麻育秧膜对机插水稻秧苗根区氧供应及根系呼吸代谢的影响

Matting a bast fiber seedling film on the bottom surface of seedling tray significantly promotes rice seedling root growth and improves its quality, however, the mechanism is not clear. Previous studies showed a highly consistency in root characteristics between the rice seedlings raised by bast fiber seedling film and by oxygen-enriched culture. Considering that the rice seedling before three-leaf stage is susceptible to hypoxia as a result of lack of mature aerenchyma, we speculate that bast fiber seedling film could increase root oxygen intake by increasing direct contact area of root epidermal cell with air, consequently promote root respiratory metabolism of rice seedling, especially rice seedling before three-leaf stage. This project aims to explore the mechanism from the perspective of oxygen supply in root zone, and further to explore the effect of rhizosphere aeration on rice seedling and its relationship with leaf age. The main content includes: exploring effects of bast fiber seedling film on oxygen supply in root zone through investigating the spatial and temporal distribution of oxygen concentration in seedling tray by direct measurement and indirect observation; exploring effects of bast fiber seedling film on root respiratory metabolism of rice seedling through forward and backward analysis, with a clear definition to the role of oxygen supply; exploring response of root respiratory metabolism to oxygen supply in root zone and its relationship with leaf age through two ways: raising rice seedling in seedling strays of different oxygen environment by aeration under their bottom, and raising rice seedling in aerated culture solution. This project will provide theoretical basis for improving raising technology of machine-transplanted rice seedling.

在育秧平盘底面垫铺麻育秧膜可显著促进机插水稻秧苗根系生长发育，提高秧苗素质，其机理尚不明确。前期研究表明麻育秧膜秧苗根系特征与增氧栽培水稻根系具有高度一致性，考虑到三叶期前水稻秧苗尚未形成完善的通气组织，易处于缺氧状态，我们推测麻育秧膜增加了根表皮细胞与空气的直接接触，提高了根系摄氧，进而促进了秧苗特别是三叶期前秧苗根系呼吸代谢。本项目拟从根区氧供应的角度，探索麻育秧膜在水稻机插育秧中的作用机理，并进一步探索根际增氧对水稻秧苗的影响及其与叶龄的关系。包括：通过直接测量和间接观测分析秧盘中氧浓度时空分布规律，研究麻育秧膜对秧苗根区氧供应的影响；通过正向和逆向分析麻育秧膜对秧苗根系呼吸代谢的影响，明确氧供应在其中的角色；通过主动通气在育秧硬盘中创造不同氧浓度环境进行育秧，结合通气水培育秧，研究根系呼吸代谢对根区氧供应的响应及其与叶龄的关系。项目实施可丰富水稻机插育秧理论，完善水稻机插育秧技术。

麻育秧膜是针对我国水稻机插盘育秧中普遍存在的难起秧、易散秧、秧苗素质不稳定问题而研发的新型膜材料，大量的应用实践表明其可显著促进秧苗根系生长发育，促进根系盘结成毯，同时提高稻谷产量。然而，其作用机理尚未明确。本项目研究麻育秧膜对机插水稻秧苗根区氧供应的影响，从土壤酶活性、微生物组成和养分含量以及秧苗植株可溶性糖含量等方面探索了麻育秧膜提升水稻机插育秧素质的作用机理，初步形成了完整的作用机理链。结果表明：.（1）麻育秧膜具有独特的孔隙结构，可在育秧盘底面形成一层多孔的气体通道，氧气分子通过育秧盘底面的透气孔进入麻育秧膜后，可经由这些孔隙迅速转移到育秧土底面，补偿土壤微生物呼吸作用消耗的氧气，保持育秧土底层氧气浓度，从而达到类似于增氧栽培的效果。.（2）麻育秧膜的增氧效应改变了秧苗根区土壤酶活性和土壤微生物组成，进而影响了土壤养分，最终促进水稻幼苗的生长发育。相比无膜对照，麻育秧膜秧苗根区育秧土中的脲酶活性略有提高，有机质含量和土壤细菌群落的Chao1指数和香农指数均有降低，土壤细菌群落中的酸杆菌门和芽单胞菌门的相对丰度有增加的趋势。在应用麻育秧膜10天后，相比对照，麻育秧膜秧苗根区土壤的全氮、硝态氮、铵态氮和碱解氮分别提高4.9%、25.4%、2.3%和 9.3%；应用20天后，分别提高4.7%、39.3%、14.6%和11.5%。.（3）应用麻育秧膜提高了水稻植株可溶性糖含量，进一步的研究表明水稻秧苗植株可溶性糖含量解释了73.6%-75.4%的发根力变异，硝态氮含量解释了7.3%-14.2%的发根力变异，表明秧苗植株可溶性糖含量是影响其发根力的关键因素。.总的说来，麻育秧膜可以补偿水稻根区土壤微生物呼吸作用消耗的氧气，保持育秧土底层氧气浓度，改变秧苗根区土壤酶活性和土壤微生物组成，进而影响土壤养分，促进水稻幼苗的生长发育，提高秧苗素质尤其是提高植株可溶性糖含量，秧苗发根力更高，在机插后返青快、分蘖早、成穗率高、有效穗多，最终具有更高的稻谷产量。