Difference in Water Transport Resistance of Above-ground Parts between Napiergrass (Pennisetum purpureum Schumach.) and Maize (Zea mays L.)

Abstract

The hydraulic resistances of each organ in napiergrass and maize shoots were measured with a pressure flow meter. The results obtained were as follows: 1) Hydraulic resistances of the shoot, leaf and stem, R_shoot, R_leaf and R_stem, respectively, in napiergrass were significantly higher than those in maize. Particularly, R_stem in napiergrass was about four-fold larger than that in maize. 2) The cross sectional area of a stem (SA) was smaller in napiergrass than in maize, and the difference between napiergrass and maize in R_stem normalized by SA (R^S_stem) was smaller than that in R_stem. However, R^S_stem in napiergrass was still about two-fold larger than that in maize, indicating that napiergrass has a higher hydraulic resistance in the stem due to the synergistic effect of these two factors. 3) The hydraulic resistance of a stem was divided into three components, the resistance toward the leaf sheath of the nodal stem (γ_γ), the resistance toward the stem apex of the nodal stem (γ_a) and the resistance of the inter-nodal stem (γ_in). Both γ_γ and γ_a were high in napiergrass and the difference between napiergrass and maize was particularly large in γ_γ. These results suggested that a high R^S_stem in napiergrass was related with the water transport through the nodal stem. It was considered that a small stem diameter and high hydraulic resistance of nodal stem would result in a high resistance to water flow in napiergrass stem.