Question

Cork is impervious to water due to the presence of in its cell wall. (a) sillica (b) \(\mathrm{CaCO}_{3}\) (c) suberin (d) cuticle

Short answer

Cork is impervious to water due to the presence of suberin in its cell wall, making the correct answer (c) suberin.

Step-by-step solution

Understanding the question

The exercise requires knowledge of the composition of cork cells and which substance makes them impervious to water. The task is to identify the correct substance from the given options.

Analyzing the options

Research and understanding of the properties of cork cell walls indicate that they contain a unique substance that provides water resistance.

Identifying the correct substance

Suberin is known to be the substance that makes cork cells water-resistant. It is a complex fatty substance found in the cell walls of cork tissue, thus making the cells impervious to water. Therefore, the correct answer is option (c) suberin.

Key concepts

Cork Cell Structure

Cork cells, which form the outer bark of cork oak trees, are unique in their structure and serve as a natural barrier. These cells are dead at maturity and have a honeycomb-like arrangement that offers both flexibility and durability. Within the cell walls, cork cells are infused with a waxy substance called suberin, which is crucial in rendering these cells impermeable to water and gases.

Interestingly, it is this arrangement and composition that allows cork to float, making it useful in various applications such as wine stoppers and other buoyant materials. The presence of air trapped within the cells enhances this buoyancy and provides thermal insulation properties as well.

Plant Cell Water Resistance

In the plant kingdom, water resistance is a vital characteristic that varies greatly among different cell types and structures. The wall of a plant cell is the key to this resistance, designed to regulate water intake and loss. Some plants, like the cork oak, have taken this to an advanced level.

The role of suberin in these cells is to prevent water from penetrating the bark of the tree, which is essential for protecting the plant from water loss and pathogen invasion. This adaptation is not just about survival in dry conditions, but is also key to the plant's overall health and ability to transport nutrients and water effectively within its system.

Cell Wall Composition

Diving deeper into cell wall composition, it's not just about suberin but also about other components that contribute to the cell's function. Typical plant cell walls are composed of cellulose, hemicellulose, and pectin, which provide structure and support. In cork cells, however, suberin takes center stage along with lignin, which adds rigidity and strength.

Suberin layers specifically, termed 'suberized lamellae', are deposited in the walls of cork cells, and they act like a sealant. This special 'corky' layer differentiates these cells from other plant cells, which may not have such a pronounced water-resistant feature. Understanding this composition not only explains how plants maintain their water balance but also opens doors to biomimicry in waterproofing materials.