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干旱胁迫对乐昌含笑幼苗生长及生理特性的影响

Effects of Drought Stress on Growth and Physiological Characteristics of Michelia chapensis Seedlings

  • 摘要: 为探究乐昌含笑幼苗对干旱胁迫的生长、生理适应机制,通过盆栽控水试验,设置CK、轻度干旱、中度干旱和重度干旱4个水分处理梯度,测定胁迫60 d后幼苗的生长、光合及生理生化指标,进行多重比较及相关性分析。结果表明:随着干旱胁迫加剧,幼苗株高、地径增长量及叶长、叶宽、叶面积均显著降低,重度干旱下根长与生物量降幅超过30%;净光合速率、气孔导度、胞间CO2浓度、蒸腾速率及光合色素含量均下降,重度干旱组显著低于其他处理;脯氨酸、可溶性蛋白含量及超氧化物歧化酶活性、丙二醛含量随干旱程度加深显著升高,可溶性糖含量则呈先降后升趋势,于中度干旱时最低。株高增长量与叶片形态指标呈显著正相关,与脯氨酸、丙二醛含量呈显著负相关;总叶绿素含量与可溶性蛋白、丙二醛含量呈显著负相关。本研究揭示了乐昌含笑幼苗对干旱胁迫具有阶段性响应特征,乐昌含笑幼苗可通过形态调整、光合抑制及渗透调节等机制适应轻中度干旱,但重度干旱会导致不可逆损伤。

     

    Abstract: To investigate the growth and physiological adaptive mechanisms of Michelia chapensis seedlings under drought stress, a pot experiment with controlled watering was conducted. Four soil moisture treatments were established: CK, mild drought, moderate drought, and severe drought .After 60 days of treatment, growth, photosynthetic, and physiological-biochemical indices were measured. The results indicated that as drought stress intensified, the increments in plant height and ground diameter, along with leaf length, width, and area, decreased significantly. Under severe drought, root length and total biomass declined by over 30%. Net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, and chlorophyll content were all reduced, with the severe drought group exhibiting significantly lower values than other treatments. Conversely, the contents of proline and soluble protein, as well as the activity of superoxide dismutase (SOD) and the content of malondialdehyde (MDA), increased significantly with intensifying drought. The soluble sugar content exhibited a "V-shaped" trend, reaching the lowest level under moderate drought and then rising under severe drought.Correlation analysis revealed that the increment in plant height was significantly positively correlated with leaf morphological traits, but significantly negatively correlated with proline and MDA contents. Additionally, photosynthetic pigment content showed a significant negative correlation with soluble protein and MDA contents. These findings reveal that M. chapensis seedlings exhibit distinct stage-specific responses to drought stress: they can tolerate mild-to-moderate drought through morphological adjustments, photosynthetic down-regulation, and osmotic regulation; however, severe drought induces irreversible physiological damage. This study provides a theoretical basis for seedling cultivation and water management of this species in arid regions.

     

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