Dynamic leaf morphology of Monstera tenuis

Light availability in the tropical forest increases rapidly with height. There is also considerable horizontal variation in light associated with canopy openings. Vines begin life in the shaded understory and gain access to high light as they grow up trees. Monstera tenuis is a vine that undergoes a dramatic change in leaf morphology during its development. Its small, round juvenile leaves grow closely pressed against its support tree trunk. As the vine grows vertically, the leaves become larger, but at some point the leaves become very large and dissected and are held away from the host tree trunk on stout petioles. The juvenile leaf morphology is well-suited for diffuse light capture while the adult morphology enhances exposure to direct light. Light availability and a threshold juvenile leaf size have been hypothesized to influence this dramatic morphological change. We measured the height of morphological change and leaf diameter of the last leaf to not change morphology for 24 individuals growing over a range of canopy openness. Diffuse light intensity was measured with a light sensor to estimate light availability to each plant. We found that the change in morphology occurred at a lower height in habitats with more available light and that the size of the last juvenile leaf increased with light availability. These results are consistent with the hypothesis that there is a threshold of available light necessary to induce morphological change.

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