Characteristics of Endogenous Hormone Variations in the Roots of Alfalfa(Medicago sativa L.) Cultivars of Different Fall Dormancies During SpringRegrowth Stage

Regrowth traits of alfalfa (Medicago sativa L.) in spring are closely related to its fall dormancy before winter. In order todetermine the relationship between fall dormancy (FD) grade and hormone variation pattern and provide academic referencesfor the variety improvement and production of alfalfa, the variations of gibberellins (GA3), indole-3-acetic acid (IAA), andabscisic acid (ABA) in alfalfa roots during regrowth period in spring were examined by high performance liquidchromatography (HPLC). The study involved seven alfalfa cultivars that belonged to four fall dormant grades, i.e., 2, 4, 6,and 8. The results showed that the differences in spring regrowth among the alfalfa cultivars were partially associatedwith their root hormone levels. The alfalfa cultivars that belonged to the same dormancy grades presented similarvariation trends in endogenous hormone content in their roots during the spring regrowth stage. At the early regrowthstage, cultivars with a higher dormant grade had a higher GA3 concent and a lower ABA content in their roots than thecultivars with a lower dormant grade; and IAA content in roots of non- and semi-fall dormancy cultivars was higher thanthat of fall dormancy cultivars. During the whole period of spring regrowth, the root ABA content of fall dormancy alfalfacultivar is significantly higher than those of semi- and non-fall dormancy cultivars. GA3 contents in the roots of allcultivars under study showed a double-peak dynamic curve; root IAA contents of the studied cultivars presented adownward trend. But the trend did not significantly differed among the different fall dormant cultivars. The higher GA3content and lower ABA content in root of non-fall dormancy alfalfa lead to its earlier regrowth. Regrowth time and rate ofalfalfa can be regulated by exogenous GA3 or ABA at the early regrowth stage to meet producing requirement.