Leaf recruitment and elongation:: an adaptive response to flooding in Villarsia reniformis

Villarsia reniformis (Menyanthaceae) responds to flooding by rapid leaf elongation and continual recruitment of young, submerged leaves (4.3-6.5 per week). Leaf production is influenced by nutrient availability and water depth. Leaves are submerged and die as the water level rises, but are replaced by younger leaves able to broach the surface. Young petioles may elongate at more than 10cm per day, but lose the ability to elongate after the blades are exposed to air more than twice. Young petioles produce new cells and existing cells elongate, but in older petioles fewer new cells are produced and cell elongation, whilst limited, is the main mechanism for petiole elongation. Continual recruitment implies a high cost for production of structural tissue, but ensures that leaves capable of rapid extension are within reach of the water surface and the plants can respond quickly to flooding. (C) 2001 Elsevier Science B.V. All rights reserved.