Understanding plant anatomy is vital for plant systematics and palaeobotany and evolutionary biology, physiology, ecology, and the rapidly growing field of developmental genetics. The chapter, which has been thoroughly rewritten and updated, covers all comparative plant structure and development elements in a series of different topics on the stem, root, leaf, flower, seed, and fruit.  The external morphology of larger living organisms, plants and animals, clearly shows structural similarities and variances. Similarly, examining the underlying structure reveals some commonalities as well as variances. This chapter describes the internal structure and functional organization of higher plants. Anatomy is the study of the interior structure of plants. Plants have cells as their basic unit, and cells are organized into tissues, which are then organized into organs. The internal anatomy of different organs in a plant differs. The monocots and dicots of angiosperms are likewise physically distinct. Internal structures exhibit adaptations to a variety of situations as well.

A tissue is a group of interdependent identical or non-identical cells and intercellular substances having a common origin performing a specific function in multicellular organisms.

Meristematic tissue

Meristematic tissue is a type of plant tissue that can divide itself actively throughout its life. These cells continue to divide until they get differentiated and lose the ability to divide.

Types of meristematic tissues

1. Apical meristematic tissue: Apical meristem is a region of cells in the root, shoot, and leaf tips capable of division and growth. These meristems produce the primary plant body and extend its roots and shoots. It generates new leaves. Hence, these are called the primary tissues in plant growth.
2.  Lateral meristematic tissue: Lateral meristem is present on the lateral side of the stem and root. It helps increase the plant's thickness and is responsible for its secondary growth.
3.  Intercalary meristematic tissue: This meristematic tissue is associated with the growth in length in the middle position of plants. These tissues are chiefly located in the leaves and internodes at the intercalary position. These help increase the size of the internode.

Permanent tissue

Permanent tissues are a group of living or dead cells formed by meristematic tissues that have lost their ability to divide. Permanent tissue cells are matured, assuming a definite shape, size and function. These cells are also modified to perform specific functions.

Types of permanent tissues

Permanent tissues are a group of living or dead cells formed by meristematic tissues that have lost their ability to divide. Permanent tissue cells are matured, assuming a definite shape, size and function. These cells are also modified to perform specific functions.

Types of permanent tissues

1. Simple tissue:  These simple tissues are made up of similar permanent cells that carry out the same function or a similar set of functions. There are mainly three types of simple tissues: parenchyma, collenchyma, and sclerenchyma.

1. Parenchyma: Such tissues have cells with thin primary walls made of cellulose with intercellular spaces.

2. Collenchyma: They are formed of living, closely packed isodiametric cells. Their cells are living, elongated, and have irregularly thickened corners. Collenchyma may form cylinders or discrete strands.

3. Sclerenchyma: It is formed of dead cells with thick, lignified walls meant for mechanical support. They have two types of cells: fibres and sclereids.

2. Complex tissue: These tissues are composed of different types of cells that have related functions. Xylem and phloem are two types of complex issues.

1. Xylem: It is one of the two types of transport tissue in vascular plants. It conveys water and dissolved minerals from the root to the rest of the plant and provides physical support.

2. Phloem: Phloem is the living tissue in plants that transports the soluble organic compounds made during photosynthesis. Phloem consists of different cells called sieve tubes, companion cells, phloem fibres, and parenchyma cells.

In Plant Anatomy NCERT, tissues are classified based on the type of cell present in them. Tissues vary in plant bodies by their location. Their function and structure also depend on location. Generally, there are three types of tissue systems based on their structure and function: 

• • Epidermal tissue system: It forms the outermost covering of the plant body. It is elongated. Generally, single-layered cells are arranged to form a continuous layer. This system contains epidermal cells and stomata.

  • Ground tissue system: Tissues other than the epidermis and vascular bundles form ground tissue. Simple tissues like parenchyma, collenchyma, sclerenchyma come under this system. Ground tissue consists of thin walls with cells called mesophyll, which have several chloroplasts.

  • Vascular tissue system: They contain complex tissues, xylem, and phloem. Xylem and phloem together constitute the vascular bundles. In dicotyledonous plant stems, cambium is present between the xylem and phloem. Because of its presence in the vascular tissue, the system can form secondary xylem and phloem tissue, called open vascular bundles.

 

The dicotyledons, dicots, or dicotyledonous plants are one of the two categories of flowering plants. The embryos of seeds of such plants also have a pair of leaves or cotyledons. They have two layers, the outermost epidermis, which sometimes forms root hairs. Unusually, dicotyledonous plants have solid stems. The secondary tissues in dicotyledonous roots are similar to those in dicotyledonous stems, but the process starts much differently. Some examples are sunflowers and mango.

Monocotyledons are grass-like flowering plants. Their seeds contain only one embryonic leaf. In monocotyledons, the xylem and phloem tissue bundles are arranged circularly around the central pith, containing ground tissue. Monocotyledonous roots have several vascular structures as compared to dicot roots. Some examples are maize, corn, grass, and wheat.

NCERT Class 11 Biology: Anatomy of Flowering Plants defines primary growth as the growth of roots and stems occurring with the help of the apical meristem. Dicotyledonous plants also show an increase in girth, which is called secondary growth. Lateral meristems, vascular cambium, and cork cambium are some tissues involved in secondary growth.

1. Explain three basic tissue systems in the flowering plants from Chapter 6 of NCERT Solutions for Class 11 Biology.

A. There are three basic tissue systems in flowering plants: epidermal tissue, ground tissue, and vascular tissue.

1. Epidermal tissue system: It is the outermost covering of the plant body. It consists of tissues like the epidermis, stomata, epidermal appendages, etc. The epidermis is generally composed of a single layer of parenchymatous cells compactly arranged without intercellular spaces.

2. Ground tissue system: It is the tissue that lies between the epidermis and vascular bundles. The ground tissue of the vascular plant stores carbohydrates produced by the plant. It consists of three simple tissues: parenchyma, collenchyma, and sclerenchyma.

3. Vascular tissue system: It is a complex conducting tissue in vascular plants formed from more than one cell type. This system contains complex tissues, xylem and phloem, that together form vascular bundles.

2. Why are phloem as well as xylem known as complex tissues?

A. Xylem and phloem are called complex tissues as they are made up of more than one type of cell. These cells work in a             coordinated manner as a unit to perform the tissues' various functions.  Xylem and phloem are also complex tissues                 because they consist of various elements, which are given below:

• • • Xylem: This conducting tissue is composed of four elements:

• • • • • Tracheids: They help conduct water along the plants' stems and provide mechanical support.

        • Vessels: A long, cylindrical, tube-like structure with lignified walls and a wide central cavity. Its functioning is almost similar to tracheids.

        • Wood fibres: These are found in both primary and secondary xylem. These are cellulosic elements that are extracted from trees for commercial purposes.

        • Wood parenchyma: The primary xylem parenchyma cell walls are thin and made of cellulose. It is used to store food material in the form of fat.

• • • Phloem: Another conducting tissue, it consists of four elements:

      • • Sieve cells: These are long, slender tube-like structures arranged in longitudinal series. Generally, they act as a channel for transporting sugar through plants.

        • Companion cells: These are specialized parenchyma cells closely associated with the sieve tube elements in their origin and function. They are used to provide energy to the sieve tube elements during translocation.

        • Phloem parenchyma: This is made up of elongated, living cells with dense cytoplasm and nuclei. These are also called transfer cells for transferring food.

        • Phloem fibres: These are much elongated, unbranched cells with pointed ends. Their cell wall is thick with slightly bordered pits. It supports the conductive cells to provide strength to the stem.

3. What will I learn from Chapter 6, Anatomy of Flowering Plants of NCERT Solutions for Class 11 Biology?"

A. Chapter 6 Anatomy of Flowering Plants Class 11 covers various important concepts like:

• • • Anatomy of flowering plants

    • The tissues

    • The tissue system and functioning

              (The three tissue systems are the dermal tissue system, the ground tissue system, and the vascular tissue                           system.)

• • • Anatomy of dicotyledonous and monocotyledonous plants.