Page 111 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

Fragmentation

We often see slimy green patches in stagnant water. These are plant-like living
organisms called algae (singular alga). An alga has a filamentous body that can break

into smaller fragments. Each fragment then develops into a new individual. For
example, Spirogyra.

Spore Formation
In this asexual mode of reproduction, organisms, such as fungi, produce hundreds of

tiny microscopic structures called spores. Such organisms bear sac-like reproductive
structures called sporangia (singular sporangium), which produce and bear spores.

Each spore is covered with a hard outer protective covering that enables it to
withstand extreme conditions of temperature and lack of moisture and nutrients.

As soon as they find favourable conditions, they germinate and form new organisms.
Certain fungi like Rhizopus and plants, such as mosses and ferns, reproduce by spore

formation.
Vegetative propagation.

Vegetative propagation is a type of asexual reproduction in which the vegetative
parts of the plants, such as roots, stems, leaves and buds give, rise to new plants,

vegtative propagation can be done through natural or arifical methods.
Natural vegetative propagation occurs naturally in plants without any human

interference by leaves, by roots or by stems. for example
(a) in bryophyllum, small plantlets arise at laf tip which when reach the soil, gwow

into a new plant.
(b) plants, such as sweet potato have swollen roots, also called tuberous roots

which develop into advextitious buds that grow into new plants.
(c) like roots, underground modified stems also help in developing new plants.

These include tuber bulb, shizone, etc.
Artificial methods of vegetative propagation are:

(a) Cutting is a method in which a cutting from a plant is taken & planted to grow
new plants. For example, rose.

(b) Grafting is similar to cutting except that the cut part of the plant is attached to
another rooted plant of similar variey. For example, apple.

(c) Layering is a method where a nature branch of the parent plant is bent down in
the soil. It develops into a new plant. For example, strawberry.

(d) Tissue culture is the cultivation of plant cells, tissues or organs in specially
formulated nutrient media. It is also called micropropagarion & is widely used

in forestry & horticulture.

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