Effects of LBD on improving heat tolerance in creeping bentgrass

LBD is a new type of biostimulant based on amino acids and polypeptides, which can improve plant heat tolerance. However, the physiological mechanisms by which it works are not clear. This study examines the effects of LBD on creeping bentgrass (Agrostis stolonifera) turf quality, yellow leaf rate, chlorophyll content, net photosynthesis rate, transpiration rate, MDA content, root length, and the ratio of root and shoot under heat stress conditions that last for 15 d. The results showed that three LBD treatments: spraying LBD once before heat stress (L-preH-1), spraying LBD once after heat stress (L-aftH-1), and spraying LBD twice before and after heat stress(L-2), resulted in significantly higher turf quality and lower yellow leaf rate than did treatments involving spraying LBD and Primo MAXX together once before heat stress (LP-preH-1), spraying foliar fertilizer once before heat stress (Y-preH-1), and spraying Primo MAXX alone once before heat stress (P-preH-1) (P < 0.05). In addition, the LBD treatments resulted in leaves that maintained a high level of cell membrane stability, higher net photosynthesis rate, increased root length, and an increased ratio of root and shoot. Furthermore, chlorophyll content and transpiration rate were significantly higher in the L-preH-1 treatment than in the L-aftH-1 treatment (P < 0.05), and better than that in the L-2 treatment according to the cost control. Our data indicate that spraying LBD was more effective than spraying Primo MAXX, foliar fertilizer, or LBD + Primo MAXX; meanwhile, spraying LBD before heat stress was more advantageous for improving heat tolerance of creeping bentgrass.