| With global warming,the problem of water shortage is becoming more and more prominent.Drought has become a major factor restricting plant growth.Sphaeropteris lepifera have strict environmental requirements in the process of growth and development,and often face the problem of drought discomfort.Therefore,it is of great value to study the physiological mechanism of drought resistance in Sphaeropteris lepifera and take measures to alleviate drought stress.In order to explore the alleviating effect of exogenous substances on the growth of Sphaeropteris lepifera under drought stress and its physiological mechanism,the Sphaeropteris lepifera seedlings cultured in the laboratory were subjected to natural drought stress,and the leaves were sprayed with69.06 mg·L-1,138.12 mg·L-1 and 207.18 mg·L-1 SA solution,0.1 mg·L-1,0.2 mg·L-1and 0.3 mg·L-1 EBR,11.614 mg·L-1,23.228 mg·L-1 and 34.842 mg·L-1 MT solution,50 mg·L-1,100 mg·L-1 and 150 mg·L-1 PP333 solution,277.46 mg·L-1,554.92 mg·L-1and 1109.84 mg·L-1 Ca Cl2 solution were used to determine the growth and related physiological indicators of seedlings.The results are as follows:(1)Drought stress resulted in a significant decrease in the growth of plant height and a significant increase in the growth of roots.The application of exogenous SA,EBR,MT,PP333 and Ca Cl2 significantly alleviated the plant height of seedlings,made the growth close to the normal watering state,and further promoted the growth of roots.Among them,SA and EBR treatment had the most obvious alleviating effect on the plant height,and SA,EBR and Ca Cl2 treatment had the most obvious promoting effect on the growth of underground part.(2)Drought stress reduced the photosynthesis of Sphaeropteris lepifera seedlings,which was manifested by reducing the net photosynthetic rate,stomatal conductance,transpiration rate and chlorophyll content.The net photosynthetic rate,stomatal conductance and transpiration rate of seedling leaves treated with SA,EBR,MT,PP333and Ca Cl2 remained at a high level,so that the assimilation ability of plants remained at a high level.Compared with drought treatment,the chlorophyll content of plants treated with exogenous substances also increased.Among the five exogenous substances,SA and MT had the best alleviation effect on photosynthesis of Sphaeropteris lepifera seedlings under drought stress.(3)Drought stress increased malondialdehyde production,it intensifies the membrane peroxidation,increases the relative conductivity and increases the membrane permeability.Exogenous spraying of SA,EBR,MT,PP333 and Ca Cl2 could effectively slow down the accumulation of malondialdehyde,reduce the relative conductivity and reduce the degree of membrane lipid peroxidation.SA and EBR had the best remission effect.(4)With the intensification of drought stress,the activities of superoxide dismutase and peroxidase first increased and then decreased,and the activity of catalase decreased significantly.Exogenous spraying of SA,EBR,MET,PP333 and Ca Cl2 could maintain the activities of the three enzymes under drought stress.(5)Drought stress significantly increased the osmotic and regulatory capacity of soluble sugar and proline in plants.The application of exogenous SA,EBR,MT,PP333and Ca Cl2 significantly alleviated the accumulation of soluble sugar,which may be related to factors such as exogenous material treatment enhanced the activity of plant antioxidant enzymes,it reduces the accumulation of reactive oxygen species and causes less damage to plants in the early stage.In conclusion,drought stress exacerbated membrane lipid peroxidation,improved membrane permeability,reduced aboveground growth,the net photosynthetic rate,stomatal conductance,transpiration rate and chlorophyll content,and significantly damaged Sphaeropteris lepifera.Foliar spraying of five kinds of exogenous substances can alleviate the growth of the Sphaeropteris lepifera seedlings under drought stress,improve photosynthesis intensity,enhance reactive oxygen species scavenging ability,reduce cell membrane damage,thereby improving the drought tolerance of plants.Among them,207.18 mg·L-1 SA solution,23.228 mg·L-1 and 34.842 mg·L-1 MT solution and 0.3 mg·L-1 EBR solution had the best remission effect. |
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