Revision: Structural Organisation in Plants and Animals >> Anatomy of Flowering Plants Biology Science (English Medium) Class 11 CBSE

A group of similar cells, along with intercellular substances which perform a specific function, is called a tissue.

• Cells that perform a particular function always live in a group. This group of cells is called a tissue.
• For example, blood, phloem, muscle, etc. are examples of tissues.

A group of similar cells which perform a specific function.
example: Muscular tissue in animals.

A tissue is a group of cells that are similar in structure and are organized together to perform a specific task.

The tissue is a group of cells of similar structure and function.

Vascular tissue is the complex plant tissue in higher plants that are composed of xylem and phloem and is concerned with conducting water, minerals, and organic food throughout the plant body.

A tissue, in biology, is defined as a group of cells that have a similar structure and perform a specific function. The word tissue originates from French, which means "to weave."

Meristematic tissue is a group of cells that constantly divide and produce cells indefinitely throughout the life of the plant.

Permanent tissue refers to a group of cells which temporarily or permanently cease to divide and thus assume permanent form and function

• Anatomy = Study of Internal Structure - Plant anatomy is the study of the internal structure of plants, which includes the organisation and structure of tissues.
• Basic Unit = Cell - The basic unit of plants is the cell. Cells are organised into Tissues → Organs (organisational hierarchy).
• Tissue Definition - A tissue is a group of similar cells having a common origin that perform a specific function together.
• Monocots vs. Dicots - Anatomical (internal structural) differences exist between monocots and dicots, so it's important to know them separately.
• Internal Structure Adapts - The internal structures of plants adapt according to their environment (e.g., water availability, climate), and structural similarities exist in both external and internal morphology of organisms.

• Meristematic tissue consists of cells that can divide and is restricted to specialised regions of the plant.
• Apical meristem is found at the root and shoot tips, is a primary meristem and increases the length of the plant.
• Intercalary meristem is found between mature tissues, is a primary meristem and helps form branches and flowers.
• Lateral meristem is found in mature regions, is a secondary meristem and is responsible for secondary growth (e.g. vascular cambium, cork cambium).
• Axillary bud is present in the axils of leaves and is responsible for forming branches or flowers.

• Parenchyma has thin-walled cells with intercellular spaces; the cell wall is made of cellulose. It performs photosynthesis, storage and secretion.
• Collenchyma is made of living, closely packed cells that are thickened at corners due to the deposition of cellulose and pectin. It provides mechanical support to young stems and petioles.
• Sclerenchyma is made of dead cells with thick, lignified walls and has two types of cells: fibres and sclereids.

Xylem

• Xylem consists of tracheids, vessels, xylem fibres and xylem parenchyma. It conducts water and minerals from roots to other parts of the plant.
• In stems (endarch), protoxylem is towards the centre and metaxylem towards the periphery. In roots (exarch), protoxylem is towards the periphery and metaxylem towards the centre.

Phloem

• Phloem consists of sieve tube elements, companion cells, phloem fibres and phloem parenchyma. It transports food from leaves to various parts of the plant.
• Mature sieve tube elements lack a nucleus, so their functions are controlled by the nucleus of companion cells.
• Protophloem has narrow sieve tubes (first formed), and metaphloem has bigger sieve tubes (later formed).

• Epidermal tissue is the outermost covering of the plant body, made up of epidermal cells, stomata, trichomes and root hairs.
• Epidermis is a single layer of compactly arranged parenchymatous cells covered with a waxy cuticle (absent in roots) to prevent water loss.
• Stomata regulate transpiration and gaseous exchange; each stoma has two bean-shaped guard cells (dumb-bell shaped in grasses).
• Stomatal apparatus = stomatal aperture + guard cells + subsidiary cells.
• Root hairs are unicellular extensions of epidermal cells that absorb water and minerals from the soil.
• Trichomes are stem hairs that may be branched, unbranched or secretory, and help prevent water loss.

• Ground tissue includes all tissues except epidermis and vascular bundles, and is made up of parenchyma, collenchyma and sclerenchyma.
• In dicot stems and roots, ground tissue is divided into hypodermis, cortex, endodermis, pericycle, medullary rays and pith.
• Parenchyma cells are found in the cortex, pericycle, pith and medullary rays in primary stems and roots.
• In leaves, ground tissue is called mesophyll, which consists of thin-walled cells containing chloroplasts.

• Vascular bundles = Xylem + Phloem together, and they form the vascular tissue system.
• Open vascular bundles are found in dicot stems where cambium is present between xylem and phloem, allowing the formation of secondary tissues.
• Closed vascular bundles are found in monocot stems where cambium is absent, so no secondary growth takes place.
• Radial bundles have xylem and phloem placed on different radii (alternating with each other) and are found in roots.
• Conjoint bundles have xylem and phloem on the same radius, with phloem always on the outer side of xylem, and are found in stems and leaves.

• The epidermis is the outermost layer and bears unicellular root hairs.
• The cortex is comparatively narrow in dicot roots.
• The number of xylem and phloem bundles is limited, usually ranging from 2 to 5.
• The pith is either absent or very small in size.
• Secondary growth occurs due to the formation of vascular cambium.

• The cortex is very wide in monocot roots.
• The xylem and phloem bundles are numerous, usually more than six (polyarch condition).
• The pith is large and well-developed.
• Casparian strips are clearly visible in the endodermis.
• Secondary growth is absent in monocot roots.

• The vascular bundles are arranged in a ring.
• The vascular bundles are open, as cambium is present between xylem and phloem.
• The ground tissue is differentiated into cortex, endodermis, pericycle, and pith.
• The hypodermis is made of collenchymatous cells that provide mechanical support.
• The stem shows secondary growth due to the activity of the cambium.

• The leaf has distinct upper (adaxial) and lower (abaxial) epidermis.
• The abaxial epidermis contains more stomata than the adaxial epidermis.
• The mesophyll is differentiated into palisade parenchyma and spongy parenchyma.
• The vascular bundles are present in the veins and midrib and are surrounded by a bundle sheath.
• The leaf shows reticulate venation.

• Stomata are present on both upper and lower surfaces of the leaf.
• The mesophyll is not differentiated into palisade and spongy parenchyma.
• Bulliform cells are present and help in reducing water loss during stress conditions.
• The vascular bundles are surrounded by a bundle sheath.
• The leaf generally shows parallel venation.

• The leaf has distinct upper (adaxial) and lower (abaxial) epidermis.
• The abaxial epidermis contains more stomata than the adaxial epidermis.
• The mesophyll is differentiated into palisade parenchyma and spongy parenchyma.
• The vascular bundles are present in the veins and midrib and are surrounded by a bundle sheath.
• The leaf shows reticulate venation.