What is the Difference Between Leucoplast and Chloroplast

The main difference between leucoplast and chloroplast is that leucoplast does not contain any pigments whereas chloroplast contains pigments such as chlorophyll and carotenoids. 

Leucoplast and chloroplast are two types of plastids present in plants. They perform unique functions in plants. Furthermore, leucoplasts are a type of plastids which store nutrients including starch, fat, and proteins in plants while chloroplasts are responsible for undergoing photosynthesis.

Key Areas Covered

1. What is Leucoplast
     – Definition, Structure, Function
2. What is Chloroplast
     – Definition, Structure, Function
3. What are the Similarities Between Leucoplast and Chloroplast
     – Outline of Common Features
4. What is the Difference Between Leucoplast and Chloroplast
     – Comparison of Key Differences

Key Terms

Chlorophyll, Chloroplast, Leucoplast, Photosynthesis, Plastids, Storage

What is Leucoplast

Leucoplast is a type of plastid that performs a storage function inside the plant cell. Unlike chromoplasts and chloroplasts, leucoplasts are non-pigmented plastids. That means; they do not contain pigments like chlorophyll and carotenoids; thus, they remain colorless. Also, due to the lack of these pigments, leucoplasts generally occur in the non-photosynthetic and unexposed parts of plants including roots, bulbs, and seeds.

Figure 1: Amyloplasts in Potato

However, leucoplasts perform a storage function by storing starch, fat, and proteins. Furthermore, amyloplasts store starch; elaioplasts store fat; proteinoplasts store proteins. Also, the chloroplasts of vascular plants form pockets filled with tannin, transforming the chloroplast into a tannosome, which is a type of leucoplast. The breaking off of these pockets form a large vacuole of tannins later. Apart from the main storage function, some leucoplasts have essential biosynthetic functions including the synthesis of fatty acids.

What is Chloroplast

Chloroplast is the green color plastid found in plants responsible for photosynthesis. The green color comes from chlorophylls, the main types of photosynthetic pigments found in plants. The main function of chlorophylls is to capture energy from sunlight and store this energy in ATP and NADPH molecules during the light reaction of photosynthesis. The formed energy molecules are used to synthesize glucose by combining carbon dioxide and water during the dark reaction of photosynthesis. Apart from photosynthesis, chloroplasts may perform other functions including fatty acid synthesis, amino acid synthesis, and immune function in plants.

Figure 2: Chloroplasts

Furthermore, chloroplasts are characterized by the presence of two membranes and chlorophyll in a higher concentration. Also, chloroplasts contain DNA, proving their emergence in eukaryotic cells through endosymbiosis. Moreover, chloroplasts in ripening, aging or stressed parts of plants transform into chromoplasts through a massive increase in the accumulation of carotenoid pigments.

Similarities Between Leucoplast and Chloroplast

• Leucoplast and chloroplast are two types of plastids present in plants.
• Undifferentiated plastids known as proplastids may differentiate into both types of plastids: leucoplast and chloroplast.
• Furthermore, both are rounded in shape.
• They contain DNA.
• Also, they are enclosed by two membranes.
• Moreover, both plastids perform important functions in plants.
• And, both leucoplast and chloroplast are capable of transforming into other types of plastids.

Difference Between Leucoplast and Chloroplast

Definition

Leucoplast refers to a colorless organelle found in plant cells, used for the storage of starch or oil, while chloroplast refers to a plastid in green plant cells which contains chlorophyll and in which photosynthesis takes place. Thus, this is the fundamental difference between leucoplast and chloroplast.

Pigments

While leucoplast does not contain pigments, chloroplast contains pigments including chlorophylls and carotenoids. This is the main difference between leucoplast and chloroplast.

Color

Therefore, leucoplast is colorless while chloroplast is green in color.

Internal Structure

Furthermore, leucoplasts contain a cisternal or tubular stroma reticulum connected with the intermembrane space of the envelope while chloroplasts contain an autonomous central system of thylakoids structurally independent from the envelope. Hence, this is another difference between leucoplast and chloroplast.

The density of the Stroma

Also, another difference between leucoplast and chloroplast is that the stroma of the leucoplast is less dense while the stroma of the chloroplast is denser.

Function

Functionally, leucoplast is responsible for the storage of nutrients including starch, fat, and proteins while chloroplast is responsible for undergoing photosynthesis. Hence, this is the functional difference between leucoplast and chloroplast.

Other Functions

Moreover, leucoplasts are involved in the biosynthesis of fatty acids such as palmitic acid, many amino acids, and tetrapyrrole compounds such as heme while chloroplasts are involved in the biosynthesis of fatty acids and amino acids and perform an immune function in plants.

Occurrence

Another difference between leucoplast and chloroplast is that leucoplasts mainly occur in the unexposed parts of a plant while chloroplasts occur in the photosynthetic parts exposed to the light. 

Transformation

Leucoplast can transform into amyloplasts, elaioplasts or proteinoplasts while chloroplasts in aging, ripening or stressed parts of the plant transform into chromoplasts through a massive increase in the accumulation of carotenoid pigments. This is one other difference between leucoplast and chloroplast.

Conclusion

Leucoplast is a type of plastid responsible for storing nutrients including proteins, starch, and fat. Also, it does not contain pigments; therefore, leucoplast is colorless. In addition, it occurs in the unexposed parts of the plant. In comparison, chloroplast is the plastid responsible for undergoing photosynthesis in plants. It contains photosynthetic pigments known as chlorophyll and carotenoids. Therefore, chloroplasts are green in color and they occur inside the cells of the photosynthetic parts of the cell. This is the difference between leucoplast and chloroplast.

References:

1. 1. Kochunni, Deena T, and Jazir Haneef. “Plastids – Leucoplasts, Chromoplasts and Chloroplasts.” Biology Exams 4 U, Available Here.
2. Carde, J P. “Leucoplasts: a Distinct Kind of Organelles Lacking Typical 70S Ribosomes and Free Thylakoids.” Current Neurology and Neuroscience Reports., U.S. National Library of Medicine, May 1984, Available Here.

Image Courtesy:

1. “Potato – Amyloplasts” (CC BY-SA 3.0) via Commons Wikimedia  
2. “Plagiomnium affine laminazellen” By Kristian Peters — Fabelfroh – Self-photographed (CC BY-SA 3.0) via Commons Wikimedia