Study On The Alleviating Effect Of Dopamine Pretreatment On The Drought Stress Of Watermelon

Watermelon production plays an important role in the agricultural structure of our country.Among all the environmental factors that affect watermelon yield,drought is one of the most important limiting factors.Drought not only seriously affects the growth of watermelon,but also restricts the development of agriculture in China.Dopamine can regulate cell activities,scavenge reactive oxygen species,and improve the ability of plants to resist drought,high temperature,high salt,cold and other adversity.Therefore,it is important to study exogenous dopamine for the growth of watermelon under drought stress.In this test,drought-sensitive cultivar‘Jingxin No.2’and drought-tolerant cultivar‘Nongkeda No.11’were selected as experiment material for pot experiment,and dopamine was used for root treatment.Measure the watermelon growth and physiological indicators every 10 days,study the exogenous dopamine on the growth of watermelon under drought stress,explore the physiological role and mechanism of exogenous dopamine when resisting drought stress,and provide a theoretical reference for the relief of watermelon drought.The results showed as follows:1. Exogenous dopamine treatment can significantly promote the increase of watermelon plant height,stem thickness,leaf number and leaf area under drought stress,increase dry and fresh weight of above-ground and underground parts of watermelon and increase root vitality,and promote the plant’s effect on water and nutritional elements.Absorption and utilization alleviate the change of the tissue structure of watermelon leaves and ensure the healthy growth of watermelon plants.Moreover,the effect of‘Jingxin No.2’,which is weaker in drought resistance,is more significant than that of‘Nongkeda No.11’.2. Under drought stress,the content of chlorophyll a,chlorophyll b and carotenoids of two watermelon varieties increased significantly,and‘Nongkeda No.11’increased more than‘Jingxin No.2’.Exogenous dopamine pretreatment significantly increased the content of chlorophyll and carotenoids in watermelon leaves under drought stress,increased the net photosynthetic rate（Pn）of watermelon leaves,effectively promoted the photosynthesis of watermelon under drought stress and promoted the plant material Volume accumulation.It effectively relieved the decrease of Fm,Fv/Fm,Y（Ⅱ）and the increase of NPQ and Fo caused by drought stress.3. Drought stress promoted a large accumulation of reactive oxygen species such as H₂O₂ in the leaves of two watermelon varieties,which caused membrane peroxidation,increased MDA content and relative conductivity,increased membrane permeability,and proline accumulation to cope with the effects of drought stress.Comparing‘Jingxin No.2’and‘Nongkeda No.11’found that under drought stress,the former accumulated more MDA and H₂O₂ than the latter,while the accumulation of proline was the latter more than the former.Dopamine pretreatment under normal pouring can reduce the content of MDA and H₂O₂.Exogenous dopamine treatment significantly alleviated the accumulation of H₂O₂under drought stress,reduced the relative conductivity and MDA content of watermelon,and further increased the Pro content.At the same time,the activities of catalase（CAT）and ascorbate peroxidase（APX）are increased and the activity of peroxidase（POD）is reduced,which improves the antioxidant capacity of the plant and promotes the plant’s defense against drought stress.Exogenous dopamine treatment can effectively alleviate the inhibitory effect of drought stress on sucrose synthase（SS）,at the same time increase the activity of acid invertase（AI）,alkaline invertase（NI）,sucrose phosphate synthase（SPS）,and enhance the coordination of watermelon plants the ability of carbon metabolism.4. Exogenous dopamine treatment significantly increased the weight of the horizontal,vertical and single melon of watermelon fruits,reducing the organic acid content and soluble sugar content that affected fruit quality,while increasing the protein content,effectively alleviating drought stress on watermelon fruit yield and the impact of quality.In summary,exogenous dopamine treatment can effectively alleviate the accumulation of active oxygen,promote the activities of antioxidant enzymes and carbon metabolism-related enzymes,regulate the metabolism of substances in the plant,promote the growth of watermelon plants,and effectively alleviate the effects of drought stress on plants.