适度土壤干旱对贪青小麦茎鞘贮藏性糖运转及籽粒充实的影响

Effects of Controlled Soil Drought on Remobilization of Stem-stored Carbohydrate and Grain Filling of Wheat with Unfavorably-delayed Senescence

选用春性小麦品种扬麦 15 8和扬麦 11为材料 ,设置出穗后高氮和正常氮两个水平及土壤水分胁迫处理 (WS) ,以正常浇水为对照 (WW) ,研究适度土壤干旱对贪青迟熟小麦籽粒灌浆和茎鞘贮藏性碳水化合物分配的影响。结果表明 ,在始穗期施用过量氮肥 (HN)导致小麦贪青迟熟 ,主要表现为灌浆速率和产量降低 ,茎鞘中滞留大量贮藏性糖。在灌浆中后期 ,适度土壤干旱显著降低植株中午叶片水势 ,促使贪青植株衰老进程加快。在适度土壤干旱状况下 ,灌浆速率分别提高 9 6 %～ 2 1 5 % (NN)和 4 0 9%～ 5 0 5 % (HN) ;灌浆持续期分别缩短 4 9～ 6 1d(NN)和 6 2～ 9 7d(HN)。与对照相比 ,适度土壤干旱降低了正常施氮处理 (NN)的籽粒产量 ,但显著增加了高氮处理的产量 (与HN WW相比 )。在成熟时 ,土壤干旱显著地促进了茎鞘中贮藏性糖和14 C的运转。其对籽粒产量的贡献分别是对照 (正常浇水处理 )的 2 0～ 2 1倍 (NN)和 4 8～ 5 3倍 (HN)。说明适度土壤干旱能够起到改善贪青麦株籽粒充实不良的作用。

Two spring wheat cultivars (cvs Yangmai 158 and Yangmai 11) were grown in the field and two levels of nitrogen, normal (NN) and high (HN), were applied at heading. Controlled soil water deficiency was imposed at 9 d after anthesis. Results showed that plant senescence was unfavorably delayed by high nitrogen application, which resulted in a slow grain filling and low grain yield as well as more water soluble sugar (WSC) stored in stem. Water deficiency significantly reduced mid-day leaf water potential and enhanced plant senescence at mid-later stage of grain filling. Such drought stress significantly increased grain-filling rate by 9.6%-21.5% at NN and 40.9%-50.5% at HN, and shortened grain-filling period by 4.9-6.1 d at NN and 6.2-9.7 d at HN, respectively, as compared to well-watered treatments. The grain weight and grain yield under water deficiency were significantly decreased at NN, but significantly increased at HN. At maturity, WSC in stem and sheath was greatly reduced, and the greater proportion of pre-fed 14C in the stems and sheaths was repartitioned into grain by soil drought in both nitrogen treatments. The contribution of stored WSC to grain yield under drought stress was greatly increased and was 2.0-2.1 times at NN and 4.8-5.3 times at HN respectively higher than that of well-watered condition. In conclusion, a controlled soil drought can play a positive role and improve grain filling when plant senescence is unfavorably delayed.