Problem 15 - Objective Biology for NEET

Question

Cells that further make up the plant body (a) Loose capacity to divide (b) Loose capacity to grow (c) Loose capacity to differentiate (d) None of these

Step-by-Step Solution

Answer

The correct answer is (a) Lose capacity to divide. The cells that make up the plant body are mature cells and have typically passed the stage of cell division, thus generally losing this ability.

Step 1: Analyzing the capacity to divide

Plant cells which have formed the plant body are basically mature cells. They have crossed the stage of cell division. Hence, they generally do not divide further.

Step 2: Analyzing the capacity to grow

Despite being mature cells, plant cells retain the capacity to grow. A distinct characteristic of plant cells is that they can expand and grow bigger in size. Therefore, they do not lose the ability to grow.

Step 3: Analyzing the capacity to differentiate

Differentiation is a stage that occurs before the cell matures and forms part of the plant body. These cells have already differentiated to take on specific roles in the plant body. Therefore, they do not lose their ability to differentiate as it is a stage they have already passed.

Key Concepts

Cell Division in Plants

Plant development hinges on the pivotal process of cell division, a mechanism that enables growth and regeneration. This process, known in botanical terms as mitosis, involves a series of intricate steps where a single cell splits into two identical daughter cells, each preserving the complete genetic blueprint of the original.

Consider a stem cell in the meristematic tissue, the growth engines of plants located at the tips of roots and shoots. These cells are remarkable for their capacity to divide almost indefinitely. As plants mature, certain regions cease to divide and enter a state commonly referred to as 'differentiation'. However, it's important to remember that plants maintain meristematic regions as they grow, ensuring a supply of new cells ready to divide and adapt based on the plant's needs.

Without this dynamic cell division, plants would be unable to grow taller or repair damaged tissues, highlighting its significance in the life cycle of a plant.

Plant Cell Growth

While some animal cells grow by cell division alone, plant cells uniquely expand even after division has ceased. This growth predominantly occurs by cell elongation, enabled by the cell's vacuole, which absorbs water and increases in volume, thus stretching the cell wall and expanding the cell size.

Cell Wall Elasticity

Unlike animal cells, plant cells are ensconced in a rigid cell wall composed of cellulose. Initially, this cell wall is flexible, allowing for the expansion as the vacuole accumulates water. The cell wall secretion of additional polysaccharides consolidates and strengthens the cell's structure.

Despite the cessation of division in mature cells, the capability for growth remains intact, manifesting as an increase in cell size rather than cell number. This accords plants the ability to keep growing throughout their lifespan, making growth a perpetual characteristic of most plant cells.

Cell Differentiation

Specialization of Function

Cell differentiation is fundamental in the plant kingdom, endowing cells with specialized functions necessary for the plant's survival. Through the process of differentiation, undifferentiated cells of the meristem specialize into various cell types such as vascular tissue, epidermal cells, or ground tissue, each performing unique and essential roles.

Once a cell differentiates, it typically sustains that function for the remainder of its life, contributing to the specific tissue it forms part of. It is a misconception to think that mature plant cells 'lose' the capacity to differentiate. In fact, differentiation is a one-time developmental stage, after which a cell has achieved its specialized state and thus does not revert to an undifferentiated state.

Understanding cell differentiation not only enlightens our grasp of plant biology but also informs practices such as tissue culture and the harnessing of stem cells for regenerative purposes in agriculture and horticulture.