In temperate regions, exchange activity varies throughout the year. Currency activity is very intense during spring and summer, gradually decreasing in the fall until it ceases completely in the winter.
At the end of summer, when it is ending another cycle of activity, the gearbox produces thick-walled, narrow-lumen woody vessels, which make up the summer wood. In the spring, when resuming its operation after winter rest, the cambium produces woody vessels with thin walls and large lumen, which constitute the spring wood.
Tree trunks that live in temperate regions therefore have springwood rings. When these trunks are observed in cross section, these rings are easily identifiable and The number of ring pairs corresponds to the age of the tree.
Growth and development
Plant growth begins from seed germination. Hydration of the seed, for example, activates the embryo. The reserves contained in the endosperm or cotyledons are hydrolyzed by enzymatic action. Embryonic cells receive the necessary nutrients, metabolism increases and the cell divisions that will lead to growth begin.
The root is the first structure to immerse; Then the stem is externalized and the seedling begins a long process that will culminate in the adult vegetable.
What is the difference between growth and development?
These two terms are often used synonymously. However, there is a difference between them:
- O growth corresponds to an irreversible growth in the size of a plant, and is given by the addition of cells resulting from mitotic divisions, in addition to the individual size of each cell. In general, growth also involves increasing the volume and mass of the vegetable. Growth involves measurable quantitative parameters (size, mass and volume).
- O development It consists of the appearance of different cell types and the various tissues that are part of the plant organ. It is certainly a phenomenon related to the process of cell differentiation. The development involves quantitative aspects related to the increasing complexity of the plant.
The occurrence of these two processes is simultaneous. A vegetable grows and develops at the same time.