NCERT Class 9 Science — Chapter 2: Tissues

Correct Option

The correct option is

Exchange of gases and transpiration

Explanation

Stomata are minute pores found primarily in the epidermis of leaves and young stems. Each stoma is bordered by two specialized epidermal cells known as guard cells, which regulate the opening and closing of the pore based on turgor pressure changes.

Option Analysis:

• Storage of food is incorrect. The storage of food is primarily the function of ground tissues, specifically parenchyma cells. In leaves, the mesophyll tissue (containing chloroplasts) is responsible for photosynthesis and temporary storage, not the stomatal pores themselves.
• Mechanical support is incorrect. Mechanical support is provided by specialized supporting tissues such as collenchyma (in young stems and petioles) and sclerenchyma (in mature plant parts), rather than the stomatal apparatus.
• Exchange of gases and transpiration is correct. The stomata serve two critical physiological functions:
  1. Transpiration: The loss of water in the form of water vapor occurs primarily through stomata. This process generates the transpirational pull required for water transport.
  2. Gaseous Exchange: Stomata facilitate the diffusion of gases between the plant and the atmosphere, allowing Carbon Dioxide ($CO_2$) to enter for photosynthesis and Oxygen ($O_2$) to exit.
• Transport of water from roots is incorrect. The transport of water and dissolved minerals from the roots to the leaves is the specific function of the vascular tissue known as Xylem.

Key Takeaway:

Stomata are essential epidermal structures that regulate transpiration and facilitate the exchange of gases ($CO_2$ and $O_2$) necessary for photosynthesis and respiration.