Question

Which of the following has a haplontic life cycle?
A. Wheat
B. Funaria
C. Polytrichum
D. Ustilago

Answer 1

Hint: In haplontic life cycle ,the dominant phase is haploid. The diploid phase is represented by zygote only. In this life cycle the dominant, photosynthetic phase of such plants is free-living gametophyte.

Complete answer:
1. Ustilago undergoes haplontic life cycle .
- In ustilago sporophytic generation is represented only by the one-celled zygote. There are no free-living sporophytes.
- Meiosis in the zygote results in the formation of haploid spores.
- The haploid spores divide mitotically and form the gametophyte.
- The dominant, photosynthetic phase in such plants is the free-living gametophyte.

2. Wheat undergoes a diplontic life cycle.
- In this the diploid sporophyte is the dominant, photosynthetic, independent phase of the plant.
- The gametophytic phase is represented by the single to the few-celled haploid gametophyte. This kind of life cycle is termed as diplontic.

3. Funaria and Polytrichum are both bryophytes. These undergo haplo -diplontic life cycle.
- These have an intermediate condition, both the phases are multicellular. However, they differ in dominant phases.
- A dominant, independent, photosynthetic, thalloid or erect phase is represented by a haploid gametophyte and it alternates with the short-lived multicellular sporophyte totally or partially dependent on the gametophyte for its anchorage and nutrition.

Hence, the correct answer is option D.

Note: In pteridophytes, the diploid sporophyte is represented by a dominant, independent photosynthetic, vascular plant body. It alternates with multicellular, saprophytic/autotrophic, independent but short-lived haploid gametophyte. Such a pattern is known as haplo-diplontic life cycle. All pteridophytes exhibit this pattern.