Angel Rajput will describe about science( biology ) subject topics, genetics , some helping tools like calculator, screen recorder, image resizer and many more.
Vegetative Propagation :-
vegetative propagation involves production of new individuals from some vegetative plant propagules such as buds, tubers, rhizomes etc. Every part of the plants body take part in vegetative propagation such as roots, stem, leaves and buds .
Examples - i)potato tubers possess buds which grow into new plants very
ii) Adventitious buds of Bryophyllum leaves grow to form new plants
Methods of vegetative propagation:- It has been further divided into two types:- a) Natural b) Artificial
Here we only discuss about natural vegetative propagation.
1. NATURAL VEGETATIVE PROPAGATION:-
It takes place naturally by following methods.
i) Roots
ii)underground stems
iii) creeping stems
iv) aerial stem
v)leaves
vi) bulbils
vii)turions
i) ROOTS:- modified tuberous roots can be propagated vegetatively when planted in soil. The buds presents on the roots grow in leafy shoots also (known as slips) above ground and adventitious roots at their base. e.g sweet potato, Dahlia. Adventitios buds develop on the ordinary roots which grow to form new plant e.f populas, guava, Dalbergia sissoo.
ii) Underground stems: underground stems such as suckers, rhizomes, corms, bulbs, and tubers possess buds which grow into new plants.
a) Suckers- These arise from the base of erect shoot, grow horizontally in the soil and then come out to form new aerial shoots. These shoots become independent plants when sucker break away from the parent plant. e.g Mint, Chrysanthemum (dhania).
b) Rhizomes:- these serves as means of vegetative propagation by perenating under unfavorable conditions and producing new aerial shoots during the favourable conditions. E.g ginger, turmeric water hyacinthetc. A single plant of water hyacinth produce more then 65000 plants in one growing season of about 8 months.
c) Corms:- These are highly condensed and specialised underground stems which bear many buds. they perennate the unfavorable conditions and produce new plants under favourable conditions, e.g Banana, crocus etc.
d) Bulbs:- These serve as means of vegetative propagation by producing new plants when sown in the soil. E.g Onion, garlic,lilies etc.
e)Tubers :- These are modified underground stem branches having several buds. Each eye of the potato is a bud which grow into a new potato plants when planted with a portion of the swollen tubers.The potato crop is raised by tubers not with seeds. potatos have eyes known as nodes or bud of the potato.
iii) Creeping stems :- these are of 3 types- Runners, stolons, offsets
a) Runners:- These are creeping modified stems which produce adventitiuos roots at nodes . Each node give rise to aerial shoot which become a new plant E.g Cynodon(doob grass), Oxalis( wood sorrel) etc.
b) stolons :- These are arched runners which cross over small obstacles and develop small plantlets at their nodes .E.g vallisneria, strawberry
c) Offsets:- These are one internode long runners which tuft of leaves at the apex , E.g Pistia(water lettuce).
iv) Aerial Stem:- These develop new plants when stem segment fall on ground and act as means of vegetative propagation. E.g Opuntia
v)Leaves:- Some plants develop adventitious buds on their their leaves which get separated and develop new plants. e.g Bryophyllum. But some get injured or detached and placed in moist soil , deveolpbuds and grow in new plant. e.g Begonia, kalanchoe.
vi) Bulbils:- These are fleshy buds produced in the axils of foliage leaves in place of axillary buds. They grow to form new plants when shed and falls on the ground e.g lily. Pineapple Dioscorea, Agava sp. etc.
vii) Turions:- These are special type of fleshy buds that develop in aquatic plants for vegetative propagation. e.g Utricularia, potamogeton etc.
Parthenogenesis
It is the modification of sexual reproduction in which an egg develops into a complete offspring without fertilization.
It is mono parental.I is found in many nonvertebrates e.g rotifiers, aphids, bees and crustaceans.
I is also found in a few vertebrates.
Types:- Parthenogenesis is of two types:-
i) Natural ii) Artificial
1) Natural Parthenogenesis:- It is a regular phenomenon in the life history of some animals. It may be complete. incomplete or peadogenetic.
a) Complete (obligatory Parthenogenesis):- It occurs in some rotifiers and a few vertebrates. There are no males at all. So there is no biparenteal sexual reproduction. The females develops exclusively by parthenogenesis. e.g rock lizard, Lacerta sexicola armaniaca, Indian snake Typhlina brahmina shows complete parthenogenesis and there are no males.
b) Incomplete (cyclic) Parthenogenesis:- some animals have both sexual and parthenogenetic individuals, whic may alternate. In these animals, female can produce unfertilized and fertilized eggs, depending upon the environmental conditions. Example - In Daphnia, a water crustacean, female lays unfertilized eggs that develop parthenogenetically under favourable conditions and fertilized eggs during the time of environmental stress. In Honey bee, unfertilized eggs develop into male bee(drones) with haploid cells, and fertilized eggs give rise to females(Queen bee and worker bees) with diploid cells.
c) Paedogenetic Parthenogenesis:- In certain insects , Larvae lay eggs which develop parthenogenetically into a new generation of larvae. Parthenogenesis in larvae is called paedogenesis ( pais- child, genesis- origin).
2) Artificial Parthenogenesis:- Eggs of certain animals, such as annelids, mollusks, starfish, frog, hen, rabbit etc. , can be induced to develop parthenogenetically by artificial stimuli. Artificial stimuli may be i) physical, which may be , pricking of needles, electric shock, change in tempreature or pH (ii) Chemical stimuli such as addition of urea, fatty acids, ether, chloroform, to water.
Syngamy:- It is the fusion of two entire gametes ( one male and the other is female) to form a zygote. The fertilization includes all the associated events that ultimately leads to the syngamy.
Types of Syngamy:-a) Regards to the fusion of gametes:-
i) Endogamy:- It involves self- fertilization, i.e the fusion of two gametes of the same parent.So, it is , thus, uniparental. E.g tapeworm.
ii)Exogamy:- It involves crosss- fertilization, i.e the fusion of two gametes formed by different parents. So, it is, thus biparental.e.g frog, rabbit, human.
b) Regards to the structure of fusing gametes:-
i)Isogamy:- In this the fusing gametes are similar in structure but they have behavioural differences. In this , the gametes produced by one parentdonot fuse with each other.So the gametes similar morphologically are known as isogametes e.g as in protozoans .and the fusion is known as isogamy.
ii)Anisogamyor Heterogamy:- In this the fusing gametes are diffrent in form, size, structure, and behaviour . Sucha gametes rae known as anisogametes or heterogametes and their fusion is known as anisogamy or heterogamy . e.g as in frog, human.
The differences highlight the contrasting strategies organisms use to ensure the continuation of their species and cope with varying environmental challenges. Asexual reproduction is often more efficient for stable environments, while sexual reproduction provides advantages in terms of adaptability and genetic diversity.
DIFFERENCE BETWEEN ASEXUAL AND SEXUAL REPRODUCTION:-Asexual reproduction and sexual reproduction are two distinct methods of producing offspring in living organisms. Here are the key differences between the two:
REPRODUCTION:-A biological process in which an organism gives rise to young ones(offspring)similar to itself is called reproduction.
TYPES OF REPRODUCTION:- Two types:
a) SEXUAL REPRODUCION
b) ASEXUAL REPRODUCTION
SEXUAL REPRODUCTION: It involves the fusion of two sex gametes to form the new individual. it involves the two participation of two separate parents .
ASEXUAL REPRODUCTION: It involves the participation of single individual parent. The new individual are produced by any means other than the fusion of two sex gametes.e.g -Amoeba
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