2003 Volume 26 Pages 53-58
Relationship between growth light intensity condition and water transport regulation in napiergrass plants was examined from the responses of photosynthetic rate (Pn) and transpiration rate (Tr) directly after the plant excision treatment and the difference in exudation rates (ER) between the upper and lower positions of the nodal stem. Pn and Tr in the plants grown in full sunlight condition rapidly and largely increased by excising the leaf sheath that was at the upper position of the nodal stem, while ER at this position was lower than that at the lower position of the nodal stem. However, small increases in Pn and Tr were shown after the rhizome excision, and ER at two positions were almost same in shade-grown plants. These findings suggest that water transport to the leaf was strongly regulated by the nodal stem, but the regulation in the nodal stem decreased in shade condition. Shade plants showed higher water status in stem, and this may be involved in the decrease in water transport regulation in the nodal stem. Pn also decreased in shade condition, but because of high stomatal conductance (Gs) and maintenance of mesophyll conductance (Gm), there was not a significant difference in Pn between treatments.
