The seed – the mature and fertilized ovule of the plant – begins to grow by absorbing water from the soil and consuming its own reserves of nutrients. When the first leaves appear, the plant begins to generate nutrients through photosynthesis, absorbing water, light and carbon dioxide from the environment. Tree is the name given to large woody vegetation, over 3 meters high and formed by root, stem, branches and leaves. They are classified in angiosperms (when they give flowers and the seeds are protected by a fruit) and gymnosperms (plants without fruits and whose seeds have no protection). It is estimated that there are about 100,000 species of trees, which represents 25% of all plant organisms on the planet today. ;-]
GROWTH SHOW
Evaporation of water by the leaves stimulates the rise of minerals captured by the root
The tree begins to “be born” when germination occurs and the three main parts of the seed come into play:
• The integument protects the internal content;
• The embryo is formed by microstructures, such as the radicle (or embryonic root) and the cotyledons, which will give rise to the first leaves;
• The endosperm is a nutritional reserve tissue
Under favorable conditions of water, temperature and light, the embryo leaves the state of latency and begins to develop. The seed absorbs water from the soil and increases in volume. This growth causes the bark to break and the radicle, the structure that gives rise to the root, elongates towards the ground.
The next step is the development of the seedling, name given by botanists to the young plant, still incapable of carrying out photosynthesis. At this stage, the root elongates and branches into the ground to anchor the tree to the ground.
At about the same time, aerial parts such as the stem and cotyledons develop. Also called “first leaves”, they are rich in nutrients and “feed” the seedling in the initial growth phase, when it does not yet have “true” leaves capable of carrying out photosynthesis.
In photosynthesis, sunlight is absorbed by chloroplasts – microstructures that store chlorophyll, the substance that gives green color to leaves. Chlorophyll and solar energy transform, through chemical reactions, the water captured by the root and the carbon dioxide (CO2) taken from the atmosphere into glucose and other nutrients.
Tiny pores on the leaves open to capture CO2 and lose water through evaporation. To compensate for dehydration, the water absorbed by the root, rich in mineral salts such as potassium, phosphorus and nitrogen, travels to the top of the plant through a set of tissues and vessels called xylem.
While the xylem carries water and minerals to the leaves, the phloem distributes the sap that “feeds” the entire plant. The sap is a liquid formed by sugars, amino acids and organic acids resulting from photosynthesis.
Thickening of the trunk and branches occurs when vascular cambium cells multiply, generating xylem and phloem. The dead cells of the xylem form the heartwood fibers – the tissue that supports the plant. Chlorophyll accumulates in the innermost tissues and the stem ceases to be green.