Modulation of physiological plasticity through structural and functional modifications in Stipagrostis plumosa L. for adaptability to hyper-arid environments

Abstract

The role of morpho-physiological attributes along with the antioxidant potential of Stipagrostis plumosa L. populations collected from arid regions in adaptability to aridity was evaluated. Root to shoot length, chlorophyll, carotenoids, and organic osmolytes (total free amino acids, total soluble proteins, glycinebetaine, and proline) increased with more activities of antioxidant enzymes (APX, CAT, POD, and SOD). Root and shoot fresh:dry weight ratio and leaf area decreased with increasing dryness ratio (D: 8.40?30.49) and decreasing precipitation (519 mm to 143 mm). Hyperarid populations [Noorpur Thal - NpT (D: 10.90; P: 400 mm) and Cholistan - Cho (D:30.49; P: 143 mm)] relied on reduced leaf area and plant biomass, longer roots, more activities of antioxidant enzymes with higher accumulation of organic osmolytes, and better compartmentation of ions in root and shoot. Root and leaf epidermal thicknesses, epidermal cell area, the proportion of cortical parenchyma, metaxylem cell area, abaxial stomatal density and area reduced significantly while stem epidermis thickness, cortical cell area, and metaxylem cell area increased in relatively less arid populations [Neela WahnNeW (D: 8.40; P: 519 mm) and Kallar Kahar-KKr (D: 8.99; P: 485 mm)]. In conclusion, survival of S. plumosa under water deficit was directly linked to the plasticity in morpho-physiological and anatomical traits such as epidermal hairs, thick leaves, intense sclerification in roots epidermis, cortex and endodermis, and vascular bundle. These traits not only accounted for the movement of water and solutes but also help conserve water and provided mechanical strength for survival in hyperarid environments.