Plasticity in morphology, proximate composition, and energy content of Hygrophila polysperma (Roxb.) Anders

Submerged Hygrophila polysperma (Roxb.) Anders. were collected in September 1987. Apical shoots were planted in prepared soil and grown under controlled conditions either in water (submerged) or air (emerged). Submerged plants grew little. Emerged shoots differed in morphology (more numerous short, broad leaves, shorter internodes, relatively more development of the roots), growth (greater for all plant components), and proximate composition (higher level of structural carbohydrate in the stem, higher level of soluble carbohydrate and lower level of protein in the leaves) from submerged shoots. The response of H. polysperma in terms of the allocation of the energy of production following transfer of the shoots to emerged conditions reflects an increase in availability of light and CO₂ and a decrease in available water in the emerged habitat.