​A plant species with unisexual flowers has the following traits: floral longevity = 12 hours, pollen:ovule = 10:1, male and female flowers with synchronized anthesis. Given these, which of the following mutations would be most detrimental to seed set in this plant species?​

Correct option is A

(a) The pollen:ovule ratio drops to 3:1

The pollen:ovule ratio is a key indicator of reproductive success in flowering plants. A ratio of 10:1 in unisexual plants indicates a balance where sufficient pollen is produced to fertilize ovules effectively. Dropping this to 3:1 drastically reduces pollen availability, increasing the chance that ovules remain unfertilized. This can severely reduce seed set.

In wind or insect-pollinated plants, some pollen loss is expected during transfer. A lower pollen:ovule ratio means reduced fertilization efficiency, especially in species with short floral longevity (12 hours) and no overlap in flower sex organs (unisexual). Thus, mutation (a) severely compromises reproduction.

Hence, the correct answer is (a) The pollen:ovule ratio drops to 3:1.

Additional Information (All Options Explained):

• Option (a) – Correct: A significant drop in pollen:ovule ratio drastically reduces fertilization chances. Most detrimental to seed set.

• Option (b): Increasing floral longevity gives more time for pollination, possibly even benefiting seed set. Not harmful.

• Option (c): A 2-hour delay might slightly reduce efficiency, but not as severely as reducing pollen quantity. Not most detrimental.

• Option (d): Higher pollen:ovule ratio means more pollen – this might be energetically costly but not harmful to seed set.