Hormonal Correlates of Seedling Growth of Two Vallisneria Species Grown at Different Current Velocities

Abstract

Seedling survival and growth of two common Vallisneria species in China, Vallisneria natans and Vallisneria spinulosa were quantified experimentally for current velocities from 0 to 40 mm/s. At the same time, changes in the concentrations of three hormones (IAA, ZR, and GA3) in the leaves were compared to identify how current velocity influenced the two Vallisneria seedlings growth discrepantly. All plants survived in all treatments and showed positive growth. The most rapid growth for both species was found at the velocity of 10 mm/s. Although V. spinulosa showed faster growth than V. natans at the beginning of the experiment, there was no significant difference on final biomass. Higher IAA and ZR contents were measured in seedlings of both species grown under low current velocity. The time reaching the maximum for IAA and ZR was just around the time of a maximum seedling growth rate. IAA and ZR contents were positively correlated with growth rate. However, GA3 was negatively associated with growth rate and more GA3 in V. natans seedlings was induced by high current velocity.