不同品种紫花苜蓿氮代谢的Cd耐性评价及其鉴定指标筛选

为评估不同品种紫花苜蓿氮代谢对Cd的耐性并筛选可靠评价指标,以20个紫花苜蓿(Medicago sativa L.)品种为植物材料,以0、50 mg·kg~(-1)两个Cd处理浓度为土壤条件,开展温室盆栽试验。测定各品种的株高、生物量、全氮含量、硝态氮含量、脯氨酸含量、游离氨基酸含量、可溶性蛋白含量及氮代谢关键酶(硝酸还原酶、谷氨酰胺合成酶、谷氨酸合酶和谷氨酸脱氢酶)活性指标,计算Cd胁迫后各指标的变化率;分析各指标变化率之间的相关性,并利用主成分分析法和隶属函数法计算各品种的综合评价值(D),建立D值的回归模型并筛选Cd耐性的评价指标。结果显示,Cd胁迫后,11个指标在不同品种中的变化率各不相同,其中增幅最大的指标是品种"WL525HQ"中的硝态氮含量(122.24%),降幅最大的指标则是品种"WL525HQ"中的硝酸还原酶活性(-83.00%)。在株高、生物量、全氮含量、可溶性蛋白含量、脯氨酸含量、硝酸还原酶活性、谷氨酰胺合成酶活性和谷氨酸合酶活性8个指标之间,呈两两显著正相关关系(P0.05或P0.01)。20个紫花苜蓿品种中,"巨人"的D值最大(0.89),其氮代谢具有最强的耐Cd性,而"三得利"的D值最小(0.04),其氮代谢Cd耐性最弱。多元线性回归分析筛选出株高、谷氨酰胺合成酶、谷氨酸脱氢酶、硝态氮、硝酸还原酶和生物量6个单项指标作为评价紫花苜蓿氮代谢Cd耐性的主要指标,为紫花苜蓿Cd耐性品种的筛选与鉴定提供依据和数学模型。

Cadmium tolerance evaluation and evaluation index screening in nitrogen metabolism of different alfalfa cultivars

To evaluate cadmium tolerance in nitrogen metabolism of different alfalfa (Medicago sativa L.) cultivars, greenhouse potted experiments of 20 alfalfa cultivars were conducted, with soils treated with 0 (control) and 50 mg·kg^-1 cadmium stress. Eleven evaluation indexes, including plant height, biomass, total nitrogen content, nitrogenous compounds content in different forms (nitrate, proline, free amino acid, and soluble protein), and nitrogen metabolism key enzyme activities (nitrate reductase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase) were measured. The change rates of the above indexes were calculated between the control and treatment groups. Correlations between each two index change rates were analyzed. The comprehensive evaluation value (D) of each cultivar, which was used to evaluate the cadmium tolerance, was calculated based on principal component analysis and membership function method. The multiple linear regression analysis of D was then used to screen the main indexes to establish the mathematic model for the D calculation. The results showed that the change rates of all 11 indicators varied with different cultivars, among which the largest increase (122.24%) was in nitrate content and the largest decrease (-83.00%) was in nitrate reductase activity that were observed in WL525HQ. Correlation analysis showed that there were significant positive pairwise correlations (P<0.05 or P<0.01) among the change rates of plant height, biomass, total nitrogen content, soluble protein content, proline content, nitrate reductase activity, glutamine synthetase activity, and glutamate synthase activity. Out of the 20 alfalfa cultivars, Juren had the largest cadmium tolerance in nitrogen metabolism (D value was 0.89); whereas, Sandeli had the weakest cadmium tolerance (D value was 0.04). Based on the multiple linear regression analysis, plant height, glutamine synthetase activity, glutamate dehydrogenase activity, nitrate reductase activity, nitrate content, and biomass were screened as the main indexes. Based on these six indexes. A regression model was established, which could be used to evaluate cadmium tolerance of alfalfa.