Tag: the origin of cells and cell division

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Multiple choice botany modes of reproduction introduction to flower pre fertilization - plants sexual reproduction in flowering plants the origin of cells and cell division

In mesogamy, pollen tube enters the ovule through

  1. Middle of integuments after piercing the tissues

  2. Middle of integuments without piercing the tissues

  3. Chalaza

  4. Middle of micropyle
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Mesogamy is the entry of pollen tube in the ovule through the integuments. The pollen tube enters the ovule laterally through integuments by piercing the tissue in the middle and finally enters the embryo sac through micropylar pole, whereas, entry of pollen tube through chalaza is called chalazogamy and through micropyle is called porogamy.
So, the correct answer is A. 
Multiple choice botany modes of reproduction introduction to flower pre fertilization - plants sexual reproduction in flowering plants the origin of cells and cell division

Entry of pollen tube through chalazal end is

  1. Syngamy

  2. Porogamy

  3. Mesogamy

  4. Basigamy
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
•Syngamy is the fusion of male and female gamete which results in the formation of a diploid zygote.
•Porogamy is the entry of pollen tube in the ovule through micropyle.
•Mesogamy is the entry of pollen tube in the ovule through the integuments or nucellus.
•Basigamy is also known as Chalazogamy. It is the entry of pollen tube in the ovule through the chalaza.
So, the correct answer is D.
Multiple choice botany modes of reproduction introduction to flower pre fertilization - plants sexual reproduction in flowering plants the origin of cells and cell division

Pollen tube usually enters the embryo sac

  1. Through one of the synergids.

  2. Directly penetrates the egg.

  3. Between one synergid and central cell.

  4. By knocking of antipodal cells.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Synergids attract the pollen tube by secreting some chemotactic substances and guide the pollen tube entry. Synergids are ephemeral i.e. short-lived structures. In embryo sacs, which have two synergids, one synergid degenerates before the entry of pollen tube. This degenerated synergid provides the way for pollen tube entry in the embryo sac. The pollen tube discharges its content in the degenerated synergid. The other synergid which is the persistent synergid degenerates shortly after the pollen tube has released its contents in the embryo sac.
Hence, pollen tube enters the embryo sac through one of the synergids.
So, the correct answer is A.
Multiple choice botany modes of reproduction introduction to flower pre fertilization - plants sexual reproduction in flowering plants the origin of cells and cell division

Commonly the pollen tube enters the ovule through

  1. Hilum

  2. Chalaza

  3. Funicle

  4. Micropyle
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Pollen tube may enter the ovule via any of the following routes:
1.  Porogamy- when the pollen tube enters the ovule through micropyle. It is common in most of the angiosperms.
2. Mesogamy- when the pollen tube enters through the integuments or through funiculus.
3. Chalazogamy- when the pollen tube enters through the chalazal tissues.
Thus, pollen tube commonly enters the ovule through micropyle.
So, the correct answer is D.
Multiple choice botany modes of reproduction introduction to flower pre fertilization - plants sexual reproduction in flowering plants the origin of cells and cell division

Normally how many pollen mother cells are necessary for formation of $400$ seeds.

  1. $200$
  2. $500$
  3. $100$
  4. $400$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Each seed requires one male gamete and one female gamete. One pollen mother cell (PMC) produces 4 microspores, each forming a pollen grain with 2 male gametes. However, only one pollen grain is needed per seed. Thus, 400 seeds require 400 pollen grains. Since 1 PMC produces 4 microspores, 400/4 = 100 PMCs are needed.

Multiple choice botany modes of reproduction introduction to flower pre fertilization - plants sexual reproduction in flowering plants the origin of cells and cell division

Through which cell of the embryo sac, does the pollen tube enter the embryo sac-

  1. Persistant synergid

  2. Egg cell

  3. Central cell

  4. Degenerated synergid
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The pollen tube enters the embryo sac through the micropylar end. It can enter directly through the synergid or can enter from between the egg cell and synergid.

The answer is D- Degenerated synergid. 
So the correct option is D.