水稻抛栽秧苗立苗中的形态与生理变化

起身立苗是抛秧稻特有的一个基本过程,在生产实践中,能否及时起身立苗,无疑是决定抛秧稻成败的关键和应用的前提。以南粳44为试验材料,设置带土直立苗、带土倾斜苗、带土平躺苗、无土平躺苗、无土手栽苗等不同模拟苗姿,较系统地研究立苗期间的形态、生理变化。结果表明,①非直立苗起立期间分蘖节弯曲,秧苗基部下侧具有伸长功能的细胞生长快于上侧细胞,分蘖节下部发生大量新根,扎入土中,成为秧苗直立的支点。②带土倾斜苗、带土平躺苗、无土平躺苗的立苗时间分别是4d、8d和12d。③立苗过程中,带土直立苗和带土倾斜苗的发根优势明显、根系活力强,至第4天根量显著大于带土平躺苗、无土平躺苗和无土手栽苗。④无土秧苗活棵期间植株含水率比立苗初期下降快,后逐渐上升,10d后接近带土秧苗。⑤带土直立苗、带土倾斜苗抛后叶绿素含量高于无土手栽苗,无土平躺苗叶绿素含量低于无土手栽苗,带土平躺苗和无土手栽苗没有多大差异,所有处理秧苗除无土平躺苗外10d后叶绿素含量逐渐恢复正常。⑥栽后2d所有处理秧苗的根系、地上部的可溶性总糖在活棵立苗中被消耗,抛后4d无土秧苗地上部可溶性总糖开始增加,带土直立苗与带土倾斜苗活棵立苗快,栽后糖分消耗多。⑦立苗期间,各种苗姿植株地上、地下部的N、P、K积累量都增加,平均增速以带土秧苗大于无土秧苗,直立苗大于平躺苗。⑧各苗姿秧苗的理论产量、实际产量均是带土直立苗带土倾斜苗无土手栽苗带土平躺苗无土平躺苗。由此说明,带土秧苗比非带土秧苗立苗活棵立苗早,直立苗比非直立苗活棵早。因此,生产上抛秧稻要选择带土秧苗,提高直立苗比例,减少平躺苗比例,提高抛秧稻群体起点质量。

Morphological and Physiological Changes in Seedling Standing and Establishment of Broadcasted Rice Seedlings

Seedlings standing and establishment is a special process for broadcasted rice. And whether the seedlings could establish timely is the basis of high yield. In this research, rice cultivar Nanjing 44 was adopted, and five treatments with different seedling poses and with or without soil were set artificially including the upright seedlings with soil (USWS), the leaning seedlings with soil (LESWS), the lying seedlings with soil (LASWS), the lying seedlings without soil (LASWTS), the upright seedlings without soil (USWTS). The morphological and physiological changes were studied during the process of seedling standing and establishment. Results were as follows: (1) The crown of the lying seedlings bent its lower side that produced more new roots as a pivot for standing. In the curvature zone of the lying seedling, actively elongated cells of the lower side grew faster than those of the upper side, which led to an asymmetric growth. (2) The time of seedling standing of LESWS, LSWS and LSWTS was 4 d, 8 d, and 12 d, respectively. (3) USWS and LESWS produced more roots during seedling standing period, whose activity was stronger. (4) The water content of the seedlings without soil decreased fast during the early period then increased during the later period, which was near to that of the seedlings with soil from 10 days after transplanting. (5) The chlorophyll contents of LASWS, LASWTS, and USWTS were lower than those of USWS and LESWS during the early period, those of all treatments restored to the normal level from 10 days after transplanting except LASWTS. (6) Total soluble sugar of any treatment’s roots and aboveground part was consumed at two days after transplanting, then that in aboveground plants of LASWTS and USWTS began to increase. USWS and LESWS consumed more total soluble sugar. (7) The N, P, and K accumulation increased in root and aboveground parts. The average increasing rates of N, P and K accumulation were higher in the seedlings with soil than in the seedlings without soil and also higher in the upright seedlings than in the lying seedlings. (8) Theoretical yield and practical yield were all shown as below: USWS>LESWS>USWTS>LASWS> LASWTS. And it could be concluded that, the time of seedling standing and establishment was earlier in the seedlings with soil than in the seedlings without soil and also earlier in the upright seedlings than in the leaning and lying seedlings. Therefore, in production we should choose the seedlings with soil, increase the proportion of the upright seedlings and reduce the proportion of the lying seedlings, as a result, improve the population quality for broadcasted rice.