CUET UG Biology Booster Test 2 Seed, Fruit, and Special Mechanisms

According to NCERT, most zygotes divide only after a certain amount of endosperm is formed. This is an adaptation to provide assured nutrition to the developing embryo (A)-(II). The proembryo stage marks the initial multicellular phase found in both dicotyledonous and monocotyledonous embryogeny (B)-(III). Nutrition provision for the embryo is handled by the primary endosperm cell which triggers the development of the endosperm (C)-(IV). Finally, because the egg cell is located at the lower region of the embryo sac, the embryo is situated at the micropylar end of the embryo sac (D)-(I). This maps perfectly to Option A.

Embryogeny shows a clear structural timeline. The proembryo acts as the immediate cellular precursor to the globular stage (C)-(IV). The globular embryo forms a uniform, spherical multicellular mass of dividing tissues (B)-(I). As the two cotyledons begin to branch out in dicotyledonous plants, the embryo assumes a distinct two-lobed, heart-shaped configuration (A)-(II). This setup culminates in the mature embryo, which possesses a fully differentiated embryonal axis alongside its cotyledons (D)-(III). This sequence matches Option A.

Peeling a mature dicotyledonous seed reveals a clear outer-to-inner layout. The absolute boundary layer is the seed coat (II). Moving past this covering exposes the two fleshy cotyledons (IV) that store nutrients. Deep inside the cotyledons sits the main embryonal axis. Along this axis, moving from the upper shoot tip down past the cotyledonary node leads first through the epicotyl zone (III) and then down into the lower hypocotyl region (I). This radial progression corresponds to (II) > (IV) > (III) > (I), matching Option A.

Moving from the shoot pole (stem tip) down to the root pole along the embryonal axis follows a straight path. The uppermost terminal tip is the plumule (I). Directly below the plumule is the epicotyl (IV), which is the segment of the axis above the cotyledons. Passing the cotyledonary node leads into the hypocotyl (III), which is the cylindrical segment located below the cotyledonary level. This section terminates at the lower tip in the radicle (II), which forms the root cap zone. This layout gives the sequence: (I) > (IV) > (III) > (II), matching Option A.

In monocotyledonous embryos of the grass family, the single cotyledon is called the scutellum. The region of the embryonal axis situated above the level of attachment of the scutellum is the epicotyl. The epicotyl includes the shoot apex and a few leaf primordia, both enclosed within a hollow, protective foliar sheath called the coleoptile. The radicle (root tip), however, is located at the lower end of the embryonal axis. Because it belongs to the lower root zone, it is not involved in the upper structure above the scutellum attachment. This makes Option B the correct choice.

The structural layout of a grass embryo includes several specialized protective coverings. The scutellum is a large cotyledon positioned laterally along the embryonal axis, providing a protective and absorptive shield. At the lower end, the radicle and root cap are protected by an undifferentiated cellular sheath called the coleorrhiza (B). At the upper end, the shoot apex is enclosed by a hollow foliar sheath called the coleoptile (D). The epicotyl (C), however, is not a protective sheath; it is the actual internal segment of the embryonal axis located above the scutellum attachment line. This makes Option C the correct answer.

In most flowering plants, the nucellus is completely consumed during the development of the embryo sac and seed. However, in some species, a portion of the nucellus persists in the mature seed as perisperm, which serves as an additional food reserve. According to NCERT, black pepper and beet are classic examples of perispermic seeds. In contrast, castor is an albuminous (endospermic) seed, where the food reserve is retained mainly in the endosperm. It is not identified by the presence of a persistent perisperm. Therefore, Option D is the correct answer.

In most flowering plants, the nucellus is completely consumed during the development of the embryo sac and seed. However, in some species, a portion of the nucellus persists in the mature seed as perisperm, which serves as an additional food reserve. According to NCERT, black pepper and beet are classic examples of perispermic seeds. In contrast, castor is an albuminous (endospermic) seed, where the food reserve is retained mainly in the endosperm. It is not identified by the presence of a persistent perisperm. Therefore, Option D is the correct answer.

During seed maturation, dehydration reduces the moisture content, and the seed enters a state of dormancy. These adaptations allow seeds to remain viable for long periods without germinating immediately. As a result, seeds can be stored as food throughout the year, preserved for sowing in the next growing season, and maintained as a reliable resource for agriculture. If seeds underwent immediate germination upon dispersal, they could not be stored, transported, or preserved for future cultivation. Therefore, Option C is not an advantage of seed dehydration and dormancy.

During seed maturation, the integuments harden to form a tough seed coat, which protects the embryo and helps maintain dormancy by preventing premature germination. Dormant seeds are also characterized by a low moisture content (about 10–15% by mass), resulting in very low metabolic activity. In contrast, high water content in the embryo activates enzymes, increases metabolic activity, and initiates germination. Therefore, Option D is not associated with the structural maintenance of seed dormancy.

During the transformation of a flower into a fruit, the maternal ovary wall thickens and differentiates into the pericarp. In fleshy fruits like the mango, orange, or guava, this pericarp becomes highly developed, differentiated, and succulent (fleshy). In a mango specifically, the pericarp divides into a thin outer epicarp, a thick fleshy edible mesocarp, and a stony hard endocarp. Thus, its primary significance in a fleshy fruit is providing that succulent tissue layer, matching Option B.

The Passage: explicitly states: "...the transformation of ovules into seeds and ovary into fruit proceeds simultaneously." As the zygote inside the ovule develops into an embryo and the endosperm forms, the outer integuments harden into a seed coat. At the exact same time, cell divisions and expansion occur in the surrounding ovary wall to build the pericarp. Because these processes run concurrently, Option B is the correct choice.

In a minority of angiosperm species, non-ovarian floral structures fail to wither and drop off after fertilization. Instead, they proliferate alongside the maturing ovary. In the strawberry, apple, and cashew, the thalamus contributes significantly to the formation of the fruit, growing to become the prominent fleshy, edible portion. Because tissue outside the ovary forms part of the fruit mass, it is classified as a false fruit. This matches Option B.

In the vast majority of flowering plants, post-fertilization changes cause the petals, stamens, styles, and thalamus to fall away. The fruit develops exclusively from the mature ovary, and its wall develops from the ovary wall. Because no other floral organs contribute to the fruit structure, these are classified as true fruits (e.g., mango, tomato, pea). This matches Option B.

The banana is a classic example of a naturally occurring parthenocarpic fruit. Parthenocarpy is the physiological process where an ovary is triggered to grow into a fully formed fruit without undergoing fertilization. Because fertilization never takes place within the internal ovules, no zygotes or seeds are produced. This results in the characteristic seedless pulp of commercial bananas, matching Option B.

When specific plant growth hormones (such as auxins or gibberellins) are sprayed onto unpollinated flowers, they trigger chemical pathways that cause the ovary wall to expand into a fruit. Because this process bypasses pollination and gametic fusion, the ovules never develop into seeds. Consequently, inducing fruit production without fertilization always yields seedless fruits (B). This is a widely used commercial method for producing seedless varieties of watermelons, grapes, and tomatoes.

In many Citrus and mango varieties, apomictic seed production occurs through adventive embryony. In this pathway, diploid maternal nucellar cells surrounding the embryo sac start dividing rapidly. They protrude directly into the embryo sac cavity and develop into fully formed embryos (B). Because these embryos develop from diploid maternal tissue without undergoing meiosis or fertilization, they are genetic clones of the parent plant.

Hybrid seed production is expensive because farmers must buy new seeds every year. If seeds collected from a hybrid crop are planted the following season, the alleles segregate during meiosis and sexual fertilization, causing the offspring to lose the high-yield hybrid advantages. If these commercial hybrids can be engineered to reproduce via apomixis, the seeds develop without fertilization. This clonal reproduction ensures that the optimal hybrid characters do not segregate in the progeny, allowing farmers to save and replant their own high-yield seed stocks year after year. This matches Option B.

Apomixis is a specialized reproductive where the plant forms an unreduced, diploid egg cell that develops directly into an embryo without fertilization (diploid parthenogenesis). Because it skips genetic recombination and gametic fusion, it functions as a form of asexual reproduction. However, it packages this clonal embryo inside a seed, effectively mimicking sexual reproduction in its final structure and dispersal method. This matches Option B.

In nucellar polyembryony (commonly seen in Citrus and mango), additional embryos develop from the diploid cells of the maternal nucellus tissue. Because the nucellus is a somatic tissue of the mother plant, its cells divide exclusively through mitosis. This means they skip meiotic reduction and gametic fusion entirely. Consequently, all resulting nucellar embryos are genetically identical to each other and are exact clones of the parent plant (B).