Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
A tissue is a group of similar cells that perform a specific function. Plant tissues are broadly classified into Meristematic and Permanent tissues.
Meristematic Tissues consist of actively dividing cells. They have thin cellulose walls, dense cytoplasm, large nuclei, and lack vacuoles. They are found at growth points like root and shoot tips.
Apical Meristem is located at the tips of stems and roots, responsible for increasing the height/length of the plant.
Lateral Meristem (Cambium) is located on the sides of stems and roots, increasing the thickness or girth of the plant.
Permanent Tissues are derived from meristematic tissues that have lost the ability to divide and have attained a definite shape and function.
Simple Permanent Tissues consist of one type of cell. These include Parenchyma (storage and photosynthesis), Collenchyma (flexibility and support), and Sclerenchyma (strength and hardness due to lignin).
Complex Permanent Tissues consist of more than one type of cell working together. These are Xylem and Phloem.
Xylem is responsible for the upward conduction of water () and dissolved minerals from roots to leaves. It consists of tracheids, vessels, xylem parenchyma, and xylem fibres.
Phloem is responsible for the translocation of food (prepared glucose/sucrose) from leaves to other parts of the plant. It consists of sieve tubes, companion cells, phloem parenchyma, and phloem fibres.
Parenchyma containing chlorophyll is called Chlorenchyma, which performs photosynthesis represented by: .
📐Formulae
💡Examples
Problem 1:
A student observes a plant tissue under a microscope and finds cells with very thick lignified walls and no internal space (dead cells). Identify the tissue and its primary function.
Solution:
The tissue is Sclerenchyma.
Explanation:
Sclerenchyma cells are dead, have extremely thick cell walls due to the deposition of , and provide mechanical strength and rigidity to plant parts like the husk of a coconut.
Problem 2:
Compare the direction of transport in Xylem and Phloem.
Solution:
Xylem transport is unidirectional (upward), while Phloem transport is bidirectional (both upward and downward).
Explanation:
Xylem carries and minerals from the roots strictly upwards to the leaves. Phloem carries synthesized food () from the 'source' (leaves) to 'sinks' (roots, fruits, and growing tips) in both directions.
Problem 3:
Why do meristematic cells lack vacuoles?
Solution:
Meristematic cells are involved in rapid cell division and do not need to store food or waste.
Explanation:
Vacuoles are primarily for storage and maintaining turgidity. Since meristematic cells are small, actively dividing, and have a high metabolic rate, they lack the space and the requirement for large vacuoles.