MPSC 2026 Prelims Paper-I · Question 59 of 100

Correct — option (1), "New organism without fusion of gametes". Apomixis is a form of asexual reproduction that mimics sexual reproduction. In flowering plants it means seed is set — a complete, viable, dispersible seed — without fertilisation ever having occurred. No male gamete fuses with an egg, so there is no meiotic recombination and no genetic contribution from a second parent, and the offspring is a genetic copy of the mother plant. The word itself carries the definition: 'a-' meaning without and 'mixis' meaning mingling, in contrast to amphimixis, the ordinary sexual process in which gametes do fuse. Option (1) states exactly this and is the credited answer. The reason apomixis attracts so much attention is agricultural, and it is worth understanding because it is the angle from which the topic is usually examined. Hybrid varieties are prized for hybrid vigour, but that vigour does not survive into the next generation: the F1 hybrid is heterozygous, its progeny segregate, and yield falls away. So a farmer growing hybrids must buy fresh seed every season rather than saving his own. If apomixis could be engineered into hybrid crops, the hybrid genotype would be passed on intact through seed, generation after generation, with no segregation at all — the vigour of a hybrid combined with the seed-saving economics of an open-pollinated variety. That is why apomixis is a standing research goal in plant breeding. Option (4), "Embryo from nucellus", is the strongest distractor and deserves care rather than dismissal. Development of an embryo directly from the nucellus is adventive or nucellar embryony, and it is genuinely one route by which apomixis occurs — it is what happens in many varieties of citrus and mango, where cells of the nucellus surrounding the embryo sac divide and produce additional embryos alongside the sexual one, giving seeds with several embryos, a condition called polyembryony. But nucellar embryony is a particular mechanism, not the definition of apomixis. Apomixis also occurs through routes that do not involve the nucellus at all, notably where the embryo develops from an unreduced cell of the embryo sac. The stem asks what apomixis as a type of reproduction results in, which calls for the general characterisation, and the general characterisation is a new organism formed without gamete fusion. This is a useful distinction to have practised. When one option gives the definition of a category and another gives an example of it, the definition answers a question phrased in general terms. The examiner is testing whether the candidate knows the boundary of the concept, not merely one instance falling inside it.

• (2)New organism from fusion products of gametes — Option (2) describes the exact opposite of apomixis. The fusion of gametes is syngamy, and reproduction proceeding through it is amphimixis — ordinary sexual reproduction, in which the zygote formed by fertilisation develops into the embryo. Apomixis is defined by the absence of that fusion, which is what the prefix 'apo-' signals. A candidate marking this option has read the stem as asking about seed formation in general rather than about the process the stem actually names.
• (3)Embryo from endosperm — Option (3) describes something that is not a recognised developmental pathway. In an angiosperm seed the endosperm is nutritive tissue, formed in the double fertilisation process when a male gamete fuses with the polar nuclei, and its function is to nourish the developing embryo rather than to become one. Embryos arise from the egg cell in sexual reproduction, or from sporophytic tissue such as the nucellus or integuments in adventive embryony — not from the endosperm. This option pairs two real terms from the same page of the syllabus in a relation that does not exist.
• (4)Embryo from nucellus — Option (4) names a real phenomenon that really is a form of apomixis — adventive or nucellar embryony, seen in citrus and mango, where nucellar cells develop into embryos and produce polyembryonic seeds. But it is one mechanism among several, not the definition. Apomixis also occurs without any involvement of the nucellus, for instance where an unreduced cell of the embryo sac develops into an embryo. Since the stem asks what apomixis as a type of reproduction results in, the general characterisation at option (1) is what is required; option (4) answers a narrower question that was not asked.

Apomixis is reproduction without gamete fusion that nonetheless produces seed — asexual reproduction wearing the costume of sexual reproduction. Because no meiotic recombination and no fertilisation occur, the resulting plants are genetically identical to the mother, so a population reproducing apomictically is a clone. The principal routes are two. In one, the embryo develops from a cell of the embryo sac that has not undergone reduction, so the embryo carries the maternal chromosome number unchanged; diplospory and apospory belong here. In the other, adventive or nucellar embryony, embryos arise directly from sporophytic tissue of the ovule — the nucellus or the integuments — outside the embryo sac altogether. The second route commonly gives polyembryony, more than one embryo in a single seed, and it is easily observed: sowing a seed of many citrus varieties yields several seedlings, most of them nucellar clones of the parent and one of sexual origin. Apomixis occurs naturally in several families, notably the grasses and the Asteraceae, and among cultivated plants in citrus and mango.

Three neighbouring terms are regularly confused with apomixis and with one another, and separating them is worth more marks than the definition alone. Parthenocarpy is the development of fruit without fertilisation, producing a seedless fruit — the commercial banana is the standard example; the fruit forms, the seed does not. Apomixis is the reverse emphasis: seed forms, but without fertilisation. Parthenogenesis is the development of an organism from an unfertilised egg, the term used chiefly of animals, as in the male honeybee, which develops from an unfertilised egg and is haploid. Polyembryony is not a mode of reproduction at all but a result — the presence of more than one embryo in a seed — and it can arise from adventive embryony or from other causes. The examinable core is therefore a four-term table, and the discriminating questions in this area are almost always built by offering one term's definition under another term's name.

• Apomixis is a form of asexual reproduction that mimics sexual reproduction: seed is produced without fertilisation, so the offspring is genetically identical to the mother plant. Amphimixis is the contrasting term for ordinary sexual reproduction involving gamete fusion.
• Its principal routes are development of the embryo from an unreduced cell of the embryo sac, and adventive or nucellar embryony, in which the embryo arises directly from the nucellus or integuments — the route seen in many citrus and mango varieties.
• Adventive embryony commonly produces polyembryony, more than one embryo in a single seed, so one citrus seed may yield several seedlings, most of them nucellar clones of the parent.
• Apomixis is an important goal in plant breeding: hybrid vigour is lost when F1 hybrids segregate in the next generation, but an apomictic hybrid would transmit its genotype unchanged through seed, allowing farmers to save seed instead of buying it each season.
• Related but distinct terms — parthenocarpy is the development of fruit without fertilisation, giving seedless fruit as in the banana; parthenogenesis is development of an organism from an unfertilised egg, as in the male honeybee.

• Choosing a specific mechanism when the stem asks for the general definition. Nucellar embryony is a form of apomixis, not what apomixis means.
• Confusing apomixis with parthenocarpy. Apomixis gives seed without fertilisation; parthenocarpy gives fruit without fertilisation, and therefore without seed.
• Supposing an embryo can develop from the endosperm. The endosperm is nutritive tissue formed by fusion of a male gamete with the polar nuclei; embryos come from the egg or from sporophytic tissue of the ovule.
• Forgetting that apomictic offspring are genetically identical to the mother. That is the entire reason apomixis interests plant breeders, and it is the point most questions on the topic ultimately turn on.

Reproduction in flowering plants is a reliable source of questions for MPSC's general science section, and the apomixis cluster is asked in three ways. The definitional question, as here, gives the term and asks what it means, with the strongest distractor usually being a narrower mechanism that falls inside the category. The discrimination question offers two or three of the confusable terms — apomixis, parthenocarpy, parthenogenesis, polyembryony — and asks which describes a stated situation. The applied question asks why apomixis matters in agriculture, which is answered by the hybrid seed argument. Preparing the four-term table with one example each, plus the single sentence about hybrid vigour, covers the whole cluster.

No directly related past PYQ was found.

• practice — not a real PYQ

  The development of fruit without fertilisation, resulting in a seedless fruit as in the banana, is called :

  • (a)apomixis
  • (b)parthenocarpy
  • (c)polyembryony
  • (d)parthenogenesis

  Answer(b) parthenocarpy. Fruit develops but seed does not. Apomixis is the converse emphasis — seed is produced without fertilisation; polyembryony is the presence of more than one embryo in a single seed; and parthenogenesis is the development of an organism from an unfertilised egg, a term used chiefly of animals such as the male honeybee.

• practice — not a real PYQ

  Why would the introduction of apomixis into hybrid crop varieties be of great value to farmers ?

  • (a)It would make the crops resistant to all pests and diseases
  • (b)The hybrid genotype would be transmitted unchanged through seed, so farmers could save their own seed
  • (c)It would double the chromosome number and so double the yield
  • (d)It would allow the crop to be harvested twice in a single season

  Answer(b) The hybrid genotype would be transmitted unchanged through seed, so farmers could save their own seed. Hybrid vigour is lost in the generation after an F1 hybrid because the heterozygous genotype segregates, which is why hybrid seed must be bought fresh each season. Apomictic seed carries the maternal genotype intact with no segregation, combining the vigour of a hybrid with the seed-saving economics of an open-pollinated variety.