What defines pinnate leaves?

Pinnate leaves are characterized by having multiple leaflets arranged along a central stem or axis, resembling a feather. This anatomical structure allows for an efficient distribution of light and space, as the leaflets can be positioned to capture sunlight while maximizing exposure to air for photosynthesis. The arrangement can vary, with leaflets either being directly opposite one another or staggered along the rachis (the main axis of the leaf).

The other options describe different leaf types: a single broad leaf represents simple leaves, leaves arranged in a whorl constitute a specific leaf arrangement on the stem, and leaves growing directly from the stem refer to a different growth pattern commonly seen in certain plant species. Thus, the defining characteristic of pinnate leaves lies specifically in the presence of multiple leaflets arranged along a central axis.