18 Questions
What is the end result of the fusion of male and female gametes in flowering plants?
Diploid zygote
Which phase of the flowering plant life cycle involves the formation of haploid gametes?
Gametophytic phase
What is the role of flowers in the life cycle of angiosperms?
Sexual reproduction
Where are microspores formed in flowering plants?
Anther
What is the first cell of the male gametophyte in flowering plants?
Pollen grain
Where does pollination occur in the flower of a plant?
Style
What process was discovered by Strasburger in Angiosperms in 1884?
Double fertilization
What stimulates the growth of the pollen tube in angiosperms?
Sugary substances secreted by the stigma
Where does the male gamete fuse with the egg cell in angiosperms?
Embryo sac
What is the result of the fusion of one male gamete with the egg cell in angiosperms?
Diploid zygote
Where does the pollen tube generally reach near the embryo sac in angiosperms?
By penetrating the nucellus through the micropyle or the chalaza
What is formed as a result of the fusion of the other male gamete through triple fusion in angiosperms?
Triploid primary endosperm nucleus
Where does geitonogamy occur in plants?
Between flowers on the same plant
What is the term for the phenomenon where both anther and stigma mature at the same time in bisexual flowers?
Homogamy
In which plant do sessile anthers lie at the mouth of a narrow corolla tube, resulting in self-pollination?
Vinca
Which type of flowers are known as cleistogamous or closed flowers?
Bisexual flowers that never open
What is the term for self-pollination due to stigmas moving back to touch anthers in case of cross pollination failure?
Dichogamy
Which type of pollination involves transfer of pollen grains from one flower's anther to another flower's stigma on the same plant?
Geitonogamy
Study Notes
Sexual Reproduction in Angiosperms
- Angiosperms' sexual reproduction process was discovered by Strasburger in 1884.
Double Fertilization and Triple Fusion
- Fertilization occurs in the embryo sac, where compatible pollen grains germinate and produce pollen tubes to carry male gametes to the egg cell.
- The growth of the pollen tube is stimulated by sugary substances secreted by the stigma.
- A mass of cytoplasm accumulates at the tip of the pollen tube, which contains the male nuclei.
Entry of Pollen Tubes into the Embryo Sac
- Pollen tubes penetrate the nucellus through the micropyle or chalaza to reach the embryo sac.
Syngamy (True Fertilization)
- One male gamete (n) fuses with the egg cell to form a diploid zygote (2n).
Triple Fusion
- The other male gamete (n) fuses with the definitive nucleus (2n) to form a triploid primary endosperm nucleus (3n).
Life Cycle of Angiosperms
- Angiosperms have two distinct phases: diploid sporophytic phase and haploid gametophytic phase.
- The sporophytic phase is represented by the flowering plant, which bears reproductive structures in flowers.
Steps in Sexual Reproduction
Development of Haploid Male Gametes
- Formation of microsporangia in the anther of stamen.
- Microsporogenesis: meiosis in microspore mother cells to produce haploid microspores (pollen grains).
- Pollination: dispersal of microspores to the stigma of the carpel.
- Development of male gametophyte in the pollen grain, producing two male gametes (sperm).
Development of Haploid Female Gamete
- Development of ovule (megasporangium) and female gametophyte within it.
- Megasporogenesis: formation of megaspores within the female gametophyte (embryo sac).
Types of Pollination
Autogamy
- Self-pollination in bisexual plants (e.g., Tea, Wheat, Rice).
Geitonogamy
- Transfer of pollen grains from the anther of a flower to the stigma of another flower borne on the same plant.
Contrivances (Adaptations) of Self-Pollination
- Homogamy: simultaneous maturation of anther and stigma in bisexual flowers (e.g., Mirabilis, Potato, Wheat, Rice).
- Dichogamy: asynchronous maturation of anther and stigma in bisexual flowers (e.g., Sunflower).
- Cleistogamy: self-pollination in closed or cleistogamous flowers that never open.
Test your knowledge on the life cycle of flowering plants, where haploid male and female gametes fuse to form a diploid zygote. Learn about the alternating phases of diploid sporophytic and haploid gametophytic phases in flowering plants.
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