Level 3 Test: Sexual Reproduction In Flowering Plants - NEET MCQ

Synergids and antipodals are the cells that are present in the embryo sac at the time of fertilization. Once the fertilization of the male gamete and the egg occurs and the zygote is formed. The synergids and antipodal cells degenerate after that and the ovary converts into a fruit.

The ovules can develop into varying degrees with the funicle. The hemitropous ovule is placed transversely or at the right angle to the funicle.

When the anther is young, at the stage of sporogenous tissue, the cells of the tapetum contain numerous spherical bodies called pro-ubisch bodies. The number of pro-ubisch bodies increases by meiosis in Pollen mother cells. These pro-ubisch bodies get coated by sporopollenin and are called ubisch bodies or orbicules. These are involved in the formation of exine of the pollen grains. 

Assertion: Groundnut and pea are non-endospermic.
Reason: They do not synthesize endosperm.
Explanation:
The assertion states that groundnut and pea are non-endospermic, while the reason provided is that they do not synthesize endosperm. Let's break it down to understand the relationship between the assertion and the reason.
Definition of endosperm:
Endosperm is a nutritive tissue found in the seeds of flowering plants. It develops from the fertilized central cell of the ovule and provides nourishment to the growing embryo.
Groundnut and pea:
1. Groundnut (Arachis hypogaea) and pea (Pisum sativum) are both examples of flowering plants that produce seeds.
2. The seeds of groundnut and pea do not contain a significant endospermic tissue.
Non-endospermic seeds:
1. Non-endospermic seeds are those that do not have a well-developed endosperm.
2. Instead of relying on endosperm for nourishment, the embryos of these seeds receive nutrients from the cotyledons (seed leaves) during germination.
3. Groundnut and pea seeds fall into this category as they have cotyledons that store and provide nutrients to the developing embryo.
Assertion and Reason relationship:
1. The assertion is correct because groundnut and pea are indeed non-endospermic seeds.
2. The reason is incorrect because it states that the absence of endosperm is due to the seeds not synthesizing it. In reality, the absence of endosperm in groundnut and pea seeds is a natural characteristic of these plants, rather than a result of synthesis.
Conclusion:
Based on the explanations above, the correct answer is option C: Assertion is correct but Reason is incorrect.

Filiform apparatus is an apparatus that is formed inside the embryo sac of the angiosperms by the synergid cells. This apparatus helps the pollen tube towards the egg for fertilization to happen. Thus it helps in the reproduction process of the angiospermic plants.

The female gametophyte of a typical dicot at the time of fertilisation is 7 celled as shown in the diagram above.

3 antipodals, 2 synergids, 1 egg cell and 1 central cell with polar nuclei resulting in a total of 7 cells and 8 nuclei.

A typical angiosperm embryo sac, at maturity, though 8-nucleate is 7-celled. At the time of fertilization, the female gametophyte has 3 antipodal cells + 2 synergids + 1 egg cell + 1 central cell, which equals 7-celled structure. But the central cell has 2 polar nuclei, which makes it 8-nucleate. Therefore,  at maturity, the gametophyte is 7-celled and 8-nucleated.

Commelina produces two types of flower chasmogamous flowers which are similar to the flower of other species with exposed anthers and stigma, and cleistogamous flowers which do not open at all. In such flowers, the anthers and stigma lie close to each other. When anthers dehisce in the flower buds, pollen grains come in contact with the stigma to effect pollination. Thus, cleistogamous flowers are invariably autogamous as there is no chance of cross-pollen landing on the stigma. Cleistogamous flowers assure seed-setting even in the absence of pollinators. 

A. Salvia is pollinated by insects by the turn pipe mechanism.

B. Fig is pollinated by a wasp. The wasp lays egg in the fig fruits and in turn fig is pollinated.

C. Commelina is a cleistogamous flower which never opens. The pollen from anther lobe fall on the stigma of the same flower and thus, pollination is not dependent on any external agency i.e. pollinators.

D. Zostera is a marine grass which is pollinated inside water.

Hence, seed setting is assured even in the absence of pollinating agents in Commelina.

• Autogamy is pollination by transfer of pollen grains from the anther of a flower to the stigma of the same flower.
• Geitonogamy is pollination by transfer of pollen grains from the anther of a flower to the stigma of another flower of the same plant. 
• A plant having unisexual flowers is said to be dioecious. Such a flower will neither exhibit autogamy nor geitonogamy. 

• Meiotic divisions are responsible for gamete formation. 
• Pollen mother cell undergoes meiotic division to produce 4 pollen grains. 
• So, for generation of 1000 pollen grains, 1000/4 = 250 pollen mother cells undergo meiotic division.

The female gametophyte in angiosperms plants is called Embryo Sac or Megagametophyte.  In angiosperms, it is required for sexual and asexual seed development. It consists of 3 antipodal cells,  one central cell, one egg cell and two synergid cells. 

Polyploidy is the condition which has more than two sets of chromosomes. If an angiospermic male plant is diploid and female plant is tetraploid, the ploidy level of endosperm will be pentaploid because the female gametes undergoes meiosis and forms gametes (2n). This female gametes (2n + 2n of polar nuclei) fuses with the male gametes (n) .

Parthenocarpy is the development of fruit without fertilization of seeds. Another biological mechanism stenospermacarpy also produces seedless fruits, but here the seeds are aborted while they are still small. In nature, parthenocarpy occurs as a mutation. Some plants require pollination or stimulation for parthenocarpy. This is known as stimulative parthenocarpy.

Self-pollination is when pollen from the same plant arrives at the stigma of a flower or at the ovule (in gymnosperms). 

There are two types of self-pollination. 

• In autogamy, pollen is transferred to the stigma of the same flower. 
• In geitonogamy, pollen is transferred from the anther of one flower to the stigma of another flower on the same flowering plant, or from microsporangium to ovule within a single (monoecious) gymnosperm. 

Some plants have mechanisms that ensure autogamy, such as flowers that do not open, or stamens that move to come into contact with the stigma. In plants, allogamy is used specifically to mean the use of pollen from one plant to fertilize the flower of another plant. Xenogamy is fertilization of a flower by pollen from a flower on a genetically different plant.

Fruits can develop from a single ovary of a single flower(simple fruit) or from several free carpels of a single flower (aggregate) or form whole inflorescence(multiple). In total, fruits develop from ovaries. This is why, a dioecious plant (unisexual) bearing only staminate (male) flowers will not produce fruits, whereas monoecious plants (bisexual) or dioecious plants bearing only pistillate (female) lowers or pistillate and staminate both can bear fruits. So, the correct answer is 'Plant is dioecious and bears only staminate flowers'.

The plants in which male and female flowers are brone on separate individuals, are referred to as dioecious plants. e.g. papaya, date palm. Dioecious plants, exhibit xenogamy.

Wheat is an anemophilous plant. Its flowers are not very showy. They do not have petals or sepals. Each female flower consists of an ovary from which two styles emerge, finished with two feathery sticky stigmas to catch pollen.

Wind pollinated flowers generally have one or few ovules in ovaries, it increase the probability of successful pollination of each ovule.

• Zostera is the marine seagrass which gets pollinated by water. Pollens are released in water and capture by stigmas.
• In Viola, the flowers get pollinated by bees.
• In Oxalis, there is no need for pollinator as they are closed flowers. There is no chance of cross-pollination. 
• In Yucca, the flowers are pollinated by yucca moth.