干旱胁迫后叶面追施钼盐对桑树生长和部分生理指标的影响

Effects of Foliar Application of Molybdenum Solution on Growth and Some Physiological Indexes of Mulberry After Drought Treatment

钼(Mo)是植物生长发育必需的微量元素。为探索干旱胁迫及胁迫后叶面追施Mo盐对桑树生长生理的影响,将桑品种中桑5801号的2年生盆栽扦插苗干旱胁迫18 d后,对叶面分别喷施质量浓度为0 g/L(M0)、0.1 g/L(M1)、0.5 g/L(M2)和1.0 g/L(M3)的Na2MoO4溶液,连续喷施7 d后,检测分析干旱和追施Mo盐对茎生长速率以及叶片中的淀粉、渗透调节物质含量和抗氧化物酶活性的影响。干旱胁迫导致桑苗的茎生长速率及叶片中的可溶性蛋白含量和过氧化物酶(POD)活性显著降低(P<0.05),而叶片中的脯氨酸(Pro)含量、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性显著提高(P<0.05)。叶面追施Mo盐后,M1、M2、M3处理组的茎生长速率显著高于M0组,其中又以M1组的茎生长速率最高。4个处理组的桑苗叶片检测结果是,M1组的Pro含量最高,CAT活性最低(P<0.05);M3组的淀粉含量及各种抗氧化酶的活性最高,可溶性糖和可溶性蛋白含量最低(P<0.05)。以上结果表明,叶面追施Mo盐能缓解干旱胁迫对桑树生长的抑制,而生理指标的响应差异暗示M1和M3组可能诱导桑苗不同的抗逆反应,即:喷施0.1 g/L Mo盐更有利于促进桑苗叶片中的Pro积累,提高渗透调节能力,降低渗透胁迫伤害;喷施1.0 g/L Mo盐能够提高桑苗叶片中的淀粉累积,并显著激活抗氧化酶的活性以抵御氧化胁迫。研究结果初步提示,叶片追施一定浓度的Mo盐溶液有望作为对桑树干旱胁迫的"生理抢救"措施。

Molybdenum(Mo)is an essential trace element for plant growth and development.To explore how Mo affects the growth and physiological indexes of mulberry in response to drought stress,Na2MoO4 solutions with mass concentrations of 0 g/L(M0),0.1 g/L(M1),0.5 g/L(M2)and 1.0 g/L(M3)were sprayed for continuously 7 days on the leaves of two-year old saplings of mulberry cultivar Zhongsang 5801 after drought treatment for 18 d.Therefore,the effect of drought stress and Mo application on shoot growth rate,contents of starch and osmotic regulators,and activity of antioxi-dant enzyme in leaves were analyzed.The results showed that drought stress significantly decreased shoot growth rate,soluble protein content and POD activity(P<0.05),while significantly increased free proline content and CAT activity and SOD activity in leaf(P<0.05).After foliar application of Mo solution,shoot growth rates in M1,M2 and M3 groups were significantly higher than that of M0 group,among which M1 was the highest.According to detection results from sapling leaves of 4 treatment groups,M1 had the highest free proline content and lowest CAT activity(P<0.05),whereas M3 had the highest starch content and antioxidase activity but the lowest contents of soluble sugar and soluble protein(P<0.05).These results indicate that foliar application of Mo solution could alleviate the growth inhibition of mulberry under drought stress,and different physiological responses suggested that different stress reactions might be induced in M1 and M3:0.1 g/L Mo solution could alleviate osmotic stress by producing more proline and retaining high osmotic potential,whereas 1.0 g/L Mo solution could improve starch accumulation and activate antioxidase to protect mulberry against oxidative stress.These data provide preliminary experimental evidence that proper foliar application of Mo solution can be potentially used as a"physiological rescue"for mulberry to alleviate drought stress.