Question

a. Discuss why leaves are thin, only a few cells thick and why leaf cells, but not all cells in a celery petiole contain multiple chloroplasts? b. List features of plants that you think can be interpreted as adaptations to maximize energy and material gain by photosynthesis. For each feature, explain why it is such an adaptation.

Answer 1

Answer:

a):

• Leaves are thin, so that they can absorb more light.
• A thin leaf would mean short distance for the carbondioxide to diffuse in an oxygn to diffuse out.
• Celery petiole contains tissues charachterized by elongated celles and thicker cell walls.
• the primary function of these cells is to provide mechanichal support henece we find that no all cells in celery petiole contain multiple chloroplasts.

b):

• Photosynthesis is the process of preparing own food in the plants. This requires energy input.
• So, the plants absorb light energy and chlorophyll present in plants convert them to chemical energy, which is later used in the process.
• Plants develop a lot of adaptations to improve the ability of collecting the raw materials like light enegy/sunlight , water and minerals for potosynthesis.

Here are few of the adaptations of plants:

• i. Leaves are the major sunlight trapping part of plant. The leaves of plant will be wide and flat, which increases the surface area of leave to absorb lot of light energy.
• ii. Leaves of plants usually grow in tesselated manner. This avoids overlapping of leaves, thus increasing the surface area prone to sunlight.
• iii. Petioles/leaf stalks grow in different angles. This also helps leaves to grow in different angles, which helps it to trap the sunlight easily.
• iv. The waxy cuticle and the upper epidermal layer of the leves are transperent so that the light energy can pass through upper epidermis and enters into other cells.
• v. The palisade cells in the leaves contain chlorophyll, which help in photosynthesis are packed together very closely. This provides more room for chloroplasts.
• vi. palisade cells are present near upper epidermis of leaves, so that it can absorb light energy easily.
• vii. The leaves are usually thin. This creates a short diffusing path for gaseous exchange during photosynthesis (CO₂ to chloroplast and O₂ from chloroplast).
• viii. Leaf contains phloem and xylem vessels which aids in transport of sucrose produced during photosynthesis to other parts of plant and to transport water to chloroplast which is required during photosynthesis respectively.
• ix. Spongy cells present below the palisade cells have large space between them, which also provide large space for gaseous diffusion.
• x. Leaf has stomata, which allows gaseous exchange in and out of plant body during photosynthesis.

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