Test: Sexual Reproduction in Flowering Plants - 4 - NEET MCQ

Albuminous seeds are the seeds which have food stored in the special nourishing tissue called as endosperm that remains persistent till maturity. Cotyledons only act as food sucking organs and not food storage organs e.g., Castor seed. Non-albuminous seeds are the seeds which have the stored food and the cotyledons in a special structure called as a kernel. It does not remain until the embryo is mature. e.g. Pea seed.

(A)To determine the correct statements regarding the structure of a monocot seed:

- Statement I: A is pericarp.
- Explanation: The pericarp is the outermost layer of a fruit formed from the ovary wall. In the given diagram, A represents the pericarp of the seed.

- Statement II: B is the cotyledon of the monocot seed.
- Explanation: False statement as B represents the endosperm of the seed only 

- Statement III: C is triploid in nature and develops before B.
- Explanation:  incorrect statement as C is the scutellum of seed and is diploid in nature  

Therefore, the correct answer is: A: Only Statement I is correct.

In the embryo sac or the female gametophyte, two synergids and an egg form the egg apparatus at the micropylar end. The synergids have specialized thickenings called the filiform apparaus that guides the pollen tube into the embryo sac for fertilization and degenerate. After fertilization the egg forms the zygote and the polar cell forms the PEN.

Each anther lobe develops two pollen sacs. Thus, a two-lobed anther develops four pollen sacs situated at four corners of the anther. The wall layers from the periphery to centre consist of:

• A single layer of epidermis
• A single layer of endothecium
• One to three middle layers
• A single layer of tapetum

- False fruits develop not only from the ovary ,as the thalamus also contributes to fruit formation in false fruits. 

 - In the given diagram, A represents the thalamus and B represents the achene.
- Therefore, Statement I is incorrect, and Statement II is correct.
- The correct answer is option B Statement I is incorrect, Statement II is correct.

A fruit is the seed- bearing structure in flowering plants also referred to as angiosperms produced from the ovary after flowering. Rather, in some fruits, it is not the ovary that produces the fruit. In fact, other parts of the flower, just like the thalamus, inflorescence, and calyx are modified to become an area of the fruit.
 

• Spore mother cells: Meiosis is a type of cell division that occurs in spore mother cells. These cells undergo meiosis to produce haploid spores, which will later develop into gametes.

Six of the eight nuclei are surrounded by cell walls and organised into cells; the remaining two nuclei, called polar nuclei are situated below the egg apparatus in the large central cell.

Three cells are grouped together at the micropylar end and constitute the egg apparatus. The egg apparatus, in turn, consists of two synergids and one egg cell. The synergids have special cellular thickenings at the micropylar tip called filiform apparatus, which play an important role in guiding the pollen tubes into the synergid. Three cells are at the chalazal end and are called the antipodals. The large central cell, as mentioned earlier, has two polar nuclei. Thus, a typical angiosperm embryo sac, at maturity, though 8-nucleate is 7-celled

It is the ovule which develops into a seed, so number of seeds is equal to the number of ovules.

The correct option is A Both assertion and reason are true and reason is a correct explanation of the assertion.
In angiosperm, triploid endosperm is formed by fusion of secondary nucleus and second male gamete. This tissue is used by developing embryo.

Incorrect statement is B. Honey is made by bees by digesting pollen collected from flowers. As, honey is not made by bees by digesting pollen collected from flowers. Instead, bees digest nectar collected from flowers to produce honey. 

• The tapetum which is present along with the embryo to provide nourishment for the growing embryo. It is found in sporangium, particularly within the anther of flowering plants. It is important for the development of pollen grains. The cells are usually bigger and normally have more than one nucleus per cell.
• Sporogenous tissues are diploid in nature.
• Endothecium - secretes materials essential for the proper maturation of the pollen grains.
• Intine is the inner layer; outer tough layer of pollen is called as exine.

Female gametophyte or embryo sac of angiosperms develops upto 8-nudeate, 7-celled prior to fertilisation. There is a three celled apparatus (one egg cell or oosphere and two synergids), three antipodal cells and two polar nuclei. The two polar nuclei fuse to form a diploid secondary nucleus.

• Pollen grains represent the highly reduced haploid male gametophyte generation in flowering plants, consisting of just two or three cells when released from the anthers. Their role is to deliver twin sperm cells to the embryo sac to undergo fusion with the egg and central cell.
•  The female gametophyte of flowering plants, which produces the two female gametes – the egg cell and central cell – for double-fertilization by the two sperm cells of the male gametophyte

To identify A-D in the diagram of a typical dicot embryo:

- A: Plumule
- The plumule is the embryonic shoot located above the cotyledons in a seed.
- B: Hypocotyl
- The hypocotyl is the part of the embryo plant between the radicle and the cotyledons.
- C: Radicle
- The radicle is the embryonic root.
- D: Root cap
The root tip/radical is covered with a root cap.

In the provided diagram, the correct answer is option C.

The correct option is [d]. Second male gamete fuses with two polar nuclei to form a triploid Primary Endosperm Nucleus (PEN). This is called triple fusion.

In an apomictic, seeds can be produced without fertilization. This process is called apomixis. An apomixis is a form of asexual reproduction that mimics sexual reproduction. It includes abnormal sexual reproduction in which egg or other cells like synergids and antipodals develop into an embryo without fertilization and meiosis. In apomicts, somatic cells can mix up and form the embryo under natural conditions. Somatic cells like nucellus can form an embryo in nucellar apomixis.

A) Cleistogamy - It is a type of self-operating pollination technique of some plants. They are propagated by using non-opening, self-pollinating flowers. So they do not need any attractants and rewards. Thus it is the wrong answer.
B) Anemophily – it is wind pollination. Here pollen is distributed by wind. So they also do not need attractants/rewards. It is the wrong option.
C) Entomophily – it is insect pollination. Here pollen is carried by an insect. Insects are attracted by the attractants of plants and spores are distributed by them. So here attractants and rewards are required for pollination. Thus it is the correct option.
D) Hydrophily – Here pollen is distributed by the water flow. Thus it has no requirement for attractants and rewards. So it is the wrong option.

• Statement in option [A] is incorrect and can be corrected as Embryo sac is not the post-fertilisation product.
• Following are the post-fertilisation changes Ovule converted into seed.
• Ovary converted into fruit. Zygote converted into embryo. Central cell converted into endosperm.

Endospermic seeds are those that have an endosperm in the mature seed. It is fleshy, oily, surrounds the embryo, and functions as the sole food storage organ. Inside the seed coat, a thin and papery cotyledon is present. Monocot plants have endospermic seeds.

Tranverse section of a young anther.