Seasonal variations coupled with elevation gradient drives significant changes in eco-physiological and biogeochemical traits of a high altitude evergreen broadleaf shrub, Rhododendron anthopogon.

Higher elevations and, early as well as late phase of growing season are expected to be more stressful for plants in high altitudes. The present study was carried out on Rhododendron anthopogon D. Don, an evergreen shrub of Himalaya to understand variation in eco-physiological and biogeochemical traits due to combined effect of elevation gradient and growing season. We conducted our study at Rohtang, India (32°22'04″ N 77°15'17″ E) and undertook random sampling of leaves at four elevations (3200 m, 3600 m, 4000 m and 4250 m), and three time periods (late June, early August and late September) during growing season. We assessed 12 eco-physiological and biogeochemical variables and analysed results through ANOVA and multivariate analysis. It was found that leaf relative water content, nitrogen percentage (N%), carbon/nitrogen ratio (C/N ratio), total chlorophyll, malondialdehyde equivalents and proline content varied along two gradients (factors) with their interaction being statistically significant. Variance partitioning analysis of studied traits revealed that both factors contribute significantly, with 'season' component ranging between 55.75 % and 94.03 % for most of the parameters, whereas, 'elevation' component contributed more for leaf area, N% and C/N ratio (48.08 %-75.03 %). Our results suggest that eco-physiology of R. anthopogon is significantly influenced by interaction of seasonal variations coupled with elevation gradient. The study highlights the importance of examining both seasonal and elevational gradients in understanding plant adaptation strategies. Overall, our findings revealed that plasticity in eco-physiological and biogeochemical traits underline the wide distribution of R. anthopogon in the high altitudes.