Parts of a sheet and their functions

In the structure of the sheet several parts are distinguished. These are the main parts of the sheet and their functions :

Limbo

The blade , also called lamina , is what is often commonly referred to as leaf, despite the fact that the word really does all the other parts as well. It refers to the part (usually flat and wide or long) of the leaf that is responsible for collecting sunlight, hence its shape usually offers as large a surface as possible. It has two faces, the upper side or upper side and the lower side or lower side . The first tends to be smoother and shinier, while in the second we find the veins or nerves of the leaf more clearly , which can cross it giving rise to different shapes or patterns and the sap circulates through them .

In addition, if we ask ourselves what is the external part of the leaf, we may be referring to either the outer margin of the blade, which can have very different shapes, or the apex , which is the end furthest from its birth. Depending on the shape of the leaves, we can easily recognize the different species of plants and trees. Here you can learn how to identify trees from leaves .

Petiole

The petiole is what joins the blade of the leaf with the stem of the plant. It is a thin structure with an intense green color, whose function is to supply sap to the leaf and back from it, in addition to giving the blade a firm hold against the elements.

Sheath

At the base of the petiole is the sheath, which is the point where it widens to join and settle on the stem . Therefore, it is the point at which the leaf begins to grow from the stem of the plant.

Stipule

Finally we have the stipules, which grow on both sides from the petiole or the base of the leaf. Not all plants have stipules and these can have many different shapes. Its function is always to protect the stems and young leaves, which is why some fall off when the leaf matures.

In the cover image of this article and in this one below you will see a diagram of the parts of the sheet and their functions you will be able to see it more easily.

When we talk about the functions of a leaf , the main and most important of them, photosynthesis, comes to mind, but it is true that there is more:

• Perform photosynthesis . Thanks to the chloroplasts, which give the plant its green color due to the chlorophyll they contain, the plant is able to form sugars from the energy received from sunlight and the CO2 that the plant absorbs. To learn more about these topics, we recommend you read these other posts about the Difference between photosynthesis and respiration of plants and Why plant leaves are green . The function of photosynthesis is vital not only for the plant, but for the conformation of life on our planet. During the evolution of plants, photosynthesis was what allowed the Earth’s atmosphere to be enriched in oxygen, the ozone layer was created and life on Earth was possible. Thus, the plant can be nourished thanks to this process in which the plant uses the solar energy captured by the leaves to transform the raw sap that reaches them into elaborated or enriched sap, which is loaded with nutrients and is distributed to the parts of the plant that need it.
• Another function of the leaves is the respiration function . The plant absorbs the oxygen present in the atmosphere, expelling carbon dioxide in return. This respiration is produced by the stomata of the leaf .
• Finally, the leaves also fulfill the function of perspiration . The stomata, in addition to breathing, can open to release water and evaporate it, thus eliminating the excess of this and allowing the thermal and water regulation of the plant. In addition, there are theories that argue that this evaporation helps to create a negative pressure in the ducts of the plant, which allows the circulation of the raw sap from the roots, thus facilitating that even large trees can lead it to their high branches without expense. of energy.

Knowing all this, now you may also be interested in learning about the Parts of a plant and their functions and also about the Parts of a tree and their functions , because in addition to the leaves, there are many more parts that make up these vegetables.

There is a great diversity in the forms and characteristics that the leaves adopt. In fact, although most blades are flattened and wide or elongated, they do not always have that shape. Conifers, for example, are characterized by their squamiform, that is, needle-shaped leaves. Thus, we can classify the sheets according to different criteria:

• Depending on whether they are simple or compound leaves : when a blade is born from each petiole, the leaf is simple. On the contrary, if several blades are born from a single petiole, it is a compound leaf. These can be binate, ternate, quinate or finger, depending on the number of leaflets, or pinnate, if the leaflets all emerge from a single axis.
• According to the arrangement of the veins or the veins of the leaves : these can be parallelinervias, penninervias, palminervias, dichotomicos or uninervias.
• According to the shape of the leaf blade : they can be sagittate, oval, orbicular, spatulate, acicular, squamous, heart-shaped, rhomboid, lanceolate, linear, tapered, webbed or kidney-shaped.
• There are many other classifications, such as according to the shape of the edge of the blade, according to the petiole or according to the arrangement of the leaves on the stem, among others. Discover all these ways of classifying leaves with this other AgroCorrn guide on Leaf Types .