What is the Difference Between Vegetative and Generative Cell

The main difference between vegetative and generative cell is that vegetative cell produces a tube cell whereas the generative cell produces two sperm cells during the pollen development. Furthermore, the vegetative cell is responsible for the production of the pollen tube while the sperms produced from the generative cell are responsible for undergoing fertilization.

Vegetative and generative cell are two types of cells present in the pollen grain of higher plants. Moreover, vegetative cells are non-reproductive while generative cells are reproductive.

Key Areas Covered

1. What is a Vegetative Cell
     – Definition, Structure, Importance
2. What is a Generative Cell
     – Definition, Structure, Importance
3. What are the Similarities Between Vegetative and Generative Cell
     – Outline of Common Features
4. What is the Difference Between Vegetative and Generative Cell
     – Comparison of Key Differences

Key Terms

Fertilization, Generative Cell, Pollen Grain, Pollen Tube, Sperm Cell, Vegetative Cell

What is a Vegetative Cell

The vegetative cell is one of the two types of cells present in the pollen grain in higher plants, and the second type of cells is generative cells. Both types of cells are formed by the asymmetric cell division of the microspore nucleus formed by meiosis during the early stages of pollen development. Prior to this asymmetric cell division, the nucleus of the microspore migrates into one side of the cell and a large vacuole is also formed. Following asymmetric cell division, a large vegetative cell and a small reproductive cell occur. Here, both types of cells are haploid as the microspore nucleus is haploid.

Figure 1: Fate of vegetative and Generative Cells

Furthermore, following pollination, the vegetative cell produces the pollen tube by serving as the pollen tube cell. The pollen tube is responsible for carrying sperm nuclei from the stigma to the ovule of the flower of angiosperms. But, it does not undergo fertilization by fusing with egg cells. Therefore, the vegetative cell is considered as a non-reproductive cell. Thus, the morphology and the physiology of the vegetative cell also do not resemble a reproductive cell as the generative cell does. Furthermore, the cytoskeleton of vegetative cells is highly dynamic and it polymerizes at very high rates, providing the characteristic mechanical properties to the pollen tube. Pollen tube undergoes destruction after the pollen tube rupture to release sperm cells.

What is a Generative Cell

The generative cell is the second type of cells produced through the asymmetric cell division of the microspore. Following the cell division, the formation of the cell wall of the generative cell is marked by the accumulation of osmiophilic lipid droplets in the cytoplasm of the vegetative cell lining the cell wall of the generative cell. In addition, the vegetative cell shows accumulations of amyloplasts packed with starch in its cytoplasm followed by the cell division.

Figure 2: Double Fertilization in Angiosperms

However, the main function of the generative cell is to serve as the reproductive cell of the pollen grain. Therefore, following pollination, it develops two sperm cells in angiosperms. One sperm cell fuses with the egg cell to form the zygote, which develops into a seed later. The second sperm cell fuses with the binucleate central cell, forming a primary endosperm cell. We call this process double fertilization.

Similarities Between Vegetative and Generative Cell

• Vegetative and generative cell are two types of cells in the pollen grain of higher plants.
• They occur in all seed plants.
• Also, both are surrounded by a thin, delicate cell wall known as intine and a tough, resistant outer layer known as exine.
• Furthermore, both types of cells are haploid and they are produced through the asymmetric mitotic cell divisions of the haploid microspore.
• They play an important role in the fertilization of the female gamete in these plants.
• Moreover, both cells contain replication-dependent, somatic types of histones.

Difference Between vegetative and Generative Cell

Definition

Vegetative cell refers to one of the two cells that is produced by division of the microspore nucleus in the development of the male gametophyte in higher plants and that functions in the development of the pollen tube. In contrast, generative cell refers to a cell of the male gametophyte or pollen grain in seed plants that gives rise to the sperm cells. Thus, this explains the main difference between vegetative and generative cell.

Reproductivity

A major difference between vegetative and generative cell is that vegetative cell is non-reproductive while generative cell is reproductive.

Size

Moreover, vegetative cells are large than generative cells.

DNA Repair

While vegetative cell lacks DNA repair mechanisms, generative cell efficiently undergoes DNA repair mechanisms.

Nucleus

The nucleus is also a difference between vegetative and generative cell. The former contains a dormant nucleus while the latter contains an actively-dividing nucleus.

Amount of DNA

Moreover, the vegetative cell contains a small amount of DNA while the generative cell contains a higher amount of DNA.

Chromatin

While the vegetative cell contains diffuse chromatin, the generative cell contains highly-condensed chromatin.

Histones

In addition, the vegetative cell contains replication-independent, vegetative nucleus-specific histone variant (H3. 3) while generative cell contains replication-independent, generative and sperm nuclei-specific histone variants (H2A, H2B, and H3).

Nucleolus

Furthermore, the nucleolus of the vegetative cell is large while the nucleolus of the generative cell is small.

Cytoskeleton

The vegetative cell contains a highly dynamic cytoskeleton with high rates of proliferation while the cytoskeleton is not dynamic in the generative cell.

Cytoplasm

Whereas the cytoplasm of the vegetative cell is short-lived,  the cytoplasm of the generative cell is longer-lived.

Organelle Distribution

Organelle distribution is also a difference between vegetative and generative cell. The cytoplasm of the vegetative cell contains more amyloplasts and osmiophilic lipid droplets while the cytoplasm of the generative cell does not accumulate amyloplasts and osmiophilic lipid droplets.

RNA in the Cytoplasm

Additionally, the cytoplasm of the vegetative cell is rich in RNA while the cytoplasm of the generative cell contains no RNA.

Amount of Proteins

Another difference between vegetative and generative cell is that the vegetative cell contains two-times the amount of proteins than the generative cell.

Acidity of Proteins

Moreover, the proteins in the vegetative cell are more acidic while the proteins in the generative cell are less acidic.

Following Pollination

The vegetative cell produces the pollen tube while the generative cell produces two sperm cells. Hence, this is also an important difference between vegetative and generative cell.

Function

Most importantly, vegetative cells are responsible for delivering sperm cells to the ovule while sperm cells produced from the generative cell are responsible for undergoing fertilization by fusing with the egg cell.

Conclusion

The vegetative cell is one of the two cells in the pollen tube. It is responsible for the production of the pollen tube following pollination. Moreover, the pollen tube delivers the sperm cells through the tissues of the female parts of the flower to the ovule. The generative cell is the other type of cell in the pollen. It produces two sperm cells after pollination. One of these sperm cells fuses with the egg cell and the other takes part in the formation of the endosperm in angiosperms. Therefore, the main difference between vegetative and generative cell is their function.

References:

1. Tanaka, Ichiro. “Differentiation of Generative and Vegetative Cells by Unequal Cell Division.” Plant Morphology, vol. 18, no. 1, 2006, pp. 13–18., doi:10.5685/plmorphol.18.13.

Image Courtesy:

1. “Angiosperm life cycle diagram-en” By LadyofHats Mariana Ruiz – Based on an image from Judd, Walter S., Campbell, Christopher S., Kellog, Elizabeth A. andStevens, Peter F. 1999. Plant Systematics: A PhylogeneticApproach.Sinauer Associates Inc.ISBN 0-878934049. (Public Domain) via Commons Wikimedia  
2. “Double Fertilization” By original uploader – Triploid at English Wikipedia. – Transferred from en.wikipedia to Commons. (CC BY 3.0) via Commons Wikimedia