Plant Anatomy: Tissue Types

Tissue Types

• Parenchyma, collenchyma, and sclerenchyma are three main tissue types.

Meristematic Tissue

• Main site of cell division.
• Types: apical, lateral, and intercalary meristems.

Ground Tissue

• Neither vascular nor dermal.
• Functions: support of the plant.
• Consists of parenchyma, collenchyma, and sclerenchyma.

Ground Parenchyma

• Uniformly thin-walled, alive at maturity.
• Functions: photosynthesis, storage, secretion, wound-healing, and cloning.
• Generic plant cell, spherically shaped.
• Most abundant and versatile.
• Functions include food storage, flesh of fruit, storage in roots and seeds, and basic metabolism.
• Has the primary cell wall (cellulose).

Types of Ground Parenchyma Cells

• Chlorenchyma: photosynthetic parenchyma cells, contain chloroplasts.
• Storage parenchyma: contain lots of amyloplasts.
• Aerenchyma: large air spaces.
• Stellate parenchyma: highly branched with adjacent cells connected by branches.

Ground Collenchyma

• Unevenly thickened walls, irregular, alive at maturity.
• Functions mainly for support in primary growth.

Ground Sclerenchyma

• Evenly thickened walls, dead at maturity.
• Provides strength, support, and protection.
• Do not retain their protoplasts at maturity.
• Cell walls absorb stains, often very visible.

Fibers and Sclereids

• Fibers: unbranched, for conduction of water, sugar, nutrients.
• Sclereids: for protection, have both primary and secondary cell walls (lignified).

Types of Sclereids

• Brachysclereids: stone cells.
• Macrosclereids: rod-like.
• Osteosclereids: bone cells.
• Astrosclereids: star cells.

Vascular Tissues

• Transport substances through the plant body.
• Consists of xylem and phloem.
• Xylem: conducts water and nutrients from roots to shoots.
• Phloem: conducts sugars and amino acids from leaves to roots or flowers.

Dermal Tissues

• Outer layer of tissues surrounding the entire plant.
• Functions: protection, gas exchange, and water absorption.
• Epidermis: made of parenchyma cells in a single layer.
• Cuticle: comprised of a single layer of epidermal cells, provides protection.

Epidermal Structures

• Stem: has cuticle for prevention of water loss.
• Roots: aid in water and mineral absorption, lack a cuticle.
• Stoma/stomatal pore: for entry and exit of gases.
• Guard cells: regulate the size of stomata, control gas exchange and water loss.
• Trichomes: hairs on the epidermis for protection and prevent water loss.
• Root hairs: increase the root surface area for absorption.