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Vegetable Nutrition


How plants nourish themselves

Plant nutrition is autotrophic, in this it differs from animal nutrition, which is heterotrophic.

While animals obtain food by eating other living things, plants themselves make the organic matter they feed them. For this they use carbon dioxide from the air and water and mineral salts (inorganic nutrition) taken from the ground.

Inorganic Nutrition

When we talk about inorganic nutrition, we are actually referring to absorption of mineral nutrients essential for good plant development. These nutrients exist in the substrate on which the plant lives (soil, water, and eventually aerial medium) and are mainly absorbed by the roots. Often, leaves also perform this role. Root absorption is effected from the piliferous zone, region in which the absorption surface is increased by the existence of the absorbent hairs.

When a nutrient is used in large quantities by a vegetable, it is considered a macronutrient. If used in small quantities, it is considered a micronutrient. These terms do not relate to the size of the nutrient, but to the amount in which they are used.
Micronutrients include manganese, copper, zinc and iron.

The table below summarizes the role of some macronutrients in the plant organism.

Nutrient

Physiological role

Nitrogen (N)

Essential for protein and nucleic acid synthesis.

Phosphorus (P)

Essential for the synthesis of ATP and nucleic acids.

Potassium (K)

Related ionic exchanges between cell and medium; involved in the opening movements of the stomata.

Sulfur (S)

Used for synthesis of essential amino acids.

Magnesium (Mg)

Chlorophyll molecule component.

The humus

Decomposition of plant debris in the soil by fungi, bacteria, worms, insects, etc. results in the mineralization of nutrients (carbon, nitrogen, phosphorus, sulfur, etc.), which are directly assimilated by plants or form other compounds.

Humus stabilizes soil structure, increasing its ability to absorb mineral ions (potassium, ammonium, magnesium and calcium) and regulating moisture, thus constituting an irreplaceable agent for soil fertility and conservation.

Organic Nutrition - Photosynthesis

Photosynthesis occurs mainly in the leaves of a tracheophyte. It is now convenient to give an idea of ​​the internal morphology of this organ related to organic nutrition.
Two epidermis, formed by flattened cells, cover an inner layer consisting basically of two tissues: the fill fabric it's the conductive fabric. The filling tissue is known as the parenchyma and is generally made up of two layers of living chlorophyll cells.
The layer near the upper epidermis has cells arranged in a palisade and is therefore called a palisade parenchyma. The other layer, near the lower epidermis, has irregular cells that are arranged leaving gaps between them, which gives this layer a spongelike appearance - it is the lacunous parenchyma. The cells in these layers are rich in chloroplasts. The conductive tissue makes up the ribs. Here the vessels are arranged in bundles of conductive tissue sheathed by special parenchymatic cells.

There are two types of vessels: those that bring to the leaf the water needed for photosynthesis, in addition to other inorganic substances - xylem vessels - and those that carry the food produced by the leaves to the stem and root - phloem vessels.

It is up to the chlorophyll parenchyma (another name given to the set formed by the palisade parenchyma and lacunous parenchyma) the role of nourishing the vegetable as the organic food necessary for its survival, from the realization of photosynthesis.

The light and dark stages of photosynthesis occur in chloroplasts. In the light (or photochemical) phase there is the participation of water and light, with oxygen release and ATP and NADPH production.2. In the dark (or purely chemical) phase occurs the Calvin cycle or the pentose cycle, during which there is a sequence of reactions involving carbon dioxide and the use of ATP and NADPH.2, produced in the clear phase, resulting in glucose molecules.

To learn more about photosynthesis, visit our material on the subject.