Test: Sexual Reproduction in Flowering Plants - 2 - NEET MCQ

• It’s the nucellus. Nucellus is the place where the embryo sac rests.
• It is made up of cushiony cells called parenchymatous cells.
• Nucellus helps in the nourishment of the embryo sac.

Topic in NCERT: Ovule Structure and Development

Line in NCERT: "Enclosed within the integuments is a mass of cells called the nucellus."

• They are the 3 mature cells in the embryo sac present opposite to the micropylar end.
• The function of the antipodal cells is to provide nutrition and nourishment to the embryo sac.

Topic in NCERT: Embryo Sac Structure

Line in NCERT: "Three cells are at the chalazal end and are called the antipodals."

The mature anther consists of four microsporangia which contain four layers. The inner most layer is called tapetum that provide nutrient to growing microspores and tissues inside it are called microspore mother cell that produce pollen grain.

Topic in NCERT: Structure of microsporangium

Line in NCERT: "Four wall layers, the epidermis, endothecium, middle layers and the tapetum surround the microsporangium."

Each Sporogenous cell under meiotic division to form tetrad of megaspores. The three megaspores degenerate and only one megaspore develops into embryo sac or female gametophyte.

Topic in NCERT: Female gametophyte

Line in NCERT: "one of the megaspores is functional while the other three degenerate. Only the functional megaspore develops into the female gametophyte (embryo sac)."

Each microsporangium has 100 microspore mother cells which by meiosis form 400 microspores ( 100 × 4). In an anther there are four microsporangia , so, total number of microspores will be 4 × 400 = 1600 4 × 400 = 1600 . As each microspore forms one male gametophyte, hence , 1600 male gametophytes can be produced.

Topic in NCERT: Microsporogenesis

Line in NCERT: "Cells of the sporogenous tissue lying in the centre of the microsporangium, undergo meiosis (microsporogenesis) to form tetrads of microspores."

Pollen grain consists of hard covering of exine but their viability may lost with time. For Hybridisation pollen grains are collected and stored in liquid nitrogen below -196 degree Celsius temperature.

Topic in NCERT: Pollen Viability and Storage

Line in NCERT: "it is possible to store pollen grains of a large number of species for years in liquid nitrogen (-196°C)."

Inbreeding depression is the reduced biological fitness in a given population as a result of inbreeding, or breeding of related individuals. Continued self-pollination reduces the fertility and even productivity of the plant.
Thus, the correct answer is option A.

Large amount of fossilized pollen grain are found during excavation process of older parts due to tough covering of Sporopollenin that make the outer wall of pollen grain, exine. This substance cannot be hydrolyzed by any enzyme known.

Topic in NCERT: Pollen Grain Structure and Function

Line in NCERT: "The hard outer layer called the exine is made up of sporopollenin which is one of the most resistant organic material known."

• Embryogeny is the study of the changes that take place when an embryo develops from a zygote.
• It occurs near the embryo sac’s micropylar end.
• The nucellus and integuments unite at the base of the ovule, or chalaza, in plants.
• It can be found on an ovule opposite the micropylar end.
• Chalaza is the pathway via which plant nutrients are delivered to the nucellus.
• Three antipodal cells form from the chalazal end of the embryo sac’s cells.

Topic in NCERT: Embryo

Line in NCERT: "Embryo develops at the micropylar end of the embryo sac where the zygote is situated."

• Stigma - It is the head of the pistil.
  • It receives pollen, which begins the process of fertilization.
• Style - It the stalk of the pistil.
  • It is a long, slender stalk that connects the stigma and the ovary. 
  • When pollen reaches the stigma, it begins to grow a tube through the style called a pollen tube, which eventually reaches the ovary.
• Ovary - It is the base of the pistil.
  • It holds the ovules for fertilization.
• Thalamus - It is present near the stalk of the flower.
  • It supplies nutrients to the flower.
  • It is a condensed axis of the flower from which all floral parts arise.

Topic in NCERT: The Pistil, Megasporangium (ovule) and Embryo sac

Line in NCERT: "The gynoecium represents the female reproductive part of the flower. Each pistil has three parts, the stigma, style and ovary."

Endosperm cells are triploid as they are formed by triple fission of two polar nuclei and one male gamete. So, haploid cell will contain 8 chromosomes only. Root cells are diploid. Hence root cell will contain 16 chromosomes.

The meiocytecell are diploid so, haploid cell will contain 16 chromosomes. The endosperm cell are formed by fusion of two polar nuclei and one male gametes so, endosperm cells are triploid that will contain 16x3= 48 chromosomes.

The female gametophyte (embryo sac) develops from a single functional megaspore. This megaspore undergoes three successive mitotic divisions to form eight nucleate embryo sacs.

The first mitotic division in the megaspore forms two nuclei. One nucleus moves towards the micropylar end while the other nucleus moves towards the chalazal end. Then, these nuclei divide at their respective ends and re-divide to form eight nucleate stages. As a result, there are four nuclei each at both the ends i.e., at the micropylar and the chalazal end in the embryo sac. At the micropylar end, out of the four nuclei only three differentiate into two synergids and one egg cell. Together they are known as the egg apparatus. Similarly, at the chalazal end, three out of four nuclei differentiates as antipodal cells. The remaining two cells (of the micropylar and the chalazal end) move towards the centre and are known as the polar nuclei, which are situated in a large central cell. Hence, at maturity, the female gametophyte appears as a 7-celled structure, though it has 8 nucleate.

Topic in NCERT: Female gametophyte development

Line in NCERT: "The mature embryo sac is 7-celled and 8-nucleate. At the micropylar end is the egg apparatus consisting of two synergids and an egg cell. At the chalazal end are three antipodals. At the centre is a large central cell with two polar nuclei."

• A. Funicle – V (Stalk of ovule):
  Funicle is the stalk that attaches the ovule to the placenta.

• B. Hilum – IV (Region where body of ovule fuses with funicle):
  Hilum is the attachment point where the ovule joins with the funicle.

• C. Integument – III (One or 2 protective layers of ovule):
  Integument forms the protective layer(s) around the ovule to safeguard the embryo sac.

• D. Chalaza – II (Basal part of ovule):
  Chalaza is the base of the ovule where the integuments and nucellus meet.

• E. Nucellus – I (Mass of cells within ovule with more food):
  Nucellus is the food-rich tissue inside the ovule that nourishes the embryo sac.

Final Match:

• A - V, B - IV, C - III, D - II, E - I

Thus, the correct answer is Option B.

The number of ovule present in ovary determine the number of seeds produced inside the fruit. Mango and neem produce single seed in each fruit. Lemon contain a number of seeds but orchid contain many small size seeds.

Dormancy is the state of state of inactivity during which metabolic process slows down. Seed may remain viable to several months to years depending upon type of seeds and condition.

Topic in NCERT: Embryo

Line in NCERT: "The general metabolic activity of the embryo slows down. The embryo may enter a state of inactivity called dormancy."

1. Sporogenous tissue – III (Formation of microspore tetrad by meiosis):

   • The sporogenous tissue is responsible for undergoing meiosis to form microspores, which eventually lead to microspore tetrads.

2. Microspore tetrad – II (Microspores arranged in cluster of four cells):

   • A microspore tetrad is a group of four microspores formed after meiosis, arranged in a cluster.

3. Microsporogenesis – I (Process of formation of microspores from PMC by meiosis):

   • Microsporogenesis is the process of formation of microspores from pollen mother cells (PMC) through meiosis.

4. Tapetum – IV (Nourishes pollen grains):

   • The tapetum is a nutritive layer that provides nourishment to the developing pollen grains.

Final Match:

• 1-III; 2-II; 3-I; 4-IV

Thus, the correct answer is Option B.

(i) It is 8-nucleate and 7-celled at maturity: True. The typical female gametophyte (embryo sac) of flowering plants is 8-nucleate and 7-celled at maturity.
(ii) It is cellular during the development: Not true. The female gametophyte is initially multinucleate (syncytial) and becomes cellular later.
(iii) It is situated inside the nucellus: True. The female gametophyte is located within the nucellus of the ovule.
(iv) It has an egg apparatus situated at the chalazal end: Not true. The egg apparatus is located at the micropylar end, not the chalazal end.
Thus, statements (ii) and (iv) are not true.
Topic in NCERT: female gametophyte

• Statement 1:
  Parthenocarpy (the development of fruit without fertilization) can indeed be induced by the application of growth hormones like auxins or gibberellins.
  This statement is true.
• Statement 2:
  The small opening at the tip of the ovule is called the micropyle, not the germ pore. This terminology is incorrect.
  This statement is false.
• Statement 3:
  In flowering plants, the development of the endosperm (nourishing tissue) typically begins before the development of the embryo after fertilization.
  This statement is true.
• Statement 4:
  Apomixis (asexual reproduction without fertilization) has advantages in horticulture and agriculture because it allows for the production of genetically identical plants.
  This statement is true.

Line from Ncert ( Correction for statement 2) Integuments encircle the nucellus except at the tip where a small opening called the micropyle is organised. 

• Statement 1: Michelia (now often classified under Magnolia) does indeed have a polycarpellary, apocarpous gynoecium, meaning it has multiple separate carpels.
• Statement 2: Papaya and orchids do have many ovules present in their ovaries. This statement is correct.
• Statement 3: Hibiscus does have yellowish, powdery pollen grains. This statement is correct.
• Statement 4: If pistils are fused together, they form a syncarpous gynoecium, which is a single compound structure. A monocarpellary gynoecium refers to a single carpel, not a fused structure. Therefore, the statement about pistils forming a monocarpellary syncarpous gynoecium is incorrect because these terms are mutually exclusive.

Thus, Statement 4 is incorrect.
Topic in NCERT: The Pistil, Megasporangium (ovule) and Embryo sac
Line in NCERT: "The gynoecium may consist of a single pistil (monocarpellary) or may have more than one pistil (multicarpellary). When there are more than one, the pistils may be fused together (syncarpous) or may be free (apocarpous)."