Q37.2-1ITD - Campbell Biology

Question

How do the young leaves differ in appearance from the older leaves?

Step-by-Step Solution

Answer

The color is the distinguishing factor between young and older leaves. The appearance of older leaves is greener than yellow-colored young leaves.

Step 1: Leaf

The photosynthetic organ attached directly to the stem and responsible for manufacturing food for plants is called a leaf. The distinct internal parts of the leaf are stomata, upper epidermis, lower epidermis, chloroplasts, and guard cells.

The leaf acts as a site for photosynthesis (making of food), transpiration (water loss through plant leaves), and gas exchange (occurs through stomata).

Step 2: Plant pathology

The branch of agriculture and biological science in which pathogen identification, plant disorder, and plant resistance are studied to improve food quality for humans and animals is called plant pathology.

Examples of plant diseases include leaf rust, canker, blight, powdery mildew, and black spot.

Step 3: Leaf appearance

The new or young leaves turn yellow due to necrosis and results in rapid cell death, leading to the death of leaves. The presence of more numbers of chlorophyll in older leaves makes them greener than young leaves. 

The anthocyanin pigment produces yellow color in new leaves, chlorophyll goes away, and other pigments show their color in leaves.