Abstract:

In order to explore the physiological response of Brassica napus at seedling stage under aluminum stress, in this study, two oilseed rape varieties with significant difference in aluminum toxicity tolerance of R178 (Al-resistant) and S169 (Al-sensitive) as experimental materials were cultured in the nutrient solution to measure morphological and physiological indexes after 4 weeks with treatments of 0, 50, 100, 150, 200 and 300 μmol·L^-1 aluminum (pH 4.5). The results showed that the main root length, total root length, total root surface area, root average diameter and total root volume of R178 had no significant difference in 50 μmol·L^-1 aluminum , while compared with the control group, the root-related morphological indexes of S169 had significant difference. In addition, the total number of root tips increased first and then decreased with the increase of aluminum treatment concentration, and other morphology parameters decreased continually with the increase of aluminumconcentration; Under the treatment of 300 μmol·L^-1 aluminum , the relative elongation of the main root decreased 65.7% and 79.7%, respectively, in the two varieties than the control group. The content of soluble protein and proline in the seedlings roots of the two varieties increased first and then decreased with the increase of aluminum concentration, with the content of soluble protein decreased and proline increased in leaves with the increase of aluminum concentration, respectively. Under aluminum stress, the plasma membrane permeability of decrease both roots and leaves at seedling stage of two varieties increased significantly, under the treatment of 300 μmol·L^-1 aluminum concentration, the relative electrolyte exosmosis rate in roots of R178 and S169 increased by 54% and 59%, and in leaves increased by 82% and 90%, respectively. Under the same treatment, the electrolyte exosmosis rate of R178 roots and leaves was lower than that of S169. The activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in the roots of two varieties first increased and then decreased with the increase of aluminum concentration. SOD activity in R178 leaves increased with the increase of aluminum concentration, SOD activity in leaves of S169 first increased and then decreased and when the aluminum concentration is 200 μmol·L^-1, it reached the maximum value. The activities of POD, CAT and APX in the leaves of two varieties showed the same trend that increased first and then decreased with the increase of aluminum concentration. The results showed that aluminum stress inhibited root growth significantly and damaged the integrity of cytoplasmic membrane of rapeseed. Rape seedlings resist aluminum stress by accumulating the protein and proline content and increasing protective enzyme activity. These results provide a theoretical basis for the selection of resources and breeding of new cultivars of aluminum-tolerant rapeseed.

Key words: aluminum stress, seedlings of Brassica napus L., morphological parameters, physiological characteristics

摘要：

为探讨油菜幼苗在不同浓度铝胁迫下的生理响应,以2个耐铝毒差异显著的油菜品种(耐铝品种R178和铝敏感品种S169)为试验材料,在营养液培养条件下,共设置0(对照)、50、100、150、200和 300 μmol·L^-1 6个铝(pH值4.5)处理,研究铝胁迫对油菜根系形态及生理指标的影响。结果表明,50 μmol·L^-1铝处理下R178各根系形态指标与对照相比均无显著差异,而S169根系各形态指标与对照均差异显著,其中总根尖数随着铝处理浓度的增加呈先升高后降低的趋势,其他根系指标均随着铝处理浓度的增加呈逐渐减少的趋势,300 μmol·L^-1铝处理下,2个品种的主根相对伸长率较对照分别减少65.7%和79.7%。随着铝处理浓度的增加,2个品种幼苗根系中可溶性蛋白和脯氨酸含量均呈先升高后降低的趋势,叶片中可溶性蛋白含量呈降低趋势,而脯氨酸含量则呈升高的趋势。铝胁迫导致2个品种幼苗根系和叶片的质膜透性显著增加,300 μmol·L^-1铝处理下R178和S169根系相对电解质外渗率较对照分别增加54%和59%,叶片中分别增加82%和90%,同一处理下R178根系和叶片电解质外渗率均小于S169。随着铝处理浓度的增加,2个品种根系中的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性均呈先增加后降低的趋势;R178叶片中SOD活性呈增加趋势,而S169则呈先增加后降低的趋势,且在200 μmol·L^-1时达到最大值;2个品种叶片中的POD、CAT和抗坏血酸过氧化物酶(APX)活性均呈先增加后降低的趋势。综上,铝胁迫显著抑制了油菜根系生长,破坏了细胞质膜的完整性,油菜幼苗通过蛋白质和脯氨酸含量的积累以及保护酶活性的增高抵抗铝胁迫。本研究结果为耐铝油菜资源筛选和新品种选育提供了理论依据。

关键词: 铝胁迫, 油菜幼苗, 形态指标, 生理特性