Ecotypic adaptations in Bermuda grass (Cynodon dactylon) for altitudinal stress tolerance

Three ecotypes [foot hill (700 m), mid hill (1571 m) and top hill (2804 m)] of a Bermuda grass Cynodon dactylon (L.) Pers. from Pir Chinasi Hill in Western Himalaya were evaluated for their degree of tolerance to altitudinal stress. Differential response of all ecotypes in terms of adequate structural modifications to different elevation leveis was an evident to confirm the hypothesis that plants inhabiting different altitudes show variation in structure (internal modifications) and strategic (response) due to heterogeneity in environmental gradients. Soil at top hill site was more acidic and displayed significant increase in ionic content and total nitrogen. High elevation had severe impact on morpho-anatomical and physiological attributes. A significant decline in shoot fresh weight and total leaf area was observed in top hill ecotype. With exception of Ca2+ and carotenoid, other ionic and chlorophyll content were significantly declined at high elevations. Anatomical alterations such as, increased leaf thickness, intensive sclerification around the vascular bundle and pith area, reduced metaxylem vessel area, high number of silica bodies, high pubescence (increased microhair and trichome density) were some of the promising anatomical adaptations in top hill ecotype which played an important role in high degree of tolerance of this grass to cope with altitudinal stresses. Increased leaf thickness might be a response to lower temperature that protects mesophyll cells and high density of trichomes may be involved in blocking transpiration water and internal heat. The pattern of constant variation suggests that differential response of these ecotypes is highly related to air temperature, pattern of rainfall, availability of nutrients.