As important as it is the fruit of some plants, the leaves of some species are extremely useful to man, directly or indirectly. It feeds and nourishes them the cattle, which hardly survive without pasture. The leaves of certain vegetables, such as lettuce, cabbage, spinach and chard, to name a few, come to our table and we know perfectly their texture, flavor, color, moisture and composition.
The functions of the plant leaves
Each sheet we see in a plant, is a specialized organ that has the primary function of photosynthesis. That is why the sheets are generally wide and flat, so that exhibit a high surface to sunlight. Its morphology is also suitable for gas exchange (oxygen, carbon dioxide and water vapor).
Develop, grow and acquire its final size, especially in spring. As no meristematic tissue, its duration is short. They do not live long, a few weeks in desert plants, a few months in most of the trees, and three or four years in the evergreens.
Characteristics of the leaves of the plants
A typical blade is formed by a shaft called petiole which joins the stem and a wide blade or lamina, which can be simple or compound. The petiole can be long, short, or absent. In cross-section and is regarded that the microscope comprises, like the stem; by vascular bundles, at one end attached to the stem and on the other to the main rib of the limbus. In the lamina repeatedly beams diverge to form the sheet rib.
A cell layer protects the leaves, forming what is called the epidermis, it is found in numerous pores or stomata, that control the flow of water and gas exchange. In the presence of sunlight, there performs photosynthesis, forming glucose and other active substances. In absence of light, the photosynthesis is suspended.
The veins of a leaf, as mentioned, forming a thin branch network. Each rib has tissues xylem and phloem, two types of fibrous tissues that are also on the inside of the stem bark and trunk. With these veins are formed which lead the water, minerals and nutrients in general, also serving to support the fabric sheet softer.
The leaves of certain plants are thick and fleshy desert and serve to store water and to retain it, are some layers of cells together, with thicker cuticles stomatal closure of the epidermis somewhat hollow, to reduce perspiration.