The effect of different water depths on the growth of wild rice

The effect of different water depths on wild rice plants (Zizania aquatica L.) was assessed in terms of morphological and dry weight changes which occurred during a complete life cycle. Specifically, plant heights, number and area of leaves, dry weights of leaf, stem, root, and flower were determined for plants grown under controlled environmental conditions and those under field conditions at Long Point, Lake Erie.Three distinct phases in plant height increase, and associated morphological changes characterized the life cycle of wild rice. While the duration of phases one and three was unaffected by water depth, the time spent in phase two increased with depth and resulted in plants flowering later than those at shallower depths. Sufficient water is required to cover the submersed leaves and to support the floating leaves, while plants at the aerial stage survived with no free water above the rooting media. Yield in terms of dry weight of plant parts is decreased by water depths less than 8 cm and greater than 110 cm. The decline of wild rice in many areas of Ontario is attributed to either excessively low or high water levels during the critical submersed and floating leaf stages.