There is usually a main root that grows into the earth, from which other secondary roots arise. Many absorbent hairs emerge from the roots , which are responsible for absorbing water and mineral salts.
Axonomorphic or pivoting: several secondary roots emerge from the main root, which is thicker.
Fasciculated: the main root cannot be distinguished from the secondary ones, they all have a similar thickness.
Napiform: the root thickens by accumulating reserve substances, such as carrots, radishes or turnips.
Adventitious or aerial: they do not come from the embryo of the plant, but from another place, such as in the nodes of the stems. This type of root is used by some plants for climbing (such as ivy) or for spreading along the ground.
It contains in its interior the conductive vessels through which water and mineral salts (crude sap) are transported from the root to the leaves (through the xylem), and the organic matter (processed sap) produced in the leaves by photosynthesis from the leaves to the rest of the plant (through the phloem).
Stems grow by multiplying the cells that form their buds. The buds can be:
Terminal or apical buds: at the ends of the stems. They are responsible for the growth in length of the stems.
Axillary or lateral buds. They are responsible for the appearance of branches and leaves on the stems.
The stem has knots, thickenings where the axillary buds are found, from which the branches come out, and internodes, spaces without branches.
The leaves can also be transformed to perform other functions, such as:
Some transform into scales to protect the buds.
Some become spines to protect themselves from desiccation and herbivores.
Some transform into fleshy leaves to store water.
Leaves have three parts:
Blade: is the flat part of the leaf. It is green in color because of the chlorophyll of the chloroplasts, the cellular organelles responsible for carrying out photosynthesis.In the limbus the conductive vessels (nerves) can be distinguished. The upper part of the limb is called the upper part, and the lower part, the lower part . It contains the stomata, which carry out gas exchange .
Petiole: it is the corner that joins the blade with the stem.
Sheath: it is the widest part of the petiole, with which it joins the stem.
The leaves can have very varied shapes , which can be classified according to different criteria:
Depending on the number of limbs: they can be simple (only one) or compound (several).
Depending on the shape of the blade: heart-shaped, rounded, acicular, etc.
Depending on the edge of the blade: serrated, toothed, whole, etc.
According to the arrangement of the nerves: uninervias, parallelinervias, palmatinervias, etc.
According to their arrangement along the stem: alternate, opposite.
Depending on whether or not it has a petiole: petiolate and seated.
Spermatophytes (seed plants) are classified into two groups:
Gymnosperms. They are the oldest. They are plants that produce seeds but are not contained within a fruit. Their ovules are naked , without an ovary, so after fertilization only the seed is produced and the fruit does not appear. For example, the pine.
Angiosperms. Its flower has an ovary that contains ovules that are fertilized with the arrival of the pollen grain. A seed is formed enclosed within that ovary which later develops into a fruit. For example, the almond tree.
Monocots (with a single leaf when the seed germinates).
Dicots (with two leaves when the seed germinates).