What is the Difference Between Chlorenchyma and Aerenchyma

The main difference between chlorenchyma and aerenchyma is that chlorenchyma is a form of parenchyma, containing chloroplasts, but aerenchyma is another form of parenchyma, containing large air spaces. Furthermore, chlorenchyma mainly occurs in the mesophyll of leaves of all green plants, but aerenchyma occurs in the stems and leaves of aquatic plants. Moreover, the main function of chlorenchyma is to undergo photosynthesis, but the main function of aerenchyma is to provide buoyancy and to help aquatic plants to float. 

Chlorenchyma and aerenchyma are two types of parenchyma cells. Generally, parenchyma is a form of ground tissue with living cells, having primary cell walls. Also, it may occur in the cortex,  pericycle,  pith, and medullary rays in the primary stem and root of plants. 

Key Areas Covered 

1. What is Chlorenchyma
     – Definition, Structure, Function
2. What is Aerenchyma
     – Definition, Structure, Function
3. What are the Similarities Between Chlorenchyma and Aerenchyma
     – Outline of Common Features
4. What is the Difference Between Chlorenchyma and Aerenchyma
     – Comparison of Common Features

Key Terms 

Aerenchyma, Aquatic Plants, Chlorenchyma, Mesophyll, Parenchyma, Photosynthesis

What is Chlorenchyma 

Chlorenchyma is a type of parenchyma cells; especially, containing chloroplasts. Here, the parenchyma is a type of ground tissue with living cells and whose main function is to fill spaces in different parts of the plant body. However, as chlorenchyma contain chloroplasts, its main function is to undergo photosynthesis. Hence, chlorenchyma cells occur in all types of green plants in the mesophyll of leaves. Furthermore, the mesophyll layer occurs just below the epidermis, and it is is the primary location for photosynthesis. Besides, in most flowering plants and ferns, two layers of mesophyll occur immediately beneath the epidermis. They are palisade parenchyma and spongy parenchyma. 

Figure 1: Mesophyll

Of the above two layers, the palisade parenchyma is the upper layer of parenchyma, containing vertically elongated cells. Also, the two significant features of them are the presence of small air spaces between cells and numerous chloroplasts in comparison to the bottom spongy parenchyma. In contrast, the spongy parenchyma is more spherical in shape and contain large air spaces. Moreover, the leaf is the main organ responsible for undergoing photosynthesis, showing adaptations to increase the efficiency of the process. So, the above air spaces connect with the stomata underside of the leaf for efficient gas exchange.  Also, apart from the mesophyll, photosynthetic parenchyma may occur in other photosynthetic parts of the plant as well. 

What is Aerenchyma 

Aerenchyma is another specialized form of parenchyma, containing large air intercellular air spaces or air channels. Usually, this type of air spaces can occur in the leaves, stems, and roots as well. However, these air-filled cavities permit efficient gas exchange by providing low-resistance internal pathways. Furthermore, aerenchyma especially occurs in the leaves and stems of aquatic plants. Thus, this helps to float plants by providing buoyancy.

Figure 2: Aerenchyma

Moreover, in wetlands, aerenchyma prevents hypoxia in the soil. Normally, soil microorganisms use oxygen at a rate higher than the rate of diffusion of oxygen to the soil through the water. Therefore, the soil becomes hypoxic in wetlands. Also, aerenchyma in aquatic plants such as water lilies produces a mass flow of atmospheric air through the leaves to rhizomes where the leakage of oxygen through the pores of rhizomes produces a small rhizosphere of oxygenated soil. 

Similarities Between Chlorenchyma and Aerenchyma  

• Chlorenchyma and aerenchyma are two forms of parenchyma cells.  
• However, they are specialized forms of parenchyma to a certain function apart from filling spaces.  
• Both remain alive even after their maturation.  
• They have a thin cell wall. 

Difference Between Chlorenchyma and Aerenchyma 

Definition 

Chlorenchyma refers to a type of parenchyma tissue that contains chloroplasts, which is photosynthetic. Meanwhile, aerenchyma refers to another type of parenchyma tissue, which contains air spaces and is mainly found in many aquatic plants. 

Significance 

Cholerenchyma contains chloroplasts, while aerenchyma contains large air spaces. 

Occurrence 

Chlorenchyma mainly occurs in the mesophyll of leaves of all green plants while, aerenchyma occurs in the stems and leaves of aquatic plants.  

Function 

The main function of chlorenchyma is to undergo photosynthesis, but the main function of aerenchyma is to provide buoyancy and to help aquatic plants to float. 

Conclusion 

Chlorenchyma is a type of parenchyma tissue, especially containing chloroplasts. Therefore, it undergoes photosynthesis. Also, this type of parenchyma cells occurs in the mesophyll of all green plants. On the other hand, aerenchyma is another type of parenchyma, containing large air-filled spaces. So, it is responsible for providing buoyancy to the aquatic plants, aiding their floating. On that account, aerenchyma cells occur in their stems and leaves. Nevertheless, both chlorenchyma and aerenchyma are two types of specialized parenchyma cells. However, the difference between chlorenchyma and aerenchyma is due to their form of specialization. 

References:

1. “Ground Tissue.” Wikipedia, Wikimedia Foundation, 14 Feb. 2020, Available Here.
2. “Aerenchyma.” Wikipedia, Wikimedia Foundation, 7 Nov. 2019, Available Here.

Image Courtesy:

1. “Leaf Tissue Structure” By Zephyris – Own work (CC BY-SA 3.0) via Commons Wikimedia   
2. “Aerenchyma2” By User:Bb143143 – Self-photographed (CC BY-SA 3.0) via Commons Wikimedia