Meristems are important regions for the plant and can be defined as tissues that have preserved their ability to divide. They are, therefore, the tissues responsible for plant growth, as they add cells indefinitely to the plant.
→ Meristem characteristics
The meristem is a tissue that constantly supplies cells to the plant because of its intense capacity for cell division. Its cells are small, do not have a secondary cell wall, have very small vacuoles, and have undifferentiated plastids.
→ Classification of meristems
Meristems can be classified in different ways, one of which is based on their position in the plant body. According to this classification, they can be apical and lateral.
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Apical meristems: are those found at the tip of the root and at the tip of the stem and its branches. They guarantee the growth in length of the plant and therefore enable the primary growth of the plant.
The apical meristems give rise to primary meristems (protoderm, fundamental meristem and procambium), which are partially differentiated tissues that remain meristematic for a certain time until they start to differentiate. THE
protoderm generates the epidermis; O fundamental meristem form the parenchyma, collenchyma and sclerenchyma, it's the prochange gives rise to the xylem and to the phloem. All tissues formed by primary meristems are called primary tissues. Lateral meristems: they are located parallel to the surface of the stem and root. These meristems (vascular exchange and phelogen) are related to secondary growth of the stem and root (growth in thickness). O vascular exchange it is responsible for producing secondary vascular tissues: secondary xylem and secondary phloem. O phelogen, in turn, produces the periderm, a set of tissues that replaces the epidermis.
Intercalated meristem: meristem located between mature tissues.
We can classify meristems also according to their origin. So they can be primary and secondary.
Primary meristems: are those that are present in the plant from the embryo.
Secondary meristems: are those that are formed from already differentiated primary tissues and are responsible for originating secondary tissues.
By Ma. Vanessa Sardinha dos Santos
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/biologia/o-que-e-meristema.htm
