2011-11-16 / Features

The Life Cycle Of Leaves

BY KARLA MONTALVO

The change of season from summer to fall has been like a roller coaster ride this year. Clear skies and warm weather one day, snowstorms and hail storms the next.

It might be hard to tell that fall has arrived had it not been for the traditional change of red, yellow and brown colored leaves.

A leaf, an organ of a tree or a plant, can come in many different types of colors and shapes.

However, the life cycle of leaves is mainly the same for all.

The birth of a leaf begins in the springtime when it starts out as a bud on a branch. During its first stage of life a leaf will start to produce sugar sap, the nourishment needed by the tree. A tree will absorb water and nutrients from the ground in exchange for the sugar sap. This is the food exchange process between the leaf and the tree.

A leaf is also made up of inner and outer tissues of which there are three major parts.

The interior of a leaf is the mesophyll tissue. The mesophyll tissue is made up of two layers, the palisade layer and the spongy layer. This is where photosynthesis occurs. The outside tissue of a leaf is the epidermis, which covers and protects the surface of the leaf.

The third major part of a leaf is its veins. The veins are also made up of tissues and are located in the spongy layer of the mesophyll.

Veins are responsible for the transportation of sugar sap, water and nutrients. Veins also give each leaf its shape and form.

When temperatures begin to drop trees stop supplying leaves with nutrients, sometimes referred to as scarring. This is the reason why leaves change color in the fall. The color cycles includes red, yellow, purple and then brown. The outer layer (the epidermis tissue) becomes brittle and as the leaf dries up it will eventually fall off. Each individual leaf is affected differently so no two leaves will ever look the same. This life cycle will begin again once the weather starts getting warmer, and trees will bloom new leaves.

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