Sexual Reproduction in Flowering Plants – Lecture Review

These flashcards provide question-and-answer practice covering definitions, structures, processes, adaptations, and examples related to sexual reproduction in flowering plants.

What is sexual reproduction in plants?

The process of producing new organisms through the formation and fusion of gametes.

Which plant organs are specialized for sexual reproduction in angiosperms?

Flowers.

How is a flower botanically defined?

A modified shoot with highly condensed internodes and leaves specialized as floral parts.

Name the four floral whorls of a complete flower.

Calyx, Corolla, Androecium, and Gynoecium.

Which floral whorls are called essential whorls and why?

Androecium and Gynoecium because they directly participate in reproduction.

What is the unit of the androecium called?

A stamen (microsporophyll).

List the two main parts of a typical stamen.

Filament and anther.

How many microsporangia are present in a typical anther?

Four, arranged as two per lobe.

Name the four wall layers of an anther from outside to inside.

Epidermis, Endothecium, Middle layer, Tapetum.

Which anther layer nourishes developing pollen grains?

Tapetum.

What is microsporogenesis?

The formation of microspores (pollen grains) from microspore mother cells by meiosis.

What is a microspore tetrad?

A group of four haploid microspores produced from a single MMC after meiosis.

State the composition of the pollen grain wall.

Outer exine made of sporopollenin and inner intine made of cellulose and pectin.

What is a germ pore?

A region on the pollen exine where sporopollenin is absent, allowing pollen tube emergence.

During micro-gametogenesis, what two cells form inside a two-celled pollen grain?

A vegetative (tube) cell and a generative cell.

At the three-celled stage, what does the generative cell produce?

Two male gametes.

What is the free unit of the gynoecium?

A pistil or carpel (megasporophyll).

Name the three parts of a carpel.

Stigma, style, ovary.

What is an ovule also called?

A megasporangium.

List any four parts of an ovule.

Funicle, hilum, micropyle, integuments, nucellus, chalaza (any four).

Define megasporogenesis.

Formation of megaspores from a megaspore mother cell via meiosis.

How many functional megaspores normally develop, and where are they located?

One, at the chalazal end of the linear tetrad.

How many nuclei and cells are present in a mature angiosperm embryo sac?

Eight nuclei but seven cells.

Name the cells of the mature embryo sac at the micropylar end.

One egg cell and two synergids (egg apparatus).

What is the function of the filiform apparatus in synergids?

Guides the pollen tube into the embryo sac.

Define pollination.

Transfer of pollen grains from anther to stigma of the same or another flower of the same species.

Differentiate autogamy and geitonogamy.

Autogamy is pollen transfer within the same flower; geitonogamy is between different flowers on the same plant.

What are cleistogamous flowers?

Flowers that never open, ensuring self-pollination.

Give one example of a chasmogamous flower.

Hibiscus (others possible: Sunflower).

What is dichogamy?

Maturation of stamens and carpels at different times to prevent self-pollination.

Distinguish protandry and protogyny.

Protandry: anthers mature first; Protogyny: carpels mature first.

What is self-incompatibility?

A genetic mechanism preventing pollen of the same flower from germinating on its stigma.

State one advantage of self-pollination.

Maintains genetic purity of the line.

State one disadvantage of self-pollination.

Leads to inbreeding depression and weaker progeny.

Give one advantage of cross-pollination.

Introduces genetic variation leading to evolution and healthier offspring.

Name two abiotic agents of pollination.

Wind and water.

List two typical traits of wind-pollinated flowers.

Small, colourless flowers; large feathery stigmas (others possible).

In hydrophily, how are pollen grains adapted?

They are small, unwettable, non-sticky, and often coated with wax.

What is entomophily?

Pollination by insects.

Why are ornithophilous flowers usually odourless?

Birds rely mainly on sight, not smell, for locating flowers.

Which pollination type involves bats?

Chiropterophily.

Define pollen-pistil interaction.

The recognition process by which a stigma determines pollen compatibility, promoting or inhibiting its growth.

What two key steps make artificial hybridization possible?

Emasculation (removal of anthers) and bagging (covering stigmas to avoid unwanted pollen).

What is double fertilization?

One male gamete fuses with the egg to form a zygote, the other fuses with the secondary nucleus to form primary endosperm nucleus.

Who discovered double fertilization and in which year?

S. G. Nawaschin in 1898.

What is triple fusion?

Fusion of the two polar nuclei with the second male gamete, initiating endosperm development.

Name the three types of endosperm.

Nuclear, cellular, helobial.

Which part of a tender coconut represents free-nuclear endosperm?

Coconut water.

During dicot embryo development, what does the hypophysis form?

Radicle and root cap.

What covers plumule and radicle in monocot embryos like grasses?

Coleoptile (plumule) and coleorhiza (radicle).

Differentiate albuminous and ex-albuminous seeds.

Albuminous seeds retain some endosperm; ex-albuminous seeds consume it completely during embryo development.

What is perisperm?

Persistent nucellus tissue in certain seeds, e.g., black pepper.

Define true fruit.

A fruit formed solely from the ovary after fertilization.

Why is an apple called a false fruit?

Its edible part develops mainly from the thalamus, not just the ovary.

What is parthenocarpy?

Development of seedless fruits without fertilization.

List the three layers of pericarp.

Epicarp, mesocarp, endocarp.

Define apomixis.

Formation of seeds without fertilization, mimicking sexual reproduction.

What is polyembryony?

Presence of more than one embryo in a single seed, e.g., in citrus.