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Tissues and the Primary Growth of Stems - Coggle Diagram
Tissues and the Primary Growth of Stems
Basic Types of Cells and Tissues
Parenchyma: Most common type of cell and tissue constituting all soft parts pf a plant.
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Thin Primary walls. Typically alive at maturity. Many functions.
Sclerenchyma
Primary walls plus secondary walls. Provides elastic support and some water transport.
Sclereids and fibers are mechanical noncuducting sclerenchyma
Tracheids and vessel elements are conducting sclerenchyma.
Collenchyma
Unevenly thickened primary walls. Typically alive at maturity. Provides plastic support.
Types of plant body
Primary plant body: usually herbaceous parts of a plant and derived from shoot and root apical meristems
Secondary plant body: Derived from meristems other than apical meristems usually the woody parts of plants like wood and barks.
External Organization of Stems
Arrangement of terms stem and shoot are nodes, internodes, leaf axil, axillary bud, bud scales, and terminal buds.
Arrangement of leaves on the stem, called phyllotaxy as a positioning leaves so they don't shade each other.
Leaves of pistachio are modified bud scales just as of pear buds modified spines.
Internal Organization of Stems: Arrangement of primary tissues.
Cortex
Interior to the epidermis is the cortex composed of photosynthetic parenchyma and collenchyma.
cortex of this stem of buttercup (ranunculus) is narrow band of cells between the epidermis.
Vascular Tissues
Two vascular tissue occur in plants as xylem and phloem
Phloem
Distributes sugar and minerals.
Vascular Bundles
Epidermis
Outermost single layer of parenchyma cells.
In most plants some epidermal cells elongate outward and become trichomes also called hairs.
Xylem
Conducts water and minerals
Stem Growth and Differentiation
Stems grows longer by creating new cells at their tips, in regions known as shoot apical meristems.
Region below apical meristem is the sub-apical meristem and its cells are also dividing and growing producing cells for region below.
Flowering plants discussed here are formally classified as division Magnoliophyta, informally as angiosperms.
