Stomata: Types, Structure, Mechanism & Functions

Types of Stomata Overview

Plants are fascinating organisms that have a unique way of interacting with their environment. One of the key features that enable plants to do this is stomata. Stomata are tiny openings in the leaves and stems of plants that allow for gas exchange between the plant and its surroundings. In this blog post, we will take a closer look at what stomata are, their structure, types, functions, and mechanisms of opening and closing. We will also explore the different subsidiary cells that accompany stomata and how photosynthesis occurs through them. Additionally, we will delve into transpiration through stomata and compare different types of stomata found in plants. Finally, we will discuss the importance of stomata in plants' survival and growth.

What are Stomata?

Stomata are tiny openings on leaves that enable plants to exchange gases, regulating carbon dioxide intake and oxygen and water vapour release. Guard cells surround each stoma, managing its opening and closing. The quantity and arrangement of stomata differ among plant species and depend on environmental conditions like light levels and humidity.

Structure of Stomata

1. Stomata are small pores or openings on leaf surfaces in plants.
2. They are surrounded by subsidiary cells, including guard cells that control their opening and closing.
3. Stomata enable gaseous exchange, allowing plants to take in carbon dioxide and release oxygen during photosynthesis.
4. Different types of stomata exist based on their structure and function:
5. Diacytic stomata are found in monocots and ranunculaceous plants.
6. Caryophyllaceous plants possess cyclocytic stomata with dumbbell-shaped subsidiary cells.
7. Stomatal closure is a mechanism that reduces water loss, particularly during drought.
8. It helps maintain turgor pressure within plant cells, preventing dehydration.

Key Features of Stomata Structure

1. Minute pores called stomata facilitate gaseous exchange in plants.
2. Stomata allow carbon dioxide absorption and oxygen release.
3. Guard cells regulate the opening and closing of stomata.
4. The opening/closing of the stomata depends on turgor pressure changes.
5. Stomata exist in various types: paracytic, diacytic, anomocytic, anisocytic, and gramineous stomata.
6. Each type of stomata has unique structures and functions.
7. Accessory or subsidiary cells, located within the epidermal cells, support the action of guard cells in opening and closing stomatal pores.

Types of Stomata

Stomatal pores are tiny openings found on the surface of leaves that play an important role in gaseous exchange. There are different types of stomata based on their structure and function. These include anomocytic, paracytic, diacytic, cyclocytic, actinocytic, helicocytic, and anisocytic stomata. Anomocytic stomata have irregular-shaped cells surrounding the pore, while paracytic stomata have two to three subsidiary cells that run parallel to the pore. Diacytic stomata have two subsidiary cells perpendicular to the pore. In contrast, cyclocytic stomata have a single ring of subsidiary cells around the pore.

The number and arrangement of subsidiary cells surrounding the stoma can also vary depending on the type of stomata. For instance, some types have a limited number of subsidiary cells like caryophyllaceous or dumbbell-shaped guard cells found in ranunculaceous plants. Anisocytic stomata have accessory cells that differ from epidermal cells in shape and size.

The structure of guard cells that regulate opening and closing differs according to plant species and environmental conditions. Chloroplasts in guard cells aid in the process of photosynthesis and also regulate turgor pressure. The closure of stomata during nighttime reduces water loss by transpiration, whereas the opening of stomata during daytime facilitates carbon dioxide uptake for photosynthesis.

Anomocytic Stomata

Minute pores called stomata present on the surface of leaves aid in essential processes like gaseous exchange and transpiration. Anomocytic stomata, the most common type of stomata found in plants, appear as simple round shapes without any specialized cells around them. You can find them on both sides of the leaves. These tiny pores play an important role in adapting to changes in environmental conditions.

Secondary keyterms used: subsidiary cells, subsidiary, stoma, pore, paracytic, guard cell, diacytic, anomocytic, transpiration, minute pores, leaf surface, different types of stomata

Anisocytic Stomata

Found in many dicotyledonous plants, anisocytic stomata consist of a kidney-shaped guard cell with a single crescent-shaped pore. These stomata play an important role in regulating the exchange of gases and water vapor between the plant and its environment while maintaining the balance between photosynthesis and transpiration. Their unique structure makes them resistant to environmental stressors such as drought, extreme temperatures, and pollution. Anisocytic stomata contribute significantly to the survival of plants.

Paracytic Stomata

Stomata are minute pores present on the surface of leaves and stems that enable gaseous exchange between plant cells and the environment. Paracytic stomata, one of the different types of stomata found in plants, are present in plants that grow in arid or semi-arid environments. These stomata have a parallel arrangement of guard cells and subsidiary cells, which helps reduce water loss through transpiration. The number and distribution of paracytic stomata can vary depending on the species of plant. They play an important role in regulating the exchange of gases such as carbon dioxide and water vapour between the plant and its environment.

Diacytic Stomata

Located on the lower surface of leaves in plants growing in hot and dry environments are diacytic stomata. The tiny dumbbell-shaped pores facilitate gaseous exchange between the plant and its surroundings while conserving water by reducing transpiration rate. Flanking the guard cells are two subsidiary cells that help maintain turgor pressure and facilitate stomatal closure during excess water loss. These unique structures play a crucial role in adapting to arid conditions without compromising photosynthesis or respiration.

Gramineous Stomata

Found only in grasses and with a distinct structure different from other types of stomata. This type of stomata has kidney-shaped guard cells flanking the opening regulating it for gaseous exchanges between plants and their surroundings. Gramineous stomata enable photosynthesis to occur while containing chloroplasts that convert CO2 into O2. Dumbbell-shaped subsidiary cells play a crucial role in maintaining turgor pressure throughout daytime. These minute pores also assist in controlling water loss from leaves via transpiration rate.

Functions of Stomata

1. Stomata are vital for regulating gaseous exchange in plants.
2. They control water vapor loss through transpiration.
3. Stomata help regulate carbon dioxide levels for photosynthesis.
4. They respond to external stimuli like light and temperature.
5. Various types of stomata exist in different plant species.
6. Each type has unique adaptations and specialized functions.
7. Subsidiary cells alongside guard cells are crucial for maintaining turgor pressure.
8. Turgor pressure determines the opening or closing of stomatal pores.
9. Studying different stomata types reveals plant adaptation to the environment.

Opening and Closing of Stomata

Opening Stomata:

• Guard cells regulate the opening and closing of stomata on leaf surfaces.
• Environmental cues like light and temperature trigger the opening mechanism.
• Opening stomata impact water regulation and gaseous exchange, including oxygen and carbon dioxide.

Closed Stomata:

• Guard cells regulate the closing of stomata on leaf surfaces.
• Environmental cues like light and temperature trigger the closing mechanism.
• Closed stomata help regulate water loss and reduce gaseous exchange.

Additional Information:

• Sunken or amphistomatous leaves have different types of stomata with unique adaptations to their environment.
• These adaptations provide crucial insights into plant physiology for better agricultural strategies.

Subsidiary Cells of Stomata

1. Subsidiary cells in plants play a crucial role in gas exchange through stomata.
2. Subsidiary cells include guard cells and accessory cells.
3. They assist in regulating water loss via the stomatal pore.
4. Diacytic stomata are found in caryophyllaceous plants, while anomocytic stomata are found in ranunculaceous plants.
5. Actinocytic or cyclocytic stomata are present in rubiaceous plants.
6. Environmental factors such as light intensity, humidity, and temperature influence the opening and closing of stomata.
7. Turgor pressure changes, induced by these factors, control the minute pore's behaviour.

Photosynthesis and Stomata

1. Stomata play a crucial role in photosynthesis, the process by which plants convert sunlight, water, and carbon dioxide into glucose and oxygen.
2. During photosynthesis, stomata facilitate the uptake of carbon dioxide from the atmosphere, which is an essential component for the synthesis of glucose.
3. Stomata also allow the release of oxygen, a byproduct of photosynthesis, back into the atmosphere.
4. The opening and closing of stomata are tightly regulated during photosynthesis to balance the exchange of gases and prevent excessive water loss through transpiration.
5. Environmental factors such as light intensity, humidity, and temperature influence the opening and closing of stomata, optimizing the photosynthetic process.
6. Proper functioning of stomata is crucial for efficient photosynthesis and the overall growth and development of plants.

Chloroplasts in Stomata

Tiny pores called stomata are found on the surface of leaves and allow for gaseous exchange between plants and their environment. Chloroplasts, which are organelles responsible for carrying out photosynthesis in plant cells, are located in the cells surrounding these minute pores known as stomatal openings. Through this opening and closing of stomata regulated by turgor pressure in subsidiary cells like guard cells and accessory cells plays an important role in regulating water loss from plants and their rate of transpiration.

Mechanism of Closing of Stomata

1. The process of closing stomatal pores in plants involves complex regulation by guard cells. Light, humidity and CO2 levels affect this process.
2. The opening and closing of stomatal pores are controlled by guard cells through changes in their turgor pressure, leading to changes in shape.
3. Loss of water causes the guard cells to become flaccid resulting in the closure of these tiny pores on leaf surfaces.
4. Some plants have evolved specialized stomata that only open at night to reduce daytime water loss.

Transpiration through Stomata

1. Stomata regulate the exchange of gases and water vapour in plant cells.
2. They are tiny pores on the epidermis of leaves.
3. Guard cells surround the stomatal pore and control its opening and closing.
4. Transpiration rate is influenced by factors such as light intensity, humidity, carbon dioxide concentration, and temperature.
5. Different types of stomata exist, including caryophyllaceous, rubiaceous, and ranunculaceous.
6. Stomata can have parallel subsidiary cells (paracytic), kidney-shaped subsidiary cells (diacytic or cyclocytic), or limited subsidiary cells (actinocytic or anisocytic).
7. The structure of stomata varies depending on the plant species and habitat conditions.

Differences between Paracytic and Diacytic Stomata

Anisocytic and Anomocytic Stomata – A Comparison

Importance of Stomata in Plants

The importance of stomata in plants is as follows:

1. Stomata act as essential gatekeepers, facilitating gaseous exchange for plants.
2. These minute pores regulate water loss through transpiration.
3. Stomata enable the uptake of carbon dioxide and release of oxygen during photosynthesis.
4. The structure of stomata includes guard cells, subsidiary cells, and stomatal pores.
5. Turgor pressure changes control the opening and closing of stomata.
6. Various types of stomata, like paracytic or diacytic, have distinct adaptations to environmental conditions.
7. Some stomata are specialized for excess water conservation, while others optimize gas exchange efficiency.

Things to Remember about Stomata

1. Minute pores in leaf epidermis are crucial for plant life.
2. Stomata enable gaseous exchange between plant cells and the surrounding air.
3. Different types of stomata exist on leaf surfaces: diacytic, anisocytic, paracytic, anomocytic (caryophyllaceous), ranunculaceous or actinocytic (dumbbell-shaped), and cyclocytic.
4. Diacytic stomata have two parallel kidney-shaped subsidiary cells.
5. Anisocytic stomata consist of one large subsidiary cell and two smaller ones.
6. Paracytic stomata have at least two subsidiary cells on each side of the guard cell pair.