干旱胁迫及复水对‘波叶金桂’生理特性的影响

以‘波叶金桂’Osmanthus fragrans ‘Boyejingui’幼苗为材料，采用人工控制水分模拟干旱及复水的处理方法，对‘波叶金桂’在抗旱防御反应系统中渗透调节物质和抗氧化酶的生理响应调控机制进行了研究。结果显示:随着干旱胁迫时间延长，叶片相对含水量和叶水势均下降，干旱胁迫20 d时分别比对照降低了28.0%和76.9%（P < 0.05）；可溶性糖、甜菜碱和游离脯氨酸等渗透调节物质质量分数随干旱天数的增加而升高，干旱胁迫16 d可溶性糖和甜菜碱分别比对照增加了48.7%和53.5%（P < 0.05），干旱胁迫20 d时，游离脯氨酸比对照增加了3.44倍（P < 0.05）；随着干旱胁迫时间延长，叶绿素（叶绿素a，叶绿素b和总叶绿素）质量分数呈降低的趋势，干旱胁迫20 d分别比对照降低了19.0%，16.2%和18.4%（P < 0.05），叶绿素a/b趋势为先降低后增加；随着干旱胁迫时间的延长，超氧阴离子（O₂·-），过氧化氢（H₂O₂）质量摩尔浓度逐渐增加，相应膜脂过氧化作用加强，膜被损伤，叶片的伤害率增加，干旱胁迫20 d时，各指标均达到最大值；过氧化物酶（POD），过氧化氢酶（CAT）和超氧化物歧化酶（SOD）活性随着干旱胁迫延长表现为先升后降，干旱胁迫16 d时SOD和CAT分别比对照增加了31.7%和89.6%（P < 0.05），POD活性比对照增加了1.36倍（P < 0.05）。复水6 d后，各指标都能得到一定程度的恢复。由此可见，在干旱胁迫前期，‘波叶金桂’通过增加渗透调节物质、抗氧化酶活性等保护自身不受干旱胁迫伤害；随着胁迫时间延长和胁迫度提高，抗氧化酶活性下降，可溶性糖和甜菜碱质量分数稍有减少，游离脯氨酸质量分数持续上升，说明渗透调节物质在抗旱胁迫中发挥主要作用，增加植物的抗干旱能力；复水后，‘波叶金桂’的各生理指标得到恢复，表现出较强的耐旱特性。

Physiological characteristics of Osmanthus fragrans 'Boyejingui' with drought stress and rewatering

To reveal the physiological response mechanism for osmotic adjustment substances and antioxidant enzymes in a drought-resistant defense response system, seedlings of Osmanthus fragrans 'Boyejingui' were used as materials to artificially control the water levels and simulate drought stress and rewatering. Results showed that with prolongation of drought stress, there was a significant decrease (P < 0.05) in the relative water content (28.0%) and leaf water potential (76.9%) of leaves at 20 d compared to the ck. At 16 d of drought stress, the content of soluble sugar significantly increased 48.7% and betaine 53.5% compared with the ck (P < 0.05), and free proline significantly increased 3.44 times compared with the ck at 20 d (P < 0.05). Chlorophyll content at 20 d significantly decreased with the prolongation of drought stress (Chl a--19.0%, Chl b--16.2%, and Chl total--18.4%) (P < 0.05) compared with the ck. With prolongation of drought stress, the superoxide anion (O₂·-) and hydrogen peroxide (H₂O₂) contents increased gradually, membrane lipid peroxidation increased, the membrane was damaged, and the damage rate of the leaves increased. When drought stress was 20 d, each indicator reached its maximum value. With prolongation of drought stress, at 16 d SOD significantly increased (P < 0.05) (31.7%) and CAT significantly increased (P < 0.05) (89.6%), with POD content significantly increasing (P < 0.05) 1.36 times compared with the ck. Thus, in the early stage of drought stress, 'Boyejingui' protected itself from drought stress by increasing osmotic adjustment substances and antioxidant enzyme activities; with the prolongation of stress time and an increase in stress level, the antioxidant enzyme activity decreased, the content of soluble sugar and betaine decreased slightly, and the content of free proline continued to increase indicating that osmotic adjustment substances played a major role in drought resistance and increased the drought resistance of plants; after rewatering, the physiological indexes of O. fragrans 'Boyejingui' were restored showing strong drought tolerance characteristics.