野生和栽培马蹄金抗旱性比较及其抗旱机制初探

COMPARATIVE STUDY OF DROUGHT TOLERANCE AND TOLERANCE MECHANISMS IN WILD AND CULTIVATED DICHONDRA REPENS

为了鉴别野生和栽培马蹄金(Dichondra repens)的抗旱性,探讨其抗旱适应性的生理机制,对野生和栽培马蹄金进行了土壤水分胁迫处理,系统测定了野生和栽培马蹄金叶片内超氧化物歧化酶(SOD)、过氧化物酶(POD)、硝酸还原酶的活性和游离脯氨酸、可溶性糖、可溶性蛋白、NO2-/NO3-含量以及总DNA片断化程度。结果表明野生和栽培马蹄金在抗旱适应性上存在显著差异。随水分胁迫强度的增加,野生马蹄金叶片内抗氧化酶活性及其升高幅度,渗透调节物质的积累量及积累速度均高于栽培马蹄金,而叶片含水量下降的程度、DNA片断化程度低于栽培马蹄金,其中野生和栽培马蹄金叶片内NO2-/NO3-含量,硝酸还原酶的活性变化差异尤其显著,野生马蹄金叶片内的NO2-/NO3-含量、硝酸还原酶的活性明显高于栽培马蹄金,二者最大含量分别相差10和2.2倍。研究结果说明了野生马蹄金对干旱环境的适应性强于栽培品种;在干旱逆境下马蹄金叶片内的NO2-/NO3-含量的变化在一定程度上可能反映了内源NO的变化,内源NO浓度的高低可能是野生和栽培马蹄金不同抗性的真正原因。

Aims Dichondra repens is a warm-season lawn substitute that remains green for long periods and reproduces strongly. Dichondra repens forms short, dense cover and is important in conservation of water and soil. It retains its green color during winter to - 8 ℃ with only slight leaf browning and is resistant to diseases and heavy metals contamination. Little is known about the drought tolerance of wild and cultivated D. repens. Our objectives were to determine the drought-tolerant characteristics of wild and cultivated D. repens and explore the physiological foundations for drought tolerance in both. Methods We watered wild and cultivated D. repens every 3, 7 and 15 days from March 1 to May 1, 2004 and made growth and development measurements after water treatment. As soil drought conditions developed, we measured changes in superoxide dismutase activity （SOD）, peroxidase activity （POD）, nitrate reductase activity, soluble sugar content, free proline content, soluble protein, nitrate and nitrite （NO2^-/NO3^-） content and DNA fragments of leaves. Important findings Under drought stress, the content of free proline, soluble sugar and NO2^-/NO3^- in wild and cultivated D. repens leaves was enhanced. Activities of SOD and POD were regulated, protecting leaf cells of wild and cultivated D. repens from oxidative damage caused by drought stress. There were marked differences in drought resistance between the wild and cultivated D. repens. Antioxidant enzyme activities and osmotic adjustment substance content in wild D. repens leaves were higher than in cultivated D. repens leaves, while damage to DNA of wild D. repens was less serious than in cultivated D. repens. NO2^-/NO3^- content and nitrate reductase activity in wild D. repens leaves were significantly higher than in cultivated D. repens. Maximum NO2^-/NO3^- content and nitrate reductase activity in wild D. repens leaves were 10 and 2.2 times larger, respectively, than that in cultivated D. repens leaves. Wild D. repens had more antioxidant response to drought stress than cultivated D. repens. Under drought stress, change of NO2^-/NO3^- content may be associated with endogenous NO concentrations, which probably cause the drought tolerance of wild D. repens to be greater than that of cultivated D. repens.