What is Cleistogamy?
Cleistogamy is a phenomenon that occurs in different types of plants. Here, fertilisation generally occurs in closed plants that do not open. They follow self-pollination and undergo fertilisation. Pollination is the process of transferring pollen grains from a flower's male anther to its female stigma. Every living organism, including plants, strives to produce offspring for the next generation. Plants can produce offspring in a variety of ways, including by producing seeds. The transfer of pollen grains from the anther to the stigma of the same flower is known as self-pollination.
We will discuss every detail about cleistogamous flowers, cleistogamy pollination, and cleistogamous flowers’ example in this article along with some FAQs. This topic is full of facts and should be revised frequently. Studying this topic will also help students understand the whole chapter accurately.
What is Cleistogamy Pollination?
Cleistogamy pollination is a type of pollination in a specific type of flower that does not open at all, not even for pollination or fertilisation. Such flowers are known as cleistogamous flowers. The literal meaning of cleistogamy is closed marriage. The flowers that follow this phenomenon undergo self-pollination and self-fertilisation. This phenomenon is also known as autogamy. Autogamy is a type of self-pollination, where the flowers self-pollinate themselves.
Types of Cleistogamy
Cleistogamy is further divided into 4 types that are described below as follows:
Parenthesis Cleistogamy: In this type of cleistogamy, pollination occurs when the flower is in its bud stage and opens during the later stage of life. An example of it is Cuscuta.
Pseudo Cleistogamy: Here, both kinds of flowers are present, i.e., open and closed flowers, but only the closed flowers perform cleistogamy.
Complete Cleistogamy: Here, only closed flowers are present that perform self-pollination.
True Cleistogamy: The open flowers and closed flowers are morphologically different. The open flowers are large compared to the closed flowers. Therefore, only the closed flowers are modified to perform autogamy.
What are Cleistogamous Flowers?
It is a type of flower that performs cleistogamy. The cleistogamous flowers do not open and follow autogamy or self-pollination. These flowers produce a specific set of seeds as they do not have to depend on any external factor for pollination. In cleistogamous flowers, the male and female reproductive parts are smaller. Cleistogamous flower examples are peas, peanuts, etc.
Advantages of Cleistogamy
The advantages of cleistogamy are as follows:
As the flowers following cleistogamy are self-pollinated, they do not depend on any other external factor for fertilization.
It helps the plants produce a specified number of seeds even if the environmental conditions are adverse.
The flowers can avoid the synthesis of large amounts of pollen grains and nectar as there is no chance of loss in cleistogamy.
Through this method, the population of plants is maintained even in adverse environmental conditions.
Disadvantages of Cleistogamy
There are a few disadvantages to cleistogamy such as plants following cleistogamy have reduced genetic variation, which can lead to inbreeding depression. Inbreeding depression may result from continued self-pollination. This self-pollination does not aid in the development of new varieties and species. Cleistogamous flowers are almost always autogamous. As a result, there is no chance of cross-pollination.
Conclusion
Cleistogamy is a way through which flowers pollinate, but the unique part about cleistogamy pollination is that the flowers self-pollinate themselves. Here, the flowers remain close throughout their lives and undergo self-pollination. There are various advantages and disadvantages of cleistogamy, like how it reduces the dependency of the plant on external factors for pollination but loses the genetic variation that causes inbreeding depression. Cleistogamous flowers are those that exhibit cleistogamy. It is well known among members of the grass family, including peas, peanuts, and pansy.
This article mentions all the necessary concepts related to cleistogamy. This is an important topic for Class 12 under the chapter ‘Sexual Reproduction of Plants’ and this article would help students gain an understanding concept of the given topic.
FAQs on Cleistogamy
1. What is cleistogamy in flowering plants?
Cleistogamy is a mechanism of self-pollination that occurs in certain plants where the flowers never open. In these cleistogamous flowers, the anthers and stigma are located close together and mature simultaneously within the permanently closed bud. This arrangement ensures that pollen grains are transferred directly to the stigma, leading to successful fertilisation without any external pollinating agents.
2. What is the main difference between cleistogamous and chasmogamous flowers?
The main difference lies in their structure and pollination method. Cleistogamous flowers are those that remain closed, enforcing self-pollination. In contrast, chasmogamous flowers are typical open flowers with exposed anthers and stigmas, which can undergo either self-pollination or cross-pollination.
3. What are some examples of plants that exhibit cleistogamy?
Several plants produce cleistogamous flowers as a reproductive strategy. Common examples mentioned in the CBSE syllabus for the 2025-26 session include:
- Viola (Common Pansy)
- Oxalis (Wood Sorrel)
- Commelina (Dayflower)
- Arachis hypogaea (Peanut)
4. What are the key advantages of cleistogamy for a plant?
Cleistogamy offers several advantages, making it a successful survival strategy:
- It guarantees an assured seed-set because it does not depend on external pollinators like insects or wind.
- It is highly energy-efficient, as the plant does not need to produce large, colourful petals, nectar, or fragrance to attract pollinators.
- It helps in maintaining the purity of parental lines, which can be advantageous in stable environments.
5. What is the major genetic disadvantage of continuous cleistogamy?
The primary disadvantage of cleistogamy is the severe lack of genetic variation. Continuous self-pollination leads to inbreeding depression over successive generations. This reduces the population's ability to adapt to changing environmental conditions, diseases, or pests, potentially threatening its long-term survival.
6. How does cleistogamy guarantee an 'assured seed-set' for a plant?
Cleistogamy guarantees seed production by eliminating all uncertainties related to pollination. Since the flower never opens, the anthers dehisce (release pollen) directly onto the stigma located in close proximity. This ensures that pollination and subsequent fertilisation occur irrespective of external factors like the availability of pollinators or adverse weather conditions, thus assuring a seed-set.
7. Are cleistogamy and autogamy the same thing?
No, they are related but not identical. Autogamy is the broad term for self-pollination, meaning the transfer of pollen from the anther to the stigma of the same flower. Cleistogamy is a specific adaptation or mechanism that ensures autogamy by keeping the flower permanently closed. Therefore, all cleistogamous flowers are autogamous, but not all autogamous flowers are cleistogamous, as an open (chasmogamous) flower can also self-pollinate.
8. Why do some plants produce both cleistogamous and chasmogamous flowers?
Producing both types of flowers is a clever evolutionary strategy to balance survival and adaptation. The cleistogamous flowers act as a fail-safe, guaranteeing seed production for the plant's survival, even in years with few pollinators. The chasmogamous flowers, which open up, allow for the possibility of cross-pollination. This introduces valuable genetic variation into the population, which is crucial for adapting to future environmental changes and avoiding the negative effects of inbreeding depression.
