Sexual Reproduction in Flowering Plants Online Quiz

Endosperm is consumed during development in non-endospermic seeds (like pea and bean) and persists in endospermic seeds (like castor and coconut).

In coconut, the liquid endosperm is free-nuclear, while the surrounding white kernel is the cellular endosperm.

The primary function of the endosperm in angiosperms is to provide nutrition to the developing embryo.

Male 2n -> gamete n. Female 4n -> egg 2n, polar nuclei 2n+2n. Embryo = 2n (egg) + n (sperm) = 3n. Endosperm = 2n+2n (polar) + n (sperm) = 5n.

Double fertilization in angiosperms consists of two processes: syngamy (fusion of one male gamete with the egg) and triple fusion (fusion of the second male gamete with two polar nuclei).

Emasculation is the removal of anthers from a bisexual flower to prevent self-pollination. In unisexual flowers, the plant already produces separate male and female flowers, so emasculation is unnecessary.

Artificial hybridization involves selecting desired parents, emasculating the female parent, bagging the flower to prevent contamination, dusting with desired pollen, and rebagging to ensure fertilization by the chosen pollen.

Pollen germination experiments in biology labs often use various common garden plants like Vinca, Pea, Chickpea, and Crotalaria to demonstrate the growth of the pollen tube in a sugar solution.

Pollen-pistil interaction is a dynamic process where the stigma recognizes compatible pollen and promotes its germination, while simultaneously inhibiting incompatible or foreign pollen.

In the majority of angiosperms, the pollen tube enters the ovule through the micropyle, which is the small opening in the integuments.

Dioecious plants have male and female flowers on different individuals, which physically prevents both autogamy (self-pollination within a flower) and geitonogamy (pollination between flowers on the same plant).

Monoecious plants have male and female flowers on the same plant. This arrangement prevents autogamy (self-pollination within the same flower) but does not prevent geitonogamy (pollination between flowers on the same plant).

Outbreeding devices are strategies plants use to encourage cross-pollination. These include unisexual flowers, monoecious conditions, and physiological mechanisms like self-incompatibility.

Outbreeding devices include dichogamy (asynchrony of maturation), herkogamy (spatial separation), and self-incompatibility, all of which reduce self-pollination.

Continued self-pollination leads to the accumulation of recessive deleterious alleles, resulting in a reduction in fitness known as inbreeding depression.

Plants provide various rewards to pollinators, including nectar, pollen, and safe sites for egg-laying, as seen in the symbiotic relationships of Yucca and Amorphophallus.

Flowers attract pollinators through various signals like color, fragrance, and foul odors, and offer rewards like nectar and pollen to ensure successful pollination.

Biotic pollination involves a wide range of animals, including insects like bees, as well as vertebrates like rodents, geckos, and birds, which are attracted to specific floral traits.

Flowers pollinated by abiotic agents like wind and water do not need to attract pollinators with color or nectar, as these are traits specifically evolved for biotic (animal) pollination.

In water-pollinated species, pollen grains are often coated with a mucilaginous substance to prevent them from becoming waterlogged or damaged during transport through the water.

Different aquatic plants have evolved different strategies: some like water hyacinth emerge above water and use insects/wind, while others like Vallisneria and sea grasses use water for pollination.

Pollination by water is relatively rare in angiosperms, occurring in about 30 genera, mostly monocots. Examples include Vallisneria, Hydrilla, and Zostera.

Wind-pollinated plants require light, non-sticky pollen, well-exposed stamens, and feathery stigmas to maximize the chances of capturing pollen from the air.

Plants utilize both abiotic (wind, water) and biotic (animals) agents for pollination, with wind being the most common abiotic agent.

Cleistogamous flowers do not open, meaning pollination occurs within the closed flower. Therefore, they do not require external pollinators.

Cleistogamous flowers are closed, forcing self-pollination. This process is known as autogamy.

Viola, Oxalis, and Commelina are classic examples of plants that produce both chasmogamous (open) and cleistogamous (closed) flowers.

Geitonogamy involves the transfer of pollen to the stigma of another flower on the same plant. Because the pollen comes from the same plant, it is genetically similar to autogamy, even though it requires a pollinator.

The transfer of pollen from the anther to the stigma of another flower on the same plant is the definition of geitonogamy.

A mature angiosperm embryo sac contains 8 nuclei but only 7 cells, because the two polar nuclei reside in a single large central cell.

The central cell of the mature embryo sac contains two polar nuclei, which eventually fuse to form a diploid secondary nucleus.

The filiform apparatus consists of cellular thickenings at the micropylar end of the synergids, which guide the pollen tube into the embryo sac.

The egg apparatus is composed of one egg cell and two synergids, and the synergids possess the filiform apparatus.

Three antipodal cells are grouped at the chalazal end of the embryo sac (opposite the micropyle). Their function is not fully understood but they may provide nutrition.

The three cells located at the micropylar end constitute the egg apparatus, which includes the egg cell and two synergids.

The two polar nuclei are located in the large central cell, situated just below the egg apparatus at the micropylar end.

In the 8-nucleate embryo sac, 6 nuclei are surrounded by cell walls (3 in the egg apparatus and 3 antipodals), while the 2 polar nuclei remain in the large central cell.

Free nuclear division is a process where nuclear division is not immediately followed by cytokinesis (cell wall formation).

The mitotic divisions that create the 8-nucleate stage in the embryo sac are free nuclear divisions, meaning no cell walls form until the final organization stage.

The megaspore mother cell undergoes meiosis to produce four haploid megaspores, of which three typically degenerate.

The megaspore mother cell differentiates in the nucellus, the nutritive tissue of the ovule. The nucellus is enclosed within the integuments.

The nucellus is enclosed within the integuments, contains abundant reserve food materials, and houses the embryo sac (female gametophyte). It provides nutrition to the developing embryo.

Ovules typically have 1-2 integuments that encircle the nucellus except at the micropyle (opening). The chalaza is the base opposite the micropyle where integuments fuse with nucellus.

The ovule attaches to the placenta via the funicle (stalk). The hilum is the junction point where ovule and funicle connect, analogous to a seed's attachment point.

Megasporangia are the structures that develop into ovules. Both terms refer to the same reproductive structure within the ovary.

The placenta is the tissue within the ovary where ovules are attached. The space inside the ovary is known as the ovarian cavity or locule.

The pistil consists of three parts: the stigma, the style, and the ovary. The style is the elongated, slender part connecting the stigma to the ovary.

A pistil (or carpel) is composed of three distinct regions: the stigma, the style, and the ovary.

When a gynoecium consists of multiple pistils that are fused together, it is termed syncarpous. Apocarpous refers to free pistils.

Pollen viability varies significantly among species. Cereals like rice and wheat have short viability, while families like Rosaceae and Leguminosae maintain it for months.

Pollen grains are highly nutritious and are marketed as food supplements to improve performance in athletes and racehorses.

Pollen grains from many species, including the invasive Parthenium (carrot grass), are known to cause severe allergies and respiratory issues.

In the pollen grain, the generative cell undergoes mitosis to produce two male gametes.

Angiosperms shed pollen at either the 2-celled stage (about 60 percent of species) or the 3-celled stage (the remainder).

The generative cell is small and floats in the cytoplasm of the vegetative cell; it contains a nucleus and dense cytoplasm.

A mature pollen grain consists of a large vegetative cell with food reserves and a smaller generative cell floating within it.

The cytoplasm of the pollen grain is enclosed by the plasma membrane, which is then surrounded by the cell wall (exine and intine).

The intine is the inner, thin, and continuous layer of the pollen wall, composed of cellulose and pectin.

The exine is the outer, hard layer of the pollen grain, known for its diverse patterns and designs.

Sporopollenin is an extremely resistant organic material that protects pollen grains, allowing them to be well-preserved as fossils.

Germ pores are specific regions on the exine where the sporopollenin layer is absent, allowing the pollen tube to emerge.

Sporopollenin is highly resistant to chemical and biological degradation, including enzymes, strong acids, and high temperatures.

Pollen grains are generally spherical, 25-50 micrometers in diameter, and possess an outer exine (sporopollenin) and an inner intine (cellulose and pectin).

Pollen grains are the immature male gametophytes in seed plants. They contain the male gametes necessary for fertilization.

Anthers release thousands of pollen grains when they dehisce (open). Each microsporangium contains numerous pollen grains, making 'several thousands' the accurate answer.

After meiosis, the microspore tetrads dissociate as the anther matures. Each individual microspore then develops into a pollen grain.

Microsporogenesis is the specific process by which microspore mother cells undergo meiosis to produce microspores.

The formation of microspores from the sporogenous tissue involves the reduction of chromosome number, which is achieved through meiotic cell division.

Tapetum cells are indeed dense and often multinucleate to support pollen development, and the sporogenous tissue is located in the center of the microsporangium.

Pollen sacs are the chambers within the anther that contain the developing and mature pollen grains.

As the microsporangia develop and mature, they expand and become the pollen sacs that house the pollen grains.

A typical angiosperm anther is bilobed, with each lobe containing two theca, making it dithecous.

The proximal end of the stamen filament is attached to either the thalamus (receptacle) or the petal of the flower.

A stamen consists of two main parts: the long, slender stalk called the filament and the terminal, bilobed structure called the anther.

The male reproductive structure is the androecium (composed of stamens) and the female reproductive structure is the gynoecium (composed of pistils/carpels).