盐胁迫下外源褪黑素和Ca^(2+)对甜瓜幼苗的缓解效应

Alleviation effects of melatonin and Ca^(2+) on melon seedlings under salt stress

以甜瓜品种‘羊角酥瓜’为试材,利用人工气候室控制环境条件(昼/夜25/18℃),研究盐胁迫条件下外源褪黑素(MT)和Ca^(2+)对甜瓜幼苗根系和叶片中Cl^-、Na^+、K^+、Mg^(2+)、Ca^(2+)离子含量,Na^+/K^+、Na^+/Ca^(2+)、Na^+/Mg^(2+)值,以及H^+-ATP酶活性、渗透调节物质积累和细胞膜质过氧化的影响.结果表明:与对照相比,盐胁迫处理显著抑制甜瓜幼苗生长,增加根系和叶片中Cl-、Na^+含量,降低K^+、Mg^(2+)、Ca^(2+)含量.盐胁迫下,喷施外源MT或Ca^(2+)处理均可以显著降低甜瓜根系和叶片中Cl^-、Na^+含量,提高K^+、Mg^(2+)、Ca^(2+)含量,植株体内Na^+/K^+、Na^+/Ca^(2+)和Na^+/Mg^(2+)值下降;同时也提高了根系和叶片H^+-ATP酶活性及叶片渗透调节物质的含量,降低盐胁迫对细胞膜的伤害,表现在甜瓜叶片相对电导率和丙二醛含量降低.总之,在盐胁迫条件下,外源MT、Ca^(2+)单独和复配处理均可通过提高H^+-ATP酶活性来降低盐害离子的含量,改善甜瓜幼苗中的离子平衡,同时增加渗透调节物质的含量,降低膜质过氧化水平,从而增强其对盐胁迫的适应性,其中MT和Ca^(2+)复配处理时的效果更好.复配外施MT和Ca^(2+)在诱导甜瓜幼苗提高耐盐方面具有协同增效作用.

To assess the role of exogenous melatonin （MT） and Ca〉 in melon under salt stress, the content of mineral elements （ Cl-, Na＋, K＋, Mg〉, Ca〉 ） , the values of Na＋/K＋, Na＋/Ca2＋, Na＋/Mg2＋, the activity of H＋-ATP, the accumulation of osmotic substances and membrane lipid peroxidation in melon under salt stress were investigated in the environmental conditions （day/night 25/18 ℃ ） controlled by artificial climate chamber. The results showed that salt stress significantly inhibited growth of the melon seedlings with the increased contents of Cl- and Na＋ in roots and lea- ves, and the decreased contents of K＋, Mg2＋ and Ca〉, compared with the control. Under salt stress, exogenous application of MT or Ca〉 remarkably reduced the contents of Cl- and Na＋ in roots and leaves, increased the contents of K＋, Mg〉 and Ca〉, and decreased values of Na＋/K＋, Na＋/ Ca2＋and Na＋/Mg2＋. Additionally, exogenous melatonin or Ca〉 increased H＋-ATP activity and os- motic adjustments, and further alleviated cell membrane injuries imposed by salt stress, displaying lower MDA content and relative conductivity. Collectively, this work suggested that bined applications of exogenous MT and Ca2＋ effectively reduced the content of single or com- and Na＋, ira- proved ion balance by enhancing H＋-ATP activity, and increased the content of osmotic adjustment substances for ameliorating membrane lipid peroxidation, thereby enhancing plant adaptation to salt stress, especially combined applications of exogenous MT and Ca2＋. Our results further showed that the combined application of exogenous MT and Ca〉 resulted in a synergistic effect on increasing salt tolerance in melon seedlings.