Structural and functional modifications in a typical arid zone species Aristida adscensionis L. along altitudinal gradient

摘要

Aristida adscensionis L. is a widely distributed grass species that particularly invades Potohar region (arid/semi-arid conditions) of the country. Exploration of adaptive components in this grass in relation to altitudinal gradient is the first attempt. Plant samples were collected from 6 different altitudinal ranges, viz. 400, 600, 800, 1000, 1200 and 1400 m a.s.l. Morpho-anatomical and physiological features along altitudinal gradient varied significantly that showed phenotypic plasticity in this species to inhabit a variety of environmental conditions. Stomata at 400 m altitude were larger and rhomboid-shaped, which changed to narrowly elliptic at moderate elevations and circular at high elevations. Growth and biomass production were maximum at 800-1000 m a.s.l. along with most of the morpho-anatomical and physiological features like proportion of vascular tissue, nutrient uptake, and chlorophyll pigments. Xeromorphy was high in plants colonisng at 1200 m elevations, which was indicated by an intensive sclerification, increased amount of storage parenchyma, increased vascular bundle number, deeply grooved bulliform cells, and dense pubescence on adaxial leaf surface. Leaf succulence was the unique feature in plants inhabiting 1400 m elevation. Another prominent feature was the development of chlorenchyma inner to stem epidermis. All these features reflect the tolerance capacity of A. adsecnsionis against environmental adversaries like salinity, aridity and low temperatures of the Potohar region.