海滨滨麦叶片和根对不同厚度沙埋的生理响应差异分析

以烟台海岸抗风沙植物滨麦为研究材料,通过对不同厚度沙埋下其叶片和根部抗氧化酶活力(超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT))、丙二醛(MDA)含量和渗透调节物含量变化的分析,探讨了叶片和根部对沙埋生理响应的差异。试验按滨麦成株株高(约40 cm)对其进行了轻度沙埋(在株高1/4处)、中度沙埋(2/4处)和重度沙埋(3/4处)。在沙埋第6天,分别测定了不同厚度沙埋处理下,植株各段叶片和根抗氧化酶活力、MDA和渗透调节物含量。结果表明,轻度和中度沙埋均加速植株生长。与对照相比,经轻度、中度沙埋处理6 d,叶片平均MDA含量增加,在重度沙埋下降低。不同厚度沙埋6 d,叶片平均SOD活力和脯氨酸含量增加,而CAT活力、可溶性糖和可溶性蛋白质含量下降。但不同厚度沙埋均使沙上叶片MDA、脯氨酸、可溶性蛋白质含量和SOD和CAT活力增加,尤其是叶片顶部增加最为明显,使沙下叶片MDA、可溶性糖、可溶性蛋白质含量和CAT活力下降,导致同株沙上和沙下叶片MDA、脯氨酸、可溶性糖、可溶性蛋白质含量和SOD和CAT活力差异显著(P0.05)。与叶片相比,根中MDA、可溶性蛋白质含量和SOD和CAT活力较低,而POD活力和可溶性糖含量较高并与叶片差异显著(P0.05)。不同厚度沙埋6 d,滨麦根中MDA和可溶性蛋白质含量变化较小,可溶性糖含量和CAT、POD、SOD活力略有降低。研究表明,滨麦根和叶片对不同厚度沙埋的生理响应不同。沙埋直接作用于叶片并诱发叶内氧自由基积累,但叶片通过快速激活的抗氧化酶保护系统(CAT、SOD)维持氧自由基代谢平衡,以及渗透调节物(脯氨酸、可溶性糖)的积累维护细胞水分代谢平衡,并满足能量的需求和快速生长。但在不同厚度沙埋下,由于根系不受沙埋直接影响而生理变化较小,并且还维持较低的膜脂过氧化水平,这可能是根能维持正常的吸水输水功能并在沙埋处理过程中和沙埋后地上叶片快速生长摆脱沙埋的重要物质基础。

Analysis of the different physiological responses of Leymus mollis (Trin.) Hara leaves and roots to sand burial on the coast of Yantai, China

In this study, we tested the physiological responses of Leymus mollis (Trin.) leaves and roots to sand burial on the Yantai coast of China to understand the biochemical and physiological adaptive mechanisms of this species to sand burial. Based on the height of L. mollis (about 40 cm) four levels of sand burial treatments were set up: no-sand burial (control), light sand burial (1/4 plant height), moderate sand burial (1/2 plant height), and severe sand burial (3/4 plant height). After 6 days of sand burial, samples were taken from the leaves and roots of plants in each treatment. Changes in malonaldehyde (MDA) content, an osmotic regulator, in addition to antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activity, were measured in the leaves above and below the sand and in the roots at various depths. Plants under light and moderate sand-burial grew fast until they protruded from the sand, becoming taller than control plants after 6 days. Compared to the control, the average MDA content increased in whole leaves under light and moderate sand burial, but and decreased in leaves subject to severe sand burial. In all three sand burial treatments, SOD activity and proline content increased in whole leaves, whereas CAT activity and soluble sugar and soluble protein contents decreased. In all three burial treatments, MDA, proline, and soluble protein content increased in leaves above the sand, along with SOD and CAT activity, especially in the top section of the leaves. In contrast, MDA, soluble sugar, and soluble protein content, in addition to CAT activity, decreased in the leaves beneath the sand. This resulted in significant differences in MDA, proline, soluble sugar, and soluble protein content, in addition to SOD and CAT activity, between leaves above and below the sand (P< 0.05). Compared to above ground leaves, underground roots had lower MDA and soluble protein content, in addition to lower SOD and CAT activity, but higher POD activity and soluble sugar content. After 6 days of sand burial, there was a small change in MDA and soluble sugar content, with soluble sugar content and CAT, POD, and SOD content slightly decreasing in the roots. On the same plant, leaves above ground had significantly higher (P<0.05) MDA and soluble protein content, along with higher CAT and SOD activity, than the underground roots. This result indicates that sand burial had a greater effect on the aboveground structures (branches and leaves) above ground compared to the underground structures. Sand-burial caused the accumulation of oxygen free radicals in the cells, which induced lipid peroxidation and activated the antioxidant enzymatic protection system to scavenge oxygen free radicals and maintain the metabolic balance of oxygen free radicals. This action also promoted osmotic adjustments to maintain the balance of water metabolism and provide energy and nutrition. Thus, under sand burial, it may be important to enhance cell antioxidant and osmotic adjustment capacity rapidly to maintain the balance of oxygen free radical metabolism and metabolic water balance, a key physiological regulation strategy for L. mollis for sand burial adaptation. Moreover, the root system was not affected by the different levels of sand burial, and continued to sustain lower levels of lipid peroxidation, allowing the roots to maintain normal functions of water suction and transportation, and to support the fast growth of leaves out of the sand.