生物炭延缓水稻生育后期根系衰老的调控机制

Root senescence usually occurred in the critical period of rice yield formation. Premature senescence of root can seriously decrease rice yield. Therefore, it is possible to break the choke point of increasing yield through delaying root senescence and maintaining root activities. Biochar could improve the soil structure and maintain long-term higher soil productivity. The study showed that biochar could improve soil aeration and delay the root senescence. However, little information is available concerning on how to change the rhizosphere microenvironment and the regulation mechanism concerning biochar delaying root senescence. In this project, rice straw and other agricultural wastes as raw materials will be used to produce biochar under different pyrolysis temperature. The physical, chemical properties and adsorption characteristics for the biochar will be tested. The effects of biochar on soil physical and chemical properties and microbial community diversity will be investigated in the paddy fields, and the objective to find out the relationship between biochar, soil microorganism and root senescence. Furthermore, the morphological, physiological characteristics and the expression of key genes in the root senescence of rice will be studied after the addition of biochar. The physiological mechanism of the biochar regulating and delaying the root senescence will be also explored. The purpose of this project is to have important theoretical and practical significance for high-yielding cultivation of rice.

根系衰老发生在水稻产量形成的关键时期，衰老过早会严重影响水稻产量。通过适当的方式延缓水稻根系衰老，维持根系代谢活性是打破水稻增产瓶颈的关键突破口。生物炭可以改善土壤结构，长久维持土壤生产力。前期研究表明，生物炭的添加能够改善土壤通气状况，延缓根系的衰老。然而，生物炭如何改变根际微环境延缓根系衰老的调控机制尚未明确。本项目以水稻秸秆等农业废弃物为材料制备生物炭，研究不同材料、热解条件下生物炭的理化特性及吸附特征，深入研究生物炭对后期稻田根际土壤理化特性及微生物功能群落多样性的影响，明确“生物炭-土壤微生物-根系衰老”的关系；进一步通过研究生物炭输入后水稻根系衰老的形态、生理特性及关键基因表达的变化，揭示生物炭调控根系衰老的生理机制，本研究对水稻高产栽培具有重要的理论和实践意义。

根系早衰是影响作物产量提升的关键因素之一，适当延缓根系衰老可能突破粮食增产的瓶颈。本项目以水稻秸秆等农业废弃物为材料制备生物炭，通过田间试验，从栽培学-微生物学等多学科、多角度探究秸秆生物炭对水稻生育后期根系衰老生理以及根际微生物学机制。研究结果表明，在稻田土壤中添加生物炭能够显著降低了土壤酸度，提高土壤氧化还原电位，改善了稻田土壤的透气性和磷、钾等养分的有效性。由于生物炭具有强的吸附能力，维持齐穗后土壤较高的速效氮含量，促进植株生育后期对氮素的吸收利用，同时，显著增加了土壤中NO3--N的含量，改善了根际养分的组成，有助于水稻对氮素的吸收和利用。增施生物炭显著增加稻田根际土壤细菌群落结构和细菌丰度，显著增加了硝化螺旋菌门4-29、GOUTA19、LCP-6、硝化螺旋菌（Nitrospira）等好氧优势菌属和伯克氏菌属（Candidatus_Koribacter）等优势生防细菌的相对丰度，显著降低了产甲烷菌（Candidatus_Methanoregula）、厌氧绳菌属（Anaerolinea）、厌氧粘细菌属（Anaeromyxobacter）等厌氧优势菌属的相对丰度。在田间剖面挖掘发现，添加生物炭显著增加了水稻深层根系10~25cm所占比例，有利于根系吸收更多的养分。施用生物炭显著增加水稻生育后期的根系的生物量，根系中丙二醛（MDA）含量显著降低，超氧化物歧化酶（SOD）活性等显著提高。生物炭的添加改善水稻根系生长的环境，根系中脱落酸（ABA）含量显著降低，生长素（IAA）和细胞分裂素（CTK）等明显提高；同时显著增加了抽穗后水稻根系伤流量，增加伤流液中生长素和细胞分裂素的含量，有利于延缓水稻生育后期根系的衰老，促进根系代谢和氮素等养分的吸收。生物炭提高了水稻有效穗数、每穗粒数与结实率，显著提高了水稻的产量，平均增产约9.6%。