Age of a tree can be estimated by :

1. biomass

2. number of annual rings

3. diameter of its heartwood

4. its height and girth

Heartwood differs from sapwood in

1. presence of rays and fibres

2. absence of vessels and parenchyma

3.  having dead and non-conducting elements

4. being susceptible to pests and pathogens

For a critical study of secondary growth in plants, which one of the following pairs is suitable :

1. Sugarcane and sunflower

2. Teak and pine

3. Deodar and fern

4. Wheat and maiden hair fern