摘要
摘要:为探明土壤含水量和密度对棉苗花芽分化的调控效应及其生理学机制，于2019年在河北农业大学清苑试验站进行大田试验，以‘农大601’为材料，采用二因素裂区设计方法，主区为水分处理[充分灌溉（CK）和干旱（D）]，副区为密度处理（6万株·hm^-2、9万株·hm^-2和12万株·hm^-2），共6个处理，研究土壤含水量和密度对棉花花芽分化起始及进程的影响。结果表明：1）微观结构观察发现，干旱会加快棉花茎尖生长点的分化速度；高密度下，茎尖生长点横纵比变小，会减缓分化速度；同一密度处理，干旱下棉花始果枝节位有所降低；而同一水分处理下，增加密度棉花始果枝节位显著提高，两因素互作效应显著。2）干旱和密度处理对棉花茎尖生长点的可溶性蛋白质、可溶性糖及内源激素含量产生显著影响（P < 0.05）。2叶期时，干旱条件下，低密度处理可溶性蛋白质、可溶性糖和内源激素GA₃含量较高，ZR含量较低，随着密度的增加，IAA/ABA、ZR/ABA和（IAA+ZR+GA₃）/ABA比值呈增加趋势；随着花芽分化进行，各处理可溶性蛋白质和可溶性糖含量差异不显著，但高密度处理IAA/ABA、ZR/ABA和（IAA+ZR+GA₃）/ABA比值显著低于其他处理，GA₃/ABA比值高于其他处理。3）对调控花芽分化各指标的主成分分析结果表明，棉花2~3叶期时，茎尖生长点可溶性糖含量和内源激素ZR含量对花芽分化起始调控效应影响最大。因此，干旱条件下，6万株·hm^-2处理棉花茎尖生长点分化速度较快，营养物质与内源激素GA₃含量较高，ZR含量较低，有利于棉花花芽分化；而12万株·hm^-2处理棉花茎尖生长点横纵比小，内源激素GA₃/ABA比值高，减缓了花芽分化。研究结果为棉苗花芽分化的调控提供了理论依据。
关键词:棉花/
花芽分化期/
土壤含水量/
密度/
可溶性蛋白质/
可溶性糖/
内源激素
Abstract:Improving the characteristics of cotton flower bud differentiation is important for coordinating the relationship between vegetative growth and reproductive growth in cotton plants, building a good cotton population structure, and increasing yield. To explore the regulatory effects and physiological mechanisms of the water supply and planting densities on cotton seedling flower bud differentiation, this study employed two split-plot designed experiments in 2019 on the Qingyuan Experimental Plot of Hebei Agricultural University. The main plot had two water treatments[full irrigation (CK) and drought (D)], and the sub-plot contained three density treatments[6×10⁴ plants·hm^-2 (low density), 9×10⁴ plants·hm^-2(medium density), and 12×10⁴ plants·hm^-2 (high density)]. By using 'Nongda 601' as the experiment material, the effects of different water supplies and planting densities on floral bud differentiation stage and progression, and the related physiological indexes (hormone, soluble sugar, and soluble protein contents) of cotton seedlings were studied. Before cotton sowing, different amounts of soil moisture were set: the control treatment was 900 m³·hm^-2, and the drought treatment was 450 m³·hm^-2. The results of microstructure showed that: 1) The differentiation speed of cotton shoot apical meristem accelerated under drought conditions. Under high-density conditions, the aspect ratio of cotton shoot apical meristem decreased, which slowed the differentiation rate. Under the same planting density, the position of the first fruit branch lowered down, but under the same water treatment, the position of the first fruit branch significantly raised with increased planting density (P < 0.05). Therefore, the interaction effect of the two factors is significant. 2) The drought and density treatments significantly impacted the soluble protein, soluble sugar, and endogenous hormone contents of the cotton shoot apical meristem. At the 2-leaf stage, the soluble protein and soluble sugar contents of the low-density treatment were significantly higher than those of the other two treatments, and the contents of endogenous hormone gibberellin (GA₃)was higher. The cytokinin (ZR) content was also lower. The ratios between endogenous hormones of indole-3-acetic acid/abscisic acid (IAA/ABA), ZR/ABA, and (IAA+ZR+GA₃)/ABA increased with increasing plant density. With flower bud differentiation, there was no significant difference in the contents of soluble protein and soluble sugar among the treatments. However, the ratios of IAA/ABA, ZR/ABA, and (IAA+ZR+GA₃)/ABA in the high-density treatment were significantly lower than those in other treatments (P < 0.05). The GA₃/ABA ratio was higher than that in other treatments. 3) Principal component analysis of the indexes of flower bud differentiation showed that the contents of soluble sugar and ZR at the shoot apical meristem had the greatest influence on initial flower bud differentiation at the 2-leaf and 3-leaf stages. Therefore, under drought conditions, the shoot apical meristem of cotton at a density of 6×10⁴ plants·hm^-2 differentiated faster, the nutrient substance and GA₃ content were higher, and the ZR content was lower, all of which was conducive to the initiation of cotton flower bud differentiation. However, the 12×10⁴ plants·hm^-2 treatment reduced the aspect ratio of the shoot apical meristem, increased the GA₃/ABA ratio, and slowed flower bud differentiation. The results provide a theoretical basis for the regulation of flower bud differentiation in cotton.
Key words:Cotton/
Flower bud differentiation stage/
Soil moisture/
Planting density/
Soluble protein/
Soluble sugar/
Endogenous hormones



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