Features of Biomorph of Hydrilla verticillata (Hydrocharitaceae)

The biomorphological features of Hydrilla verticillata (L. fil.) Royle in tropical and temperate regions of the Eurasian part of the geographical range have been studied. The shoot system is long-growing and sympodial, consisting of (annual)oligoennial monopodial shoots of main and subordinate orders. The number of leaves per node; shape, length, and width of leaf blade; branching peculiarities; and the length of the internode are the most variable signs. Hydrilla verticillata is a perennial (vegetatively oligoennial) polycarpic rooting long-shoot high turion-tuber vegetative–mobile hydrophyte. The flexibility of biomorphs in different biotypes is manifested by the duration of shoot ontogenesis and by a change in the ratio of the specialized vegetative diasporas. Turions and tubers are the two alternative models for maintaining the population.