CUET UG Biology Booster Test 3 Seed, Fruit, and Special Mechanisms

In angiosperms, double fertilization gives rise to both a zygote and a primary endosperm nucleus. The endosperm development precedes embryo development (A)-(III) because it is a vital adaptation to provide assured nutrition to the upcoming embryo. Consequently, the zygote exhibits a period of zygote dormancy (B)-(IV) as it waits for this nutrient cushion to form, which marks the initial phase of zygotic division. As development begins, the embryo advances from the proembryo to the globular stage (C)-(II), which establishes the foundational blueprint for nutrient accumulation for the future plant. Finally, monocot and dicot embryos share highly similar early stages (D)-(I) during the early stages of dicot/monocot embryogeny, diverging structurally only in later phases. This maps directly to Option A.

The morphological timeline of dicot embryogeny proceeds through clear structural stages. The zygote initially divides to form the simple cellular proembryo (A)-(II). As cell division continues, it forms a uniform, spherical configuration called the globular stage (C)-(III), which is the geometric shape that precedes the heart-shaped stage. This configuration then transitions into the two-lobed heart-shaped stage, which completes its differentiation to become the mature embryo (B)-(I). The polarized division occurs at the basal end division (D)-(IV), which marks the specific site of embryo development at the micropylar pole of the embryo sac. This sequence matches Option A.

Traced from the absolute center outward, the innermost tissue of the seed is the central embryonal axis containing the radicle/plumule (I). Moving outward, this core axis is flanked and enclosed by the fleshy, leaf-like cotyledons (V) which store nutrients. Surrounding the embryo are the maternal integuments of the ovule (II), which undergo physical structural modifications during maturation. Finally, these integuments dry down and harden to form the absolute outermost protective barrier of the seed, known as the seed coat (Testa) (IV). This direct radial sequence from inside to outside is represented by (I) > (III) > (II) > (IV), which perfectly matches Option B.

Moving from the shoot pole down to the root pole along a fully differentiated dicot embryonal axis follows a linear structural path. The uppermost terminal tip is the plumule (I), which forms the future shoot system. Directly below this tip is the epicotyl (II), defined as the segment of the embryonal axis located above the attachment level of the cotyledons. Passing past the cotyledonary attachment node leads into the hypocotyl (III), which is the cylindrical segment located below the cotyledons. This segment terminates at its lower end in the radicle (IV), which forms the future root system. This top-to-bottom sequence is (I) > (II) > (III) > (IV), matching Option A.

In the embryos of monocotyledonous plants (such as the grass family), only a single cotyledon develops. This single cotyledon is called the scutellum, and it is attached to one side (laterally) of the central embryonal axis. The structural development of monocots bypasses the symmetrical heart-shaped symmetry of dicots because it does not form two balancing cotyledonary lobes. Since heart-shaped bilateral symmetry is unique to dicot development, it plays no role in positioning the monocot scutellum, making Option C the correct choice.

In monocot grass embryos, the upper portion of the axis is the epicotyl region (D). This region contains the shoot apex along with a few developing leaf primordia (B). These delicate shoot structures are enclosed within a hollow, protective foliar sheath called the coleoptile (A). The coleorrhiza (C), however, is located at the opposite root pole of the embryo, where it forms an undifferentiated protective sheath around the radicle and root cap. Because it belongs to the root system, it is not involved in protecting the shoot apex. This makes Option C the correct answer.

Castor plants are unique because they are dicotyledonous species (D) that produce albuminous seeds. Instead of consuming all nutrient reserves during embryonic development, castor seeds feature the retention of endosperm during seed maturation (A). This stored endosperm tissue provides food for the seedling, ensuring its use during seed germination (B). Because castor seeds retain this endosperm at maturity, they are classified as albuminous seeds, meaning they cannot be associated with a classification as non-albuminous (C). This makes statement (C) the correct choice.

Young seedlings obtain nourishment from stored food reserves until they are capable of photosynthesis. In non-albuminous seeds, the food reserve is stored in the cotyledons, whereas albuminous seeds retain the endosperm, which supplies nutrients during germination. In some species, the persistent nucellus (perisperm) also serves as a food reserve. However, immediate photosynthesis upon seed coat rupture is not a nutritional strategy of young seedlings. After germination, the seedling must first emerge, develop chlorophyll-containing green leaves, and receive sufficient light before it can synthesize its own food through photosynthesis. Therefore, Option C is correct.

Lupinus arcticus has historically been reported as a seed capable of surviving an exceptionally long period of dormancy. It was recovered from the Arctic Tundra (A), was estimated to have remained dormant for nearly 10,000 years (B), and was reported to have germinated and flowered after excavation (C). However, King Herod's palace is not associated with Lupinus arcticus. It is associated with the famous date palm (Phoenix dactylifera) seed recovered near the Dead Sea, which successfully germinated after approximately 2,000 years of dormancy. Therefore, Option D is the correct answer.

For a dormant seed to germinate, it must be exposed to favourable environmental conditions that reactivate the embryo's metabolism. These conditions include adequate moisture (A) for imbibition and enzyme activation, oxygen (B) for aerobic respiration, and a suitable temperature (C) to support metabolic activities and enzyme function.

In contrast, maintaining a low moisture content of about 10% (D) helps preserve seed viability and keeps the seed in a dormant state during storage. Germination begins only after the seed absorbs sufficient water, increasing its moisture content well beyond this level.

Therefore, Option D is the correct answer.

The coordinated development of floral parts provides a clear survival advantage. As internal fertilized ovules mature and lose water to enter a safe state of dormancy, the surrounding maternal ovary wall thickens to form the pericarp. This synchronized timeline ensures the seed is protected by the pericarp as it enters dormancy (Option B), shielding the vulnerable embryo from environmental stress, pathogens, and physical damage during its resting phase.

The provided text highlights that fruits can be classified into different structural types based on the physical nature of the mature pericarp layer. It notes that fruits can be fleshy (as seen in guava, orange, and mango) or dry (as seen in groundnut and mustard). Therefore, in a mango, the pericarp forms a fleshy wall differentiated into edible pulp, while in a groundnut, it forms a dry wall that acts as a protective outer shell. This matches Option C.

In the majority of plant families, accessory floral structures like the calyx, corolla, and thalamus wither and fall away after fertilization. However, in a few species like apple, strawberry, and cashew, the non-ovarian thalamus contributes to fruit formation alongside the ovary. In the cashew specifically, the thalamus swells into a large, fleshy, edible structure that carries the true nut fruit below it. Because tissue outside the ovary helps build the fruit mass, it is classified as a false fruit, matching Option B.

Angiosperm fruit types are categorized based on their structural origin. A fruit is classified as a true fruit when it develops through the exclusive involvement of the ovary in fruit formation (B), and its outer wall is derived solely from the maternal ovary wall. Examples include mangoes, tomatoes, and peas. Because no accessory structures (like the thalamus or calyx) contribute to the final fruit mass, it is a true fruit.

Parthenocarpy is the physiological process where an ovary develops into a complete fruit without undergoing pollination or fertilization. Because fertilization is bypassed, the internal ovules never develop into seeds. For commercial plant breeders, inducing parthenocarpy is a valuable tool to create seedless varieties that are more desirable to consumers (Option B) in high-value crops like watermelons, grapes, oranges, and bananas. Seedless fruits improve the eating experience and streamline industrial food processing.

While both processes bypass standard sexual fertilization, they result in completely different seed structures. Parthenocarpy results in a seedless fruit because fruit growth is induced without any seed development occurring inside the ovules. In contrast, apomixis results in a fruit with seeds (Option A). Apomixis is an asexual mechanism where the plant produces fully formed, viable seeds containing clonal embryos without undergoing fertilization.

Apomixis is defined as an asexual reproductive mechanism that successfully replicates the final output of sexual reproduction. In normal plant lifecycles, a seed is the definitive product of sexual fertilization. An apomictic plant bypasses meiotic reduction and fertilization, yet it still produces seeds without the process of fertilization (Option B). Because it creates a standard seed structure through an asexual pathway, it mimics sexual reproduction.

Commercial hybrid crops offer increased vigor and higher yields. However, when these hybrid plants undergo normal meiosis and sexual fertilization, allele pairs separate. This segregation of characters in the progeny causes the offspring to lose their hybrid advantages, meaning farmers must buy expensive new hybrid seeds every year. If these hybrid crops can be engineered to reproduce via apomixis, the seeds will develop as clones of the parent plant. This prevents genetic segregation, allowing farmers to safely save and replant their high-yield seed stocks year after year, solving the cost issue. This matches Option B.

Polyembryony is the occurrence of more than one embryo within a single seed. In nucellar polyembryony, observed in plants such as Citrus and mango, some diploid nucellar cells surrounding the embryo sac undergo repeated mitotic divisions. These cells protrude into the embryo sac and develop into additional embryos alongside the normal zygotic embryo. Since these embryos originate from the maternal nucellus without fertilization, they are genetically identical (clonal) to the parent plant. Therefore, Option B is correct.

The seed industry faces a major challenge because hybrid crops lose their optimal trait combinations in the F2 generation due to genetic segregation during sexual reproduction. Transferring apomictic genes into commercial hybrid varieties would switch their reproduction from sexual to asexual. This change prevents the segregation of desirable hybrid characters in saved seeds (Option B). It allows farmers to harvest high-yield crops, save the resulting seeds, and replant them the next season without losing any parental performance advantages.