Maharashtra Board Class 11 Biology Chapter 8 Plant Tissues and Anatomy PDF Download

Plant Tissues and Anatomy

8.1 Tissue

Anatomy is the study of internal structure of organism. Organs are made up of group of cells. A group of cells having essentially a common function and origin is called as tissue. Plant tissues are grouped as meristematic tissue and permanent tissue on the basis of its ability to divide.

8.2 Meristematic Tissue

It is a group of young cells. These are living cells with ability to divide in the regions where they are present. These are polyhedral or isodiametric in shape without intercellular spaces. Cell wall is thin, elastic, mainly composed of cellulose. Protoplasm is dense with distinct nucleus at the center and vacuoles if present, are very small. Cells show high rate of metabolism. These cells are immature.

Teacher's Note

Meristematic tissue helps plants grow taller and bigger. Just like how your bones have growth plates that help you grow, plants have meristematic tissue at their tips.

Exam Trick

Remember: Meristematic = Dividing cells. These are young and can divide, like baby cells in plants. Permanent tissues cannot divide, like adult cells.

Points to Remember

Meristematic tissue cells can divide and make new cells.

These cells have thin cell walls and dense protoplasm.

They are found at the tips of roots and shoots.

They help plants grow longer and taller.

A. Classification of Meristem

1. Origin

Primordial meristem or promeristem is also called as embryonic meristem. Usually occupying very minute area at the tip of root and shoot. Primary meristem originates from the primordial meristem and occurs in the plant body from the beginning, at the root and shoot apices. Cells are dividing and different permanent tissues are produced from primary meristems. Secondary meristematic tissues develop from living permanent tissues during later stages of plant growth; hence are called as secondary meristems. This tissue occurs in the mature regions of root and shoot of many plants. Secondary meristem is always lateral (to the central axis) in position e.g. fascicular cambium, inter fascicular cambium, cork cambium.

2. Position

Apical meristem is produced from promeristem and forms growing point of apices of root, shoot and their lateral branches. It brings about increase in length of plant body and called as apical initials. Shoot apical meristem is terminal in position whereas in root it is subterminal i.e. located below the root cap. Intercalary meristematic tissue is present in the top or base area of node. Their activity is mainly seen in monocots. These are short lived.

Lateral meristem is present along the sides of central axis of organs. It takes part in increasing girth of stem or root. eg. intrafascicular cambium. It is found in vascular bundles of gymnosperms and dicot angiosperms.

Teacher's Note

Different types of meristem are found at different places in the plant. Apical meristem is like the factory that makes the plant grow upward, like how a tree grows taller every year.

Exam Trick

Remember: Apical = At the apex (tip). Lateral = On the sides. Intercalary = In between nodes. This helps you remember where each type is found.

Points to Remember

Apical meristem is at the tip of roots and shoots and makes plants grow taller.

Lateral meristem is on the sides and makes plants grow thicker.

Intercalary meristem is found at the base of leaves in monocots.

3. Function

Young growing region of the plant has Protoderm that forms protective covering like epidermis around the various organs. Meristem called Procambium is involved in developing primary vascular tissue while the other structures like cortex, endodermis, pericycle medullary rays, pith are formed from the region of Ground meristem. These are three groups of meristem based on function.

Parenchyma has distinct intercellular spaces. Sometimes, cells may show compact arrangement. The cytoplasm of adjacent cells is interconnected through plasmodesmata and thus forms a continuous tissue. These cells are distributed in all the parts of plant body viz. epidermis, cortex, pericycle, pith, mesophyll cells, endosperm, xylem and phloem. These cells store food, water, help in gaseous exchange, increase buoyancy, perform photosynthesis and different functions in plant body. Dedifferentiation in parenchyma cells develops vascular cambium and cork cambium at the time of secondary growth.

Teacher's Note

Meristems have different functions. Some make the protective layer, some make the tubes for water, and some make the food storage areas. Just like different departments in a factory do different jobs.

Exam Trick

Remember: Protoderm makes skin, Procambium makes tubes, Ground meristem makes everything else. These three work together like a team.

Points to Remember

Protoderm forms the outer protective layer of plants.

Procambium develops into xylem and phloem tissues.

Ground meristem forms cortex, pith, and other tissues.

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