甜瓜幼苗生长及生理特性对碱胁迫的响应

以"羊角酥"甜瓜(Cucumis melo L.)为试材,分别利用浓度为12.5、25.0、37.5、50.0、62.5、75.0 mmol·L-1Na2CO3进行梯度胁迫处理,对碱胁迫下甜瓜幼苗生长状态、光合特性以及抗氧化能力进行分析,以期为甜瓜碱胁迫的适应性机制研究提供参考依据。结果表明:当Na2CO3浓度为75.0 mmol·L-1时,幼苗株高、茎粗及叶面积受到显著抑制。随着Na2CO3浓度增加,净光合速率(Pn)呈降低趋势,胞间CO2浓度(Ci)变化趋势反之;叶绿素(Chl)含量呈降低趋势;丙二醛(MDA)含量呈上升趋势,游离脯氨酸(Pro)含量在高浓度Na2CO3时急剧增加;超氧化物歧化酶(SOD)和过氧化物酶(POD)活性均显著高于对照。Pn下降的主要原因是非气孔限制,高浓度(75.0 mmol·L-1)碱胁迫下,幼苗生长势受抑制,且MDA含量增加显著,Pro积累有利于提高幼苗自身的抗碱性。

Response on Growth and Physiological Characteristics of Melon Seedlings Under Alkali Stress

The growth potential,photosynthetic indexes,chlorophyll contents,chlorophyll fluorescence parameters and antioxidant enzyme activities of’Horn crisp’muskmelon(Cucumis melo L.)annual seedlings was measured under treatments with different Na2CO3 concentrations(0 as the control,12.5,25.0,37.5,50.0,62.5,75.0 mmol·L-1),in order to provide theoretical basis for the research on the adaptive mechanism of muskmelon seedlings under alkali stress.The results showed that seedling height,stem diameter and leaf area significantly decreased under 75.0 mmol·L-1 Na2CO3 treatment,compared with the control.With the gradual increase of Na2CO3 concentration in treatments,the net photosynthetic rate(Pn)of the seedlings decreased,whereas the intercellular CO2 concentration(Ci)increased;the chlorophyll(Chl)content showed a decreasing trend,the malondialdehyde(MDA)content,however,was elevating,whereas the free proline(Pro)content increased sharply under high concentration of Na2CO3.The enzyme activity of superoxide dismutase(SOD)and peroxidase(POD)under treatment were significantly higher than the control.The decrease of Pn of seedlings may be a result of non-stomatal restriction.Under high concentration(75.0 mmol·L-1)alkali stress,the growth potential of melon seedlings was impaired,whereas the significantly increased MDA content and accumulation of Pro might have enhanced the resistance of melon seedlingsto alkalinity in later stage.