NIOS Biology Chapter 06 Root system

NIOS Class 12 Biology Intext Solutions Chapter 6

INTEXT QUESTIONS 6.1

1. Name the plant organ which grows towards gravity and water but away from light?

Ans: Root

2. From which part of the germinating seed does the root develop?

Ans: Radicle

3. Which root system gives better anchorage and why?

Ans: Tap root systems provide very strong anchorage as they can reach very deep into the soil, and branches profusely, which ramify through large areas in the soil.

4. Give two examples each of plants having fibrous and tap root system?

Ans: Fibrous root system in maize, sugarcane, and tap root system in sunflower, mango.

5. Mention three characters by which you can say that carrot which you eat is a root.

Ans: Carrots lack nodes and internodes, buds, and leaves. They also grow underground.

INTEXT QUESTIONS 6.2

1. Name the structure which protects the root apical meristem.

Ans: Root cap

2. Give in a sequence, the various regions of root from its tip towards its base.

Ans: Root cap region, region of meristematic cells, region of elongation, region of maturation.

3. Into which tissues do dermatogen and plerome differentiate?

Ans: The dermatogen gives rise to the epidermis of stems and the epiblema of roots. Plerome gives rise to the central meristematic region – pericycle, pith, and vascular tissue.

4. Which region of root absorbs water and mineral salts?

Ans: Root hair or piliferous region /Region of maturation, having unicellular hairs which absorb water and mineral salts from the soil.

INTEXT QUESTIONS 6.3

1. Are carrot, radish and turnip roots? Justify. Why have they become fleshy?

Ans: Yes, they are roots since they do not have nodes and internodes, buds, or leaves; they become fleshy for the storage of food.

2. Name the type of root modification found in plants growing in marshy areas. What is their function?

Ans: Pneumatophore, respiration

3. What is the tissue in aerial roots of epiphytes known as which helps in absorption of moisture from the atmosphere?

Ans: Velamen

4. What are the two main functions of roots?

Ans:

Anchorage – Roots anchor the plant firmly to the soil (mechanical function).
Absorption – Roots absorb water and mineral salts and conduct them upwards (physiological function).
Special functions – By undergoing modifications in their structure, roots perform special physiological functions like food storage, assimilation, absorption of atmospheric moisture, sucking food from the host, better gaseous exchange, and mechanical functions like floating (buoyancy), stronger anchorage, and climbing.

5. Match the items of column A with those in column B.

Column A	Column B
(a) Prop roots	(i) Storage
(b) Haustorium	(ii) Jussiaea
(c) Sweet potato	(iii) Banyan
(d) Floating roots	(iv) Cuscuta

Ans: (a) – (iii); (b) – (iv); (c) – (i); (d) – (ii)

INTEXT QUESTIONS 6.4

1. Name the condition where protoxylem lies towards the periphery and metaxylem towards centre.

Ans: Exarch

2. Why is it difficult to pluck lateral roots from carrot?

Ans: Because these arise from the inner layer, i.e.pericycle/ endogenous origin.

3. What is the seat of origin of lateral roots and cambium?

Ans: Pericycle

4. Name the endodermal cells which do not possess casparian strips and help in the movement of water?

Ans: Passage cells

5. Give two major differences between a dicot and monocot root.

Ans:

Dicot Root	Monocot Root
There are 2-6 (di-hexarch) vascular bundles	Many (polyarch) bundles are seen
Percycle is the seat of only the lateral roots	Pith is small or absent
Cambium is present	Cambium is absent
Secondary growth present	No secondary growth
Pith is small orabsent	Large pith is seen

6. If the number of xylem bundles is 4 (tetrarch), how many lateral roots will be formed in that area?

Ans: Four, as the number of lateral roots corresponds to the number of xylem bundles.

INTEXT QUESTIONS 6.5

1. Name the lateral meristems found in old dicot roots? What is their function?

Ans: Vascular cambium and cork cambium; Vascular cambium forms secondary vascular tissue while cork cambium forms cork and secondary cortex.

2. From which layer does the vascular cambium originate?

Ans: Pericycle and conjunctive tissue.

3. What is the conjunctive tissue?

Ans: Conjunctive tissue is the parenchyma tissue lying between xylem and phloem patches that are arranged radially in roots.

4. Define periderm. What role does it play in a root?

Ans: Periderm is a tissue that is formed during secondary growth and consists of phellem, phellogen, and phelloderm. The periderm of the root is protective in function.

5. Do primary roots of dicot plant possess cambium?

Ans: No, cambium is absent in the primary dicot root. Both vascular and cork cambium are secondary in origin.