Elevational gradients impose strong environmental constraints that alter plant structure and function. The study was conducted to compare morpho-anatomical variation in Cannabis sativa L. through a strong lowland-highland gradient (120-1770 m a.s.l.) in the Koh-e-Sulaiman region in Pakistan. The high-elevated populations (Fort Munro Lake, Fort Munro Road, and Fort Munro Hills) were of low temperature (6-8 oC), moderate precipitation (245-255 mm), and low soil salinity (ECe 1.21-1.34 dS m-1), and the low-lands populations (Dera Ghazi Khan, Taunsa Sharif, and Shadan Lund) were of higher temperature (44-48 oC), less rainfall (170-210 mm), and higher salinity level. There were more morphological changes in the lowland populations, with longer root and shoot lengths, more leaves, and greater leaf area, compared with the highland populations, which tended to be shorter. Anatomical observations of ecotypes showed structural changes in plant parts. The plants in the highland exhibited more reinforced protective and regulatory tissues, such as increased cortical and endodermal layers in roots and increased epidermal thickness in the leaves, which showed structural changes towards a colder and fluctuating environment. In contrast, the lowland populations had increased lamina and mesophyll thickness, greater size of the vascular bundles, increased stomata number and size, and increased pith tissues, which caused the increased conductivity of water and its gaseous exchange in warmer and saline conditions. Statistical analyses showed that there is a significant difference in traits along the elevational gradient. These findings indicate strong phenotypic plasticity of C. Sativa in terms of morpho-anatomical adaptations that support the ecological adjustment of the species to both extreme climatic and edaphic conditions of the Koh-e-Sulaiman region.
Hussain et al. (Wed,) studied this question.