Abscisic Acid and Glycine Betaine Mediated Tolerance Mechanisms under Drought Stress and Recovery in Axonopus compressus: A New Insight

Abstract

Changing climatic scenarios affect plant growth and consequences are more malicious in drought conditions. This study was performed for better understanding of tolerance mechanisms under prevailing drought stress and succeeding recovery in Axonopus compressus by exogenously applied abscisic acid (ABA) and glycine betaine (GB). three A. compressus accessions (A-38, A-58 and A-59) were subjected to well-watered (100% field capacity) and drought (40% field capacity) conditions. Two weeks later, plants were recovered from drought by re-watering. Water (control), GB, ABA and their combination were foliar applied on plants under drought twice a week until recovery. Drought stress decreased photosynthetic pigments and increased reactive oxygen species, lipid peroxidation, osmolytes and antioxidants in all accessions of A. compressus. Nonetheless, exogenous ABA and GB alone or in combination improved drought tolerance in all accessions which was maintained even after recovery. Maximum decrease in hydrogen peroxide and malondialdehyde, and increase in soluble sugars, proteins, proline, phenolics and chlorophyll contents, and superoxide dismutase, catalase, peroxidase and ascorbate peroxidase activity was recorded when GB was applied alone under drought. Order of improvement in drought tolerance among accessions was A-58 > A-59 > A-38. In conclusion, improved drought tolerance mechanisms by ABA and GB in A. compressus were retained even after recovery. Plants experience recurrent drought conditions which is one of the major negative forces for growth and productivity of biological systems 1,2. Drought stress is one of the key ecological effectors which causes alterations at morpho-physiological, biochemical and molecular levels 3. Water deficit reduces cell division and elongation, disturbs tissue water status, causes stomatal closure, damages photosynthetic machinery, limits the photosynthesis, and hampers nutrient uptake and translocation ultimately affecting plant growth and productivity 3-5. In addition, drought stress enhances production of reactive oxygen species (ROS) viz. singlet oxygen (O *), hydroxyl radicals (OH • .), superoxide (O 2 −) and hydrogen peroxide (H 2 O 2) 6,7 , which causes exaggerated lipid peroxidation of cellular membranes 7,8 , denaturation of proteins, destruction of nucleic acid ultimately disrupting homeostasis 6,9,10. Plants have devised tolerance mechanisms which potentially promote their survival in drought stressed environments 11,12. Abiotic stress induced ROS production activates the signaling mechanisms in plants 8,13,14 , which induce hormonal modifications mainly increase in endogenous ABA, and activates the genes for production of osmolytes and antioxidant enzymes 3,15-17. Compatible solutes such as proline, glycine betaine, soluble proteins ad sugars, organic acids and phenolic compounds are accumulated in plants in response to drought which improve the water potential, detoxify ROS, and protect cellular membranes and macromolecules from lipid peroxidation 11,18,19. In addition, ac...

Insight of Transcriptional Regulators reveals the Tolerance Mechanism of Carpet-grass (Axonopus compressus) Against Drought

“…Plant defense mechanisms for abiotic stress are already being studied, but the response to drought has always been a complex event with several critical indicators to be examined. Drought stress signi cantly increased ROS formation and imposes oxidative stress on the plant [26,31]. Since lipid peroxidation is one of the earliest indicators of oxidative damage, MDA was estimated as an index for production of drought induced ROS [31].…”

“…At different time interval leaf water potential (LWP) in leaf was measured by Scholander chamber (SF-PRES-70, Solfranc Tecnologías SL, Vila-Seca, Spain). Electrolyte leakage (EL) was measured by estimating the electrical conductivity [26]. In the solution, the electrolyte leakage (S1) was measured using a conducti-meter after 22 h of oating at room temperature (Mettler-Toledo Instruments Co., Ltd, Shanghai, China).…”

Insight of Transcriptional Regulators reveals the Tolerance Mechanism of Carpet-grass (Axonopus compressus) Against Drought

“…Plant defense mechanisms for abiotic stress are already being studied, but the response to drought has always been a complex event with several critical indicators to be examined. Drought stress signi cantly increased ROS formation and imposes oxidative stress on the plant [26,32]. Since lipid peroxidation is one of the earliest indicators of oxidative damage, MDA was estimated as an index for production of drought induced ROS [32].…”

“…At different time interval leaf water potential (LWP) in leaves was measured by Scholander chamber (SF-PRES-70, Solfranc Tecnologías SL, Vila-Seca, Spain). Electrolyte leakage (EL) was measured by estimating the electrical conductivity [26]. In the solution, the electrolyte leakage (S1) was measured using a conducti-meter after 22 h of oating at room temperature (Mettler-Toledo Instruments Co., Ltd, Shanghai, China).…”

Insight of Transcriptional Regulators reveals the Tolerance Mechanism of Carpet-grass (Axonopus compressus) Against Drought

“…The leaf water potential (LWP) was measured by Scholander chamber (SF-PRES-70, Solfranc Tecnologías SL, Vila-Seca, Spain). Electrolyte leakage (EL) was measured by estimating the electrical conductivity [26]. In the solution, the electrolyte leakage (S1) was measured using a conducti-meter after 22 h of oating at room temperature (Mettler-Toledo Instruments Co., Ltd, Shanghai, China).…”