棉花缺钾引起的形态和生理异常

随着棉花新品种特别是转Bt(Bacillus thuringiensis)基因抗虫棉应用于生产和单位面积产量不断提高，棉花缺钾现象在许多植棉国家已越来越普遍和严重。棉花缺钾症状通常首先表现在棉株中下部的老叶上，但近年来也发现症状首先表现在中上部嫩叶上的状况。缺钾导致棉花生育异常，突出表现为叶面积系数，光合速率和于物质生产降低，但比叶重提高、棉花早熟。土壤供钾不足，钾吸收受抑，高产转基因棉花品种的应用以及不良环境因子的胁迫等是导致缺钾的重要原因。缺钾时单叶光合速率的下降主要是叶片气孔导度降低、叶绿素含量减少、叶绿体超微结构受损、光合产物运转不畅、RuBP羧化酶活性降低等所致。群体光合能力的下降则源于单叶光合速率降低和叶面积系数下降。棉株上部功能叶的叶片和叶柄中的K^ 含量可作为缺钾的诊断指标。

Morphological and Physiological Disorders of Cotton Resulting from Potassium Deficiency

As modern cotton varieties including Bt (Bacillus thuringiensis) transgenic cotton are adopted and the yield per unit area continues to increase,potassium deficiency is occurring at a rising frequency in many cotton-growing countries.Symptoms of K deficiencies used to occur on the older or mature leaves at the bottom of a plant,but more recently described symptoms show up on young leaves near the top of the plant.Potassium deficiency leads to numerous disorders in cotton,including decreased leaf area index,photosynthesis and plant biomass,but enhances specific leaf weight and early maturity.Low supply and uptake of K,adoption of modern cotton varieties particularly Bt transgenic cotton,and environmental stress are obvious contributors to potassium deficiency.Single leaf photosynthesis (Pn) reduction results mainly from decreased stomatal conductance,low chlorophyll content,poor chloroplast ultrastructure,restricted saccharide translocation,and decreased synthesis of RuBP carboxylase under K deficient conditions.Canopy photosynthesis reduction in K-deficient plants is mainly attributed to both inhibited single leaf Pn rate and decreased leaf area index.Potassium concentrations in both blade and petiole of top fully expanded leaves on main stem are good indicators of K deficiency.