Plant Kingdom 4 Flashcards
what are the 2 main whorls in a plant?
(i) Reproductive whorl
- Androecium
unit: stamen
stamen consists of filment( sterile) and enther ( fertile.
- gynoecium
unit: pistil/carpel
pistil/carpel has stigma, style and ovary.
(ii) Accessory whorl
-Corolla
unit: petals
colurful and fragrant for attraction of pollinating agents and secrete nectar
-Calyx
unit: sepals
usually green and photosyntheitic, provide protection to flower at bud stage
what is thalamus and pedicle
thalamus is the part that bears the flower
pedicle is the flower stalk
what is a perianth
if calyx and corolla are fused it is called perianth. Its unit is tepals. found in family lilliaceae
explain the structure of pollen grain
The pollen grain has two layers :
(i) intine- inner layer m/o pectin and hemicellulose
(ii) exine- outer layer m/o sporopollenin, which is the hardest material and cannot be broken by any acid, mechanical strength etc.
There are certain regions where the exine is absent called germpore. The pollen tube comes out through germpore.
Inside the pollen grain, there are 2 cells:
(i) Vegetative cell/tube cell: this is the larger cell which has the vegetative nucleus. this gives rise to pollen tube.
(ii) Generative cell- it is the smaller cell. When there is only one generative cell it is called 2 cell stage.
The generative cell undergoes mitossi and forms two cells. These are the two male gametes. This stage is called 3 -celled stage.
explain the structure of ovule
ovule has a mass of diploid cells called nucellus, which is covered by integuments or walls. There are two ends of the ovary, micropyle end which is open and opposite to it is chalazad end.
ANy one cell from nucellus will become megaspore mother cell and divide meiotically and form 4 megaspores. From this any one spore will become the functional female gamete while other 3 will degenerate.
describe the formation of embryo-sac
The functional megaspore (n) undergoes free nuclear division ( only karyokinesis) three times and forms 8 nuclei. Then there is rearrangement of nuclei and formation of wall leading to the formation of 1 egg cell, 2 synergids, 3 antipodal cells and 2 polar nuclei.
The egg cell and synergids are present at micropyle end. The synergids are at chalazad end, while polar nuclei are present in the centre.
This is called 7 celled & 8 nucleated female gametophyte or
embryo sac. The entire embryo sac is haploid.
what is filliform apparatus
these are present in the micropyle end of embryo sac and guide the entry of pollen tube.
what is triple fusion
it is the fusion of secondary nucleus ( formed by fusion of 2 polar nuclei) and 1 male gamete.
which has most developed:
(i) sprophyte
(ii) gametophyte
which has least developed
(iii) sporophyte
(iv) gametophyte
(i) angiosperm
(ii)moss
(iii) thallopyta
(iv)angio
which is the last division to have:
(i) antheridia
(ii archegonia
(i) pteridophyte
(ii) gymnospemr