不同氮肥吸收利用效率水稻基因型叶片衰老特性

选用氮肥利用高效型和低效型具有代表性的12个粳稻品种,研究225kghm-2施氮条件下其氮素吸收积累特性。与氮低效基因型相比,氮高效基因型水稻在拔节至抽穗、抽穗至成熟阶段的氮素吸收速率、氮素积累量和积累比例均具有明显优势,其中以抽穗至成熟阶段的优势尤为显著。该阶段水稻各器官逐渐衰老,植株各项生理功能逐渐衰退,为明了水稻衰老与植株中后期氮素吸收与积累、氮肥吸收利用效率的相互关系,相继研究了花后各基因型水稻的衰老特性。结果表明,齐穗后的不同时期,氮高效基因型水稻的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性均显著高于氮低效基因型,而膜脂过氧化产物丙二醛(MDA)的含量却要显著低于氮低效基因型水稻。相关性分析表明,水稻的氮肥利用效率与齐穗后剑叶中的SOD、POD和CAT活性呈极显著正相关,而与其剑叶中的MDA含量呈极显著负相关。由此说明,与氮低效基因型相比,氮高效基因型水稻生育后期剑叶中用于清除活性氧自由基的SOD、POD、CAT活性较高,能有效阻止高浓度氧的积累和膜脂过氧化作用,降低MDA的含量,因而降低叶片的衰老进程,在维持较长光合功能期的同时能增强物质积累,促进植株对氮肥的吸收和利用。

Characteristics of Leaf Senescence in Rice Genotypes with Different Nitrogen Use Efficiencies

Although excessive use of N fertilizer can result in the rapid decrease of N use efficiency and other serious environment problems, N fertilizer is yet the most important and largest input in modern rice production. Previous researches have been demonstrated that variation in N use efficiency existed among rice genotypes. Therefore, it is of urgent importance to elucidate the physiological mechanism of rice N absorption and utilization for increasing N use efficiency. In this research, field experiment with 225 kg ha^-1 N fertilizer application was carried out in 2006 on the farm of Yangzhou University, Jiangsu province, China. Twelve rice genotypes (six N efficient and six N inefficient) selected from one hundred and twenty rice cultivars grown in Yangzhou during 2004 and 2005 were adopted to investigate the characteristics of N absorption and accumulation. Compared with N inefficient genotypes, N efficient genotypes had more obvious advantages in N absorption rate, the amount and the percentage of N accumulation during the growth phases from elongating to heading and from heading to maturing. And of which the advantage during the growth phase from heading to maturing was particularly significant. Since rice organs aged and the plant physiological functions declined gradually from heading to maturing, the characteristics of rice senescence was then studied to understand the relationships between rice senescence and the N absorption and accumulation, and the N use efficiency. Results showed that, during the period of grain filling, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in flag leaf of N efficient genotypes were obviously higher than those of N inefficient genotypes. Contrarily, content of malondialdehyde (MDA), which is the product of membrane lipid peroxidation, was lower in N efficient genotypes than in N inefficient genotypes significantly. After the stage of full heading, N use efficiency was positively correlated to the activities of SOD, POD, and CAT in flag leaf of rice and negatively correlated to the content of MDA. So it reveals that, at late growth stages of rice, the activities of SOD, POD, and CAT of N efficient genotypes were higher than those of N inefficient genotypes in flag leaves, which could eliminate reactive oxygen species, inhibit the membrane lipid peroxidation and decrease the content of MDA more efficiently in N efficient rice genotypes. Therefore, compared with the N inefficient genotypes, the leaf senescence of N efficient genotypes was relatively slower, which could prolong the functional period of leaves, enhance the organic matter accumulation and improve the efficiency of N absorption and utilization.