Can Ethylene Induce Heterophyll in Marsilea quadrifolia

Abstract

Individuals of Marsilea quadrifolia, an amphibious fern, experiencing extreme variations in environment develop heterophyll with different morphological characteristics. The objective of this study is to investigate if ethylene can induce floating type of leaves in this fern. To achieve this goal, ratio of stomatal density on abaxial and adaxial leaf surfaces (stomatal ratio) and the mass per unit length of petiole (PML), on leaves of terrestrial shoots sprayed with an ethylene gas releaser, Ethephon, were compared with those of leaves produced by submergence of terrestrial shoots. Leaves with different stomatal ratio and PML, corresponding to that of terrestrial type and floating type of leaves, were produced when terrestrial shoots of M. quadrifolia were submerged. The result reveals that the plasticity of leaves to respond to submergence depends on leaf's age. Application of Ethephon significantly altered the stomatal ratio of young leaves on terrestrial shoot but not their PML. Leaves response to Ethephon treatment was also age dependent. These results indicate that ethylene might be involved in the formation of floating leaves in M. quadrifolia.