为探讨春季低温导致小麦粒重下降的生理机制,以春性品种扬麦16和半冬性品种徐麦30为材料,分别于倒二叶出生期、孕穗期和开花期对小麦进行人工气候室低温处理,研究不同时期低温对小麦光合生理特性、干物质积累和转运及强、弱势粒粒重形成的影响.结果表明,不同时期低温对叶片SPAD值的影响均表现为低温处理开始至结束后3 d持续下降,结束后6～9 d逐渐回升,两品种在低温处理结束当天和处理后3 d均以孕穗期低温处理下SPAD值降幅最大.不同时期低温处理显著降低叶片净光合速率和气孔导度,并影响花前干物质转运和花后干物质积累.与孕穗期、开花期低温处理相比,倒二叶出生期低温处理显著降低小麦花前干物质转运量,但提高花后干物质积累及其对籽粒产量的贡献率,千粒重降幅最小,扬麦16和徐麦30分别仅为4.49％和4.20％.不同时期低温处理下小麦强势粒粒重的降幅均小于弱势粒,倒二叶出生期低温处理下弱势粒粒重降幅显著低于孕穗期和开花期低温处理.相关性分析表明,低温胁迫下小麦平均千粒重和强势粒粒重相关性不显著(r=0.319,P＞0.05),但与弱势粒粒重显著相关(r=0.691,P＜0.05).综上,春季低温胁迫主要通过影响小麦开花前后的光合作用和同化物向籽粒的转运,限制弱势粒的灌浆充实,最终导致粒重下降.

Jiangsu, China Abstract: Grain yield and the number of grains per ear of wheat decreased under the low temperature after jointing stage. In order to explore the physiological reasons of the decrease of grains number per ear by low temperature in spring, the spring wheat variety Yangmai 16 and the semi-winter wheat variety Xumai 30 were used as tested varieties to analyze the effects of low temperature in spring on the fertility of pollen and the formation of grain numbers at the appearance of the penultimate leaf stage (5 / ℃ –3 , day/night), booting stage (8 / ℃ ℃ –1 , day/night), and anthesis stage ( ℃ 12 /4 , day/night). The results showed that low ℃ ℃ temperature at the appearance of the penultimate leaf stage and booting stage resulted in abnormal metabolism of starch and protein in the anther both at the binuclear and tri-nuclear pollen stages and delayed degradation of the tapetum. The low temperature at the booting stage caused abnormal meiosis of pollen mother cells, abnormalities in chromosome pairing, which formation of male gametophyte. The abortion rate of pollen was more significantly increased under low temperature at the appearance of the penultimate leaf stage than that at the booting stage, and it was the minimum at anthesis stage. The abortion rate of pollen in Xumai 30 was higher than that in Yangmai 16. The low temperature at three stages had significant effects on the number of spikelets, the number of fertile spikelets and the number of grains per spikelet. The effect of low temperature at the appearance of the penultimate leaf stage on grains number per spikelet was the most significant. There was a significant positive correlation between the number of grains per spike and pollen fertility, which was affected by abnormal meiosis, delayed degradation of the tapetum, and undersupply of nutriment for anther development. Therefore, the decline of pollen fertility caused by low temperature in spring is the main reason for the decrease of grains number per spike.

为探讨江苏淮北地区稻茬半冬性小麦节氮增效的可行性,以半冬性小麦徐麦33为材料,研究了稻茬条件下不同密度、氮肥施用量和比例对小麦籽粒产量、氮肥利用效率和群体生长特征的影响,并分析了提高产量与与氮效率的协同性.结果表明,密度与氮肥施用存在一定的互作补偿作用.当密度由150×104株·hm-2增至225×104株·hm-2时,在不降低籽粒产量的基础上可减少15％～30％的施氮量,并显著提高氮肥农学效率(NAE).在一定产量范围内,产量与NAE、氮素吸收效率(RE)呈显著或极显著的正相关,实现了产量及氮效率同步提升.产量及氮效率的提高与优良的群体结构密切相关,籽粒产量、NAE、RE与孕穗期叶面积指数(LAI)、花后21 d LAI、花后干物质积累量、群体总结实粒数均呈显著正相关,与LAI下降速率呈显著负相关.本试验中,在密度225×104株·hm-2、施氮量229.5 kg· hm-2、施氮比例为5∶1∶2∶2的组合下小麦籽粒产量、NAE最高.

A container experiment was designed to investigate the effects of shading,waterlogging and combined waterlogging-shading on seedling morphology and growth.Cultivars commonly grown in the Yangtze River Basin of China in three different decades were selected: Yangmai 1(1970s),Yangmai 158(1990s),and Yangfumai 4(2010s).Shading significantly postponed leaf stage and decreased number of tillers per plant,but there was no significant difference between waterlogging and drainage treatment.Waterlogging and shading significantly reduced adventitious roots per plant,leaf area,weight,shoot dry weight and root dry weight,which was effected by shading more seriously than by waterlogging.But it only showed additive effect of waterlogging and shading on specific leaf weight,shoot dry weight,root dry weight,and root/shoot ratio.After a 20-day recovery phase,leaf stage,seedling height and specific leaf weight only by water logging generally recovered to control level,and adventitious roots per plant only by waterlogging and root dry weight by different treatments showed recovery tendency.Comparing with Yangmai 1,Yangfumai 4 and Yangmai 158 showed higher adventitious roots per plant and specific leaf weight.However,Yangfumai 4 showed the lowest percentage change in all parameters after both waterlogging and recovery.These results could reveal Yangfumai 4 had better resistance to waterlogging and weak light at seedling stage.

Lodging is an important limiting factor in wheat because it affects growth, yield and grain quality. Plant growth regulators (PGRs) are often used to restrain elongation of internodes, improve lodging traits, and protect yield potentials. An experiment was set up in the greenhouse at the Ottawa Research and Development Centre (ORDC) to study the effect of the selected PGRs (Manipulator, the active ingredient of which is chlormequat; and Palisade, the active ingredient of which is trinexapac-ethyl) on yield, stem height and morphological traits in six spring wheat cultivars (AC Carberry, AAC Scotia, Hoffman, Fuzion, FL62R1, and AW725). Both PGRs reduced plant height and caused a 6% to 48% reduction in the length of the second basal internode. The mixture of the two PGRs had a synergistic affect and made the stem shorter. The application of PGRs significantly reduced lodging, increased stem diameter, thickness, filling degree, and stem strength, and increased leaf relative chlorophyll content. However, application of PGRs significantly reduced grain yield, and the combination of the two PGRs (Manipulator and Palisade) had a synergistic effect and lowered the yield. In general, the effect of Palisade was more evident than that of Manipulator.

In order to provide the information on high and stable yield of wheat in the middle and lower reaches of the Yangtze River,a greenhouse experiment,using wheat variety Yangfumai 4,was designed to investigate the effects of 5-,10-and 15-day waterlogging at elongation stage and after anthesis on yield,yield components,dry matter and nitrogen accumulation and remobilization in wheat.Waterlogging treatment at both of the two stages significantly decreased the yield,kernels per spike,1000-kernels weight,dry matter and nitrogen accumulation amount of root and shoot at maturity and post-anthesis shoot,and root-shoot ratio.An increasing trend of waterlogging-induced reduction in yield,yield components,dry matter and nitrogen accumulation and remobilization was observed along with the extended waterlogging duration.No significant differences between 5-and 10-day waterlogging treatments were found in yield,kernels per spike,post-anthesis dry matter and nitrogen accumulation amount in shoot,and root-shoot ratio,while the results between 5-and 15-day waterlogging treatments showed significant difference.There were no significant differences between/among short-term waterlogging treatment at elongation and after anthesis.However,the yield under 15-day waterlogging after anthesis was significantly lower than that at the elongation stage.In general,the effects of waterlogging after anthesis on 1 000-kernels weight,post-anthesis dry matter and nitrogen accumulation in shoot,and pre-anthesis dry matter remobilization in shoot were significantly higher than that at elongation.It was suggested that the effects of waterlogging on yield,yield components,dry matter and nitrogen accumulation and remobilization in wheat relies on the waterlogging stage and its duration.

Waterlogging is a major constraint on wheat (Triticum aestivum L.) production, especially in the Yangtze River Basin of China (YR). A container experiment was designed to investigate wheat-seedling growth and short-term recoveryin response to waterlogging. Cultivars commonly grown in theYR from three different decades, namely, Yangmai 1 (1970s), Yangmai 158 (1990s), and Yangfumai 4 (2010s), were selected. Seedling waterlogging significantly postponed leaf development, as well as decreased the number of tillers and adventitious roots per plant, seedling height, leaf area, specific leaf dry weight, shoot dry weight, root dry weight, and root/shoot ratio. After a 20-day recovery phase, the leaf stage, seedling height, and root/shoot ratio recovered to the control level, whereas the adverse effects of waterlogging on the number of tillers per plant, leaf area, and shoot dry weight intensified. Significant differences were found in seedling growth among the three wheat cultivars. Yangfumai 4 showed the highest number of adventitious rootsper plant and the highest specific leaf dry weightbut the lowest seedling height, leaf area, and dry weights of shoots and roots. However, Yangfumai 4 showed the lowest percentage decrease in all growth parameters after both waterlogging and recovery. These results suggested thatimprovement inadventitious root numberper plant and specific leaf dry weight may be indicators ofresistance to waterlogging in wheat.