VEGETATIVE PROPAGULE PRODUCTION AND ALLOCATION OF CARBON AND NITROGENBY MONOECIOUS HYDRILLA-VERTICILLATA (LF) ROYLE GROWN AT 2 PHOTOPERIODS

Plants of Hydrilla verticillata (L.f.) Royle were grown under two phot operiods (11 or 15 h) in a greenhouse. Under the 11 h photoperiod, Hyd rilla produced geotropic shoots after 34 days, tubers were first obser ved at 48 days, and turions after 76 days. During this study, Hydrilla plants grown under the 11 h photoperiod produced 317 tubers, and thos e grown under the 15 h photoperiod produced two tubers. C and N were d irected from other plant structures, especially shoots and roots, into newly formed tubers and turions. C was allocated to new tubers at a r ate that was about 43 times that for N. After 12 weeks, about 15 times more C and N were allocated to tuber production than to turion produc tion. Nutrient use efficiency for N increased significantly in both ph otoperiods. N use efficiency was not a good indicator of the onset of tuber or turion production.