THE STRATEGIES OF MORPHOLOGY, REPRODUCTION AND CARBOHYDRATE METABOLISM OF Hydrilla verticillata (Linn.f.) Royle IN FLUCTUATING WATERS

Hydrilla verticillata (Linn.f.) Royle is usually employed as a pioneer species for vegetation replanting in China. The morphology, reproduction and carbohydrate storage of H. verticillata were examined at different water depth gradients (30, 60, 90, 120 and 150 cm) in an outdoor mesocosm with 10-week experiment duration. The results indicated that H. verticillata could acclimatize itself to different water depths and conditions via physiological and morphological changes in the life history. However, in different water depth, the strategies of morphology acclimations, reproduction and carbohydrate metabolism showed various states, and some significant differences were detectable between them in most measured indexes. The relative growth rate (RGR) of the plants increased with water depth until 120 cm, which were 74.1 +/- 2.5 mg.g(-1).d(-1) dry weight (DW) and 68.6 +/- 2.2 mg.g(-1).d(-1) DW at 120 and 90 cm water levels. The number of ramets and shoots, especially the flowering buds number & biomass, which is important for colonization and the maintenance of macrophyte populations, were relatively higher at 90 cm water level. Among the three different non-structural carbohydrates (soluble sugar, reducing sugar and starch) measured, which can increase the ability of the plant to re-grow, or survive time periods of seasonal dormancy, H. verticillata in 90 cm water depth allocated and stored significantly higher contents of starch and soluble sugar (P<0.05). Consequently, 90 cm would be the optimal water depth for the growth of H. verticillata compared with the other levels.Hydrilla verticillata (Linn.f.) Royle is usually employed as a pioneer species for vegetation replanting in China. The morphology, reproduction and carbohydrate storage of H. verticillata were examined at different water depth gradients (30, 60, 90, 120 and 150 cm) in an outdoor mesocosm with 10-week experiment duration. The results indicated that H. verticillata could acclimatize itself to different water depths and conditions via physiological and morphological changes in the life history. However, in different water depth, the strategies of morphology acclimations, reproduction and carbohydrate metabolism showed various states, and some significant differences were detectable between them in most measured indexes. The relative growth rate (RGR) of the plants increased with water depth until 120 cm, which were 74.1 +/- 2.5 mg.g(-1).d(-1) dry weight (DW) and 68.6 +/- 2.2 mg.g(-1).d(-1) DW at 120 and 90 cm water levels. The number of ramets and shoots, especially the flowering buds number & biomass, which is important for colonization and the maintenance of macrophyte populations, were relatively higher at 90 cm water level. Among the three different non-structural carbohydrates (soluble sugar, reducing sugar and starch) measured, which can increase the ability of the plant to re-grow, or survive time periods of seasonal dormancy, H. verticillata in 90 cm water depth allocated and stored significantly higher contents of starch and soluble sugar (P