What are Stomata?


Introduction

Plants are complex organisms that have evolved unique structures to carry out various functions. One such structure is the stomata, which plays a crucial role in plant survival. Stomata are tiny pores found on the surface of plant leaves, stems, and other plant organs that allow gaseous exchange, particularly the uptake of carbon dioxide for photosynthesis and the release of oxygen and water vapor.

Stomata

Stomata are an essential component of the plant's respiratory system, which is responsible for the exchange of gases between the plant and the environment. They are typically found in the epidermis, the outermost layer of cells that cover the surface of the plant. Stomata are typically more numerous on the underside of leaves, where they are less exposed to sunlight and wind, and where there is a higher humidity level.

Stomatal Structure and Types

Stomata consist of two specialized cells called guard cells that surround a small pore or opening. The guard cells are kidney-shaped and are responsible for controlling the opening and closing of the stomata. The opening and closing of stomata are influenced by several environmental factors, such as light, temperature, humidity, and the concentration of carbon dioxide in the air.

Stomata are not only found in leaves, but they are also found in other plant organs, such as stems and flowers. In flowers, stomata are typically found on the petals and play a role in regulating water loss and gaseous exchange during pollination.

There are different types of stomata found in different plants, such as grasses, dicotyledonous plants, and cacti. Each type of stomata has a unique structure that suits the specific needs of the plant species.

There are mainly three types of stomata found in different plants, which are as follows −

Anisocytic Stomata

Anisocytic stomata are found in dicotyledonous plants, and they are characterized by a single large pore surrounded by three subsidiary cells. The two lateral subsidiary cells are smaller than the central cell, and they are usually oriented perpendicular to the stomatal pore. Anisocytic stomata are particularly common in plants belonging to the family Solanaceae, such as tomatoes and peppers.

Paracytic Stomata

Paracytic stomata are also found in dicotyledonous plants, and they are characterized by two parallel rows of subsidiary cells that run parallel to the stomatal pore. The two subsidiary cells are located on opposite sides of the stomatal pore, and they are often elongated and narrow. Paracytic stomata are common in plants belonging to the family Rubiaceae, such as coffee and gardenia.

Cyclocytic Stomata

Cyclocytic stomata are found in monocotyledonous plants, and they are characterized by a single large pore surrounded by two or more subsidiary cells that are arranged in a circular or semi-circular pattern. The subsidiary cells are usually smaller than the central cell and are often oriented perpendicular to the stomatal pore. Cyclocytic stomata are particularly common in grasses, such as wheat, rice, and corn.

The different types of stomata found in plants have evolved to suit the specific needs of different plant species. Each type of stomata has a unique structure that allows for efficient exchange of gases while minimizing water loss. The study of stomata and their types is essential for understanding how plants adapt to their environment and how they regulate gaseous exchange and water use.

Stomatal Adaptations

Stomata have evolved by various adaptations to suit the specific needs of different plant species and their environments. These adaptations enable stomata to regulate gas exchange, conserve water, and protect against environmental stresses. Some of the different adaptations of stomata include −

Density and Distribution of Stomata

Plants that grow in arid or dry environments, such as deserts, often have fewer stomata or clustered stomata. This adaptation helps to reduce water loss by limiting the amount of water that can escape through the stomatal pores. In contrast, plants that grow in wet environments, such as tropical rainforests, tend to have more stomata to allow for increased gas exchange.

Size of Stomata

The size of stomata can vary between plant species and can also change in response to environmental conditions. Smaller stomata are generally better at conserving water, while larger stomata allow for increased gas exchange. Some plants, such as succulents, have small, sunken stomata that are protected from the wind and heat to prevent water loss.

Stomatal Movements

Stomatal movement occurs in response to various environmental factors, like light, temperature, humidity, and the concentration of carbon dioxide in the air. Some plants, such as cacti, have stomata that only open at night to reduce water loss during the day. Other plants, such as the Venus Flytrap, have modified stomata that can close rapidly in response to touch or other stimuli.

Subsidiary Cells

Subsidiary cells are specialized cells that surround the stomatal pore and play a role in regulating stomatal movements. The size, shape, and orientation of subsidiary cells can vary between plant species and can affect the rate of gas exchange and water loss through the stomata.

Opening and Closing of Stomata

When the guard cells are filled with water, they become turgid, and the stomata open, allowing the exchange of gases. Conversely, when the guard cells lose water, they become flaccid, and the stomata close to conserve water.

The opening and closing of stomata is a finely-tuned process that is regulated by ion channels and pumps in the guard cells. This process is influenced by several environmental factors, including light, humidity, and temperature, which affect the movement of water and ions into and out of the guard cells.

The opening and closing of stomata is a finely-tuned process that is regulated by ion channels and pumps in the guard cells. The process is affected by various factors such as light, humidity, and temperature, that influence the movement of water and ions into and out of the guard cells.

Function

Stomata are critical for photosynthesis, which is the process by which plants use light energy to produce food in the form of sugars.

During photosynthesis, carbon dioxide is taken up through the stomata and combined with water to form glucose, which is then used by the plant for energy. Oxygen is also produced as a byproduct of photosynthesis, which is released through the stomata.

The role of stomata is not limited to gaseous exchange; they also play a vital role in regulating water loss through the process of transpiration. Transpiration is the loss of water vapor from the plant's surface to the atmosphere, which occurs when water is pulled up through the plant's roots and transported to the leaves.

Stomata regulate transpiration by opening and closing in response to environmental conditions, such as temperature and humidity.

Stomata are also essential for the uptake of essential nutrients, such as potassium, calcium, and magnesium. These nutrients are typically found in the soil and are taken up by the plant's roots.

However, to reach the plant's leaves, these nutrients must be transported through the plant's xylem, which is a network of tubes that runs throughout the plant. The stomata create a pathway for the movement of nutrients from the xylem to the plant's leaves.

Conclusion

In conclusion, stomata are a crucial component of plant anatomy that play a vital role in regulating gaseous exchange, transpiration, and nutrient uptake. The opening and closing of stomata are finely-tuned processes that are influenced by a range of environmental factors.

The study of stomata has significant implications for agriculture, plant biology, and our understanding of the Earth's climate history. Stomata have been fine-tuned through evolution to suit the specific needs of different plant species, and scientists can develop new strategies for improving crop yields and understanding the Earth's climate by studying them.

FAQs

Q1. What is the function of stomata in plants?

Ans. Stomata are small pores found on the surface of leaves, stems, and other plant organs. Their primary function is to regulate gaseous exchange in the plants by allowing carbon dioxide to enter and oxygen to exit. Stomata also play a critical role in regulating water loss by opening and closing in response to environmental conditions.

Q2. What are the different types of stomata found in plants?

Ans. There are three types of stomata found in plants: anisocytic, paracytic, and cyclocytic.

  • Anisocytic Stomata: These are found in dicotyledonous plants and have a single large pore surrounded by three subsidiary cells.

  • Paracytic Stomata: These are also found in dicotyledonous plants and have two parallel rows of subsidiary cells that run parallel to the stomatal pore.

  • Cyclocytic Stomata: These are found in monocotyledonous plants and have a single large pore surrounded by two or more subsidiary cells that are arranged in a circular or semi-circular pattern.

Each type of stomata has a unique structure that allows efficient exchange of gases while minimizing water loss.

Updated on: 27-Mar-2023

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