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Petiole (botany)
From Wikipedia, the free encyclopedia
In botany, the petiole ('pet-ee-ohl'; from Latin peciolus "little foot," diminutive of pediculus "foot stalk," itself a diminutive of pes "foot") is the small stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the leaf. Clasping leaves of the Poaceae have an extra structure called the ligule.
Phyllodes are modified petioles. In some plants, the petioles become flattened and widened, while the leaf itself becomes reduced or vanishes altogether. Thus the phyllode comes to serve the purpose of the leaf. Phyllodes are common in the genus Acacia, especially the Australian species, at one time put in Acacia subg. Phyllodineae. Sometimes, especially on younger plants, partially formed phyllodes bearing reduced leaves can be seen.
Acacia Aneura have phyllodes that are thick thereby getting the stomata deeper and hence minimising the loss of water via transpiration. These also have tiny hair on them that trap the moisture that is lost by transpiration. This enables photosynthesis to occur at the maximum rate.
The petiole allows partially submerged hydrophytes to have leaves floating at different depths.
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