Question

Select the correct option:In (i) protoxylem lies towards periphery and metaxylem lies towards centre. Such an arrangement of primary xylem is called as (ii)

(i)	(ii)
stems	endrach
stems	exarch
roots	endrach
roots	exarch

• A. A-stems ,B-endrach
• B. A-stems , B-exarch
• C. A-roots, B-endrach
• D. A-roots, B-exarch

Answer 1

The correct option is D A-roots, B-exarch

• Endarch condition involves the development of protoxylem from the innermost procambial cells adjacent to pith. Development is inward to outward. Hence, protoxylem is found inside to metaxylem . This is considered to be centrifugal pattern of arrangement. It is found in stems.
  
• Exarch condition involves the development of protoxylem from the outermost edge of procambial cylinder. Development is from outside to inside. Protoxylem is found outside the metaxylem . This is considered to be centripetal pattern of arrangement. It is found in roots.
  

So, the correct option is 'A-roots, B-exarch'.