Past Entrance Papers

Hint

[NCERT-pg no. 11]

 Some examples of water pollinated plants are Vallisneria and Hydrilla which grow in fresh water and several marine sea-grasses such as Zostera. Not all aquatic plants use water for pollination. In a majority of aquatic plants such as water hyacinth and water lily, the flowers emerge above the level of water and are pollinated by insects or wind as in most of the land plants. In Vallisneria, the female flower reach the surface of water by the long stalk and the male flowers or pollen grains are released on to the surface of water. They are carried passively by water currents (Figure 1.11a); some of them eventually reach the female flowers and the stigma. In another group of water pollinated plants such as seagrasses, female flowers remain submerged in water and the pollen grains are released inside the water. Pollen grains in many such species are long, ribbon like and they are carried passively inside the water; some of them reach the stigma and achieve pollination. In most of the water-pollinated species, pollen grains are protected from wetting by a mucilaginous covering.

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Answer (1)
Sol. The given diagram shows a wind pollinated plant showing compact inflorescence and well exposed stamens.
Stamens are exposed so complete autogamy does not occur.

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Answer (3)
Sol. Synergids are the cells of gametophyte and hence these are haploid Zygote is formed by fusion of two gametes and thus it is diploid.
Primary endosperm nucleus is formed by the fusion of diploid secondary nucleus with a male gamete. Therefore, it is triploid.

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Answer (1)
Sol. Large, colourful, fragrant flowers with nectar attract biotic pollinators (insects), thus, they are seen in insect pollinated plants.

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Answer (4)
Sol. Among the animals, insects, particularly bees are the dominant biotic pollinating agents.

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(b) : In angiosperms, the functional megaspore is the first cell of female gametophyte. It enlarges and undergoes few mitotic divisions to form embryo sac.

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(a) : Entomophily is the most common type of zoophily where pollination takes place through the agency of insects. Entomophilous flowers are brightly coloured and secrete nectar to attract visiting insects.
Anemophily (wind pollination) and hydrophily (water pollination) do not require attractants or rewards due to the involvement of abiotic pollinating agents. Cleistogamy is self pollination in closed flowers.

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(b) : Single ovule in the ovary and flowers packed into inflorescence are characteristics of wind pollinated flowers.

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(a) : Dioecious plants are those plants in which male flowers and female flowers are bome on different plants. Therefore, they prevent both autogamy and geitonogamy.

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(c) : Double fertilisation is the characteristic feature of angiosperms. Here, two male gametes are released in the embryo sac or female gametophyte. One male gamete fuses with the egg cell to form zygote that gives rise to embryo whereas the other male gamete fuses with the secondary nucleus to form primary endosperm nucleus (PEN) that gives rise to endosperm.

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(c)

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(b) : In aquatic plants with emergent flowers e.g., water lily, water hyacinth pollination takes place by wind or insects.

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(a) : The ovule of an angiosperm is equivalent to integumented megasporangium.

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(b) : Coconut has multicellular endosperm (called coconut meal) in the outer part and free nuclear as well as vacuolate endosperm (called coconut milk or coconut water) in the centre.

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(c) : Tapetum is the innermost wall layer of microsporangium that nourishes developing pollen grains.

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(b) : Apomixis is a reproductive process which does not involve gametic fusion. In apomictic flowering plants there is no fertilisation and embryos develop simply by division of a cell of ovule.

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(c) : Pollen-pistil interaction is the group of events that occur from the time of pollen depositionover the stigma to the time of pollen tube entry into ovule. It is a safety measure to ensure that illegitimate crossing does not occur. Pollen grains of number of plants may settle over a stigma. The pollens belonging to same species would germinate while other fail to do so but the pollen tube of the compatible pollen will grow through the style to reach the ovule whereas growth of incompatible pollens will be arrested at stigmatic disc or sometimes in the beginning part of style.

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(b)

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(b) Filliform apparatus is a mass of finger like projections of the wall into the cytoplasm. It is present in synergids (help cells) of the embryo sac, in the micropylar region. It guards the pollen tube inside the ovule towards the embryo sac.

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(a) : In angiosperms, microsporogenesis i.e., formation of microspores (or pollen grains) occurs by the meiotic divisions of diploid microspore mother cells (or pollen mother cells). Microsporogenesis takes place in the anther. Megasporogenesis i.e. formation of megaspores occurs by the meiotic divisions of diploid megaspore mother cells. Megasporogenesis takes place in the ovule.

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(d) : In cucumber, unisexual flowers i.e., separate male and female flowers are present on the same plant (monoecious plant).

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(d) : Coconut has multicellular endosperm (called coconut meal) in the outer part and free nuclear as well as vacuolate endosperm (called coconut milk or coconut water) in the centre.

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(b) : Parthenocarpic fruits are the fruits which are formed without fertilisation. These fruits are naturally seedless, e.g., banana.

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(c): The protoplast of the male gametophyte divides mitotically to produce two unequal cells a small generative cell and a large vegetative cell. The generative cell divides later into two non-motile male gametes (or sperms). Thus, the male gametophyte in angiosperms produces two sperms and a vegetative cell. The vegetative cell, later on, grows to produce pollen tube.

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(d)

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 (c) : Geitonogamy involves transfer of the pollen from one flower of a plant to the stigma of another flower of the same plant. As the pollen has to move from one flower to another flower, it requires a pollinating agent. Yet it is genetically similar to autogamy, as both the flowers of the plant, share the same genotype of the plant.

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 (b) : Honey is made from nectar through a process of regurgitation and evaporation.Honeybees transform saccharides (carbohydrates) into honey by regurgitating it a number of times, until it is partially digested. The bees do the regurgitation and digestion as a group. After the last regurgitation, the aqueous solution is still high in water, the process continues by evaporation of much of the water and enzymatic transformation. Honey is produced by bees as a food source.

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(c) : Ovule is an integumented megasporangium found in spermatophytes which develops into seed after fertilization. An angiospermic ovule is typically an ovoid and whitish structure. It occurs inside ovary where it is attached to a parenchymatous cushion called placenta either singly or in a cluster. The ovule is stalked. The stalk is called funiculus or funicle. The point of attachment of the body of the ovule with the funiculus is known as hilum. It is present as a scar on a mature seed.

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(d) : Style is traversed by the pollen tube to reach the ovule.It is of two types – hollow and solid. In hollow styles, the stylar canal is lined by glandular cells, which are usually multinucleate and polyploid whereas solid style has a core of transmitting tissue, composed of thin walled cells, through which, the pollen tube moves.

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(d) : Sexual reproduction in algae takes place through fusion of two gametes. In Spirogyra, the gametes are similar in size (isogamy) and nonflagellated (non-motile).

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(a) : Geitonogamy is the pollination taking place between the two flowers of the same plant or genetically similar plant. Hence, genetically it is self pollination but since the agency is involved, it is ecologically, cross pollination.

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 (b) : An aggregate fruit or etaerio is a group of simple fruitlets that develop from free ovaries (apocarpus condition) of a single flower (single gynoecium).

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(c) : Pollen grains are believed to be rich in nutrients (protein \(7-26 \%\) carbohydrates \(24-48 \%\), fats \(0.9-14.5 \%)\). They are taken as tablets or syrups to improve health. They also enhance performance of athletes and race horses.

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(d) : In the ovule, the pollen tube is attracted by secretions of synergids. Usually the pollen tube enters the embryo sac by passing into one of the two synergids and is guided by the filiform apparatus of the synergids in their movement. Pollen tube then breaks open and releases its contents in the embryo sac. Antipodals and synergids later degenerate.

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(d) : In majority of dicot seeds, including pea, the endosperm is consumed during seed development and the food is stored in cotyledons and other regions. They are called nonendospermic or exalbuminous seeds.

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(c) : Gemmule and conidia are asexual propagules thus no meiosis takes place in them. Megaspores are haploid which are formed as a result of meiosis of diploid megaspore mother cell. Meiocyte is any cell that undergoes meiosis.

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(d)

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(a): Both perisperm and endosperm are nutritive layers. Perisperm is residual persistent nucellus of seed prior to fertilization while endosperm develops when one of the sperm cells fuses with two haploid polar nuclei. Thus perisperm is diploid while endosperm is a triploid tissue.

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(a): Cleistogamy is the process of pollination and fertilization before the flower has opened. In such flowers, the anther 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 produce assured seed-set even in the absence of pollinators.

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(a): In angiosperms, body of the ovule consists of a mass of parenchymatous cells called nucellus, which is equivalent to megasporangium. A megasporangium alongwith its protective integuments is called as an ovule.

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(b) : A microsporangium is generally surrounded by four wall layers – the epidermis, endothecium, middle layers and the tapetum. The outer three wall layers perfom the function of protection and help in dehiscence of anther to release the pollen. The innermost wall layer is the tapetum. It nourishes the developing pollen grains. Cells of the tapetum are food rich and possess dense cytoplasm and generally have more than one nucleus. They disintegrate to liberate the contents which is absorbed by the developing spores.

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 (a) : Sexual reproduction always involves meiosis (zygotic in case of haploid individuals and gametic in case of diploid individuals). Meiosis results in crossing over between chromosomes during prophase I generating new recombinations. Besides, sexual reproduction generally involves combination of genes from two different organisms. Thus, sexual reproduction generates new genetic combinations leading to variations.

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(c) : In Vallisneria, water pollination occurs while mulberry and maize undergo wind pollination. In cucumber, animal pollination is observed.

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(a) : In some seeds, the endosperm persists in the seed as food storage tissue. Such seeds are called endospermic or albuminous, e.g., castor, maize, wheat, barley, rubber, coconut.

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(d) In angiosperms, microsporogenesis i.e., formation of microspores (or pollen grains) occurs by the meiotic divisions of diploid microspore mother cells (or pollen mother cells). Microsporogenesis takes place in the anther. Megasporogenesis i.e. formation of megaspores occurs by the meiotic divisions of diploid megaspore mother cells. Megasporogenesis takes place in the ovule.

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(a) : In cleistogamy, as the flowers never open so there is no alternative of self pollination. It is invariably autogamous. In xenogamy, pollination takes between two flowers of different plants (genetically and ecologically). It can ocur by wind, water, insects and animals.
Chasmogamy occurs when the flowers expose their mature anther and stigma to the pollinating agents. Geitonogamy is the pollination taking place between the two flowers of the same plant or genetically similar plant. Genetically, it is self pollination but as the agency is involved it is ecologically cross pollination.

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(c) : Pollen grain is a haploid, unicellular body. It is cuticularised and the cutin is of special type called sporopollenin, which is resistant to chemical and biological decomposition. It can withstand high temperatures as well as strong acids and alkalis. This is why, pollen wall is preserved for long periods in fossil deposits. In addition pollen wall possesses proteins for enzymatic and compatability reactions.

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(a) : Autogamy and geitonogamy are two forms of self pollination. In autogamy, pollen falls on stigma of the same flower. While in geitonogamy pollens from a flower fall on the stigma of some other flower on the same plant. Papaya is a dioecious plants thus both autogamy and geitonogamy are prevented in it.

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(b) : Sporopollenin is a major component of the tough outer (exine) walls of spores and pollen grains. It is chemically very stable and is usually well preserved in soils and sediments. It can withstand environmental extremes and cannot be degraded by enzymes and strong chemical reagents.

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(a) : Yeast and other ascomycetes characteristically produce ascospores. Chlamydomonas is an alga and conidia are not found in algae. Ginger propagates by rhizome not by sucker. Onion propagates by bulb which is an underground, modified stem.

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(a) : Some plants such as Viola (common pansy), Oxalis, and Commelina produce two types of flowers- chasmogamous flowers which are similarto flowers 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 produce assured seed-set even in the absence of pollinators.

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(c) : In a pollen grain, exine is thin or absent at certain places. These areas may have thickened intine or deposition of callose. They are called germ pores (if rounded) or germinal furrows (if elongated). After pollination, the pollen grain on the stigma absorbs water and nutrients from the stigmatic secretion through its germ pores. The tube or vegetative cell enlarges and comes out of pollen grains through germ pore to form a pollen tube.

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(a) : In 60% of flowering plants, the pollen grains are shed at two-celled stage (tube cell + generative cell). Further, development of male gametophyte (pollen grain) occurs on stigma. Pollen grain gives rise to pollen tube which absorbs nourishment from the cells of style for its growth. Generative cell divides to give rise to two male gametes. Out of these, one fuses with the egg to form diploid zygote (generative fertilization or syngamy) whereas the second male gamete fuses with the two haploid polar nuclei or diploid secondary nucleus of the central cell to form primary endossperrm nucleus (végetative fertilization or triplê fusion). These two acts of fertilization occur in the same embryo sac and are referred to as double fertilization.

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(d) : Anemophily is an abiotic means of pollination by wind and, being non-directional, a wasteful process as the pollen would reach the stigma through wind is a hit-or-miss affair. During the transit of pollen through wind, a considerable amount of pollen is lost because it never reaches a proper stigma. To stand this loss, anemophilous plants have to produce enormous quantities of pollen. Anemophily is also associated with reduction in the number of ovules per ovary. Some models predict that plants benefit from numerous inexpensive flowers distributed throughout the inflorescence, each with a single ovule or a few ovules. In grasses there is just one ovule per ovary. This is to increase the probability of successful pollination of each ovule.

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(c)  Filliform apparatus is a mass of finger like projections of the wall into the cytoplasm. It is present in synergids (help cells) of the embryo sac, in the micropylar region. It guards the pollen tube inside the ovule towards the embryo sac.

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(a) : In nucellar polyembryony, some of the nucellar cells surrounding the embryo sac start dividing. Then it protrudes into the embryo sac and develop into the embryos. In such species, each ovule contains many embryos. Occurrence of more than one embryo in a seed is referred as polyembryony. Nucellar polyembryony is found in many of the Citrus and mango varieties.

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(d) : Autogamy is a kind of pollination in which the pollen from the anthers of a flower are transferred to stigma of the same flower. Cleistogamy, homogamy, bud pollination are three methods of the autogamy. Cleistogamy occurs in those plants, which never open and ensure complete self-pollination. E.g., Commelina bengalensis, Oxalis, Viola etc.

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(d) : Potato is the common example of stemtuber. It stores starch as reserve food material. The potato-tubers are used for vegetative propagation. These possess axillary buds over their nodes or eyes. The buds produce new plantlets when a stem-tuber or a part of it having an eye is placed in the soil.

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(c) : Anemophily is pollination of a flower in which the pollen is carried by the wind. Examples of anemophilous flowers are those of grasses and conifers.

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(a)  : In angiosperms, the functional megaspore is the first cell of female gametophyte. It enlarges and undergoes few mitotic divisions to form embryo sac.

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(d) : Apomixis is a reproductive process in plants that superficially resembles normal sexual reproduction but in which there is no fusion of gametes. The embryos develop simply by division of a diploid cell the ovule. So, the progenies produced are identical to the parent. In vegetative reproduction also progenies produced are identical to the parent.

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(b) : Apomixis is abnormal kind of sexual reproduction in which egg or other cells associated with egg (synergids, antipodals, etc.) develop into embryo without fertilization and meiosis. Development of embryos directly from sporophytic tissues like nucellus and integuments is called adventive embryony which is also a type of apoximis. E.g., Citrus, mango.

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(b) : Geitonogamy is the transfer of pollen grains from the anther to stigma of another flower on the same plant or genetically similar plant, e.g., in maize.

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(b) : Pollination by wind is called anemophily and such plants in which pollination occurs by wind are called anemophilous plants. Anemophilous plants are characteristized by smallflowers, pollens present in large number which are small, dry and light in weight , number of ovules generally reduced in ovary (biological significance), feathery or brushy stigma (to receive the pollen). Grasses and palms are generally anemophilous.

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(c) : A – offset of water hyacinth (Eichhornia)
B – Antheridiophore of Marchantia
\(\mathrm{C}\) – Antipodals of the mature embryo sac
D – Oogonium of Chara

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(b) : In Pistia (water lettuce) vegetative propagation occurs by offset where one internode long runners grows horizontally along the soi surface and gives rise to new plants either from axillary or terminal buds.

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(c) : Vegetative propagation in mint occurs through sucker.

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(d)

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(b) : Within the embryo sac 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 plays 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, has two polar nuclei.

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(c) : Unisexuality or dicliny is a condition in which two types of unisexual flowers are present i.e., staminate (male flower) and pistillate (female flower). The plant may be monoecious or dioecious. This is a device for cross pollination (or xenogamy). Both xenogamy and geitonogamy (i.e. transfer of pollen from anther of one flower to stigma of another flower of either the same or genetically similar plant) are included under allogamy/cross pollination. Autogamy or self pollination (i.e. transfer of pollen from anther to stigma of the same flower) occurs in bisexual flower.

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(a) : Sporopollenin is a major component of the tough outer (exine) walls of spores and pollen grains. It is chemically very stable and is usually well preserved in soils and sediments. It can withstand environmental extremes and cannot be degraded by enzymes and strong chemical reagents.

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(a) : In the pollen sac (microsporangium) of the anther, haploid microspores are formed by mitosis. Mitosis then follows to produce a twocelled pollen grain with a small generative cell and a large vegetative cell. This generative cell will undergo further mitosis to form two male gametes (nuclei). The pollen tube grows through a spore in the pollen grain, with the tube (vegetative) nucleus at its tips and the male nuclei behind.

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(d) : If two plants can reproduce freely with each other and form seeds, they are concluded tobelong to same species. Plants belonging to same species have mostly every character common and will be able to reproduce freely with each other to produce new generations.

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(d) : Anther consists of microsporangia or pollen sacs. The archesporium gives rise to parietal cells and primary sporogenous tissue. Sporogenous cells divide to form pollen grain or microspore mother cells. They are diploid and connected by plasmodesmata. The microspore, mother cells consists of a callose wall inner to the cell wall. The mother cell then undergoes meiosis and forms tetrads of microspores. Finally the wall of the mother cell degenerates and pollen grains are separated.

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(c) : Development of fruits without fertilization is called parthenocarpy and such fruits are called parthenocarpic fruits. Parthenocarpic fruits are seedless. A flower is emasculated and auxins are applied to the stigma of the flower, it forms a parthenocarpic fruit. For parthenocarpy induction by auxins, these should be applied after anthesis (first opening of flower) and by gibberellins, these should be applied earlier i.e., at anthesis.

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(c) : The cotyledons are known as seed leaves, they are attached to the embryonic axis. Dicotyledons typically have two cotyledons and monocotyledons have only one cotyledon. The single shield shaped cotyledon in grains is known as scutellum.
The scutellum does not contain food and its function is to absorb food from the endosperm and transfer it to the growing parts of the embryo. The plumule consists of growing tip of the shoot along with few young leaf primordia. It is covered by a sheath called coleoptile. The radicle which lies at the base of the grain is also covered with a sheath called coleorhiza. The hypocotyl is very short and is represented by a short axis in between radicle and plumule.

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(c)

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(a) : Normal type of sexual reproduction having two regular features, i.e., meiosis andfertilization, is called amphimixis. But in some plants, this normal sexual reproduction (amphimixis) is replaced by some abnormal type of sexual reproduction called apomixis.
Apomixis may be defined as, ‘abnormal kind of sexual reproduction in which egg or other cells associated with egg (synergids, antipodals, etc.) develop into embryo without fertilization and with or without meiosis’.
Adventive embryony is a type of apomixis in which development of embryos directly takes place from sporophytic tissues like nucellus and integuments, e.g., Citrus, mango, etc.

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(a) : Depending upon position of micropyle in relation to chalaza, ovules are of 6 types in angiosperms. In amphitropous type the curvature is observed both in body of ovule and embryo sac. The embryo sac assumes horse shoe-shape. Micropyle is directed downwards. It is commonly found in families Papaveracerae, Alismaceae and Butomaceae.

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(c) : The pollen tube enters into the embryo sac at the micropylar end. This entry may be between egg and one synergid or between wall of embryo sac and synergid or through one synergid. So one synergid is always degenerated to allow the entry of the pollen tube.

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(a) : Endosperm is formed due to fusion of the haploid male gamete with the polar nucleus of the embryo sac. But in this case the male plant is tetraploid so that its gametes would be diploid. When these diploid gametes fuse with two polar nuclei of the embryo sac the resultant endosperm would be tetraploid.

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(a) : In hemianatropous or hemitropous ovule, the nucellus and integuments are at right angles to stalk or funiculus so that the ovule becomes curved. It is commonly found is Primulaceae and Ranunculus. In campylotropous ovule the body of the ovule gets curved and micropyle is directed downwards. Atropous ovule is erect and micropyle, chalaza and funiculus are in the same straight line. Anatropous ovule is the most common type of ovule in angiosperms. In this the body of the ovule gets inverted and the micropyle is on lower side.

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(d) : Anthesis is the process of opening floral buds. Reception of pollen by stigma is called pollination. Formation of pollen is called microsporogenesis.

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(b) : In flowering plants, archesporial cells are vertical rows of hypodermal cells at four angles of anther. These undergo periclinal (transverse) division to form an outer primary parietal cell and inner sporogenous cell. Primary parietal wall after few more periclinal divisions forms anther wall and sporogenous cells give rise to sporogenous tissue.

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(d) : On reaching of pollen tube inside the embryo sac, the 2 male gametes are discharged through a sub-terminal pore in pollen tube. The contents of pollen tube are discharged in the synergid and the pollen tube does not grow beyond it in the embryo sac. Further the cytoplasm of pollen tube is restricted to chalazal end of this synergid cell.

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(a) : Each microspore or pollen is having a two layered wall. Outer layer is thick tough cuticularised called exine, which is chiefly composed of a material called ‘sporopollenin’. Inner layer is thin, delicate and smooth called intine, which is made of pectocellulose.
Exine is not uniform but is thin at one or more places in the form of germ pores. Whereas intine made of pectocellulose covers the entire surface of pollen grains.

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(b) : Anatropus ovule is the most common type of ovule found in angiosperms. Here the body of the ovule gets inverted and micropyle is on lower side. It comes very close to the hilum and the chalaza is upwardly directed.

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(a) : Presence of more than one embryo inside the seed is called polyembryony. It is more common in gymnosperms than angiosperms. In angiosperms, it is generally present as an unusual feature in few cases like Citrus, mango etc. In Citrus many embryos are formed from the structures outside the embryo (like nucellus). This is commonly called adventive polyembryony.
In Citrus upto 10 nucellar embryos are formed.

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(b) : Grass is a monocot plant. Primary sporogenous cell gives rise to microspore mother cells or pollen mother cells. Each MMC on reduction division gives rise to 4 microspores or pollens and this formation of microspores or pollens is called microsporogenesis. Karyokinesis is of successive type. The successive type of cytokinesis is common in monocots. Here both meiotic I and II nuclear divisions are followed by wall formation and it leads to isobilateral tetrad.

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(d) : Anemophily is the pollination by wind. Anemophilous plants are characterized by small flowers, pollens present in large number which are small, dry and light in weight, number of ovules generally reduced in ovary, feathery or brushy stigma to recieve the pollen. All these features are shown by coconut flower.
In Vallisneria pollination occurs outside water called epihydrophily. Callistemon (Bottle brush) is pollinated by birds and is an example of ornithophily. Salvia is insect pollinated and is an example of entomophily.

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(a) : Double fertilization is the simultaneous occurrence of syngamy and triple fusion. Syngamy involves fusion of one male gamete with egg cell to form zygote. The result of syngamy is zygote (2n) which ultimately develops into embryo.
The second male gamete fuses with 2 polar nuclei or secondary nucleus to form triploid primary endosperm nucleus and this is called triple fusion. This primary endosperm nucleus (3n) ultimately develops into a nutritive tissue for developing embryo called endosperm.

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(d) : On the basis of number of megaspore nuclei taking part in development of female gametophyte or embryo sac, there are 3 types of embryo sacs-
(i) Monosporic type – In this type the single nucleus of functional megaspore undergoes 3 mitotic divisions to form 8 nuclei, 7 cells.
(ii) Bisporic type – Here embryo sac develops from 2 megaspore nuclei out of 4 nuclei formed after reduction division of MMC. It is also 8 nucleated. (iii) Tetrasporic type – Here all the 4 megaspore nuclei formed after reduction division of megaspore mother cell are functional and take part in development of embryo sac. It is further of different types. Fritillaria type, Plumbago type and Adoxa type are 8 nucleated.

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(d) : The endosperm of gymnosperms is haploid. It is a pre-fertilisation tissue and is equivalent to female gametophyte, hence it is haploid in nature but in angiosperms it is postfertilization tissue and is generally triploid in nature.

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(d) : In an orchid Ophrys speculum, there is most interesting and unique mechanism of pollination. Here pollination occurs by a wasp called Culpa aurea. In this orchid, pollination occurs by act of pseudocopulation. The appearance and odour of Ophrys is similar to female wasp and are mistake by male wasps and they land on Ophrys flowers to perform act of pseudocopulation and thus pollination takes place. This plant-insect relationship is useful only to plant.

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(a) : Sunflower (Helianthus) belongs to Family Asteraceae of dicotyledons. A dicot embryo has an embryonal axis and 2 cotyledons attached to it laterally. So the number of cotyledons in sunflower will be two.

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(c): Double fertilization is the simultaneous occurrence of syngamy and triple fusion. Syngamy involves fusion of one male gamete with egg cell to form zygote. The result of syngamy is zygote (2n) which ultimately develops into embryo.
The second male gamete fuses with 2 polar nuclei or secondary nucleus to form triploid primary endosperm nucleus and this is called triple fusion. This primary endosperm nucleus (3n) ultimately develops into a nutritive tissue for developing embryo called endosperm.

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(b) : If the female plant is tetraploid, then the central cell of embryo sac, which is a fused polar nuclei, will also be tetraploid. Fusion of the tetraploid central cell to the haploid male gamete forms a pentaploid endosperm in the given example.

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(c)

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(a) : Pollen grains or microspores are formed inside anther, which is the fertile portion of stamen or microsporophyll. Inside the anther, primary sporogenous cell gives rise to microspore mother cells or pollen mother cells (MMC or PMC). Each MMC on reduction division gives rise to 4 microspores or pollens. So, these four cells will give rise to \(4 \times 4=16\) pollen grains.

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(b) :  Anthesis is the process of opening floral buds. Reception of pollen by stigma is called pollination. Formation of pollen is called microsporogenesis.

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(c) : Pollen grains or microspores are formed inside anther, which is the fertile portion of stamen or microsporophyll. The formation of microspores or pollens is called microsporogenesis. The primarysporogenous cell gives rise to microspore mother cells or pollen mother cells. Each microspore mother cell on reduction division gives rise to 4 microspores or pollens. So for the formation of 100 pollen grains, 25 MMC are required. It involves karyokinesis followed by cytokinesis.

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(c) : Presence of more than one embryo inside the seed is called polyembryony. It is more common in gymnosperms than angiosperms. In angiosperms, it is generally present as an unusual feature in few cases like Citrus, mango etc. In Citrus many embryos are formed from the structures outside the embryo (like nucellus). This is commonly called adventive polyembryony. In Citrus upto 10 nucellar embryos are formed. 

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(b) :Geitonogamy is the transfer of pollen grains from the anther to stigma of another flower on the same plant or genetically similar plant, e.g., in maize.

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(b)

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(d) : Number of meiotic divisions required to produce 200/400 seeds of pea would be \(250 / 500\). 200 seeds of pea would be produced from 200 pollen grains and 200 eggs. 200 pollen grains will be formed by 50 microspore mother cell while 200 eggs will be formed by 200 megaspore mother cell so \(250 / 500\).

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(a) : Double fertilisation is the characteristic feature of angiosperms. This phenomenon first observed by Nawaschin, 1898 in Lilium and Fritillaria. In angiosperms one male gamete fuses with the two polar nuclei to form triploid primary endosperm nucleus. The process is called triple fusion. These two acts together are known as double fertilisation.

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(a): In hemianatropous or hemitropous ovule, the nucellus and integuments are at right angles to stalk or funiculus so that the ovule becomes curved. It is commonly found is Primulaceae and Ranunculus. In campylotropous ovule the body of the ovule gets curved and micropyle is directed downwards. Atropous ovule is erect and micropyle, chalaza and funiculus are in the same straight line. Anatropous ovule is the most common type of ovule in angiosperms. In this the body of the ovule gets inverted and the micropyle is on lower side.

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(b) : Study of formation, growth and development of new individual from an egg is embryology. Study of an individuals life cycle after the fertilization takes place till it develops into a new organism.

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(d) : Meiosis is best observed in dividing microsporocytes. Microsporocytes or microspore mother cell after meiosis give rise to microspore. Other cells do not divide by meiosis.

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(d):Double fertilization is the simultaneous occurrence of syngamy and triple fusion. Syngamy involves fusion of one male gamete with egg cell to form zygote. The result of syngamy is zygote (2n) which ultimately develops into embryo.
The second male gamete fuses with 2 polar nuclei or secondary nucleus to form triploid primary endosperm nucleus and this is called triple fusion. This primary endosperm nucleus ( \(3 n\) ) ultimately develops into a nutritive tissue for developing embryo called endosperm.

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(a): Syngamy means fusion of gametes. Syngamy is the phenomenon in which male gamete fuses with an egg.

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(d): Pollen grain is odd one among all the other three. Pollen grain is a male gametophytic structure whereas all the other three are found inside ovule (nucellus, micropyle and embryo sac).

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(b) : Antipodal cells and egg cell are haploid structures as they are formed after meiosis while the others nucellus, megaspore mother cell and primary endosperm nucleus are diploid structures.

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(c): Embryo sac occurs in ovule. Ovule is integumented megasporangium. It consists of nucleus covered by one or two integuments, mounted on a funicle, chalaza and micropyle. The ovule is vascularised.

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(c): The term pollination refers to the transfer of pollen from anther to stigma. Because pollens are found only in angiosperms and gymnosperms so this phenomenon relates to angiosperms and gymnosperms only.

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(c) : In most of the plants the pollen tube enters the ovule through the micropyle and the phenomenon is called as porogamy. Entry through chalaza is chalazogamy and through integuments or funiculus is mesogamy.

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(d): The two gametes i.e., sperm released by pollen tube and egg move in opposite direction by an unknown mechanism but most probably by streaming currents of cytoplasm i.e., due to attraction of their protoplasts. The nucleus of one male gamete fuses with the egg nucleus and the phenomenon is called fertilisation.

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(c) : Female gametophyte of angiosperms is represented by embryo sac. The polygonum type of embryo sac contains 8 -nuclei and 7 -cells. It is found in more than \(80 \%\) plant families. The nucleus of megaspore undergoes division and give rise to embryosac or female gametophyte by the process of megagametogenesis.

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(c): Male gametophyte of angiosperms is microspore. Microspore is haploid, uninucleate, minute spores produced in large numbers as a result of meiosis in microspore mother cell inside the microsporangia. These are the first cell of gametophytic generations in angiosperms.

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(d) : Young pollen grains produce androgenic haploids in anther cultures. Because rest all i.e., anther wall, tapetal layer of anther wall and connective tissue are the diploid tissue as they are part of anther pollen grains produced by meiosis.

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(a): Gametes are invariably haploid. Spores are formed in lower plants by mitotic division and they may be diploid but gametes are always be made by meiosis and they are always haploid.

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(a): Generative cell was destroyed by laser but a normal pollen tube was still formed because vegetative cell is not damaged. Each microspore divide by mitotic division making a smallergenerative cell and a larger vegetative cell or tube cell. If generative cell is damaged then the normal pollen tube will be formed because pollen tube is formed by vegetative cell not by generative cell of microspore.

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(d) : Nucellar embryo is apomictic diploid. Substitution of usual sexual reproduction by a form of reproduction which does not include meiosis and syngamy is called apomixis. In this process, embryo is developed by some other tissue without fertilisation e.g., nucellus or integuments or infertilised egg. Nucellus is a diploid tissue so nucellar embryo is apomictic diploid.

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(d) : Development of an organism from female gamete/egg without involving fertilisation is parthenogenesis and when a fruit is developed by this technique it is called parthenocarpy.

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(b): Perisperm is persistent nucellus. Endosperm formation is accompanied by degeneration of nucellus.

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(b):

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(c): For formation of 100 zygotes, 100 male gametes and 100 female gametes (eggs) are required. 100 male gametes are developed from 100 microspores (from 25 meiotic divisions) and 100 eggs are developed from 100 megaspores (from 100 meiotic division).
Hence, number of meiotic divisions necessary for 100 zygotes formation \(=25+100=125\).

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(b) : The male gametophyte or microspore is shed at 3-nucleate stage. The microspore undergoes only two mitotic divisions.

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(d) :

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(a) : Formation of gametophyte directly from sporophyte without meiosis and spore formation is apospory. The gametophyte thus has diploid number of chromosomes. Such gametophyte may form viable gametes which fuse to form tetraploid sporophyte. Apogamy is development of sporophyte directly from gametophytic tissue without fusion of gametes. Amphimixis is normal sexual reproduction. Parthenogenesis is development of embryo from egg without fertilisation.