Plant Life Leaves

Plant Life Basics
Leaves

Leaves come in a huge variety of sizes and shapes. They come in rich glossy greens, dark greens, light greens and any shades in between.

A leaf can be variegated, serrated, hairy, wavy edged, lobed and of different textures.

But this great diverseness is not just for our pleasure. Each part of a leaf has a serious role to play in the exsistence of every plant.

There are two basic leaf types:

Simple Leaf, which consists of a single unit, like the prunus (flowering cherry)

Compound Leaf where there are several leaflets like the mahonia

The main purpose of a leaf is to capture light, and by photosynthesis, manufacture food. So a leaf must be thin and also translucent to allow light in to its innermost cells.

Leaves also need to be in the best position to receive maximum light and they are usually attached to the stem by a leaf stalk or petiole.

The petiole allows leaves to follow the sun's changing position throughout the day giving them maximum exposure to light.

The petiole also gives flexibility to leaves in heavy winds and rains allowing them greater movement without breaking away from the stem.

Looking at a cross-section of a leaf shows it is made like a sandwich. Both the top and underneath sides are layers of epidermis, which have an outer cuticle layer, preventing the loss of water.

In the middle are cells containing chloroplast, called mesophyll, where photosynthesis takes place.

This middle mesophyll layer is divided in two parts. Directly below the upper epidermis are the palisade cells, which catch light as it passes through the upper epidermis.

Spongy cells underneath the palisade cells allow water vapour, carbon dioxide and oxygen to move between them.

The chloroplasts need light and the elements of water and carbon dioxide for photosynthesis to take place. These elements obtained from the atmosphere enters a leaf through pores in its surface.

These pores, of which there are thousands, are called stomata. The stomata are usually in the underneath epidermis to prevent them from being clogged by dust, which could build up on the upper surface.

A leaf is structured with a main vein known as a midrib, which is the main "backbone" of the leaf. Lateral veins come off the midrib and the lateral veins in turn have sublateral veins coming off them.

These veins contain xylem and phloem cells, which assist in carrying water and nutrients around the plant.

To learn more about plant life - the basics, just click on any of the links below.

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Plant Life BasicsLeaves

Plant Life Basics
Leaves