Which of the following has the minimum number of chromosomes in Angiosperms ?

Question

Accepted Answer

The correct option is 1: Haplopappus gracilis

*Haplopappus gracilis* (which is now often classified under the genus *Isocoma*) holds the remarkable distinction of possessing the absolute minimum number of chromosomes found within the entire Angiosperm (flowering plant) phylum. This small, North American native plant has a diploid chromosome number ($2n$) of only **4**, which means its haploid number ($n$) is just 2. In the vast and diverse world of flowering plants, where chromosome numbers can range into the hundreds, this species represents the genetic minimum, making it a record holder in plant cytology. This extremely low chromosome number made it historically and continues to make it an invaluable subject for genetic research, as it provides one of the simplest systems to study chromosome behavior during cell division (meiosis and mitosis), the fundamental organization of a plant genome, and the genetic basis of heredity. Its discovery provided a crucial baseline for understanding the incredible variability of chromosome counts across the plant kingdom.

The incorrect option is 2: Arabidopsis thaliana

*Arabidopsis thaliana* is incorrectly identified as the plant with the minimum number of chromosomes. Although it is famous as the primary model organism for plant biology due to its small size, short generation time, and manageable genome, its chromosome number is higher than the minimum. The diploid chromosome number for *Arabidopsis thaliana* is $2n=10$, which translates to a haploid number of $n=5$. This is still a relatively low number, making its genome sequencing and genetic manipulation relatively straightforward compared to other plants, but it does not hold the title for the absolute minimum number.

The incorrect option is 3: Ganoderma lucidum

*Ganoderma lucidum* is fundamentally incorrect because it is not an angiosperm. Angiosperms are flowering plants that belong to the kingdom Plantae, characterized by producing flowers and having seeds enclosed within an ovary (fruit). *Ganoderma lucidum*, on the other hand, is a species of **fungus**, commonly known as the Reishi mushroom, and belongs to the fungal division Basidiomycota. As fungi belong to a separate biological kingdom from plants, they cannot be considered in a question specifically about chromosome counts in the Angiosperm phylum.

The incorrect option is 4: Coptis teeta

*Coptis teeta* is an angiosperm, specifically a perennial herb famous for its medicinal properties, but its chromosome count is much higher than the minimum. This species typically has a diploid chromosome number of $2n=18$, which is significantly greater than the two pairs of chromosomes found in *Haplopappus gracilis*. Chromosome counts vary widely among plants, but $2n=18$ is a fairly average number for many plant families. Therefore, while correctly classified as a flowering plant, its actual chromosome number is far from the minimum.