Question

What function(s) does the carbohydrate callose have in the reproduction of flowering plants? a. Callose forms a coat that isolates young embryos during their early development. b. Callose forms a coat that isolates groups of four microspores during their early development into pollen grains. c. Callose helps to form the patterns on the sporopollenin walls of pollen grains. d. All of the above are functions of callose. e. None of the above is a function of callose.

Short answer

Option b: 'Callose forms a coat that isolates groups of four microspores during their early development into pollen grains.' is the correct function of callose in flowering plants' reproduction

Step-by-step solution

Identification of Callose

Identify callose and its function. Callose is a type of carbohydrate produced by plants. It is known for playing a significant role in plant defense against pathogens. Yet, it also has relevant functions in plant development and reproduction.

Analyze Option a

Scrutinize option a: 'Callose forms a coat that isolates young embryos during their early development.' This is not a function of callose in flowering plants. Callose is involved in the process of pollen development, but it does not form a coat around embryos.

Analyze Option b

Evaluate the statement made in option b: 'Callose forms a coat that isolates groups of four microspores during their early development into pollen grains.' This is true; during microsporogenesis, callose is deposited around the tetrad of microspores.

Analyze Option c

Look at option c: 'Callose helps to form the patterns on the sporopollenin walls of pollen grains.' This statement is incorrect, it is the sporopollenin that forms the patterns on the walls of pollen grains, not callose.

Analyze Option d

Consider if option d: 'All of the above are functions of callose' could be correct in light of our previous analyses. As we found that not all statements above are correct, this statement can't be true.

Analyze Option e

Finally, glance at the last option, option e: 'None of the above is a function of callose.' This option is not valid as we previously determined that at least one of the previous options (option b) represents a function of callose.

Key concepts

Callose

Callose is a crucial carbohydrate in flowering plant reproduction. It is a polysaccharide, a type of carbohydrate made up of glucose units. Though often associated with plant defense, callose plays a significant part in plant development. Its role is especially important during the formation of pollen. During pollen development, callose acts as a protective layer. It surrounds developing microspores, essentially encasing groups of four microspores in a tetrad. This protective shield ensures that the microspores can develop properly into viable pollen grains.

Callose's deposition is temporary; it dissolves as the microspores mature. This temporary barrier is essential in the early stages of pollen development. It helps regulate cell interactions and development. While callose does not directly form patterns on pollen walls, it is an indispensable part of the overall reproductive process in plants.

Pollen Development

The development of pollen is a critical part of plant reproduction. It encompasses several stages, ultimately ensuring the formation of male gametes. Initially, cells called microspores undergo a series of changes to become mature pollen grains.

One of the first steps in pollen development is microsporogenesis. During this stage, diploid microsporocytes undergo meiosis to produce haploid microspores. The subsequent stage, microgametogenesis, allows these microspores to develop into pollen grains, each containing two sperm cells.

Callose plays a key role during these stages by encapsulating microspores in tetrads. This isolation is pivotal as it allows the microspores to undergo necessary developmental processes without interference. Once maturity is reached, the callose sheath breaks down and the individual pollen grains are released, ready for fertilization.

Microsporogenesis

Microsporogenesis is the stage of the plant life cycle where pollen development begins. It occurs within the male sections of the flower, specifically in the anthers. During this stage, microsporocytes, which are diploid (meaning they have two sets of chromosomes), undergo meiosis. This process reduces the chromosome number by half, resulting in the formation of four haploid microspores from each microsporocyte.

At this point, callose becomes a major player. It is deposited around the newly formed microspores, creating a callose wall. This wall separates the microspores, forming clusters known as tetrads. Inside each tetrad, microspores can develop in an environment that permits regulated and controlled interactions.

As the microspores mature, the callose wall is enzymatically dissolved. This dissolution releases the microspores, allowing them to continue their development into mature pollen grains. The function of callose during microsporogenesis is crucial, as it supports the structural organization and successful development of pollen.