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

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:
1. protection against grazing
2. transpiration
3. guttation
4. fighting against infection

Grass leaves curl inwards during very dry weather. Select the most appropriate reason from the following :

1. Tyloses in vessels

2. Closure of stomata 

3. Flaccidity of bulliform cells

4. Shrinkage of air spaces in spongy mesophyll