What are leaves ? The leaves are one of the five plant organs , usually green in color due to the presence of chloroplasts containing the chlorophyll pigment.
Since they are the main carriers of chlorophyll , the leaves are responsible for the photosynthesis of plants.
They originate through the stem apical meristem and can have different formats and specializations.
Index [ hide ]
- Leaf morphology
- Leaf anatomy
- Sheet functions
- Types of leaves
- Leaf adaptations
While not all be complete, most d the sheets have four shares :
Limbo : also called leaf blade, this is the part that we popularly call leaf. It consists of epidermis, mesophyll and ribs (the vascular bundles), it is also the clean that performs photosynthesis;
Petiole : it is the stem that holds the limbus to the stem;
Stipular : it is a modified leaf, very small and that protects the stem meristem that is at the base of the petiole;
Sheath : covers the base of the petiole and stipple next to the stem, serves to protect the plant.
The leaf blade , although often thin and delicate, is a complex structure composed of many different cell types , from top to bottom we have:
Cuticle : thin layer of wax or other lipid substances that covers the epidermis;
Adaxial epidermis : covers the upper part of the leaf and can have many specializations such as trichomes, for example;
Mesophyll : composed of parenchymal cells that contains many chloroplasts, that’s why it is called chlorenchyma. The cells can be organized in two ways: palisade parenchyma (cells stacked next to each other) and lacunous parenchyma (cells arranged in a disorganized manner, forming many intercellular spaces);
Ribs : it is the branching of the vascular system within the leaves , each streak that we observe even with the naked eye in the limbus is a vascular bundle containing xylem (always facing the adaxial epidermis) and phloem (always facing the abaxial epidermis);
Abaxial epidermis : covers the underside of the leaves, most often it is where the stomata are located.
What is the function of leaves ? The main function of the leaves is to absorb the light energy from the Sun and transform it into chemical energy through the process of photosynthesis.
However, biologically they are also responsible for gas exchange that happens through the processes of sweating and breathing.
Many plant species have their leaves used as habitat for small insects, fungi and bacteria and can also be used as food by various animals.
In addition, many leaves are used by industry as a raw material for the production of medicines and cosmetics.
Types of leaves
The leaves can be separated into two large groups: simple and compound. The difference between them is in the organization of the limbo.
The simple leaves have the limbus with only one blade coming out of the petiole.
The compound leaves have more than one blade per limbus, but they all start from the same petiole. Each leaf blade of the compound leaves is called a leaflet.
Leaf Types – Simple and Compound
Also read: Classification of leaves
The leaves have many adaptations to the place where they live, they can be morphological or anatomical.
Among the anatomical sheets we can mention the presence of specialized cell types, such as bulliform cell and pulvinus that promote a small leaf movements, ensuring greater abs the sunlight rção or even protecting the excess incidence of it.
The cuticle and epidermis can also vary in thickness to increase the plant’s protection and prevent excessive water loss.
In addition, the epidermis can also specialize, presenting trichomes that can only increase the epidermal surface and provide mechanical protection as well as secrete substances.
Among the morphological changes are the size and shape of the leaf blade and the stomata that may be present on both sides of the epidermis.