Notes of class 8

Clones :- Next generation of  plants obtained by asexual method or by vegetative propagation are exact copies of parent plant, there is no genetic variations. These are called the clones.

Offsprings :- Next generations of plant obtained by sexual reproduction has some genetic variations. These are called offsprings.

Vegetative Propagation :- Reproduction in the plants by using their vegetative parts like root, stem, leaf is called vegetative propagation or vegetative reproduction.

Natural methods of vegetative propagation :- 

1. Vegetative propagation by root :- 

• Roots are underground part of plant.
• The root which store food in it, is called root tuber.
• Stored food in the root enable the root for production of next generation ( clone ) in next growing season.
• Dahalia, sweet potato are the examples.

2. Vegetative propagation by stem :-

• The stem is part of plant which has nodes and inter nodes on it.
• Node of stem has bud on it which may grow as leaf, side branch, flower etc.
• The stem in the plant may be under ground ( e.g. potato ), sub aerial ( e.g. grass ) or aerial.

(i) Vegetative reproduction by under ground stem :-

• Under ground stem store food in it and become stem tuber.
• Stored food in the stem tuber is utilized by plant for vegetative reproduction.

(a) Tuber :- 

• Potato is under ground stem tuber.
• Potato has small depressions on it called eyes. These eyes of potato are the nodes of under ground stem.
• Eyes of potato has axillary bud in it.
• Under favourable conditions of growth the axillary buds give rise new plant of potato.

(b) Bulb :- 

• Bulb is a short , flat disc like under ground stem.
• Onion is the example of bulb.
• Terminal buds and axillary buds are present on disc like stem ( bulb ).
• Axillary bud of bulb grow as aerial shoot ( green ) which develop as new plant. 

(c) Rhizome :-

• The rhizome is under ground stem which has branches.
• On the rhizome buds are present at terminal position which grow as new plant under favourable conditions.
• Ginger, Bamboo, Sugar cane, turmeric etc. are examples of rhizomes.

(d) Corm :- 

• Corm is the flat, rounded bulb. It stor food in it.
• Each corm grow as new plant.
• Each corm can give rise many small corms.
• Example is Gladiolus.

(ii) Vegetative reproduction by sub aerial stem :-

• Sub aerial stem grows horizontal to soil surface.
• From the nodes of sub aerial stem there is growth of root ( under grond ) and stem (as a new plant ).
• These horizontal running sub aerial stem are called stolon.

3. Vegetative reproduction by leaf :-

• Leaves of Bryophyllum is best example of vegetative reproduction by laf.
• Bryophyllum leaf is fleshy. It bear adventitious buds on the margin.
• Each bud can grow in to new individual plant.