Gas Exchange in Flowering Plants

Leaves as Organs for Photosynthesis

• Leaves are essential for photosynthesis, absorbing sunlight energy.

• Chloroplasts in cells contain chlorophyll, which absorbs sunlight for photosynthesis.

• Photosynthesis equation: sunlight + carbon dioxide + water → oxygen + glucose.

Adaptations of Leaves for Photosynthesis

• Leaves are flat and thin with a large surface area to maximize sunlight and carbon dioxide absorption.

• Vessels like xylem and phloem transport water, minerals, and glucose within the plant.

• Guard cells regulate gas exchange through stomata, opening and closing as needed.

Factors Affecting Photosynthesis

• Temperature: Increased temperature initially boosts photosynthesis, but enzyme denaturation beyond a certain point decreases the rate.

• Light intensity: Higher light intensity increases photosynthesis rate, inversely proportional to the square of the distance from the source.

• Carbon dioxide concentration: Higher carbon dioxide levels enhance the reaction rate.

Practical Investigations in Photosynthesis

• Using water plants like Elodea to observe oxygen bubbles released during photosynthesis.

• Experimenting with light intensity by measuring oxygen evolution at varying distances from a lamp.

• Testing carbon dioxide effects by altering sodium bicarbonate concentrations in the water.

Investigating Starch Production

• Starch production indicates photosynthesis occurrence.

• A leaf covered with oil and exposed to light will show starch presence through a color change with iodine solution.

• Variegated leaves demonstrate starch production only in green areas containing chlorophyll.

Stomata Function in Gas Exchange

• Stomata are small openings on leaf undersides regulating water loss and gas exchange.

• They facilitate the exit