Topic 2 - Gametogenesis + Fertilisation in Plants

Question 1

describe pollen formation

Answer 1

• diploid microspore mother cell in anthers undergo meiosi -> for 4 haploid microspores
• haploid microspores under go mitosis tomature into pollen grains
• pollen grains consist of 2 nuclei -> generative nucleus and the pollen tube nucleus and protective coating

Question 2

Describe ovum formation in plants

Answer 2

• diploid megaspore mother cell in ovule undergoes meiosis -> forming an ootid and 3 polar bodies which degenerate and are reabsorbed
• ootid undergoes 3 mitotic divisions to form an embryo sac.
  **Embryo sac contains ** -> 2 polar bodies (form endosperm)
  -> an egg cell (forms zygote)
  -> 2 synergids (help the generative nucleus reach egg cell)
  -> 3 antipodal cells (no established function)
  with protective coating

Question 3

random knowledge

what are synergids

Answer 3

Synergid cells are 2 specialized cells which are located into embryo sac of female gametophyte, beside egg cells. Functions: It nourishes the ovum and give direction in the pollen tube

Question 4

Describe fertilisation in plants

Answer 4

• pollen grain (composed of pollen tube nucleus and the generative nucleus) adheres to the stigma, subsequently germinates
• pollen tube grows down stlye via secreation of digestive enzymes (digest surrounding tissue + uses it as source of nutrition).
• pollen tube grows through microphle into embryo sac
• Generative nucleus of pollen divides by mitosis to produce 2 sperm cells - enter embryo sac
• Double fertilisation occurs: 1 male gamete fuses with female nucelus - form diploid zygote
• other male gamete fuses with 2 polar nuclei, form tripoid endosperm nuclei -> source of nutrients for embryo

subsequently - following