Biomass Allocation Plasticity of an Invasive Alien Weed Cannabis sativa (L.): Its Implication for Its Invasiveness in an Indian Dry Tropical Urban Region

Abstract

India is a dry tropical region with a wide variety of native flora in the past few decades; many foreign plant species started invading into its ecosystems due to its rich soil quality. Besides this, anthropogenic interruptions ongoing in the urban and peri-urban areas, provides the environment for these species to get established and thrived with ease. Any invasive weed adopts various invasive strategies to colonize and naturalize itself in the newer environments. Out of these strategies, efficient biomass allocation pattern is directly associated with their invasiveness. The present study is aimed at understanding the invasiveness of a tropical Central Asian weed, Cannabis sativa L. in an Indian dry tropical region. The weed was studied for its above ground biomass (AGB) allocation patterns, at maturing stage in different parts i.e. stem, leaves, branches and reproductive parts with their mass fractions; along with studying for other plant traits i.e. shoot length, basal diameter, number of leaves, leaf area, branches, nodes and gender of plant. Besides this, soil characteristics were also investigated for a better understanding of the dynamics. The highest aboveground biomass was allocated to stem (12.25 g/plant) followed by leaves (4.89 g/plant), branches (3.16 g/plant) and reproductive parts (2.24g/plant). Mean phenotypic plasticity index of biomass fractions plant traits was higher than for morphological plant- traits which is indicative of biomass allocation plasticity as an undisputed invasive trait in the studied weed plant. Further, relatively higher allocation into stems and leaves and less allocation into the seeds but the production of large number of seeds per plants relative to number of leaves could be directly linked to its rapidly expanding invasive trait.