Plant Kingdom 4

Question 1

what are the 2 main whorls in a plant?

Answer 1

(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

Question 2

what is thalamus and pedicle

Answer 2

thalamus is the part that bears the flower
pedicle is the flower stalk

Question 3

what is a perianth

Answer 3

if calyx and corolla are fused it is called perianth. Its unit is tepals. found in family lilliaceae

Question 4

explain the structure of pollen grain

Answer 4

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.

Question 5

explain the structure of ovule

Answer 5

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.

Question 6

describe the formation of embryo-sac

Answer 6

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.

Question 7

what is filliform apparatus

Answer 7

these are present in the micropyle end of embryo sac and guide the entry of pollen tube.

Question 8

what is triple fusion

Answer 8

it is the fusion of secondary nucleus ( formed by fusion of 2 polar nuclei) and 1 male gamete.

Question 9

which has most developed:
(i) sprophyte
(ii) gametophyte

which has least developed
(iii) sporophyte
(iv) gametophyte

Answer 9

(i) angiosperm
(ii)moss

(iii) thallopyta
(iv)angio

Question 10

which is the last division to have:
(i) antheridia
(ii archegonia

Answer 10

(i) pteridophyte
(ii) gymnospemr