Effects Of Drought On Physiological,Biochemical,Yield And Quality Of Ramie In Different Periods

Ramie(Boehmeria nivea L.),a perennial herbaceous fiber plant belonging to the genus Urtica,is an important natural textile fiber crop in China and a source of important vegetable protein feeds.The global droughts are occurring frequently.fiber ramie grow poorly in the second and third quarters of the year and the feed ramie also reduced the yield significantly with the influence of the summer drought,autumn drought,and the "fire south wind" in the Yangtze river valley.Therefore,the research on the mechanism of the change of ramie under drought stress has become a major issue that must be resolved in order to improve the drought resistance of ramie.In this study,drought stress treatments were performed on fiber ramie and feed ramie at different periods,respectively.7 physiological indexes such as leaf relative water content,soluble sugar,proline,malondialdehyde,superoxide dismutase,peroxidase,and catalase were determined.After mature harvest,the agronomic traits such as plant height,stem diameter,fresh weight of single plant,fresh weight of single stem,fresh weight of individual bark,skin thickness and the quality indexes such as fiber-containing gel fraction,breaking strength,elongation at break,and fiber fineness of fiber ramie were determined,the agronomic traits such as plant height,stem diameter,total fresh weight,fresh weight per plant,dry weight per plant,stem/leaf ratio,and nutrient quality components in stems and leaves of feed ramie were determined.Effects on physiological index,yield and quality of ramie under drought stress were analyzed.At the same time,the ramie plants were subjected to continuous drought treatment and dynamic sampling was performed to determine physiological indicators.The analysis of the physiological and biochemical indexes of ramie under drought stress and the study of the mechanism of the changes of ramie under drought stress can provide a theoretical basis for improving the drought resistance.The main results are as follows:1.The drought treatment of the fiber ramie plants in seedling stage,vigorous growth stage,and mature stage was carried out,respectively.The relative water content of leaves was significantly reduced compared with normal irrigation treatment.The soluble sugar content,proline content,and malondialdehyde content in the plants were both increased compared to normal irrigation treatments.The activity of SOD,POD and CAT in the antioxidant protection enzyme system were all higher than normal irrigation.Compared with normal irrigation,the plant height,stem diameter,fresh weight per plant,fresh weight of single stem,fresh weight per hectare and skin thickness of seedlings under drought stress treatment were not significantly affected.The plant height,stem diameter,fresh weight per plant,fresh weight of single stem and fresh weight of the vigorous growth stage plants under drought stress were significantly reduced,but the skin thickness was not significantly affected.The plant height,fresh weight of single plant,fresh weight of single stem,and fresh weight of fresh sesame in the mature stage plants under the treatment of drought stress were significantly reduced,but there was no significant difference in stem diameter and skin thickness.2.The drought treatment of the fiber ramie plants in three stages of seedling stage,vigorous growth stage and mature stage was carried out,respectively.There were no significant changes in the content of wax lipids,water solubles,pectin and lignin in fibers compared with normal irrigation treatments.The content of hemicellulose in the fiber of seedlings under drought stress decreased significantly,but there was no significant effect during the vigorous growth stage and mature stage under drought stress treatment.There was no significant effect in the content of cellulose on the drought stress treatment at seedling stage and mature stage,but it will be significantly increased at the vigorous growth stage under drought stress treatment.The fiber breaking strength of the plant at the seedling stage and vigorous growth stage under drought stress were not significantly affected,but it was significantly decreased at the mature stage plant under the drought stress treatment.There was no significant change in break elongation rate under drought stress in three stages.Moderate drought stress on the seedlings and vigorous growth plants can improve the overall quality of the fiber.The fiber breaking strength decreased under drought stress of the mature stage plants which was unfavorable to the fiber quality,but the fiber fineness was improved,which was conducive to the formation of fiber quality.3.Drought stress treatment of the feed ramie plants at the seedling stage and vigorous growth stage was carried out,respectively.Compared with the normal irrigation treatment,the relative water content of ramie leaves both decreased in three stages,the soluble sugar content,proline content and malondialdehyde content in the plants both increased.Similarly,the activities of SOD and POD in the antioxidant protection enzyme system increased,however,the activity of CAT increased at seedling stage and decreased at vigorous growth stage under drought stress.The plant height,stem diameter,total fresh weight,fresh weight per plant,and dry weight per plant of the ramie plant at the seedling stage and vigorous growth stage were all significantly affected and decreased under drought.The stem-leaf ratio was significantly increased at the seedling stage and significantly decreased at vigorous growth stage under drought.4.Compared to normal irrigation,the crude protein content of feed ramie at seedling stage had not been affected,the crude fat content increased significantly,and the crude ash content decreased significantly under drought stress.It was shown that the feed nutrient value of ramie plant increased when drought stress was encountered at the seedling stage.When vigorous growth stage ramie plants were under drought stress,the crude protein content and crude fat content were significantly reduced,and the crude fiber content was significantly increased,and the quality of ramie feed was reduced.Therefore,drought stress in vigorous growth stage will significantly affect the feed quality of ramie plants,it is necessary to fully satisfy the demand for water of ramie in the vigorous growth stage.5.For two materials of the fiber ramie and the feed ramie,the relative soil water content decreased with the extension of stress time.The soluble sugar content of the fiber ramie ncreased first and then decreased as the degree of stress increased,but it showed a trend of decreased first and thincreased in the feed ramie.The contents of proline and malondialdehyde in two ramies increased with the extension of stress time.The activity of SOD,POD,and CAT all showed a trend of increased first and then decreased with the extension of stress time.