Most of the dry mass of a plant is the result of uptake of

Most of the dry mass of a plant is the result of uptake of carbon dioxide through stoma

Explanation:

The dry mass of a plant is the mass or weight of the plant after all its water components have been removed through the drying process. Generally, the mass of any plant comes from the carbon assimilated from atmospheric carbon dioxide absorbed during photosynthesis.  During photosynthesis, the carbon from CO2 settles in glucose molecules, each of which contains 6 carbon atoms. Once the plants use up carbon for various metabolic activities and the remaining are used for building up of structural parts like leaves, stem etc. Plants use up all the remaining carbon atoms in leftover glucose to increase its biomass. Hence after drying up also, the dry mass of the plants contain carbon due to uptake of carbon dioxide