Metabolic Characteristics And Physiological Mechanism Of Carotenoids In Alfalfa Under Water Changing Conditions

Carotenoid is one important antioxidant in plants.Water is the important factor affecting the synthesis and metabolism of carotenoids in plants.It can provide theoretical basis for breeding and cultivation of drought-resistant varieties through clarifying the relationship between carotenoid content and drought-resistance in alfalfa.In this study,Xinjiang Daye alfalfa?native species?and Sanditi?introduced species?alfalfa were used as research materials.Experiments were conducted under potted plants with water and carotenoid inhibitors treatment to compare the response of morphological and physiological ecology and the differences under changing water condition during the flowering period.The main results are as follows:1.The application of a carotenoid inhibitor suppressed the expression of genes involved in the metabolism of carotenoids?PSY,LCY,CHY and NCED genes?.In the course of the decline of soil moisture,the gene expression level of Xinjiang Daye first decreased and then increased,and Sanditi showed an increase first and then decreased.Under drought and carotenoid inhibitor,the?Antheraxanthin+zeaxanthin?/?Antheraxanthin+zeaxanthin+Violaxanthin?[?A+Z?/?A+Z+V?]of alfalfa decreased.2.Photosynthetic parameters of Xinjiang Daye and Sanditi were inhibited to varying degrees during the decline of soil moisture,and Sanditi's inhibition was greater than that of Xinjiang Daye.The qP value increased and the NPQ value decreased significantly of alfalfa.The application of carotenoid inhibitors has a greater impact on the G_s values of alfalfa.WUE_i of Xinjiang Daye(the application of inhibitors and non-application of inhibitors increased from3.50 and 4.34?mol mol^-1 to 15.46 and 14.78?mol mol^-1,respectively.)rose more than Sanditi(increased from 1.80 and 2.58?mol mol^-1 to 6.60 and 8.71?mol mol^-1,respectively)under drought.3.The decrease of soil water content,MDA content and antioxidase activities increased.The application of carotenoid inhibitors had no effect on above-ground morphological indicators?plant height,leaf area,number of branches,stem diameter?and biomass of Xinjiang Daye and Sanditi,but significantly promoted the reduction of its root diameter,the root lengths and root surface areas are significantly increased below 20 cm,and the growth of root systems after applying carotenoid inhibitors tends to be finer and longer to absorb water and nutrients more effectively.In summary,drought and rewatering affected the growth,physiological,biochemical processes,and biomass allocation of the two alfalfa species,but it had a greater impact on Sanditi,and its ability to recover after rehydration was weaker than that of Xinjiang Daye.Carotenoids significantly influence the physiological processes associated with their metabolic activities under drought conditions,such as promoting stomatal closure,increasing heat dissipation in the photosystem,and increasing antioxidant enzyme activity.The physiological processes of Xinjiang Daye are more affected by carotenoids.Xinjiang Daye showed better drought resistance than Sanditi,and could be used as the preferred species for cultivation in the dryland area.