NIOS Class 12 Biology Chapter 6 Solution – Root system
NIOS Class 12 Biology Solution Chapter 6 Root system . NIOS Class 12 Biology Chapter 6 Question Answers Download PDF. NIOS Class 12 Biology Notes.
Board |
NIOS |
Class |
12th (Higher Secondary) |
Subject |
Biology |
Topic |
Question Answer, Solution, Notes |
1.) Name the plant organ which grows towards gravity and water but away from light?
Ans: Root is the organ which grows towards gravity and water but away from
Light. The root system is the descending portion of the plant axis.
2.) From which part of the germinating seed does the root develop?
Ans: Root develop from a radicle part of germinating seed. . It elongates to form primary or the tap root.
3.) Which root system gives better anchorage and why?
. Ans: Tap root system gives better anchorage because these can stretch extremely deep into the soil and offer very strong anchorage. It is the main root system of dicots e.g. gram
4.) Give two examples each of plants having fibrous and tap root system?
. Ans: Examples of plants having fibrous and tap root system are as follow:
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: Carrot is is root by showing the following characteristic:
(i)Non-green due to absence of chlorophyll
(ii) Not divided into nodes and internodes
(iii) Absence of leaves and buds;
INTEXT 6.2
1.) Name the structure which protects the root apical meristem.
Ans:Root cap protects the root apical meristem. It is a thimble-like structure produced by meristematic zone.
2.) Give in a sequence, the various regions of root from its tip towards its base.
Ans: The various regions of root from its tip towards its base are Root cap region, region of meristematic cells, region of elongation, region of maturation.
3.) Into which tissues do dermatogen and plerome differentiate?
Ans: Dermatogen divides into epiblema and cap, whereas Plerome differentiates into stele
4.) Which region of root absorbs water and mineral salts?
Ans: . Root hair or piliferous region having unicellular hairs which absorb water and mineral salts from the soil.
INTEXT 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 storage of food.
2.) Name the type of root modification found in plants growing in marshy areas.
What is their function?
Ans: The root modification found in plants growing in marshy areas is Pneumatophores. roots grow vertically up into air. Exposed root tips possess minute pores through which roots respire, appear like conical spikes coming out of water, which helps in respiration.
3.) What is the tissue in aerial roots of epiphytes known as which helps in absorption of moisture from the atmosphere?
Ans: Velamen helps in absorption of moisture from the atmosphere in aerial roots of epiphytes
4.) What are the two main functions of roots?
Ans: (i) Roots absorb water and mineral salts and conduct them upwards
(ii) Roots anchor the plant firmly to the soil.
5.) Match the items of column A with those in column B
Column A | Column B (Ans.) |
Prop roots | Banyan |
Haustorium | Cuscuta |
Sweet potato | Storage |
Floating roots | Jussiaea |
INTEXT 6.4
1.) Name the condition where protoxylem lies towards the periphery and metaxylem
towards centre.
Ans: condition where protoxylem lies towards the periphery and metaxylem towards centre is Exarch.
2.) Why is it difficult to pluck lateral roots from carrot?
Ans: It is difficult to pluck lateral roots from carrot because e these arise from the inner layer i.e.pericycle
3.) What is the seat of origin of lateral roots and cambium?
Ans: The seat of its origin is pericycle where cells opposite the protoxylem divide and form a hump in the endodermis
- Name the endodermal cells which do not possess casparian strips and help in the movement of water?
Ans: The endodermal cells which do not possess casparian strips and help in the movement of water is Passage cells. They help in the movement of water and dissolved salts from cortex directly into xylem.
5.) Give two major differences between a dicot and monocot root.
Ans: (i) Number of vascularin dicot are 2-6 (di-hexarch) whereas in monotcot root there are Many (polyarch) bundles.
(ii) In dicot root cambiam is present and in monocot roots cambiam is absent.
6.) If the number of xylem bundles is 4 (tetrarch), how many lateral roots will be formed in that area?
Ans: If the number of xylem bundles is 4 (tetrarch) will be four.
INTEXT 6.5
1.) Name the lateral meristems found in old dicot roots? What is their function?
Ans: The lateral meristems found in old dicot roots are 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: The vascular cambium originate from Pericycle and conjunctive tissue
3.) What is the conjunctive tissue?
Ans: Conjunctive tissue is the parenchyma tissue found between xylem and phloem patches that are oriented radially in roots.
4.) Define periderm. What role does it play in a root?
Ans: Periderm is a tissue which is formed during secondary growth and consists of phellem, phellogen and phelloderm. The function of Periderm is protective.
5.) Do primary roots of dicot plant possess cambium?
Ans: No, cambium is absent in the primary dicot root, but it is present in secondary dicot root.
TERMINAL EXERCISE
1.) Describe any four adventitious root modifications.
Ans: (i) Tuberous root : These are Swollen roots developing from nodes of prostrate stem
(ii) Fasciculated root : These are Swollen roots developing from cluster stems
(iii) Nodulose roots : In these type of roots only apices of roots become swollen like single beads
(iv) Moniliform roots: These roots are alternately swollen and constricted presenting a beaded or moniliform appearance
2.) Give one point of difference between:
(i) Tap root and adventitious root : Tap roots are the primary and the main root that develops from the radicle while, adventitious root developes from anywhere of the plant parts.
(ii) Prop and stilt roots: Prop Roots grow from tree branches, dangle downward, and eventually pierce the ground, supporting heavy branches while, Slit roots are additional roots that form from nodes at the stem’s base grow obliquely downward and into the earth, providing a strong anchoring.
(iii) Protoxylem and metaxylem : Metaxylem is located in the centre, while protoxylem is located on the peripheral.
(iv) Phelloderm and periderm : The cork cambium divides into secondary cortex which is Phelloderm towards inside, while periderm is formed by Phellogen, Phellem and Phelloderm .
(v) Vascular cambium and cork cambium : vascular cambium appears in the conjunctive tissue on the inner side of phloem bundle while, cork cambium differentiates in the pericycle.
3.) Describe the various types of edible roots which you have studied.
Ans: Sweet Potato : It have Swollen roots developing from nodes of prostrate stem.
Carrot : Its base is broad and tapers gradually towards apex.
Radish : It is swollen in middle, tapering towards both ends.
4.) What are pneumatophores? Where are they found and what is their function?
Ans: These roots are grown upward vertically having small pores which helps in the exchange of various gases through it.They are found in marshy places.
5.) Describe secondary growth in dicot roots.
Ans: Secondary phloem grows from the vascular cambium in the middle and secondary xylem in the periphery. In the pericycle, the cork cambium (phellogen) also differentiates, giving birth to the secondary cortex (phelloderm) on the interior and cork (phellem) on the periphery.Here , there is formation of secondary tissues due to the activity of vascular cambium and vascular cork.
6.) Why is it difficult to break the lateral roots from the main root?
Ans:The main root is thicker from the lateral root because it consist of all the nutrients which are required for a plant to grow,further it is derive from the inner layer called pericycle.
7.) What is periderm ? How is it formed?
Ans: Periderm is a tissue which is formed during secondary growth and consists of phellem, phellogen and phelloderm. The function of Periderm is protective
8.) Give four characteristics by which you can identify a root.
Ans: (i) Roots are non-green due to absence of chlorophyll
(ii) They are not divided into nodes and internodes
(iii) Absence of leaves and buds
(iv) They transfer water and mineral from soil to the plant.
9) What is the function of region of maturation?
Ans: In the region of maturation the cells develop and differentiate into several tissues, including (i) the root hair zone, which has unicellular hairs that draw water and salts from the soil, and (ii) the permanent zone, which is located behind the root hair zone and has no hairs. It creates lateral roots, stabilises the plant in the ground, and transports minerals and water upward.
10) Give one example each of plants having pneumatophores, climbing roots, floating roots and haustoria.
Ans: Pneumatophores : Mangrooves trees
Climbing roots : Hedera helix
Floating roots : Duckweed
Haustoria : Dodder
11.) A cross section of plant organ when seen under the microscope shows—radial vascular bundles, exarch xylem, single layered pericycle and unicellular hair. What organ is it?
Ans: The organ is dicot root.
12) Name the meristematic tissues which help the dicot roots to grow in length and girth.
Ans:Apical meristem help the dicot roots to grow in length and girth.
13) Name the modification of root which supports tree branches
Ans: Prop roots supports the tree branches
14.) If a transverse section of root shows polyarch condition of vascular bundles, large pith and no cambium, which type of root will it be?
Ans:Monocot roots shows polyarch condition of vascular bundles, large pith and no cambium
15.) Differentiate between stele of dicot and monocot root
Ans: Dicot root have less number of stele while monocot have large number of stele .