Biology Chapter 12: Flowers and Sexual Reproduction

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Questions and Answers

What is the male reproductive organ of a flower?

Sepal

Stamen (correct)

Petals

Pistil

What is the function of the filament in a stamen?

To produce hormones for flowering

To protect the pollen sacs

To produce pollen grains

To hold the anther in place (correct)

What is the female reproductive organ of a flower?

Androecium

Corolla

Calyx

Gynoecium (correct)

Where is the proximal end of the filament attached in a flower?

The thalamus or petal Signup and view all the answers

What is the collective term for the male reproductive structures in a flower?

Androecium Signup and view all the answers

What is the site of sexual reproduction in angiosperm?

Flower Signup and view all the answers

What is the outermost whorl of a flower that protects the reproductive organs?

Calyx Signup and view all the answers

What is the end product of sexual reproduction in angiosperm?

Both a and b Signup and view all the answers

What is the unit of the male reproductive structure that produces pollen grains?

Microsporangium Signup and view all the answers

What is the equivalent structure of stamen in pteridophytes and gymnosperms?

Microsporophyll Signup and view all the answers

What is the characteristic of an anther in the family Malvaceae?

Monothecous and bisporangiate Signup and view all the answers

What grows from archesporial cells in an anther?

Sporogenous tissue Signup and view all the answers

What is the process of formation of microspores from a pollen mother cell (PMC) through meiosis called?

Microsporogenesis Signup and view all the answers

What is the arrangement of microspores in a tetrad typically found in dicots?

Tetrahedral Signup and view all the answers

What is the number of meiotic divisions required to form 'x' number of pollen grains?

x/4 Signup and view all the answers

What is the number of microspores formed inside each microsporangium?

Thousands Signup and view all the answers

What happens to the microspores as the anthers mature and dehydrate?

They dissociate from each other Signup and view all the answers

What is the type of development of microsporangia?

Eusporangiate Signup and view all the answers

What is the characteristic of pollen grains produced by an anther?

Genetically diverse Signup and view all the answers

What is the primary function of the outer three wall layers of a microsporangium?

Protection and dehiscence of anther Signup and view all the answers

What is the characteristic of cells in the endothecium?

Fibrous thickening Signup and view all the answers

What is the function of the tapetum in a microsporangium?

Nourishment of developing pollen grains Signup and view all the answers

What is the ploidy of microspore mother cells (MMC)?

Diploid (2n) Signup and view all the answers

What is produced by the secretory tapetum?

Ubisch bodies Signup and view all the answers

What is the term for the study of pollen grains?

Palynology Signup and view all the answers

What is the function of chromoplasts in pollen grains?

To convert chlorophyll into other pigments Signup and view all the answers

What is the characteristic of pollen grains in Cyperaceae (Cyperus)?

Only one microspore remains functional Signup and view all the answers

What is the structure that unites pollen grains in Calotropis (milkweeds) and orchids?

Pollinium Signup and view all the answers

What is the typical size of pollen grains?

25-50 micrometers in diameter Signup and view all the answers

What is the structure of the pollen grain wall?

Double layered Signup and view all the answers

Study Notes

Microsporangium Development

Microsporangia development is of eusporangiate type, similar to gymnosperms and Selaginella.
Microsporangia develop into pollen sacs, extending longitudinally along the length of an anther.
Each pollen sac is packed with pollen grains.

Structure of Microsporangium

In a transverse section, a microsporangium appears near circular in outline.
It is surrounded by four wall layers: epidermis, endothecium, middle layers, and tapetum.
The outer three wall layers (epidermis, endothecium, and middle layers) provide protection and aid in anther dehiscence.
Endothecium cells have characteristic fibrous thickening.
The innermost wall layer, the tapetum, nourishes developing pollen grains and has dense cytoplasm with multiple nuclei.

Sporogenous Tissue

Cells of the sporogenous tissue are diploid (2n) and function as microspore mother cells (MMC).
Microspore mother cells are surrounded by a callose wall.

Microspore Formation

Microspore mother cells undergo meiotic divisions to form microspore tetrads.
Each microspore mother cell is capable of producing a microspore tetrad.
Microspores are arranged in a cluster of four cells, typically in a tetrahedral arrangement.

Pollen Grains

Pollen grains represent the male gametophytes.
Pollen grains are non-green due to the conversion of chloroplasts into chromoplasts.
They have a prominent two-layered wall (sporoderm) consisting of an outer exine and inner intine.
Pollen grains are generally spherical, measuring 25-50 micrometers in diameter.

Microsporogenesis

The process of microspore formation from a microspore mother cell through meiosis is called microsporogenesis.
Microspores dissociate from each other and develop into pollen grains as the anther matures and dehydrates.

Anther Structure

A typical anther is bilobed, with each lobe having two theca (dithecous).
The bilobed nature of an anther is distinct in the transverse section.
Both lobes are interconnected by a sterile tissue called connective.
The anther is a four-sided (tetragonal) structure consisting of four chambers called microsporangia located at the corners, two in each lobe.

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Description

Test your knowledge on the biology of flowers and sexual reproduction. This quiz covers the structures and events of pre-fertilization, including the morphology of flowers and the process of plant reproduction. Identify the different parts of a flower and understand the stages of sexual reproduction in plants.