Question
In some plants, the female gamete develops into embryo without fertilisation. This phenomenon is known as [NEET (National) 2019]
(a) parthenocarpy
(b) syngamy
(c) parthenogenesis
(d) autogamy
Answer/Explanation
Ans. (c)
Parthenogenesis is the process by which the female gamete develops into embryo without fertilisation. It is of two type-haploid and diploid. In former, embryo develops from haploid egg and in latter case, a diploid egg develops into embryo. Parthenocarpy is the development of seedless fruits from an unfertilised egg of the flower. Syngamy is the fusion of male and female gamete during sexual reproduction in plants. Autogamy is a type of self-pollination in which a flower is pollinated by its own pollen.
Question
Which one of the following fruits is parthenocarpic? [CBSE AIPMT 2015]
(a) Brinjal
(b) Apple
(c) Jackfruit.
(d) Banana
Answer/Explanation
Ans. (d)
Parthenocarpy is a process of developing fruits without involving fertilisation/seed formation. Therefore, the seedless varieties of economically important fruits like orange, banana, watermelon, lemon, etc. are produced using this technique. This technique involves inducing fruit formation by the application of plant growth hormones such as auxins.
Question
In a type of apomixis known as adventive embryony, embryos develop directly from the [CBSE AIPMT 2005]
(a) nucellus or integuments
(b) zygote
(c) synergids or antipodals in an embryo sac
(d) accessory embryo sac in the ovule
Answer/Explanation
Ans. (a)
Apomixis does not involve gamete formation and fertilisation as found in amphimixis. Adventive embryo formation is a type of apomixis in which embryos are formed from diploid integumental or nuceller cells.
Question
Adventive embryony in Citrus is due to [CBSE AIPMT 2001]
(a) nucellus
(b) integuments
(c) zygotic embryo
(d) fertilised egg
Answer/Explanation
Ans. (a)
Nucellus embryony occurs in crassinucellate ovules (e.g. Citrus, Opuntio). On the other hand integumentary embryony occurs in tenuinucellate ovules (e.g. Euonymus).
Question
Formation of gametophyte directly from sporophyte without meiosis is [CBSE AIPMT 1988]
(a) apospory
(b) apogamy
(c) parthenogenesis
(d) amphimixis
Answer/Explanation
Ans. (a)
Apospory is the formation of gametophyte directly from sporophyte without forming spores and meiosis. The gametophytes formed through apospory are usually diploid. Apospory leads to polyploidy and hence, new species in bryophytes and pteridophytes.
Question
Prothallus (gametophyte) gives rise to fern plant (sporophyte) without fertilisation. It is [CBSE AIPMT 1988]
(a) apospory
(b) apogamy
(c) parthenocarpy
(d) parthenogenesis
Answer/Explanation
Ans. (b)
Apogamy refers to the development of sporophyte from gametophyte without fertilisation.
In fern plant, prothallus (gametophyte) gives rise to main plant body (sporophyte) directly from somatic cell without forming gametes. Sporophyte thus formed is haploid in nature.
Question
Development of an organism from female gamete/egg without involving fertilisation is [CBSE AIPMT 1989]
(a) adventitive embryony
(b) polyembryony
(c) parthenocarpy
(d) parthenogenesis
Answer/Explanation
Ans. (d)
Parthenogenesis can be defined as formation of embryo from an unfertilised egg or female gamete. Parthenogenetic plants are homozygous so, they have more importance in plant breeding and genetics.