Field of Science

Tropical peltate leaves

While curating some recent specimens in the herbarium, this plant caught my attention because it has a very interesting leaf, quite typically tropical, quite typically monocot. This is Piper peltatum, an aptly named species because when the leaf blade surrounds the point where the petiole is positioned the leaf is termed peltate, a form that is relatively uncommon in the temperate zone. The apex forms a drip tip, which like the lip of a beaker helps water run quickly off the leaf, as do the somewhat recessed channels forms by the major veins. The "parallel" major and 2ndary veins are a "monocot" feature as are the leaf primordia encircling the stem and the scattered vascular bundles in the stem, but pipers are dicots with a lot of monocoty features as is true of a number of other dicots in a similar phylogenetic position. This leaf is about 23 cm across the widest point.

Here's another peltate leaf, the very distinctively lobed leaf of Cecropia obtusifolia. The lobes are so deep the leaf is close to being palmately compound. The trees are highly distinctive as well with candelabra branches with the leaves helically whorled around the ends of the branches looking a bit like something out of a Dr. Suess Whoville landscape. They are quite well studied both for its bird and bat dispersed seeds, its role as a pioneer species in rain forest communities, and its symbiotic association with ants of the genus Azteca, little warriors who defend their plant from all intruders. This leaf is some 40-50 cm across. Here's a young Cecropia emerging above the crown of a Pentaclethra tree (a mimosoid legume) in flower.

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