采用盆栽法,研究了0(CK)、50、100、150 和200 mmol·L^-1NaCl 胁迫处理21 d 对马齿苋(Portulaca oleracea Linn.)幼苗生长的影响,并分析了胁迫处理0、1、3、7 和15 d 时叶片中O₂^-·和MDA 含量以及SOD、POD 和CAT 活性的变化。结果表明:随NaCl 浓度的升高,幼苗株高、根长、单株叶片数、主茎直径以及单株干质量和鲜质量均逐渐降低;在50 mmol·L^-1NaCl 胁迫条件下,幼苗单株干质量和鲜质量及主茎直径均高于对照,单株叶片数、株高和根长均低于对照且差异均不显著;而在100、150 和200 mmol·L^-1 NaCl 胁迫条件下,幼苗的各项生长指标均低于对照且总体上差异显著。除50 mmol·L^-1 NaCl 处理组外,随NaCl 浓度的升高和胁迫时间的延长,各处理组幼苗叶片中的O₂^-·和MDA 含量总体上逐渐提高且均显著高于对照。随胁迫时间延长,各处理组叶片的SOD 和POD 活性均呈先高后低的变化趋势,且NaCl 浓度越高酶活性变幅越大;其中,100、150 和200 mmol·L^-1 NaCl 处理组的SOD 和POD 活性在处理前期和中期(1、3 和7 d) 均显著高于对照、而在处理后期(15 d) 则显著低于对照。随胁迫时间延长,在50、100 和150 mmol·L^-1NaCl 胁迫条件下叶片CAT 活性呈先高后低的变化趋势,其中,50 和100 mmol·L^-1NaCl 胁迫条件下CAT 活性均显著高于对照;而在200 mmol·L^-1NaCl 胁迫条件下CAT 活性则逐渐降低且均显著低于对照。综合分析结果显示:高浓度NaCl 胁迫明显抑制马齿苋幼苗生长,并导致叶片抗氧化酶活性降低;而低浓度NaCl 胁迫对其幼苗生长及部分生理指标均无明显影响,显示苗期马齿苋对NaCl 胁迫具有一定的耐性。

Effects of 0 (CK), 50, 100, 150 and 200 mmol·L^-1NaCl stressing for 21 d on seedling growth of Portulaca oleracea Linn. were studied by pot culture method, also, changes in contents of O ₂^-·and MDA, and activities of SOD, POD and CAT in leaf were analyzed when stressed for 0, 1, 3, 7 and 15 d. The results show that seedling height, root length, leaf number per plant and diameter of main stem, and fresh and dry weights per plant decrease gradually as rising of NaCl concentration; under stress of 50 mmol·L^-1 NaCl, fresh and dry weights per plant, diameter of main stem are higher than those of the control, leaf number per plant, seedling height and root length are lower than those of the control, with no significant difference; while, under stresses of 100, 150 and 200 mmol·L^-1NaCl, these growth indexes all are lower than those of the control, generally there is significant difference. Generally, as rising of NaCl concentration and prolonging of stressing time, contents of O₂^-·and MDA in leaf of seedlings in all treating groups increase gradually and are significantly higher than those of the control except the treating group of 50 mmol·L^-1NaCl. As prolonging of stressing time, activities of SOD and POD in leaf of seedlings in all treating groups appear a change trend of first high and then low, and the higher NaCl concentration the bigger changing range of enzyme activity. In which, activities of SOD and POD in treating groups of 100, 150 and 200 mmol·L^-1NaCl at early and middle states (1, 3 and 7 d) of stressing treatment are significantly higher and at later state (15 d) are significantly lower than those of the control. As prolonging of stressing time, CAT activity in leaf appears a change trend of first high and then low under stresses of 50, 100 and 150 mmol·L^-1 NaCl, in which, CAT activity in treating groups of 50 and 100 mmol·L^-1NaCl is all significantly higher than that of the control, but under stress of 200 mmol·L^-1NaCl, CAT activity decreases gradually and is significantly lower than that of the control.The result of comprehensive analysis indicates that NaCl stress with high concentration obviously inhibits growth of P. oleracea seedling and causes to decreasing of antioxidant enzyme activity in leaf, while NaCl stress with low concentration has no obvious effect on growth and some physiological indexes of P. oleracea seedling, meaning that P. oleracea at seedling stage possesses a certain tolerance to NaCl stress.