Plant Anatomy: Cells and Tissues

• Botany is the scientific study of plants

Plant Anatomy

• Plant anatomy is the study of the internal structure of plants
• It involves examining cells, tissues, and organs at macroscopic and microscopic levels

Cells and Tissues

• Plant cells are the basic structural and functional units
• Plant tissues are groups of cells performing specific functions

Cell Types

• Parenchyma cells are fundamental, involved in storage, photosynthesis, and secretion
• Collenchyma cells provide flexible support in growing regions
• Sclerenchyma cells provide rigid support and may be dead at maturity
• Xylem cells (tracheids and vessel elements) conduct water and minerals
• Phloem cells (sieve tube elements and companion cells) transport sugars

Tissue Types

• Meristematic tissues are zones of active cell division (apical, lateral, intercalary)
• Epidermis forms the outer protective layer of the plant
• Ground tissue includes parenchyma, collenchyma, and sclerenchyma
• Vascular tissue consists of xylem and phloem, for transport

Organs

• Plant organs are structures composed of different tissues, performing specific functions (roots, stems, leaves, flowers, fruits, seeds)

Roots

• Roots anchor the plant, absorb water and nutrients, and store food
• The root cap protects the root apical meristem
• The epidermis is the outer layer with root hairs for absorption
• The cortex is ground tissue for storage
• The vascular cylinder contains xylem and phloem
• Endodermis regulates movement of water and minerals into the vascular cylinder
• Lateral roots originate from the pericycle

Stems

• Stems support the plant, transport water and nutrients, and bear leaves and flowers
• Nodes are points where leaves attach
• Internodes are stem segments between nodes
• Buds develop into new shoots or flowers
• Vascular bundles contain xylem and phloem
• In dicots, vascular bundles are arranged in a ring
• In monocots, vascular bundles are scattered

Leaves

• Leaves are the primary photosynthetic organs
• The epidermis is the protective outer layer, often with a waxy cuticle
• Stomata are pores for gas exchange, regulated by guard cells
• Mesophyll is the ground tissue where photosynthesis happens (palisade and spongy)
• Vascular bundles (veins) contain xylem and phloem

Flowers

• Flowers are reproductive structures
• Sepals protect the developing flower
• Petals attract pollinators
• Stamens are male reproductive structures (anther and filament)
• Pistil (carpel) is the female reproductive structure (stigma, style, ovary)
• Ovules within the ovary contain the egg cells

Fruits

• Fruits develop from the ovary after fertilization
• They protect seeds and aid in seed dispersal
• Fruit types: simple, aggregate, multiple

Seeds

• Seeds contain the plant embryo and food reserves
• Seed coat protects the embryo
• Cotyledons are seed leaves
• Endosperm is the food storage tissue
• Embryonic root (radicle) and shoot (plumule) are present

Vascular Tissue System

• Xylem transports water and minerals from roots to shoots
• Tracheids and vessel elements are the conducting cells
• Lignin provides structural support
• Phloem transports sugars from sources to sinks
• Sieve tube elements and companion cells are the conducting cells
• Plasmodesmata connect companion cells and sieve tube elements

Specialized Structures

• Trichomes are epidermal hairs with various functions
• Glands secrete substances
• Thorns are modified stems for protection
• Spines are modified leaves for protection
• Tendrils are modified stems or leaves for climbing