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How do apical meristems extend plant roots and shoots?
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Plant development
The life cycle of the fern. (1) Clusters (sori) of sporangia (spore cases) grow on the undersurface of mature fern leaves. (2) Released from its spore case, the haploid spore is carried to the ground, where it germinates into a tiny, usually heart-shaped, gametophyte (gamete-producing structure), anchored to the ground by rhizoids (rootlike projections). (3) Under moist conditions, mature sperm are released from the antheridia and swim to the egg-producing archegonia that have formed on the gametophyte's lower surface. (4) When fertilization occurs, a zygote forms and develops into an embryo within the archegonium. (5) The embryo eventually grows larger than the gametophyte and becomes a sporophyte.
Apical meristems are regions of undifferentiated, actively dividing cells located at the tips of roots and shoots that are responsible for the primary growth of plants. They function as a continuous source of new cells, allowing plants to grow throughout their entire life span.123
How They Extend the Plant Body
The extension of roots and shoots occurs through a process of cell division and subsequent development:
- Cell Division: Within the apical meristem, specialized cells called initials undergo mitosis. When an initial cell divides, one daughter cell remains in the meristem to maintain the population of dividing cells, while the other is displaced into the plant body as a derivative cell.13
- Primary Meristems: These derivative cells form three primary meristematic tissues—the protoderm, ground meristem, and procambium—which eventually differentiate into the epidermis, ground tissues, and vascular tissues, respectively.123
- Elongation: In roots, extension is driven significantly by cell elongation in the region immediately behind the apical meristem, rather than by cell division alone.1
While shoot apical meristems produce leaves and buds, root apical meristems are protected by a root cap as they push through the soil.13