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

Phloem in gymnosperms lacks:

1. Both sieve tubes and companion cells 

2. Albuminous cells and sieve cells

3. Sieve tubes only

4. Companion cells only

Which of the statements given below is not true about the formation of Annual Rings in trees?

1. Annual rings are not prominent in trees of temperate regions.

2. Annual rings are a combination of spring wood and autumn wood produced in a year.

3. Differential activity of cambium causes light and dark bands of tissue - early and late wood respectively.

4. Activity of cambium depends upon variation in climate.

Guard cells help in
1. protection against grazing
2. transpiration
3. guttation
4. fighting against infection

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

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

Which one of the following is not a lateral meristem?

1. Intrafascicular cambium

2. Interfascicular cambium

3. Phellogen

4. Intercalary meristem

The chief water conducting elements of xylem in gymnosperms are

1. vessels

2. fibres

3. transfusion tissue

4. tracheids

Closed vascular bundles lack

1. Ground tissue

2. Conjuctive tissue

3. Cambium

4. Pith