REPRODUCTION IN PLANTS
(Chapter 16)

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

2) pollen tube grows out

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

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

5) pollen tubes enters ovule thru opening called MICROPYLE

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

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

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

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

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

mitosis occurs during this period

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

produced in meiosis

in flowering plants

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

Pedicel:
-flower stalk

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

Receptacle: enlarge end of the flower

petal: together make up COROLLA

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

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

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

Filament: holds the anther to disperse pollens

-contains vascular bundle.
>pholem
>xylem

Pollen Grains:
-contain haploid no. of chromosomes

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

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

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

Ovary:
-contains 1/>1 ovules

female gamete:
[ovum]

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

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

Pollination

Self-Pollination

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

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

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

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

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

Cross-Pollination

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

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

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

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