Abstract
Alfalfa (Medicago sativa L.) is a valuable forage legume, but its production is largely affected by high temperature. In this study, we investigated the effect of heat stress on 15 alfalfa cultivars to identify heat-tolerant and -sensitive cultivars. Seedlings were exposed to 38/35 °C day/night temperature for 7 days and various parameters were measured. Heat stress significantly reduced the biomass, relative water content (RWC), chlorophyll content, and increased the electrolyte leakage (EL) and malondialdehyde (MDA) content of heat-sensitive alfalfa cultivars. However, heat-tolerant cultivars showed higher soluble sugar (SS) and soluble protein (SP) content. The heat tolerance of each cultivar was comprehensively evaluated based on membership function value. Cultivars with higher mean membership function value of 0.86 (Bara310SC) and 0.80 (Magna995) were heat tolerant, and Gibraltar and WL712 with lower membership function value (0.24) were heat sensitive. The heat tolerance of the above four cultivars were further evaluated by chlorophyll a fluorescence analysis. Heat stress significantly affected the photosynthetic activity of heat-sensitive cultivars. The overall results indicate that Bara310SC and WL712 are heat-tolerant and heat-sensitive cultivars, respectively. This study provides basic information for understanding the effect of heat stress on growth and productivity of alfalfa.
Highlights
Heat stress is one of the major abiotic stresses limiting plant growth and development
The results suggested that some cultivars might be more sensitive to heat stress, as Agronomy 2018, 8, x FOR PEER REVIEW
The results revealed that shoot fresh weight and shoot dry weight were strongly positively correlated with total fresh biomass and total dry biomass, respectively (r = 0.94) (p < 0.01) (Table 4)
Summary
Heat stress is one of the major abiotic stresses limiting plant growth and development. When plants are exposed to high temperature, several cellular injuries, including cell death, may occur within minutes, which leads to an appalling failure of cellular organization [1,2]. The rapid closure of stomata, reduction in cell size, an increase in stomatal, trachomatous densities, and xylem vessels of both root and shoot were reported to occur in response to heat stress [3]. Different plant species may show different responses to heat stress [4]. Heat stress triggers various morphological, physiological, biochemical, and molecular changes to inhibit plant growth and development. Heat stress inhibits seed germination; causes scorching; twigs and burning of leaves, branches, and stems; leaf senescence and abscission; shoot and root growth inhibition; fruit discoloration and damage; reduced yield; and plant death [5,6]. High temperature stress affects shoot net assimilation and decreases the overall dry weight of the plant [4]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
