Comparative morphological, epidermal, and anatomical studies of Pinus roxburghii needles at different altitudes in the North-West Indian Himalayas

The aim of the present study was to understand the ecological adaptation of Pinus roxburghii Sarg. in the North-West Himalayan region. P. roxburghii needles showed morphological, epidermal, and anatomical variation at different altitudes. Needle length was negatively correlated with altitude. Stomatal characters like stomatal density, stomatal index, and guard cell lengths were found to be affected by environmental factors and showed a direct correlation with altitude. The results showed that potential conductance index was dependent on the climatic conditions of the habitat. The anatomical properties of needles exhibited variation from lower to higher elevation, especially in the number and position of resin ducts.