施氮量与播种期对棉花产量和品质及棉铃对位叶光合产物的影响

【目的】本研究旨在揭示施氮量调控不同播种期棉铃对位叶光合产物形成与运转的生理机制,以期为棉花的合理氮肥运筹提供理论依据。【方法】试验于2005和2007年在中国农业科学院棉花研究所(河南安阳,黄河流域黄淮棉区)进行,以科棉1号和美棉33B品种为材料,设置大田不同播种期(4月25日和5月25日)和不同施氮量[低氮N 0 kg/hm2(N0)、适氮N 240 kg/hm2(N240)、高氮N 480 kg/hm2(N480)]处理,研究施氮量对不同播种期棉花产量和品质及棉铃对位叶光合产物的影响。【结果】1)4月25日播种条件下,随施氮量的增加棉铃对位叶中蔗糖含量先升高后降低,淀粉含量增加;随播种期的推迟,N240、N480处理下的棉铃对位叶蔗糖和淀粉含量差异不明显,但均显著高于N0处理;花后24~45 d,棉铃对位叶中蔗糖含量与叶氮浓度呈显著正相关,且相关系数随花后天数的增加而降低;花后17~24 d,蔗糖转化量与叶氮浓度呈显著负相关,至花后31~52 d,反而呈显著正相关(P0.01)。表明棉铃对位叶中适宜叶氮浓度有利于碳水化合物的累积。2)4月25日播种条件下,N0、N480处理对棉花单株铃数、铃重和皮棉产量影响为负效应,对纤维长度和麦克隆值影响较小;晚播低温条件下,N480处理的棉花铃重、皮棉产量、纤维比强度均有所提高,麦克隆值得以优化。因此,施氮量与播种期对纤维比强度和麦克隆值的影响存在补偿效应,晚播棉花增加施氮量可减小因低温而造成的纤维比强度降低的幅度,优化麦克隆值。【结论】本试验条件下,播种期(温度)和施氮量对棉铃对位叶光合产物含量、棉花产量和品质存在互作效应,其主导因素是播种期(温度),施氮量对其有补偿效应。随播种期的推迟,施氮量N 240 kg/hm2时棉花单铃重、产量及纤维品质降低的主要原因是晚播低温使棉铃对位叶中的光合产物(蔗糖和淀粉含量)增加,抑制了光合产物向棉铃及纤维的运输。晚播低温条件下,适量追施氮肥可调节棉铃对位叶中的氮浓度并提高光合产物再利用的能力,促进棉花单铃的形成,降低棉纤维比强度的下降幅度,优化麦克隆值。

Effects of nitrogen rates and planting dates on yield,quality andphotosynthate contents in the subtending leaves of cotton boll

【Objectives】The aim for this study was to elucidate physiological mechanism on photosynthate synthesis and transport of subtending leaves of cotton boll (SLCB) under cool temperature for nitrogen fertilizer, and provide theoretical support for reasonable nitrogen application.【Methods】 To study effect of nitrogen rates on photosynthate contents and nitrogen concentrations in subtending leaves of cotton boll (SLCB) and their relationship to cotton yield and quality under different planting dates, a field experiment is conducted with two cotton cultivars, Kemian 1 and NuCOTN 33B, in the Yellow River Valley (Anyang), China. The cotton seeds were sowed on 25-Apr and 25-May in 2005 and 2007, which could result in different growth temperatures for the boll and its SLCB at the same fruiting branches, and three N levels, N 0, 240 and 480 kg/hm2, standing for low, medium and high nitrogen level (N0, N240 and N480), were applied at the flowering-boll development stage. 【Results】 1) The sucrose contents in the SLCB have a single trend following increasing nitrogen rates, and the starch contents in the SLCB are increased in the 25-Apr planting date. With the delayed planting date, the differences of the sucrose and starch contents between N240 and N480 are non-significant, but their contents are significantly higher than those of N0. In the present research, the sucrose content of the SLCB at 24-45 days after anthesis (DAA) has a significantly positive correlation with nitrogen concentration, and the correlation coefficient is decreased with the increase of DAA. In addition, the transport capacity of sucrose (Tn) has a significantly negative correlation with the nitrogen concentration at 17-24 DAA, and has a positive correlation with the nitrogen concentration at 31-52 DAA (P0.01). These results indicate that an optimal leaf nitrogen concentration is favorable for carbon accumulation and export. 2) In the 25-Apr planting date, boll number, the boll weight and lint yield are decreased in N0 and N480, and non-significant differences are observed in the two treatments. However, in the late planting date of 25-May, the boll weight and lint yield in the treatment of N480 is improved as well as fiber strength, and micronaire values is optimized, thus suggesting that nitrogen application has a compensatory effect on cool temperature due to late planting. 【Conclusions】 In this study, there is an interaction on cool temperature due to the late planting and nitrogen application for carbohydrate, cotton yield and quality. The planting date is the dominant factor, and nitrogen fertilizer has a compensatory effect on cool temperature. With the delayed planting date, the boll weight, lint yield and fiber quality under the treatment of N 240 kg/hm2 are declined, which is mainly due that sufficient non-structural carbohydrates (such as sucrose, hexose and starch) are stored in the SLCB, and carbohydrate might not be exported efficiently to cotton boll. Through increasing the nitrogen application, the decreased degree of fiber strength is less and the micronaire value is optimized, mainly due to the regulated nitrogen concentration and the improved recycling capacity of carbohydrate.