干旱胁迫下一氧化氮对小麦离体根尖离子吸收的影响

Effect of Nitric Oxide on Ions Absorption in Excised Root Tips of Wheat Seedlings under Drought Stress

为阐明干旱胁迫下一氧化氮(NO)对植物的保护机制,利用干旱敏感性不同的3个小麦(Triticum aestivum L.)品种的离体根尖,比较了NO对干旱胁迫的响应及其对离子吸收的影响。在干旱胁迫下,耐旱品种陇春8139根尖中大量产生NO,K+和Ca2+被大量吸收,而Cl-被排出体外,质膜H+-ATPase活性升高;而干旱敏感品种甘麦8号和定西24的根尖中NO、离子含量和质膜H+-ATPase活性的变化呈相反趋势。NO供体硝普纳(SNP)处理使3个品种根尖中的K+和Ca2+含量增加,Cl-含量下降,并能提高质膜H+-ATPase活力;NOS抑制剂Nω-nitro-L-arginine(LNNA)和NO清除剂2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide(PTIO)能够逆转这一效果。Na+含量在所有处理下都没有明显变化。试验结果证明,NO能够通过调节质膜H+-ATPase活力影响植物对离子的选择吸收,从而提高耐旱性。

Longchun 8139 is a wheat （Triticum aestivum L.） cultivar grown in Dingxi in Northwest China, which has stably tolerance characteristics to drought stress in morphology, physiology, and genetics. To explain the protection mechanism of nitric oxide to plants under drought stress, Longchun 8139 and two drought-sensitive cultivars Ganmai 8 and Dingxi 24 were used for testing the adaptation to drought stress. The excised root tips （2±0.02 cm） from the seedlings were treated with 20% polyethylene glycol （PEG）-6000 to simulate drought stress. In addition, the NO content in root tips was adjusted with 0.2 mmol L^-1 sodium nitroprusside （SNP, as NO donor）, and 0.3 mmol L^-1 N^ω-nitro-L-arginine （LNNA, a NO synthase inhibitor）, and 0.4 mmol L-1 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide （PTIO, a specific NO scavenger） adding in culture medium. In the root tips of Longchun 8139, the activity of NO synthase and NO content increased remarkably, the chloride （Cl^-） content decreased, whereas, the contents of calcium （Ca^2＋） and potassium （K^＋） increased, simultaneously, the activity of plasma membrane H^＋-ATPase was activated under drought stress. However, in the root tips of Ganmai 8 and Dingxi 24, the changing patterns of the parameters above were opposite. When applying SNP, changes of the contents of Ca^2＋ and K^＋, as well as the activity of plasma membrane H^＋-ATPase were observed similar to those induced by PEG in drought-tolerant cultivar, Longchun 8139. These changes in response to drought stress could be counteracted, such as, the promotion of Cl^- content, the reductions of Ca^2＋ and K^＋ content, and the decrease of activity of plasma membrane H^＋-ATPase, if LNNA and PTIO were added in the culture medium. As to Na^＋ content, no obvious variations were observed among all treatments. The results indicate that NO acts as the second messenger in inducing drought resistance through influencing ions absorption, which is dependent on the increased activity of plasma membrane H^＋-ATPase.