Zahoor Rizwan, Zhao Wenqing, Abid Muhammad, Dong Haoran, Zhou Zhiguo
Key Laboratory of Crop Growth Regulation, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, Jiangsu Province, PR China, PR China.
Key Laboratory of Crop Growth Regulation, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, Jiangsu Province, PR China, PR China.
J Plant Physiol. 2017 Aug;215:30-38. doi: 10.1016/j.jplph.2017.05.001. Epub 2017 May 4.
To evaluate the role of potassium (K) in maintaining nitrogen metabolism and osmotic adjustment development of cotton functional leaves to sustain growth under soil drought and rewatering conditions, the plants of two cotton cultivars Siza 3 (low-K sensitive) and Simian 3 (low-K tolerant), were grown under three different K rates (K0, K1, and K2; 0, 150, and 300kgKOha, respectively) and exposed to drought stress with 40±5% soil relative water content (SRWC). The drought stress was applied at flowering stage by withholding water for eight days followed by rewatering to a well-watered level (75±5% SRWC). The results showed that drought-stressed plants of both cultivars showed a decrease in leaf relative water content (RWC) and osmotic potential in the functional leaves and developed osmotic adjustment with an increase in the contents of free amino acids, soluble sugars, inorganic K, and nitrate as compared to well-watered plants. In drought-stressed plants, nitrogen-metabolizing enzyme activities of nitrogen reductase (NR), glutamine synthetase (GS), and glutamate synthase (GOGAT) were diminished significantly (P≤0.05) along with decreased chlorophyll content and soluble proteins. However, drought-stressed plants under K application not only exhibited higher osmotic adjustment with greater accumulation of osmolytes but also regulated nitrogen metabolism by maintaining higher enzyme activities, soluble proteins, and chlorophyll content in functional leaves as compared to the plants without K application. Siza 3 showed better stability in enzyme activities and resulted in 89% higher seed cotton yield under K2 as compared to K0 in drought-stressed plants, whereas this increase was 53% in the case of Simian 3. The results of the study suggested that K application enhances cotton plants' potential for sustaining high nitrogen-metabolizing enzyme activities and related components to supplement osmotic adjustment under soil drought conditions.
为了评估钾（K）在维持棉花功能叶氮代谢和渗透调节发育以在土壤干旱和复水条件下维持生长中的作用，选用两个棉花品种泗杂3号（低钾敏感型）和泗棉3号（低钾耐受型），在三种不同钾施用量（K0、K1和K2，分别为0、150和300 kg K2O/ha）下种植，并使其暴露于土壤相对含水量（SRWC）为40±5%的干旱胁迫下。在开花期通过停水8天施加干旱胁迫，随后复水至水分充足水平（75±5% SRWC）。结果表明，与水分充足的植株相比，两个品种受干旱胁迫的植株功能叶的叶片相对含水量（RWC）和渗透势均降低，并通过增加游离氨基酸、可溶性糖、无机钾和硝酸盐含量进行渗透调节。在受干旱胁迫的植株中，硝酸还原酶（NR）、谷氨酰胺合成酶（GS）和谷氨酸合酶（GOGAT）的氮代谢酶活性显著降低（P≤0.05），同时叶绿素含量和可溶性蛋白含量也降低。然而，与未施钾的植株相比，施钾的干旱胁迫植株不仅表现出更高的渗透调节能力，渗透溶质积累更多，而且通过维持功能叶中更高的酶活性、可溶性蛋白和叶绿素含量来调节氮代谢。在受干旱胁迫的植株中，泗杂3号的酶活性表现出更好的稳定性，与K0相比，K2处理下籽棉产量提高了89%，而泗棉3号的增幅为53%。该研究结果表明，施钾可增强棉花植株在土壤干旱条件下维持高氮代谢酶活性及相关成分以补充渗透调节的潜力。
