Vascular bundles in monocotyledons are considered closed because:

1.	a bundle sheath surrounds each bundle
2.	cambium is absent
3.	there are no vessels with perforations
4.	xylem is surrounded all around by phloem

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

Lenticels are involved in:
1. Gaseous exchange
2. Food transfer
3. Photosynthesis
4. Transpiration

Interfascicular cambium develops from the cells of:

1. Xylem parenchyma

2. Endodermis

3. Pericycle

4. Medullary rays

Companion cells are closely associated with:

1. Sieve elements

2. Vessel elements

3. Trichomes

4. Guard cells

Closed vascular bundles lack:

1. Ground tissue

2. Conjuctive tissue

3. Cambium

4. Pith

The chief water conducting elements of xylem in gymnosperms are:

1. vessels

2. fibres

3. transfusion tissue

4. tracheids

Which one of the following is not a lateral meristem?

1. Intrafascicular cambium

2. Interfascicular cambium

3. Phellogen

4. Intercalary meristem

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