What Is the Function for the Petiole of a Plant?

Function

• Be they trees, shrubs or weeds, all plants are fully functioning entities equipped with all the tools and parts they need to survive, bear fruit or flowers and thus produce more of their own kind. Each part on a plant works in conjunction with all the others to keep it alive until its purpose has been fulfilled, and no part is any less valuable than the others. Indeed, a plant's life can be severely compromised if just one part is affected by disease, insect infestation or other external factors. Petioles are essentially lifelines between a plant and its leaves. While they don't take up much room on a plant or appear to be all that significant, they in fact perform the crucial function of keeping the plant's main food producers attached, thus ensuring its survival.

Anatomy

• Plants are divided into two broad categories that are based on how their seeds are produced. Evergreens, including pines and firs, are gymnosperms that produce bare seeds inside cones and needles instead of leaves. Angiosperms make up about 80 percent of all plant life on Earth and are composed of plants made of stems, leaves and flowers whose seeds are generally encased in a fruit, nut or blossom. A plant in this category is made up of roots; a main stem; side, or lateral, stems or branches; leaves attached by petioles to the main stem or branch; and buds for flower, fruit and seed production.

Process

• Plants operate like many other living organisms on a system of absorption and distribution, and their leaves perform the important function of manufacturing the food they need. Water, some nutrients and minerals enter the plant through the roots and move up along a system of tiny tubes collectively called the vascular system. The tubes extend through the entire length of the plant and into the leaves through the petioles. In turn, the leaves absorb solar energy, which transforms carbon dioxide and water molecules into sugars, a process known as photosynthesis. The sugars are redistributed to the rest of the plant through the petioles, which act as conduits for an alternating exchange of moisture and nutrients for the food produced by the sunlight hitting the leaves.

Illustration

• From a simple leaf, like that of the maple (Acer spp.), to compound, like the tomato (Solanum lycopersicum), all are attached by a petiole. A good visual example can be found in the fall in the form of a maple leaf that has dropped from the tree. As daylight length decreases and temperatures drop, photosynthesis slows and finally stops altogether, and the maple tree sheds the leaves it no longer needs for food production. The junction at the base of the petiole and branch weakens to the point that the leaf is blown off by the wind and eventually decomposes on the forest floor. Smaller plants grown as annuals or perennials that die back in the fall generally wither without first shedding their leaves.