Total nonstructural carbohydrates of one temperate and two tropical grasses under varying clipping and soil moisture regimes

The distribution of total nonstructural carbohydrate (TNC) concentration and accumulation was analysed in various components of three selected grasses, a perennial C₄ (Dichanthium annulatum) and two annuals, Echinochloa colonum (C₄) and Polypogon monspeliensis (C₃). The first two species were grown during dry summer and first and third during the winter season. Three moisture regimes were chosen, viz. full field capacity, half field capacity and unirrigated condition. The plants were clipped three times; each time 40 and 80% of the current live green was removed. In all the four instances, the TNC levels increased with greater soil moisture availability. Dichanthium grown in winter showed a drastic reduction in both concentration and accumulation due to soil moisture deficit while irrigated plants reflected higher TNC compared to Polypogon. Dichanthium grown in the summer had a higher value of TNC than Echinochloa in all the components. Clipping reduced the TNC levels in all the instances except in the spike. The extent of recovery from clipping seemed to depend upon the phenophase; plants in vegetative growth recovered earlier in summer Dichanthium compared to Echinochloa and Polypogon in which spike development delayed the build-up of TNC in the leaves.