Plant Tissues and Anatomy

Plants, like animals, are made up of various types of tissues that perform specific functions. Understanding plant tissues and internal structures is important to learn how plants grow, transport nutrients, and respond to the environment.

In this chapter, we explore two main areas:

1. Plant Tissues
2. Anatomy of Plant Organs (Stem, Root, Leaf)

🧫 1. Plant Tissues

Plant tissues are broadly divided into two types:

1.1 Meristematic Tissue

These are actively dividing tissues found in regions of growth.

🔹 Types of Meristems:

1. Apical Meristem: Located at the tips of roots and shoots. Responsible for primary growth.
2. Intercalary Meristem: Found at the base of leaves or internodes. Helps in regrowth.
3. Lateral Meristem: Found along the sides of stems and roots. Responsible for secondary growth (increase in girth).

✏️ Features:

• Thin-walled, dense cytoplasm
• Prominent nuclei
• No vacuoles or intercellular spaces

1.2 Permanent Tissue

These are derived from meristematic tissues and have lost their ability to divide.

A. Simple Permanent Tissues

Comprised of similar types of cells.

1. Parenchyma:

• Living, thin-walled cells
• Functions: storage, photosynthesis (chlorenchyma), support (aerenchyma)

1. Collenchyma:

• Living, thickened corners (cellulose and pectin)
• Provides flexibility and support to young stems

1. Sclerenchyma:

• Dead, thick-walled (lignified)
• Two types: fibres and sclereids
• Provides mechanical strength

B. Complex Permanent Tissues

Made of different types of cells working together.

1. Xylem (Water-conducting tissue):

• Components: tracheids, vessels, xylem fibres, xylem parenchyma
• Function: conduction of water and minerals from roots to other parts

1. Phloem (Food-conducting tissue):

• Components: sieve tubes, companion cells, phloem fibres, phloem parenchyma
• Function: translocation of food from leaves to other parts

🌿 2. Tissue Systems in Plants

Plant tissues are arranged in three systems:

2.1 Epidermal Tissue System

• Outermost layer
• Includes: epidermis, cuticle, stomata, trichomes
• Function: protection, transpiration, gas exchange

2.2 Ground Tissue System

• Main body of plant
• Includes: cortex, pericycle, pith
• Function: storage, support, photosynthesis

2.3 Vascular Tissue System

• Consists of xylem and phloem
• Arranged in vascular bundles
• Function: transport of water, minerals, and food

🌾 3. Anatomy of Plant Organs

3.1 Dicot Stem (e.g., sunflower)

🔍 Structure (from outside to inside):

1. Epidermis: Covered with cuticle, has trichomes.
2. Cortex: Contains collenchyma and parenchyma.
3. Endodermis: Innermost layer of cortex.
4. Pericycle: May contain sclerenchyma.
5. Vascular Bundles: Arranged in a ring; conjoint, collateral, open type.
6. Pith: Central region, made of parenchyma.

📌 Special Feature:

• Vascular bundles are open (with cambium) and radial.

3.2 Monocot Stem (e.g., maize)

🔍 Structure:

• Epidermis: With cuticle
• Hypodermis: Made of sclerenchyma
• Ground tissue: Uniform, no distinct cortex and pith
• Vascular bundles: Scattered, closed, surrounded by bundle sheath

📌 Special Feature:

• Vascular bundles scattered and closed (no cambium)

3.3 Dicot Root (e.g., bean)

🔍 Structure:

• Epidermis: Called epiblema
• Cortex: Parenchyma cells
• Endodermis: Single layer, regulates entry to vascular tissues
• Pericycle: Gives rise to lateral roots
• Vascular bundles: Radial, xylem and phloem alternate
• Pith: Small or absent

📌 Special Feature:

• Exarch xylem: protoxylem towards periphery

3.4 Monocot Root (e.g., maize)

🔍 Structure:

Similar to dicot root with key differences:

• Vascular bundles are polyarch (many xylem bundles)
• Large, well-developed pith
• Xylem is exarch

3.5 Dicot Leaf (Dorsiventral Leaf)

🔍 Structure:

• Epidermis: Upper (adaxial) and lower (abaxial), with stomata mostly on lower side
• Mesophyll: Differentiated into:
• Palisade parenchyma (photosynthesis)
• Spongy parenchyma (gas exchange)
• Vascular bundles: Surrounded by bundle sheath

3.6 Monocot Leaf (Isobilateral Leaf)

🔍 Structure:

• Both epidermal surfaces have stomata
• Mesophyll not differentiated
• Vascular bundles are parallel, arranged in rows

The internal structure and arrangement of tissues in plants are adapted to perform various essential functions—support, transport, storage, and growth. Understanding plant tissues and anatomy helps us grasp how plants survive, adapt, and perform physiological activities.

For Class 11 Maharashtra Board students, this chapter builds a strong conceptual foundation for advanced studies in botany and plant physiology.