遮阴和干旱对荩草生理代谢及抗性系统影响的协同作用

引进草种在亚热带边坡草坪上常遭遇遮阴和干旱,造成草坪退化甚至死亡。以具有边坡草坪开发价值的本土植物野生荩草为材料,设置5种遮阴度和4种干旱度交互形成20种协同处理,研究遮阴和干旱对荩草生理代谢及抗性系统影响的协同作用。结果表明,荩草具有极强的耐阴和抗旱潜力,可通过光合策略、代谢策略、抗性策略使植株逐步适应或应对生境胁迫,在重度遮阴或干旱下仍可存活。遮阴或干旱对荩草光合作用、物质代谢、抗氧化酶系统和细胞膜完整性有极显著影响。遮阴和干旱对荩草光合指标、代谢指标、抗性指标和受伤害指标有显著协同作用。Pn主要受遮阴影响,Gs主要受干旱影响,适度遮阴和干旱协同处理可提高荩草光合能力。干旱对荩草物质代谢的影响大于遮阴,氮代谢比糖代谢和呼吸作用受干旱或遮阴的影响更大,适度遮阴和干旱协同作用可改变荩草代谢水平。遮阴、干旱对抗氧化酶活性的影响不同,遮阴和干旱对POD有显著协同作用,对SOD和CAT有极显著协同影响,适度遮阴和干旱协同作用可提高荩草抗氧化酶活性。遮阴、干旱对细胞膜伤害性物质的含量影响不同,遮阴和干旱对SP含量无协同作用,对Pro、H_2O_2和MDA含量有显著协同作用,协同作用增加了荩草细胞膜受伤害的风险。遮阴和干旱对生理代谢及抗性系统影响的协同作用,提高了荩草的抗逆潜力和生态适应能力。

Synergistic effects of shade and drought on the physiological metabolism and resistance system of Arthraxon hispidus

In the present study, wild Arthraxon hispidus, a plant with potential uses in sloped lawn development, was used as the test material and was subjected to 20 factorial treatments with five shade gradients (0, 10%, 30%, 50%, and 70%) and four drought gradients (enough moisture (W0), mild drought (W1), moderate drought (W2), and severe drought (W3)). After a 36 day treatment, the following indices were determined:(1) photosynthetic parameters, including photosynthetic rate (Pn), transpiration rate (Tr), intercellular CO₂ concentration (Ci), and porosity (Gs); (2) antioxidant enzyme system parameters including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT); (3) parameters associated with metabolism, including soluble sugar (SS), acetic acid (PA), and nitrate reductase (NR) activity; and (4) parameters associated with cell membrane damage, including malondialdehyde (MDA), proline (Pro), soluble protein (SP), and hydrogen peroxide (H₂O₂). The objective of the study was to analyze the synergistic effects of shade and drought on the physiology, biochemistry, and resistance system of A. hispidus. The results showed that shade, drought, and their interaction had a significant effect on photosynthetic physiology (P < 0.05). Shade was the main factor affecting Pn, whereas drought was the main factor affecting Gs, Ci, and Tr. Shade gradients of 30% or less alleviated the extent of reduction of Pn, Tr, Ci, and Gs caused by drought. The synergistic effect of shade and drought on the photosynthetic parameters decreased in the order Tr > Ci > Pn > Gs. Shade, drought, and their interaction also had a significant effect on SS, PA, and NR (P < 0.05). Drought was the main factor affecting metabolism, followed by the interaction and shade alone. The SS and PA content decreased and increased, respectively, with increasing shade gradient, whereas they both increased with the increasing degree of drought. NR activity was the most affected by drought and shade stress. Their synergistic effects on the parameters associated with metabolism decreased in the order PA > NR > SS. Shade, drought, and their interaction also had a significant effect on the antioxidant enzyme system (P < 0.05). With an increasing degree of shade or drought, the resistance index first significantly increased, and then significantly decreased. Drought was the main factor affecting the resistance index, followed by shade and their interaction. Shade gradients in the range 10%-30% increased the resistance index under moderate drought and increased SOD and POD activity under severe drought. The synergistic effect of shade and drought on the antioxidant enzymes decreased in the order CAT > SOD > POD. Shade, drought, and their interaction also had a significant effect on the membrane damage indices (P < 0.05). Drought had a greater effect on H₂O₂, Pro, and SP than did shade, whereas shade had a greater effect on MDA than did drought. Shade and drought had no synergistic effect on SP, a significant synergistic effect on Pro (P < 0.05), and a highly significant synergistic effect on H₂O₂ and MDA (P < 0.01). Thus, synergistic effects of shade and drought improved the photosynthetic capacity, metabolic rate, and resistance potential of A. hispidus, which may increase the ecological adaptability of A. hispidus.