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Questions and Answers
What does the hilum represent in an ovule?
What does the hilum represent in an ovule?
- The basal part of the ovule
- The opening of the ovule
- The junction between ovule and funicle (correct)
- The protective envelope of the ovule
What is the main purpose of the integuments in an ovule?
What is the main purpose of the integuments in an ovule?
- To support the funicle
- To house the microspores
- To provide food for the embryo sac
- To encircle the nucellus (correct)
Which of the following is NOT a characteristic of the embryo sac in an angiosperm ovule?
Which of the following is NOT a characteristic of the embryo sac in an angiosperm ovule?
- Located within the nucellus
- Formed from a megaspore
- Has one or two protective envelopes (correct)
- Usually contains abundant reserve food materials
How many ovules might be typically found in an ovary?
How many ovules might be typically found in an ovary?
What health issues are commonly associated with pollen grains?
What health issues are commonly associated with pollen grains?
What is the process of megasporogenesis?
What is the process of megasporogenesis?
Which of the following statements about pollen viability is true?
Which of the following statements about pollen viability is true?
What is the primary function of flowers in angiosperms?
What is the primary function of flowers in angiosperms?
Which of the following best describes the significance of flowers in human culture?
Which of the following best describes the significance of flowers in human culture?
What term describes a pistil that is composed of multiple fused parts?
What term describes a pistil that is composed of multiple fused parts?
What is a major use of pollen tablets in Western countries?
What is a major use of pollen tablets in Western countries?
What is the major function of the stigma in the gynoecium?
What is the major function of the stigma in the gynoecium?
How are pollen grains used in the context of crop breeding programs?
How are pollen grains used in the context of crop breeding programs?
What characteristic of flowers contributes to the diversity of angiosperms?
What characteristic of flowers contributes to the diversity of angiosperms?
In the context of sexual reproduction in flowering plants, what does 'double fertilization' refer to?
In the context of sexual reproduction in flowering plants, what does 'double fertilization' refer to?
Which of the following terms refers to the development of seeds without fertilization?
Which of the following terms refers to the development of seeds without fertilization?
In which plant family do pollen grains maintain viability for an extended period?
In which plant family do pollen grains maintain viability for an extended period?
Which of the following statements is true about flowers?
Which of the following statements is true about flowers?
What is the end product of sexual reproduction in flowering plants?
What is the end product of sexual reproduction in flowering plants?
What is the basal bulged part of the pistil called?
What is the basal bulged part of the pistil called?
Which of the following does NOT relate to the adaptations of flowers for sexual reproduction?
Which of the following does NOT relate to the adaptations of flowers for sexual reproduction?
What is the primary characteristic of cleistogamous flowers?
What is the primary characteristic of cleistogamous flowers?
What is the primary role of endosperm during seed development?
What is the primary role of endosperm during seed development?
Why are cleistogamous flowers considered autogamous?
Why are cleistogamous flowers considered autogamous?
What distinguishes xenogamy from other types of pollination?
What distinguishes xenogamy from other types of pollination?
What is a disadvantage of cleistogamous flowers for plants?
What is a disadvantage of cleistogamous flowers for plants?
Which flowers are an example of producing both cleistogamous and chasmogamous types?
Which flowers are an example of producing both cleistogamous and chasmogamous types?
What is a fundamental difference between chasmogamous and cleistogamous flowers?
What is a fundamental difference between chasmogamous and cleistogamous flowers?
In which scenario would cleistogamous flowers be particularly advantageous?
In which scenario would cleistogamous flowers be particularly advantageous?
Which of the following accurately describes geitonogamy?
Which of the following accurately describes geitonogamy?
In which of the following does polyembryony occur?
In which of the following does polyembryony occur?
What is the significance of apomixis in angiosperms?
What is the significance of apomixis in angiosperms?
Which stage of embryo development follows the globular stage?
Which stage of embryo development follows the globular stage?
What constitutes a mature dicotyledonous embryo?
What constitutes a mature dicotyledonous embryo?
What is a key characteristic of chasmogamous flowers?
What is a key characteristic of chasmogamous flowers?
Which cell division process occurs during microsporogenesis?
Which cell division process occurs during microsporogenesis?
What is the function of the bagging technique in plant breeding?
What is the function of the bagging technique in plant breeding?
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Study Notes
Flower – A Fascinating Organ of Angiosperms
- Flowers are crucial for sexual reproduction in flowering plants (angiosperms) and offer aesthetic, ornamental, and cultural value.
- Different flowers symbolize diverse human emotions and play roles in social and religious celebrations.
- Pollen can cause allergies, with Parthenium being a notable allergenic species due to its widespread presence.
- Pollen grains are nutrient-rich; use as food supplements has gained popularity, particularly in Western markets, for athletic performance boosts.
Pre-fertilisation: Structures and Events
- Pollen grains require landing on the stigma to maintain viability; their lifespan can range from 30 minutes to several months, depending on species and environmental conditions.
- Storage of pollen in liquid nitrogen for years is possible, allowing for pollen banks analogous to seed banks in agriculture.
The Pistil, Megasporangium (Ovule), and Embryo Sac
- The gynoecium is the female reproductive part, composed of one or more pistils; pistils can be monocarpellary or multicarpellary (syncarpous or apocarpous).
- Each pistil includes the stigma, style, and ovary, with the ovule developing within the ovary.
- Ovules vary in number from one to many within an ovary; the structure includes the funicle, hilum, integuments, micropyle, chalaza, and nucellus.
- The embryo sac forms within the nucellus from a megaspore through a process called megasporogenesis.
Pollination Mechanisms
- Cleistogamous flowers are self-pollinating due to their closed structure, ensuring seed set without pollinators.
- Geitonogamy involves pollen transfer within the same plant, while xenogamy entails cross-pollination between different plants.
Double Fertilisation and Seed Development
- Endosperm formation occurs before embryo development, progressing through various stages until maturation.
- Dicotyledonous embryos contain two cotyledons, while monocotyledonous embryos have one.
- After fertilisation, the ovary becomes a fruit, and ovules transform into seeds.
Apomixis and Polyembryony
- Apomixis leads to seed formation without fertilisation; it is advantageous in agricultural applications.
- Some angiosperms exhibit polyembryony, producing multiple embryos in a single seed.
Summary of Key Concepts
- Understanding the morphology and processes of sexual reproduction in angiosperms highlights their ecological significance and contributions to biodiversity.
- The versatility of reproductive strategies in flowering plants reflects their adaptations to various environments and the importance of genetic diversity.
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