Question

Distinguish between the following:

a. Exarch and endarch

b. Stele and vascular bundle

c. Protoxylem and metaxylem

d. Interfasicular cambium and intrafasicular cambium

e. Open and closed vascular bundles

f. Stem hair and root hair

Answer 1

a.

Criteria	Exarch	Endarch
Definition	Exarch is the arrangement of xylem tissue in which the protoxylem is directed towards the periphery and metaxylem towards the centre.	Endarch is the arrangement of xylem tissue in which the protoxylem is directed towards the centre and metaxylem elements towards the periphery.
Location	It is found in the roots of flowering plants.	It is found in the sterm of flowering plants.

b.

Criteria	Stele	Vascular bundle
Location	Stele is the central part of the root or stem. The tissues underlying endodermis constitute stele.	Vascular bundle is part of the stele.
Tissue involved	Stele includes pericycle, vascular bundles and pith.	Vascular bundle includes xylem and phloem.

c.

Criteria	Protoxylem	Metaxylem
Definition	The primary xylem which is formed first is called protoxylem.	The primary xylem which is formed after protoxylem is called metaxylem.
Arrangement in stem	Protoxylem is present towards the centre (pith) in the stem.	Metaxylem is present towards the periphery in the stem.
Arrangement in root	In the roots, the protoxylem lies towards the periphery.	In the roots, the metaxylem lies towards the centre.

d.

Criteria	Interfascicular cambium	Intrafascicular cambium
Definition	Interfascicular cambium is secondary cambium formed from the cells of medullary rays when they become meristematic.	Intrafascicular cambium are the cells between the primary xylem and primary phloem in dicot plants.
Type of origin	Interfascicular cambium is secondary in origin.	Intrafascicular cambium is primary in origin.

e.

Criteria	Open vascular bundles	Closed vascular bundles
Presence of cambium	Open vascular bundles have cambium present in between xylem and phloem.	Closed vascular bundles do not have cambium present in between xylem and phloem.
Secondary growth	Due to the presence of cambium, open vascular bundles are capable of secondary growth.	Due to the absence of cambium, closed vascular bundles cannot support secondary growth.
Location	Open vascular bundles are found in the dicot plants.	Closed vascular bundles are found in the monocot plants.

Diagrammatic representation


f.

Criteria	Stem hair	Root hair
Cellularity	Stem hairs are multicellular structures called trichomes.	Root hairs are unicellular structures.
Function	Stem hairs help in preventing the loss of water due to transpiration.	Root hairs help in absorption of water and minerals from soil.