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Epidermis (botany)

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**Epidermis Description:**
– The epidermis is the outermost cell layer of the primary plant body.
– Classified as dermal tissue, it is a main component of the dermal tissue system in various plant parts.
– Provides mechanical strength and protection.
– Contains cutin and cuticle to reduce water loss.

**Stoma Complex:**
– Pores known as stomata regulate gas and water vapor exchange.
– The stomata complex comprises guard cells and subsidiary cells.
– Guard cells have a distinct shape and function from epidermal cells.
– They swell in sunlight and close at night, with distribution varying on leaf surfaces.

**Cell Differentiation in Epidermis:**
– Pavement cells, guard cells, subsidiary cells, and trichomes make up the epidermis.
Trichome development is controlled by specific genes and plant hormones.
– Stomatal patterning is a controlled process influenced by environmental conditions.
– Differentiation processes differ between dicots and monocots.

**Guard Cell Function:**
– Bean-shaped cells containing chloroplasts, guard cells produce sugar through photosynthesis.
Sugar concentration affects water potential and stomatal opening.
– Guard cells become flaccid at night, closing stomatal pores to regulate water vapor escape.

**Epidermal Tissue Types:**
– Epidermis includes epidermal cells, guard cells, subsidiary cells, and trichomes.
– Trichomes develop at a distinct phase during leaf development, controlled by specific genes.
– Stomata are pores surrounded by guard cells, with patterning influenced by environmental conditions.

Epidermis (botany) (Wikipedia)

The epidermis (from the Greek ἐπιδερμίς, meaning "over-skin") is a single layer of cells that covers the leaves, flowers, roots and stems of plants. It forms a boundary between the plant and the external environment. The epidermis serves several functions: it protects against water loss, regulates gas exchange, secretes metabolic compounds, and (especially in roots) absorbs water and mineral nutrients. The epidermis of most leaves shows dorsoventral anatomy: the upper (adaxial) and lower (abaxial) surfaces have somewhat different construction and may serve different functions. Woody stems and some other stem structures such as potato tubers produce a secondary covering called the periderm that replaces the epidermis as the protective covering.

Cross-section of a flax plant stem:
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