棉花主茎叶与根系硝酸还原酶活性分布对播期和密度的响应

【目的】本研究旨在探讨大田轻简化栽培条件下棉花氮代谢随播期和密度的变化规律。【方法】选用华棉3109(G.hirsutum L.)于2014年在华中农业大学试验农场,采用裂区设计:播期为主区(S1,5月30日;S2,6月14日),密度为副区(D1,7.5株·m-2;D2,9.0株·m-2;D3,10.5株·m-2),研究了硝酸还原酶(Nitrate reductase,NR)活性在主茎叶位和根系的分布特点。【结果】1)不同播期和密度对叶片和根系NR活性平均值有显著影响。推迟播期对现蕾期棉花叶片与根系平均NR活性无显著影响,增加密度可降低叶片平均NR活性,但对根系平均NR活性无显著影响;推迟播期,显著降低初花期和盛花期棉花叶片NR活性平均值,但晚播对根系NR活性平均值的影响由侧根NR决定,增加密度,叶片和根系平均NR活性呈先升高后降低变化趋势,表明见花施肥后,晚播抑制了棉花地上部叶片氮代谢强度,而增强了地下部根系氮代谢强度;适度增加密度可显著增强棉花地上部叶片和地下部根系氮代谢强度。2)现蕾期叶片NR活性平均值初花期盛花期,根系NR活性平均值大体呈先升高后降低变化趋势。3)主茎叶位NR活性在3个时期均由上而下显著降低,以第1叶至第3叶波动较大,第4叶以下叶片间无显著差异,表明叶片NR活性与叶龄有关,幼叶氮代谢强度高于成熟叶片,成熟叶片之间氮代谢强度保持相对稳定。【结论】长江流域棉区(主要指湖北植棉区)棉花播种不应晚于6月14日,种植密度以9.0株·m-2最佳。

Nitrate Reductase Activity Distributions in Stem Leaves and Roots of Cotton in Response to Sowing Date and Planting Density

Objective] This article aims to study how cotton nitrogen metabolism changes with the density and sowing date change in simplified cultivation fields. Method] The distribution of nitrate reductase (NR) activity was measured in cotton’s main leaves and roots of Huamian 3109 using a field split-plot design with sowing date (S1: 30^th May and S2: 14^th June) as the main plot and density (plant·m^-2) (D1: 7.5, D2: 9.0 and D3: 10.5) as the subplot. Results] 1) The sowing date and planting density had significant effects on the average NR activities in the main leaves and roots. No difference was observed in the average NR activity distributions in leaves and roots after the sowing date was delayed in the squaring period, whereas an increase in the plant density had an inhibitory effect on the average NR activity in leaves. However, during the first and peak bloom periods, delayed sowing dates significantly decreased the average NR activity in leaves, whereas the effect of delayed sowing on the average NR activity in the roots was controlled by lateral root NR activity. Increasing the planting density initially improved NR activity and then subsequently decreased it, indicating that delayed sowing promoted under-ground root nitrogen metabolism instead of reducing above-ground leaf nitrogen metabolism. The optimum density increased nitrogen metabolism in leaves and roots. 2) The average NR activity in leaves decreased as the growth period progressed, namely squaring> first bloom> peak bloom, whereas the NR activity in the roots initially rose prior to the first bloom period and then subsequently decreased. 3) During the three periods, the NR activity decreased in the main leaves from the top to the bottom, and fluctuated mainly in the top 1^st to 3^rd leaf with no significant differences in the remaining leaves lower than the 4^th leaf. This implied that the intensity of the nitrogen metabolism in young leaves was higher than in mature leaves, whereas the intensity of the nitrogen metabolism in mature leaves remained constant. Conclusion] Sowing date for cotton planting in the Yangtze River region (mainly in the Hubei Province) should not be later than 14^th June, and the optimum planting density is 9.0 plant·m^-2.