干旱胁迫对食叶草种子萌发及幼苗生理特性的影响

Effects of drought stress on seed germination and physiological characteristics at seedling stage of leaf-eating grass

摘要:

【目的】研究干旱胁迫对食叶草种子萌发和幼苗生长的影响,探讨食叶草的适期播种及对干旱胁迫的响应机制。【方法】以食叶草种子为试验材料,采用盆栽方法,以不同浓度PEG模拟干旱胁迫,通过测定发芽率、叶绿素、抗氧化物酶等生理指标,分析干旱胁迫与种子萌发和幼苗生长的关系。【结果】随着PEG浓度的增加,食叶草种子的发芽率和发芽势均呈现下降的趋势,且在40% PEG和60% PEG处理下,食叶草种子均未发芽。随着PEG浓度和处理时间的增加,幼苗叶片的叶绿素、可溶性糖、可溶性蛋白、脯氨酸含量和过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)活性整体呈现先上升后下降的趋势,超氧阴离子(O₂^.-)、过氧化氢(H₂O₂)含量显著增加。表明食叶草幼苗受到干旱胁迫时,体内会出现大量的活性氧自由基,需要抗氧化酶系统协助清除。低浓度PEG干旱胁迫下,食叶草幼苗叶片会诱导脯氨酸和抗氧化酶以增强耐旱性;高浓度PEG干旱胁迫下,叶片抗氧化酶系统活性会减低,导致叶片生理代谢紊乱,食叶草耐旱性随之降低。【结论】干旱降低食叶草种子的萌发率,食叶草幼苗在干旱胁迫条件下,通过增加渗透调节物质、增强叶片酶活性、增强光合作用等来提高自身对干旱环境的适应性。

Abstract:

【Objective】The objective of this study is to study the effects of drought stress on seed germination and seedling growth of leaf-eating grass (Rumex sp. ), and to provide a theoretical basis for the appropriate sowing of leaf-eating grass and its response mechanism under drought stress.【Method】A pot experiment was conducted using leaf-eating grass seeds as experimental materials, and drought stress was simulated using different concentrations of polythylene glycol (PEG). The relationship between drought stress, seed germination, and seedling growth was studied by determining physiological indexes such as germination rate, chlorophyll content, and antioxidant enzyme activities.【Result】With the increase of PEG concentration, the germination rate and germination potential of leaf-eating grass seeds exhibited a downward trend, and the seeds of did not germinate under the of 40% and 60% PEG treatments. With the increase of PEG concentration and treatment duration, the contents of chlorophyll, soluble sugar, soluble protein, proline, peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) in seedling leaves overall increased first and then decreased, while the contents of superoxide anion (O₂^.-) and hydrogen peroxide (H₂O₂) increased significantly. These results indicated that when the seedlings of leaf-eating grass were subjected to drought stress, a large number of reactive oxygen species (ROS) free radicals were generated intracellularly, requiring the antioxidant enzyme system to assist in scavenging. Under drought stress at low concentrations of PEG, proline and antioxidant enzymes were induced in the leaves to enhance drought tolerance; but under drought stress with high concentrations of PEG, the activity of the leaf antioxidant system decreased, resulting in physiological and metabolic disorders in leaves, thereby reducing their drought tolerance.【Conclusion】Drought reduces the seed germination rate of leaf-eating grass. Under drought stress, leaf-eating grass seedlings improve their adaptability to drought environments through a series of responses, including increasing osmolyte contents, enhancing leaf enzyme activities, and enhancing photosynthesis.