Biology : reproduction in plants (chap 16)

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REPRODUCTION IN PLANTS (Chapter 16)

sexual reproduction

in flowering plants

Pollination

Cross-Pollination

DISADVANTAGES: -2 parent plants needed -have to depend on external factors ; insects, wind -more energy +pollen wasted than self-pollination

ADVANTAGES: -Offspring may inherited beneficial qualities from both parents -more seeds produced > longer survival b4 germination -higher genetic variations > increases chance of survival of the changing environment

FEATURE OF C.P PLANTS: -stima & anthers mature @ diff timings -stigma may be found further away than anthers -DIOECIOUS plants bear either male OR female part so NO self polliination

Transfer of pollen grains from 1 plant to the stigma of a flower in another plant of the same kind.

feature> insects vs. wind pollination : Petals > bright coloured petals : small & dull nectar > present : absent scent > sweet-smelling : absent stigma > small&compact : large & feathery pollen > large amount & surface : more+smooth nectar guides > present : absent

Self-Pollination

DISADVANTAGES: -Offspring may become weaker, smaller+ less resistant to dieseases -Offspring the same as parents -less adapted to changes in the environment

ADVANTAGES: -1 parent plant needed -not dependent on external factors ; insects, wind for pollination -less energy require than cross-pollination

FEATURES OF S.P PLANTS: -have male & female parts maturing @ the same time -stigma found right below anther

Transfer of pollen grains from anther to stigma of diff/same flower of the SAME plant

parts of plants: sepal->enclose + protect the flower in the bud stage.

FEMALE PARTS: Carpel (pistil) : consist of ovary, style & stigma

Style: -connects stigma to ovary -holds stigma to trap pollen grains

Ovary: -contains 1/>1 ovules

female gamete: [ovum]

-produced by meiosis-> haploid -ovule attach to placenta by a stalk (funicle)

Stigma: -receives pollen grains -secrete a sugary fluid > stimulate the pollen grain to germinate

MALE PARTS: Stamen: consist of anther & filament. (androecia)

Pollen Grains: -contain haploid no. of chromosomes

each pollen grain has 2 nuclei >Generative nucleus >Pollen Tube Nucleus(vegetative nucleus)

Filament: holds the anther to disperse pollens

-contains vascular bundle. >pholem >xylem

Anther: -2 lobes-->2 pollen sacs - produce pollen grains

petal: together make up COROLLA

insect pollinated: -brightly colored -platform for insects to land.

Receptacle: enlarge end of the flower

Pedicel: -flower stalk

*flower w/o pedicel, attached at base. this is called SESSILE

involves fusion of gametes to form a zygote, offspring diff from parents

produced in meiosis

asexual reproduction

mitosis occurs during this period

production of genetically identical offspring fron 1 parent , w/o the fusion of gametes

FERTILISATION:

9) zygote divide & develop into embryo. - endosperm nucleus divide & give rise to the food storage tissue (endosperm)

8) 1 male gametes fuses w/ ovum --> zygote(fertilisation). -The other fuses w/ definitive nucleus to form the endosperm nucleus

7) tip of pollen tube absorbs sap, burst--> releasing 2 male gametes

6) generative nucleus divides into 2. pollen tube nuleus disintergrates

5) pollen tubes enters ovule thru opening called MICROPYLE

4) as it grows, secrete enzyme to digest surrounding tissue--> penetrates thru the style

3) pollen tube nucleus control the passing in of the cytoplasm & 2 nuclei of the pollen grain

2) pollen tube grows out

1) pollen grains germinate--> sugary fluid secreted by stigma