Plant Life : The Leaf

Water and carbon dioxide

Step 1: Photosynthesis is the process by which green plants make their own food. Step 2: The equation for photosynthesis is: Carbon dioxide + Water → Glucose + Oxygen (in the presence of chlorophyll and sunlight). Step 3: So the two raw materials (inputs) are carbon dioxide (from air) and water (from soil). Step 4: Oxygen and glucose are the products of photosynthesis, not the raw materials. Step 5: Nitrogen is used by plants for growth but is not a raw material for photosynthesis. Therefore, Water and Carbon dioxide is correct.

Transpiration

Step 1: Plants absorb large amounts of water through their roots. Step 2: Only a small amount is used in photosynthesis; the rest evaporates from the surface of leaves. Step 3: This loss of water in the form of water vapour from leaves and other aerial parts is called Transpiration. Step 4: Photosynthesis is food-making; Respiration is energy release; Absorption is the uptake of water by roots – none of these match the definition given. Step 5: Therefore, Transpiration is the correct answer.

Sweet pea

Step 1: Some leaves are modified to perform special functions other than photosynthesis. Step 2: In Sweet pea, the upper leaflets are modified into thin, coiled, wiry structures called tendrils. Step 3: These tendrils are sensitive to touch and coil around nearby objects to help the weak-stemmed plant climb and support itself. Step 4: Cactus leaves are modified into spines to reduce water loss. Onion has scale leaves to store food. Pitcher plant has its lamina modified into a pitcher to trap insects. Step 5: Therefore, Sweet pea is the correct answer.

To reduce water loss from the plant

Step 1: Cactus plants grow in desert regions where water is very scarce. Step 2: Leaves have a large surface area, which leads to a lot of water loss through transpiration. Step 3: To survive in dry conditions, cactus leaves are modified into sharp spines, which have a very small surface area. Step 4: This greatly reduces the loss of water from the plant, helping it survive in the desert. Step 5: Trapping insects is a function of insectivorous plants; storing food is the function of scale leaves; climbing is the function of tendrils. So the correct answer is to reduce water loss.