As compared to a dicot root, a monocot root has : 

1. Many xylem bundles 

2. Inconspicuous annual rings 

3. Relatively thicker periderm 

4. More abundant secondary xylem 

The annular and spirally thickened conducting elements generally develop in the protoxylem when the root or stem is

1. maturing

2. elongating

3. widening

4. differentiating

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

Passage cells are thin-walled cells found in :

1. endodermis of roots facilitating rapid transport of water from cortex to pericycle

2. phloem elements that serve as entry points for substances for transport to other plant parts

3. testa of seeds to enable emergence of growing embryonic axis during seed germination

4. central region of style through which the pollen tube grows towards the ovary