头季不同施氮方式对再生稻生理生化的影响

Effect of different N application modes in the first cropping rice on the physiobiochemistry of the first cropping rice and its ratoon rice

为揭示头季不同施氮方式下再生稻的生理生化机制,在头季总施氮量为225kg·hm-2的前提下,设不同基蘖肥与穗肥的施氮比例(N1为8︰2,N2为7︰3,N3为6︰4),并以全生育期不施肥为空白对照(N0),研究再生稻叶片硝酸还原酶活性、叶绿素含量、净光合速率和根系活力的变化规律,并分析这些特性对干物质积累和产量的作用。结果表明:(1)整个再生稻生长周期内,头季不同施氮方式下,叶片硝酸还原酶(NR)活性、叶绿素含量、净光合速率变化趋势相似,表现为先上升,在头季稻孕穗期达最大,然后下降,到再生季齐穗期又达到高峰,之后又迅速下降;伤流量在头季孕穗期后大幅度下降,再生季分蘖萌发后伤流量有所回升,至再生季齐穗期又达到小高峰,随后又逐渐降低。(2)施肥有利于提高叶片硝酸还原酶活性、叶绿素含量和净光合速率及根系活力。适当增加再生稻头季中、后期施氮比例,可显著提高再生稻头季生长中、后期的叶片硝酸还原酶活性、叶绿素含量、净光合速率及伤流量,增加干物质积累,提高再生稻产量。

In order to determine physiobiochemical mechanisms of the first cropping rice and its ratoon rice under different N application modes in the first cropping rice, the different ratios of N supply for basal-tillering fertilizer to that for spike fertilizer in the first cropping rice were designed under total N supply of 225 kg？hm？-2, which were N1 （8︰2）, N2 （7︰3）, N3 （6︰4）, and zero N supply （N0） was the control. Changes in nitrate reductase activity, chlorophyll content, net photosynthetic rate, and root activity were analyzed and their effect on dry-matter accumulation and grain yield formation determined. The results show that the changing tendency in nitrate reductase activity, chlorophyll content and net photosynthetic rate in different treatments is similar under different N application modes in different developmental stages of the first cropping rice and its ratoon rice, showing increasing at the early stage, peaking at the booting stage, then gradually declining in the first cropping rice. It rapidly ascends again at full- heading stage, and then rapidly declines at the ripening stage of the ratoon rice. It is also found that bleeding rate continuously declines after the booting stage of the first cropping rice, however, during the ratooning cropping, it gradually increases at budding and tillering stages, reaches a peak at full-heading stage, then gradually declines at maturity. The result indicates that nitrogen supply enhances nitrate reductase activity, chlorophyll content, net photosynthetic rate and root activity. This therefore suggests that the proportion of N supply should be in-creased to enhance these parameters during the middle and late growth stages of the first cropping rice. The good pratoce in N application can also enhance root activity, especially at the booting stage of the first cropping rice. This, in turn, can result in in-creased dry-matter accumulation of the first cropping rice, consequently, high grain output of the ratoon rice .