DEVELOPMENTAL ANALYSIS OF LEAF PLASTICITY IN THE HETEROPHYLLOUS AQUATIC PLANT HIPPURIS VULGARIS

Abstract

Leaf development was studied in the heterophyllous aquatic plant Hippuris vulgaris in order to characterize the developmental events that lead to the formation of aerial‐ vs. submerged‐type leaves. Recent evidence that abscisic acid regulates leaf development in this species provided a basis for using abscisic acid as a developmental tool to accurately control leaf development. We found that leaf primordia were fully competent to develop into either aerial‐ or submerged‐type leaves until the 10th plastochron, when they were ca. 300 μm long. Also, leaves between about the 10th and 21st plastochron formed sectored transition leaves (i.e., the basipetal portion was composed of aerial‐type tissue and the apical portion was composed of submerged‐type tissue, or vice versa), indicating that tissue determination as one or the other leaf type occurred on a local, as opposed to whole‐leaf, level. Finally, no significant difference was observed between the apical dimensions of aerial or submerged‐type shoots. These results indicate that the final determination of Hippuris vulgaris leaves occurs a) relatively late in leaf development, and b) independently of the shoot apex, and provide a basis for using this plant in further studies concerning leaf determination and pattern formation (e.g., stomates, lateral venation) in plants.