Reproductive Parts of a Flower Quiz

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Questions and Answers

Explain the process of gemmule formation in sponges.

Gemmule is an internal bud formed in sponges, containing a mass of dormant cells called archaeocytes. These archaeocytes are coated by a thick resistant layer of secretion by amoebocytes, allowing them to develop into a new organism when conditions are favorable.

What is the purpose of gemmule formation in sponges?

Gemmule formation in sponges occurs as a survival strategy to overcome unfavorable conditions. It allows for the preservation of dormant cells that can develop into a new organism when conditions become favorable.

Define apomixis and provide an example.

Apomixis is a type of asexual reproduction where seeds are produced without fertilization. An example of apomixis is the formation of seeds from the maternal plant's ovule without the need for pollination.

Explain the concept of seed dormancy.

Seed dormancy is a period in which a seed is alive but not growing. It is a protective mechanism that prevents germination until conditions are optimal for the seed to grow into a new plant. Signup and view all the answers

Describe the process of seed germination.

Seed germination is the process where a seed develops into a new plant. It typically involves the seed absorbing water, followed by the growth of a radicle, which develops into the primary root, and the emergence of the shoot through the soil. Signup and view all the answers

What factors affect seed viability?

Seed viability can be influenced by factors such as the age of the seed, storage conditions, exposure to light, temperature, and humidity levels. These factors can impact the seed's ability to germinate and develop into a healthy plant. Signup and view all the answers

What are the two types of seeds based on the presence of endosperm in mature seeds?

Endospermic or albuminous and non-endospermic or exalbuminous seeds. Signup and view all the answers

Explain the difference between endospermic and non-endospermic seeds in terms of the fate of endosperm during seed development.

Endospermic seeds retain endosperm in mature seeds, while non-endospermic seeds absorb all food reserves from endosperm during development. Signup and view all the answers

What is the purpose of the micropyle in a seed coat?

The micropyle allows the entry of water and oxygen during soaking. Signup and view all the answers

Describe the role of cotyledons in seeds.

In some seeds, cotyledons act as food storage, while in others, they are the first photosynthetic organs. Signup and view all the answers

What is the significance of pollination in seed development?

Pollination is essential for seed production and fruit formation. Signup and view all the answers

Explain the process of seed development initiation.

Seed development is initiated by fertilization. Signup and view all the answers

What are the main categories of apomixis and how do they differ?

The main categories of apomixis are recurrent apomixis and non-recurrent apomixis. Recurrent apomixis involves the embryo sac rising from an archesporial cell or nucellus, while non-recurrent apomixis involves a haploid embryo sac formed from a megaspore mother cell. Signup and view all the answers

What is dormancy in seeds and why is it important?

Dormancy in seeds is a state of metabolic arrest that facilitates survival during adverse environmental conditions. It is important for the dispersal of seeds and ensures that viable seeds germinate only after a period of dormancy. Signup and view all the answers

Describe the process of germination in seeds.

Germination is the process where a seed sprouts and begins to grow into a new plant. It involves the seed absorbing water, activating enzymes, and initiating growth of roots and shoots. Signup and view all the answers

What is the role of apomixis in plant reproduction?

Apomixis is a form of asexual reproduction in plants where seeds are produced without fertilization. It helps in the preservation of desirable traits and genetic uniformity. Signup and view all the answers

How does seed viability relate to dormancy?

Seed viability refers to the ability of a seed to germinate and grow into a healthy plant. Dormancy ensures that viable seeds do not germinate prematurely and have a better chance of survival. Signup and view all the answers

Explain the difference between diplospory and apospory in apomixis.

In diplospory, the unreduced embryo sac is derived from the diploid megaspore mother cell, while in apospory, the nucellar cells give rise to apomictic embryo sac. Diplospory involves the formation of the embryo sac from a specific cell, whereas apospory involves nucellar cells. Signup and view all the answers

Study Notes

Gemmule Formation

Sponges reproduce asexually through gemmule formation.
Gemmules are internal buds that allow for survival in harsh conditions, acting as resistant stages.
They form within the mesohyl, the gelatinous matrix of the sponge.
Gemmules are composed of an aggregation of archaeocytes, which are undifferentiated cells.
They have a tough outer layer called a spicule, which is a protective covering.
Gemmules can survive for long periods in adverse conditions, like freezing or drought.
When conditions are favorable, gemmules release archaeocytes, which can then divide to form a new sponge.

Purpose of Gemmule Formation

Gemmule formation is a method of sexual reproduction for sponges.
The purpose is to allow sponges to survive unfavorable environments, like drought or freezing.
They function as survival mechanisms, ensuring the continuation of the sponge species.

Apomixis

Apomixis refers to a form of asexual reproduction that produces seeds without fertilization.
It is a type of parthenogenesis, where an ovule develops into a seed without fertilization.
Example: Dandelions, which produce seeds through apomixis, meaning they don't rely on cross-pollination.

Seed Dormancy

Seed dormancy is a period of suspended growth and metabolic activity in seeds.
It's a natural survival mechanism to ensure germination occurs under optimal conditions.
It prevents germination during unfavorable conditions, like winter or drought.

Seed Germination

It is the process in which a seed emerges from dormancy and begins to grow into a seedling.
It begins with imbibition, the intake of water by the seed.
The water activates enzymes within the seed, triggering metabolic processes.
The radicle, the embryonic root, emerges first and anchors the seedling.
Later, the plumule, the embryonic shoot, breaks through the soil, initiating plant growth.

Factors Affecting Seed Viability

Environmental factors like temperature, moisture, and light can affect seed viability.
Seed age also plays a crucial role, as viability tends to decrease with age.
Genetic factors within the seed contribute to its viability.
Proper storage conditions are essential for maintaining seed viability.
Seed coat thickness, hardness, and the presence of dormancy mechanisms can affect viability.

Two Types of Seeds based on Endosperm

Endospermic seeds: These contain a well-developed endosperm tissue that provides nourishment for the embryo.
Non-endospermic seeds: Endosperm tissue may be absent or consumed by the embryo during development.
These seeds rely on other nutritive tissues for embryo nourishment, like cotyledons.

Endospermic vs. Non-endospermic Seeds

In endospermic seeds, the endosperm persists as a storage tissue in the mature seed.
In non-endospermic seeds, the endosperm is either absent or absorbed by the embryo during seed development.
Cotyledons become the primary source of nutrients for the embryo.

Micropyle

It is a small opening in the seed coat, often found at the end opposite the radicle.
The micropyle allows water and oxygen to enter the seed during germination.
It also serves as the entrance point for the pollen tube during fertilization.

Cotyledon Role

Cotyledons are the first seed leaves that develop from the embryo.
For non-endospermic seeds, they serve as food storage organs for the developing seedling.
In some plants, they can also function as photosynthetic organs.

Significance of Pollination

Pollination is an essential step in seed development.
The transfer of pollen from the anther to the stigma of the flower triggers fertilization.
Fertilization leads to the formation of the zygote, which develops into the embryo.

Seed Development Initiation

Seed development starts after fertilization.
The zygote divides mitotically to form the embryo, which eventually develops into the seedling.
The ovule, which contains the developing embryo, transforms into the seed.

Apomixis Categories

Gametophytic apomixis: An unreduced egg cell develops into an embryo without fertilization, usually due to an altered megaspore or embryo sac development.
Sporophytic apomixis: The embryo develops directly from diploid sporophytic tissue without meiosis or fertilization.
Adventitious embryony: New embryos develop outside the ovule or embryo sac from vegetative tissues like the nucellus.

Dormancy in Seeds

Dormancy is a state of suspended growth and metabolism in seeds, allowing plants to survive unfavorable conditions.
It is important to ensure germination occurs at an optimal time for seedling establishment.

Process of Germination

It's the process of a seed emerging from dormancy and growing into a seedling.
Imbibition, the uptake of water, is the first step, triggering metabolic changes.
The radicle, the embryonic root, emerges first, followed by the plumule, the embryonic shoot.

Role of Apomixis in Reproduction

Apomixis allows plants to reproduce asexually, preserving identical offspring.
It enables the propagation of desirable traits, circumventing the need for seed production or fertilization.
It can ensure genetic uniformity in populations, contributing to genetic diversity within species.

Seed Viability and Dormancy

Seed viability is the ability of a seed to germinate and develop into a plant.
Dormancy can be linked to seed viability as it often acts as a mechanism to maintain viability for extended periods.
Seed dormancy can prevent premature germination, ensuring that germination occurs under favorable conditions.

Diplospory and Apospory

Diplospory: It is a type of gametophytic apomixis where the embryo sac develops directly from a megaspore mother cell without meiosis.
Apospory: It is another type of gametophytic apomixis where the embryo sac originates from diploid sporophytic cells surrounding the megaspore mother cell.
These processes result in the development of an embryo sac with unreduced chromosomes, leading to apomictic seed formation.

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Description

Test your knowledge on the reproductive parts of a flower and their functions. Identify the different components responsible for pollination, fertilization, and seed production.