Plant Reproduction Test - 6

• In the case ofdouble fertilization , which occurs in angiosperms, the primary nucleus fuses  with one of the nuclei of male gametes and produces zygote and secondary nucleus fuses with another nucleus of the male gametes and forms an endosperm.
• Endosperm provides nourishment for the developing embryo . The other male gamete which enters the embryo sac fuses with the haploid egg and forms the embryo.

Thus, the correct answer is option D.

• Synergids are haploid in nature. This means they contain one complete set of chromosomes. They are formed as a result of meiosis, a type of cell division that reduces the number of chromosomes in parent cells to half, resulting in four daughter cells, each with half the number of chromosomes of the parent cell.
• Role in Fertilization: The primary role of synergids is to help in the process of fertilization. One of the two synergids will fuse with a pollen grain (male gamete) to form the zygote, while the other synergid degenerates. The haploid nature of synergids ensures that the resulting zygote, formed by the fusion of male and female gametes, is diploid, containing two sets of chromosomes.

Hence, Option (A) is the correct answer.

Double fertilisation is a unique process observed in angiosperms (flowering plants). It involves the fusion of the male and female gametes, forming two distinct products - the zygote and the primary endosperm nucleus (PEN).

Formation of the Zygote:

• One of the two male gametes fuses with the egg cell to form the zygote. This process is known as syngamy.

Formation of the Primary Endosperm Nucleus:

• The other male gamete fuses with the two polar nuclei (found within the central cell of the ovule) to form the primary endosperm nucleus. This process is known as triple fusion because it involves the fusion of three nuclei.

Central Cell After Triple Fusion:

• After triple fusion, the central cell becomes the primary endosperm cell (PEC), which contains the primary endosperm nucleus (PEN).

Therefore, the correct answer is b. Primary Endosperm Nucleus (PEN) . This is the central cell after triple fusion in double fertilisation.

• Endosperm is  formed during double fertilization .
• It  is triploid because it  is  formed when one of the two sperm that  is  haploid enters inside the embryo  sac &fuses with two polar nuclei (each polar nuclei  is  haploid).
• So  the endosperm formed  is triploid.

Hence, the correct option is B.

• Double fertilization occurs only in angiosperms.
• The female gametophyte in angiosperms abruptly stop their growth at 8 nucleate stages.

Aleurone is a protein found in protein granules of maturing seeds and tubers. It also describes one of the two major cell types of the endosperm, the aleurone layer. It is the outermost layer of the endosperm.

Structure of Maize Seed:

 

Hence, the correct option is A.

• The pollen grains germinate on the stigma and the resulting pollen tubes grow through the tissues of stigma and style and reach the ovule.
• The pollen tubes enter the embryo-sac where two  male gametes are discharged. One of the male gametes fuses with the egg cell (syngamy) and forms a diploid zygote. The other  male gamete fuses with the diploid secondary nucleus to four primary endosperm nucleus (PEN), which is triploid in nature.
• Since, two types of fusion. Syngamy and triple fusion takes place in the embryo sac, the process is known asdouble fertilisation. 
  
• Hence, the correct option is A.

• Endosperm can be classified into two types according on how it is consumed during development: endospermic and non-endospermic.
• If the endosperm is consumed by the growing embryo, it is said to be non-endospermic.
• In some plants, the endosperm is completely absorbed by the embryo, some of the examples are peas , beans, and green gram, in this type of food is stored in dicot seeds.
• Whereas in some dicots, food is stored in endosperm examples are castor, maize, etc.
• In the case of coconut, the endosperm is present in the liquid form and it is stored.

Hence, The correct answer is option (C).

Parthenocarpy (parthenos-virgin, karpos-fruit) is the formation of seedless fruits without fertilization. The fruits developed from unfertilized ovaries  are called parthenocarpic fruits.

Fig: Parthenocarpic Fruits

Other options are incorrect because:

• In asexual reproduction, a single individual (parent) is capable of producing offspring.
• For apomixis and sexual reproduction. 

• The fusion of one male gamete with the egg cell is calledSyngamy or true fertilization while the fusion of second male gamete with two polar nuclei is called triple fusion.
• Syngamy along with the triple fusion is called double fertilization. Double fertilization is a characteristic feature of flowering plants or angiosperms.

  Hence, the correct option is B.