Tag: internal structure of root, stem and leaf

Questions Related to internal structure of root, stem and leaf

Inner darker, harder portion of secondary xylem that cannot conduct water in older dicot stem is called?

botany internal structure of root, stem and leaf internal structure of dicot stem internal structure of stem(dicot and monocot) anatomy of stem

  1. Alburnum

  2. Bast

  3. Duramen

  4. Wood

Show answer
Correct Option: C
Explanation:

A-The outer light coloured, functional secondary xylem or wood, takes up in the conduction of water of sap is called sapwood or alburnum.

B.Bast - secondary phloem formed during secondary growth from vascular cambium towards its outer side.
C. Duramen - The central or inner dark coloured non-functional wood or secondary xylem, not takes part in the conduction of water is called Duramen or Heartwood.
D.Wood - secondary xylem formed during secondary growth from vascular cambium towards its inner side.

You are given a fairly old piece of dicot stem and a dicot root. Which of the following anatomical structures will you use to distinguish between the two.

botany internal structure of root, stem and leaf internal structure of dicot stem internal structure of stem(dicot and monocot) anatomy of stem

  1. Secondary phloem

  2. Protoxylem

  3. Cortical cells

  4. Secondary xylem

Show answer
Correct Option: B
Explanation:

The anatomy of dicot root and dicot stem differ in many characters. In dicot, root epidermis contains root hairs, whereas in epidermis contains trichomes, cuticle and stomata. In dicot, root cortex shows general cortex and endodermis, whereas in dicot stem cortex shows hypodermis, general cortex and endodermis.

In dicot, root hypodermis is absent whereas, in dicot stem, hypodermis is present.

In dicot root endodermis shows Casparian bands, whereas in dicot stem endodermis contains starch grains in its cells.

In dicot root pericycle is parenchymatous, take part in the lateral formation and secondary growth, whereas in dicot stem, pericycle is discontinuous, sclerenchymatous, present in the form of patches over the vascular bundles.

In dicot root, vascular bundles are radial, whereas in dicot stem vascular bundles are collateral, conjoint, open

In dicot, root xylem is exarch, whereas in dicot stem xylem is endarch.

In dicot, root medulla is reduced, whereas in dicot stem is xylem is endarch.

In dicot root, conjunctive tissue is present, whereas, in dicot stem, medullary rays are present.

So, the correct option is ‘Protoxylem’

Which of the following characters are not applicable to the anatomy of dicot stem?
(a) Collenchymatous hypodermis
(b) Polyarch xylem
(c) Presence of casparian strips on endodermis
(d) Open vascular bundle
(e) Presence of medullary rays.

botany internal structure of root, stem and leaf internal structure of dicot stem internal structure of stem(dicot and monocot) anatomy of stem

  1. a, d and e only

  2. b and c only

  3. b and e only

  4. a, b and c only

  5. c, d and e only

Show answer
Correct Option: B
Explanation:

a) Collenchymatous hypodermis -applicable because hypodermis is made up of collenchyma.

b) Polyarch xylem – not applicable, because, xylem and phloem are present on the same radius and side by side. It is found in monocot roots.

c) Presence of Casparian strips on endodermis – not applicable, because Casparian strips appear on the radial and tangential walls of the endodermis of roots.

d) Open vascular bundle – applicable, because, cambium is present between the xylem and phloem in the vascular bundles.

e) Presence of medullary rays – applicable – because, these are the extensions of medulla between the vascular bundles.

So, the correct option is ‘b and c’.

In a mature dicot stem. which has undergone secondary growth, the youngest layer of secondary xylem is situated

botany internal structure of root, stem and leaf internal structure of dicot stem internal structure of stem(dicot and monocot) anatomy of stem

  1. In between pith and primary xylem

  2. Just outside the vascular cambium

  3. Just inner to the vascular cambium

  4. Just inner to the phellogen

Show answer
Correct Option: C
Explanation:

secondary xylem is also called wood. Any tissue located to the "outside" of the vascular cambium is considered bark and tissue side is called as wood.

So the correct option is 'Just inner to the vascular cambium.'