Problem 29 - Objective Biology for NEET

Question

Which of the following has minimum amount of water? (a) Leaf (b) Flower (c) Epidermal cell of root (d) Cork

Step-by-Step Solution

Answer

Cork (d) has the minimum amount of water among the options provided.

Step 1: Understanding the water content of each option

Each of the given options contains water, but to different extents. Leaf and flower are parts of the plant that are involved in photosynthesis and attracting pollinators respectively, hence they are expected to have high water content. Epidermal cells of roots are involved in absorption of water and nutrients, while cork, which is a part of the bark of a tree, serves as a protective layer against physical damage and infection, and typically contains less water.

Step 2: Comparing water content in each plant part

While leaves, flowers, and root cells contain water needed for their biological functions, cork is used mainly for protection and support, and is not involved in water transport. As a result, it is known to be less hydrated than the other parts listed.

Step 3: Identifying the option with minimum water content

Based on the above comparisons, Cork (d) has the least water content compared to the leaf, flower and the epidermal cell of the root.

Key Concepts

Photosynthesis and Water Content

Understanding the intricacies of photosynthesis helps streamline the role of water within the plant system. Photosynthesis is the process by which green plants, algae, and certain bacteria transform light energy into chemical energy, using water and carbon dioxide to produce glucose and releasing oxygen as a byproduct.
Water molecules are split during the light-dependent reactions of photosynthesis, which occurs within the chloroplasts. This process, known as photolysis, is vital both for the production of chemical energy carriers, like ATP and NADPH, and for providing the hydrogen ions necessary to form glucose during the light-independent reactions, also known as the Calvin cycle.

• Water is a key reactant in photosynthetic reactions.
• Plants regulate their water content to maintain optimal photosynthesis.
• Strong hydration is essential in leaves, where photosynthesis primarily occurs.

Due to these roles of water in photosynthesis, leaves exhibit a high water content, facilitating the continuous transportation of water to the chloroplasts to sustain the process. Therefore, leaves must remain well-hydrated to optimally capture light and synthesize food.

Plant Biology and Water Distribution

In plant biology, water serves as a primary substrate and plays multiple critical roles in the growth, survival, and reproduction of plants. Water is indispensable, from nutrient transportation to the maintenance of plant structure and temperature regulation through transpiration.

• Water aids in the solubility and distribution of nutrients through the plant's vascular system.
• It maintains turgor pressure in cells which supports plant structure.
• Regulates temperature through the process of transpiration.

Different parts of a plant have adaptations to manage their water content according to the necessary biological functions they perform. For example, flowers maintain adequate water content to facilitate the reproductive process, including the successful transfer of pollen. Epidermal cells of roots, meanwhile, absorb water from the soil and require a higher water content to ably transport nutrients to other plant parts. Cork cells, conversely, have a reduced water content since their main function is protection, not transportation or metabolic activities.

Epidermal Cells' Function and Water Content

The epidermal layer of plants, which include the epidermal cells, is akin to human skin. It is the outermost cell layer that covers leaves, flowers, roots, and stems. These cells have various adaptations tailored to their specific roles within different plant parts.
For the epidermal cells of roots, their primary duty is absorbing water and nutrients from the soil. These cells are often equipped with extensions called root hairs that increase the surface area available for absorption. This is an instance where water content within the cells is critical to their function.

• Root epidermal cells have a high water content for nutrient uptake.
• The presence of root hairs amplifies their absorptive capacity.

Epidermal cells can also regulate water loss through structures known as stomata, which are tiny openings on the surface of leaves. Stomatal regulation ensures that the plant maintains necessary levels of hydration across various environmental conditions, showcasing the specialized roles epidermal cells play in plant water management.