Volume

36, 1998

Issue

1

Page

40

Title

Phenological studies of carbohydrate allocation in Hydrilla

Author(s)

Owens, C. S., and J. D. Madsen

Abstract

 Hydrilla (Hydrilla verticillata (L.f.) Royle), a nonindigenous submersed aquatic plant, was first introduced into the United States in the 1960's. Hydrilla exhibits aggressive growth, forming dense canopies of biomass at the surface of the invaded aquatic systems, affecting fisheries, water quality, transportation and recreational usage. Studies of the phenological seasonal cycles of invasive plants indicate optimal timing to apply management techniques. Biomass and total nonstructural carbohydrate (TNC) allocation of dioecious hydrilla were studied in outdoor ponds in Texas between January 1994 and July 1995. Biomass increased from May through September, growing from overwintering shoots and root crowns, not tubers. Tuber germination occurred in August. Tuber and turion production occurred from October through April. A carbohydrate storage minimum was observed in late July for 1994 and June for 1995, with storage generally split between stolon (7% TNC), root crown (10% TNC) and lower stem (16% TNC). Tubers and turions ranged from 58 to 68% TNC. These studies provide more insight into the timing of major allocation shifts in the hydrilla seasonal growth cycle.

KEYWORDS: Hydrilla verticillata, total nonstructural carbohydrates, Hydrocharitaceae, dioecious hydrilla