刈割后黑麦草生理保护作用对其补偿性生长的影响

通过对黑麦草(Lolium perenne L)在轻度、中度、重度、全割刈割处理6 d和12 d后,残留叶片和叶片再生部分生长速率,超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活力,丙二醛、可溶性糖、脯氨酸含量的分析以揭示在刈割胁迫后叶片抗氧护酶活力和渗透调节物含量与其补偿性生长的关系,以及牧草耐刈性的生理调控机理。结果表明,轻度和中度及全割后叶片生长速率均高于对照,重度刈割低于对照。全割后叶片补偿性生长最明显、轻度和中度次之,重度刈割无补偿性生长。对照黑麦草叶片各部位抗氧化酶和渗透调节物含量不同,叶片顶部MDA含量较高,伴随着较高的SOD、CAT活力和较高的脯氨酸含量;叶片基部MDA含量最低,SOD、CAT活力及脯氨酸含量也较低。与对照相比,不同强度刈割6 d黑麦草再生叶和叶片平均MDA含量、SOD和CAT活力、可溶性糖和脯氨酸含量均较低。而不同强度刈割12 d,黑麦草再生叶和叶片平均MDA含量仍较低,但SOD和CAT活力增高,脯氨酸含量增加,POD活力和可溶性糖含量低于对照。这表明刈割在减少了叶面积,降低光合能力的同时,刈割伤害胁迫启动了牧草补偿性生长使残留叶片快速生长,而且残留叶片面积与其补偿生长速率成正相关。另外,虽然不同强度刈割下叶片补偿性生长速率不同,但不同强度刈割(12 d)均激活残留叶片抗氧化保护酶系统和促进脯氨酸积累。在补偿生长过程中,CAT和SOD能及时清除残留叶片中积累的氧自由基,维持较低的膜脂过氧化和细胞膜完整性,积累的脯氨酸能维护细胞水分平衡。因此,抗氧化酶(SOD和CAT)和渗透调节物(脯氨酸)在黑麦草刈割后受伤部位快速自愈及残留叶片快速补偿生长中起重要生理保护作用。

Relationship between physiological protection mechanisms and the compensatory growth of Lolium perenne L. at different cutting treatment levels

Grazing and cutting of forages can promote its compensatory growth, which plays an important role in maintaining growth, and resistance to mowing, grazing, trampling. However, little is known about the physiological mechanisms involved in the compensatory growth of grasses. In this study, the growth rate, superoxide dismutase(SOD), peroxide(POD), and catalase(CAT) activities; and soluble sugar, proline, and malondialdehyde(MDA) contents were investigated in the leaves of Lolium perenne L. Light, moderate, severe, and whole cutting levels were used to determine the relationships between antioxidant enzyme activities, osmoregulation and compensatory growth, and the physiological mechanisms of compensatory growth of grasses after cutting. The results showed that the growth rate was higher in the leaves after cutting at the light, moderate, and whole cutting levels, but was lower in the leaves at the severe cutting level than that of control. Compared to that of the control, L. perenne showed significant compensatory growth under light, moderate, and whole cutting levels, and no compensatory growth occurred under severe cutting levels. Normally, in L. perenne, the top of the leaves had higher MDA contents, SOD, and CAT activities, and the base of the leaves had lower MDA, proline contents, SOD, and CAT activities. Compared to the control, at 6 days after different cutting levels, the regrowth of L. perenne leaves had lower MDA, soluble sugar, and proline contents, and lower SOD, and CAT activities. Whereas, at 12 days after different cutting levels, the regrowth of L. perenne leaves still had lower MDA contents, but higher SOD, CAT activities, and proline content. This indicated that cutting decreased the leaf area, reduced the photosynthetic energy availability, and enhanced the compensatory growth function of residual leaves. Therefore, cutting damage was an internal factor resulting in compensatory growth. The compensatory growth rate was correlated positively with the residual leaf size. In addition, although there were differences in the compensatory growth rate in the residual leaves among different cutting levels, the different cutting levels all activated antioxidant enzymes and enhanced proline accumulation. During the compensatory growth of residual leaves, SOD and CAT could scavenge active oxygen free radicals produced during photosynthetic metabolism, inhibit membrane lipid peroxidation, maintain the balance of oxygen free radicals metabolism; and accumulated proline could maintain water balance. Therefore, antioxidant enzymes and osmoregulation play an important role in physiological protection, including photosynthesis and compensatory growth, during rapid self-healing after cutting of residual leaves in L. perenne.