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:

Closed vascular bundles lack:

1. Ground tissue

2. Conjuctive tissue

3. Cambium

4. Pith

The chief water conducting elements of xylem in gymnosperms are:

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

Anatomically, fairly old dicotyledonous root is distinguished from the dicotyledonous stem by:

1. absence of secondary xylem

2. absence of secondary phloem

3. presence of cortex

4. position of protoxylem

Guard cells help in: