表现更为明显,减产幅度明显小于受体亲本。在花后7 d开始的中、重度干旱胁迫处理下,灌浆中后期SSSL叶片相对含水量、叶绿素含量和光合速率下降幅度明显小于受体亲本,其籽粒中蔗糖合酶(sucrose synthase, SS)、酸性蔗糖转化酶(acid invertase, AINV)、腺苷二磷酸葡萄糖焦磷酸化酶(ADP glucose pyrophosphorylase, AGPP)﹑可溶性淀粉合酶(soluble starch synthase, SSS)﹑Q酶活性在灌浆前(中)期也明显上升,增强了SSSL籽粒灌浆中前期库活性。虽然持续的干旱胁迫使得上述酶活性在灌浆的中后期快速下降,导致同化物积累的活跃灌浆期缩短,但SSSL籽粒平均灌浆速率和最大灌浆速率明显高于受体亲本,这在一定程度上可弥补因灌浆期缩短导致的同化物积累损失,干旱胁迫下SSSL产量高于受体亲本,这一趋势在重度干旱胁迫下更为明显。     

Photosynthetic Response of Wheat to Soil Water Deficits in the Tropics

The changes in photosynthetic rate and translocation of photosynthates in winter wheat (Triticum Aestivum L.) grown in lysimeters were studied, in response to periodic soil water deficit during late tillering and flowering stages. Soil water deficits were imposed to previously nonstressed plants during late tillering and flowering states. Timing of irrigation was scheduled according to the ratio between irrigation water applied and cumulative pan evaporation (IW/CPE) of 0.75 (low deficit), and 0.5 (moderate deficit), as well as by suspending irrigations after crown root initiation stage (severe deficit). To determine the rate of photosynthesis, a short radioactive pulse of ¹⁴CO₂ with 300 ppm concentration was given to second leaf from the top at tillering, and to the flag leaf at flowering stages for 20 second exposure time. The translocation of photosynthates was estimated by scanning ¹⁴C activity in different plant parts. In late tillering the midday Photosynthetic rate (PR) was significantly 3 mg CO₂ dm^?2 h^?1 lower under low water deficit (WD₁) than under zero water deficit (WD₀). Under higher stress conditions, soil water acted as a limiting factor to keep the rate from rising above 13.2 during stress at late tillering (WD₂), 14.5 flowering (WD₄), and 10.0 mg CO₂ dm^?2 h^?1 for stress at both the growth stages (WD₅), respectively. The difference in daily accumulated photosynthesis (8 h), between stressed and nonstressed were 15, 40, 42, and 77 mg CO₂ dm^?2 h^?1 respectively at WD₁ WD₂, WD₄, and WD₅. The retention of ¹⁴C in flag leaf decreased considerably after 24 hours of exposure time when the labelled assimilates were translocated in bulk to the ear head. Under stressed condition a general trend was observed for upward translocation of assimilates towards the ear, even from the stem and root. The percent ¹⁴C activity observed in ear after 24 hours was greatest in severely stressed plants. The photosynthetic rate is reasonable predicted by midday LDR and surface moisture.     

Importance of P uptake efficiency versus P utilization for wheat yield in acid and calcareous soils in Mexico

There are large agricultural areas in the world where wheat yields are limited by low phosphorus (P) availability. Breeding for P uptake and P utilization efficiency may reduce this problem. This study was conducted to determine the contribution of P uptake and utilization efficiency to grain yield of selected spring wheat genotypes in different environments. Thirty-eight semidwarf spring bread wheat (Triticum aestivum) genotypes were grown in two experiments in Mexico, each on an acid Andisol under rainfed conditions and on a calcareous Aridisol with irrigation, without (−P) and with 35 kg P per ha fertilized (+P). Without P fertilization, grain yield ranged from 0.8 to 4.6 t ha⁻¹ in the acid soil and from 2.4 to 5.2 t ha⁻¹ in the calcareous soil. With P fertilization, this range was even larger. Under conditions of P deficiency, i.e. in the acid soil at −P and +P (high P adsorption) and calcareous soil at −P (P-depleted soil), P uptake explained 71–100% of the variation in grain yield, and was highly correlated with grain yield (r=0.79–0.95). In contrast, at +P in the calcareous soil, P utilization efficiency explained 60–63% of the variation in grain yield. Here, low grain P concentration was related to high grain yield (r=−0.40 to −0.59). In the calcareous soil, the harvest index was correlated with grain yield, irrespective of the P level. In the acid soil, post-anthesis P accumulation was important. It was positively correlated with grain yield, whereas in the calcareous soil, no post-anthesis-P accumulation occurred. Here, grain P accumulation at maturity was completely determined by translocation of pre-anthesis shoot P. We conclude that the combination of improved P uptake and P utilization efficiency in the same genotypes requires selection under both high and low-P conditions.     

旱稻297非结构性碳水化合物的生产与产量构成因子的关系

以旱稻297为试验材料,比较了在不施氮肥和150 kg hm-2的施氮量下旱稻297非结构性碳水化合物的生产能力、运转特点及其与产量构成因子的关系,分析了旱稻297氮肥投入与碳水化合物生产和产量形成间的关系。试验结果表明,开花前储藏的非结构性碳水化合物对产量的贡献率为32%~54%,施氮降低了开花前非结构性碳水化合物对产量的贡献率,相对而言开花后光合产物对产量的贡献率略有提高;开花前非结构性碳水化合物的转移效率为48%~65%,施氮后转移效率略有降低;总体而言,施氮降低了开花前后分配给单个籽粒的非结构性碳水化合物的数量,导致千粒重降低;在一定的范围内,随着开花期叶片中可溶性糖浓度的提高,结实率显著提高,但是随着穗中淀粉浓度的提高,结实率显著降低。因此,施氮后非结构性碳水化合物积累不足和转移效率降低同时限制了千粒重和结实率的提高,而叶片中可溶性糖浓度偏低和穗中淀粉浓度偏高限制了结实率的提高,是限制产量提高的主要原因。此外,旱稻297花后光合产物生产能力较低,是限制产量提高的又一原因。     

Grain yield of wheat (Triticum aestivum L.) under long‐term heat stress is sink‐limited with stronger inhibition of kernel setting than grain filling

The aim of the study was to investigate source‐sink relations of wheat under continuous heat stress and to identify bottle necks of yield formation. A pot experiment was conducted in two climatic chambers exposing wheat plants (Triticum aestivum L. cv. Thasos) either to day/night temperatures of 20/20°C (control conditions) or of 30/25°C (heat stress) during the whole vegetation period in the absence of plant water deficit. Plants were harvested at four phenological stages: three‐node stage (DC 33), start of flowering (DC 61), grain filling (DC 75) and maturity (DC 94). Heat stress shortened the development phases of the plants and caused a significant decrease in total above‐ground biomass between 19% and 41%. At grain filling and at maturity, the reductions in total shoot biomass mainly resulted from grain yield depressions by 77% and 58%, respectively. The ear number per plant was significantly higher under heat stress in comparison with the control, at maturity it was more than doubled. On the contrary, under heat stress, the kernel number per ear was strongly decreased by 83% and 75% during grain filling and at maturity, respectively. The decrease in individual kernel weight was 23% at maturity. Thus, the heat‐stressed plants were able to strongly increase the number of ear‐bearing tillers which were able to set only a small number of kernels, yet these kernels showed good grain filling. The harvest index (HI) of heat‐stressed plants was significantly reduced by 36% (control: HI = 50.1% ± 0.4, heat: HI = 32.2% ± 0.9***). The plants in the stress treatment adapted to the adverse conditions by less biomass production which presumably allowed a higher transpiration without an increase in total water consumption. Nevertheless, under heat stress, the water use efficiency (WUE_grain) was strongly decreased by 62% as a result of a small grain yield. In ears and grains, the sucrose, glucose and fructose concentrations were not significantly different between control and heat stress at start of flowering and during grain filling. Thus, the supply of assimilates was not restricted (no source limitation). Sink capacity was reduced by heat stress, as lesser and smaller kernels were produced than in the control. Concerning sink activity, the sink‐limiting step during kernel set is probably the active transport of hexoses across the plasma membrane into the developing kernels, which could also affect grain filling. This needs to be investigated in more detail in further studies.     

Quality and Distribution of Assimilates within the Whole Plant of Lupines (L. albus and L. mutabilis) Influenced by Water Stress

Lupine crops (Lupinus albus and L. mutabilis) often experience water deficits during grain filling, thereby altering partitioning of assimilates. Water deficit, imposed at the beginning of seed production (15 days after anthesis, daa), brought about differences in assimilate partitioning and chemical composition within the whole plant. In both species, water stress (ws) was responsible for a significant decrease in plant water status and gas exchange. In spite of little effect on total biomass, leaf area was reduced for approximately half of the control treatment. The main effects of ws on chemical composition of different organs were a decrease in total oil and an increase in total soluble sugar content in leaves; an increase in both oil and soluble sugars in stems; and a decrease in total oil and total soluble sugar content in seeds. The data suggest that under ws conditions, imposed at flowering, lupine assimilates are stored in stems and pods and later retranslocated to the developing seeds.