旱种水稻基部节间性状与倒伏的关系及其生理机制

倒伏是制约旱种水稻大面积推广的主要因素之一。以籼型杂交稻汕优63和粳稻9516为材料，研究了旱种水稻倒伏的原因及其机理。结果表明，与水种相比，旱种水稻的倒伏率明显高，结实率和粒重明显降低，产量明显降低。自抽穗至成熟，旱种水稻基部节间强度(厚度、单位长度重量)、碳水化合物(尤其是淀粉)含量低于常规水种稻，α-淀粉酶活性明显高于水种稻。水稻基部节间淀粉含量与节间厚度和单位长度重量呈极显著正相关，与α-淀粉酶活性呈显著或极显著负相关。淀粉输出与α-淀粉酶活性呈显著或极显著正相关。施用硅、钾肥能降低旱种水稻基部节间α-淀粉酶活性，提高基部节间淀粉含量，增强基部节间强度，大幅度降低倒伏率，提高旱种水稻的结实率和粒重，从而提高产量。孕穗期去1/2叶，效果则相反。表明在旱种条件下，水稻基部节间α-淀粉酶活性高，促进了节间贮存淀粉的降解，降低了基部节间强度，造成旱种水稻的倒伏。

Relationship between Characteristics of Basal Internodes and Lodging and Its Physiological Mechanism in Dry-Cultivated Rice

Lodging is one of the most important factors restricting the wide extension of dry-cultivated rice(DCR).The objective of the study was to investigate the reasons for lodging in DCR using Shanyou 63(indica hybrid combination)and 9516(japonica)as materials.The results showed that the lodging percentage in DCR was significantly higher than that in conventional moist-cultivated rice(MCR),leading to significant decrease in seed-setting percentage and grain weight,and grain yield in DCR.The mechanical strength(thickness and weight per centimeter)and carbohydrate(especially starch)content in basal internodes from heading to maturity were much lower in DCR than in MCR,while α-amylase activity in basal internodes was higher in DCR than in MCR.The starch content was very significantly and positively correlated with thickness and weight per centimeter of basal internodes,and significantly or very significantly and negatively correlated with α-amylase activity in basal internodes.The starch exportation was significantly or very significantly and positively correlated with α-amylase activity.The application of silicon and potassium fertilizers could decrease α-amylase activity and increase the starch content in basal internodes,enhance the mechanical strength of basal internodes,decrease the lodging percentage,and increase seed-setting percentage and grain weight,result in the increase of grain yield in DCR.The results were reversed when 1/2 leaves were cut at booting stage.The results above indicated that the higher α-amylase activity in basal internodes in DCR caused more starch degradation,decreasing the mechanical strength of basal internodes,and resulting in the lodging in DCR.