Effect Of Fulvic Acid On Drought Resistance Of Huangguoguo Seedlings Under Drought Stress

Sichuan Province is one of the main producing areas of citrus in China.Around 2000,Sichuan Province began to try to promote late-ripening citrus.Sichuan has a unique natural climatic condition and is a suitable planting area for late-maturing citrus.At present,the asbestos and yellow-orange industry is developing well.Due to the special growth environment of the tree species?dry and hot valley?,the demand for irrigation is large and the production management cost is increased.The large demand for water has constrained the further development of the industry.In this experiment,the effects of different concentrations of fulvic acid on the drought resistance of Huangguoguo seedlings under drought stress were studied by using Citrus‘Huangguogan'seedlings.The effects of different concentrations of fulvic acid on drought stress were compared.Photosynthetic characteristics of the lower yellow kumquat seedlings during growth.In order to improve the drought resistance of citrus fruit trees and provide scientific basis for scientific irrigation,it has guiding significance for production practice.The main findings are as follows:?1?Under drought stress,spraying different concentrations of fulvic acid?FA?increased the content of soluble sugar,soluble protein and proline in the leaves of Huangguoguo,and increased the activity of catalase?CAT?and peroxidation.The activity of enzyme?POD?and superoxide dismutase?SOD?reduced the content of malondialdehyde?MDA?and increased the relative water content?RWC?of the leaves of Huangguoguo,which improved the water retention of the leaves and eased the degree of disaster of Huangguoguo.?2?Spraying different concentrations of fulvic acid increased the net photosynthetic rate and instantaneous water use efficiency of the yellow citrus seedlings,and increased with the increase of the concentration of fulvic acid,and 600 mg·L^-11 increased the most.Under drought stress,leaf transpiration rate and leaf stomatal conductance showed a downward trend.It can be seen that the transpiration rate of plants decreased with the increase of drought stress,and the transpiration rate decreased with the increase of fulvic acid concentration.The treatment with 600 mg·L^-11 reached the lowest value,indicating that the application of fulvic acid inhibited the water content per unit area of leaf leaf transpiration,slowed the loss of water,reduced the degree of stomatal opening,and inhibited the occurrence of photosynthetic reaction.With the increase of fulvic acid concentration,the F_v'/F_m'and NPQ indexes of F_o,F_m,F_v,qP and PSII in the leaves of Huangguoguo seedlings were significantly increased,while the F_o/F_v of PSII was opposite.Spraying fulvic acid prevents the leaves from using more light energy for photochemical electron transport,improving the light inhibition of the plants under drought conditions and enhancing their drought resistance.?3?Principal component analysis showed that the weights of drought resistance physiological indexes of Huangguoguo under drought stress were:chlorophyll content?POD?proline content?soluble protein content?Tr?Gs?CAT?SOD?Pn?WUE.According to the membership function method,the drought resistance of Huangguozi treated with400mg·L^-1fulvic acid under drought stress was the strongest.