Effects Of Different Alfalfa Extract Treatment Modes On Seedling Growth And Cold Resistance Of Early Rice

Hunan Province is the main rice growing area of double season rice in China.The early rice seedling stage is easy to suffer from cold in spring and cold,which causes rotten and dead seedlings,which seriously affects the production of early rice.Alfalfa(Medicago Sativa Linn)is a perennial herb of legume,which has the characteristics of strong cold resistance and high resistance to stress.The stem and leaf extracts of alfalfa are rich in proline,and proline can protect the structure of plant cells when they are cold damaged by low temperature.Therefore,alfalfa extract may have the ability to enhance the resistance to cold damage at low temperature.As a product of phenylalanine metabolism,salicylic acid has been widely used in the research of plant resistance and other resistance.It is combined with plant extract rich in proline,which may further improve the cold resistance of rice seedling.In this study,the main early rice varieties,Lu Liangyou 996,were selected in the middle and lower reaches of the Yangtze River.The cold resistance effect was selected by studying the growth status and physiological and biochemical indexes of early rice seedlings,and the cold resistance effect was clear The processing mode that is displayed.The results are as follows:(1)Compared with the fresh water,after the alfalfa leaching solution and alfalfa extract+ salicylic acid,the plant height of early rice increased significantly,while the fresh weight of the upper part and the fresh weight in the underground decreased significantly.Among them,the chlorophyll content also increased significantly under the treatment of alfalfa extract and salicylic acid.The results showed that the application of alfalfa extract,alfalfa extract and salicylic acid had a positive effect on plant height in seedling stage,but inhibited dry fresh weight.(2)Compared with the control,the treatment of alfalfa extract and alfalfa extract +salicylic acid alleviated the inhibition of cold damage on the growth of rice seedlings.The seedling height of each treatment was significantly increased on the third and fifth days of low temperature,and the fresh weight of the underground was significantly increased in the treatment of Alfalfa leaching,alfalfa extract and salicylic acid.On the 5th day of recovery,the plant height,chlorophyll content,fresh weight on the upper ground and dry weight of the upper part of the ground were significantly higher than CK treatment,while in the alfalfa leaching solution,alfalfa extract + spraying,alfalfa extract + salicylic acid,alfalfa extract +salicylic acid and spraying treatment,the fresh weight and the dry weight of the underground were significantly higher than CK treatment.(3)On the third and fifth day of low temperature treatment,the initial fluorescence value(Fo)of rice seedling leaves increased with the time,indicating that low temperature stress damaged the PS Ⅱ reaction of seedling leaves.On the fifth day of recovery,the value of fo in rice leaves decreased significantly after the alfalfa leaching,alfalfa extract + salicylic acid and spraying treatment.Fv/Fm is an important index to study the effect of environmental stress on photosynthesis,which will be reduced by low temperature stress.At the third day of low temperature,the Fv/Fm value of alfalfa extract was significantly higher than CK treatment.On the 5th day of low temperature,Fv/Fm of each treatment gradually converged.But when the temperature was restored for 5 days,except CK,the Fv/Fm value of other treatments recovered to normal level,and was significantly higher than CK treatment.The results showed that the treatment of rice seedlings with alfalfa extract and alfalfa extract + salicylic acid could alleviate the damage of PS Ⅱ under low temperature stress to different degrees.(4)Under low temperature stress,alfalfa extract + salicylic acid soaking and spraying had significant effect on the improvement of SOD,root SOD,cat and CAT activity of leaves.During the recovery of normal temperature,SOD and pod enzyme activities of rice seedlings increased faster than CK treatment in the treatment of Alfalfa leaching solution,alfalfa extract and spraying,which indicated that the enzyme activity of rice seedlings under low temperature stress could be improved by soaking seeds from alfalfa extract,soaking in alfalfa extract and spraying treatment.(5)The content of proline and soluble protein in the seedlings was increased by soaking and spraying alfalfa extract,alfalfa extract + salicylic acid,and the content of malondialdehyde in seedling stage was decreased.The content of proline was significantly increased by seed soaking and spraying treatment,and soluble protein content was significantly increased by alfalfa extract + salicylic acid and spraying treatment,and malondialdehyde content was significantly reduced.