Comparative Studies of Monoecious and Dioecious Hydrilla (Hydrilla verticillata) Biotypes

Abstract

Selected biological and physiological parameters of hydrilla [Hydrilla verticillata(L.f.) Royle # HYLLI] biotypes were compared in growth chambers, glasshouse, or outside aquaria. Salinity tolerance was similar for both biotypes with an injury threshold of approximately 13 parts per thousand (ppt). The registered aquatic herbicides diquat (6,7-dihydrodipyrido [1,2-α:2′,1′-c] pyrazinediium ion) and dipotassium and monoamine salts of endothall (7-oxabicyclo [2.2.1] heptane-2,3-dicarboxylic acid)4produced similar injury to both biotypes. Biomass of the monoecious plants, growing in controlled environments, declined under short days. Tuber production in monoecious plants was greatest under short days and was significantly higher than in dioecious plants under the same conditions. Growth response to temperature was similar among all plants and was retarded at 15 C. Tuber germination occurred at lower temperatures in the monoecious plants, which was indicative of a lower temperature tolerance. Vegetative propagules were the only perennating structures observed in the monoecious biotype, and regrowth was entirely from tubers and turions. The annual growth habit, in conjunction with rapid and abundant propagule production, adapts the monoecious biotype to northern areas with short growing seasons.

Influence of propagule size, soil fertility, and photoperiod on growth and propagule production by three species of submersed macrophytes

“…The general pattern in this experiment agrees with that noted previously by other researchers (Hailer et aL 1976, Van et al 1978, Bowes et al 1979, Spencer and Anderson 1986, 1987, Steward and Van 1987, Van 1989. Propagule production is enhanced by short photoperiod and reduced by long photoperiod.…”

“…Previous reports have demonstrated that photoperiod (HalIer et al 1976, Van et al 1978, Bowes et al 1979, Spencer and Anderson 1986, 1987, Steward and Van 1987 and soil fertility (Bruner and Batterson 1984, Barko and Smart 1986, McFarland and Barko 1987, Spencer 1990, Spencer et al 1992) influence vegetative 134 propagule production. For many species, interactions between environmental factors and propagule production have not been studied.…”

Influence of anoxia on sprouting of vegetative propagules of three species of aquatic plant propagules

“…Dioecious Hydrilla tubers may not sprout as well at the cooler temperatures (typical of the greenhouse during the periods that the experiments were conducted) as monoecious Hydrilla or Potamogeton propagules (Steward andVan 1987, Madsen andAdams 1988).…”

Influences of Salinity and Light Availability on Abundance and Distribution of Tidal Freshwater and Oligohaline Submersed Aquatic Vegetation

“…Seasonal means (April to October) of the measurements were calculated as well as early growing season means. Early growing season was defined by temperature and included data from the first 2 months when temperatures reached 15°C, which is when experiments have shown these freshwater species, particularly H. verticillata, to sprout from tubers or germinate (Carter et al 1994;Steward and Van 1987).…”