Question

Class 10,

(a) Explain how does the exchange of gases occur in plants across the surface of stems, roots

and leaves.

(b) How are water and minerals transported in plants?​

Answer 1

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⏭️ (a) In plants, there are tiny pores called stomata on leaves and lenticels in stem which facilitate the exchange of gases. CO2 is taken in and O2 given out (during photosynthesis) and vice-versa during respiration.

⏭️ (b) Mechanism of Transport of Water and Minerals in a Plant :

• The vessels and tracheids of roots, stems and leaves in xylem tissue are interconnected to form a continuous system of water-conducting channels reaching all parts of the plant.

• The cells of the roots in contact with the soil actively take up ions which creates a difference in the ion concentration between the root and the soil.

• Thus, there is steady movement of water into root xylem from the soil, creating a column of water that is pushed upwards.

• Plant uses another strategy to move water in the xylem upwards to the highest points of the plant body.

• The water which is lost through the stomata is replaced by water from the xylem vessels in the leaf.

• Evaporation of water molecules from the cells of a leaf creates a suction which pulls water from the xylem cells of roots.

• This loss of water is transpiration which helps in the absorption and upward movement of water and minerals dissolved in it from roots to the leaves.

• Transpiration becomes the major driving force in movement of water in the xylem during the day when the stomata are open.

• This mechanism is also known as cohesion of water theory or transpiration pull.

Answer 2

⏭️ (a) In plants, there are tiny pores called stomata on leaves and lenticels in stem which facilitate the exchange of gases. CO2 is taken in and O2 given out (during photosynthesis) and vice-versa during respiration.

⏭️ (b) Mechanism of Transport of Water and Minerals in a Plant :

• The vessels and tracheids of roots, stems and leaves in xylem tissue are interconnected to form a continuous system of water-conducting channels reaching all parts of the plant.

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