The reason monocots typically have flower petals in multiples of three, while dicots often have petals in multiples of four or five, boils down to their evolutionary differences and genetic makeup.
Monocots, which include plants like grasses and lilies, are characterized by their single seed leaves or cotyledons. When it comes to flowering, their floral structures follow a pattern that reflects their overall anatomical traits. This results in flowers with petal arrangements in threes, such as in orchids and tulips.
On the other hand, dicots, which encompass a broader range of plants including roses and sunflowers, typically exhibit a more varied structure. They have two cotyledons, and their flower structures often emerge in layers or whorls, which can lead to petals being grouped in fours or fives. This fundamental difference in seed structure and genetic programming is what gives rise to these distinct floral patterns.
In summary, the differences in petal arrangements between monocots and dicots are deeply rooted in their genetic evolution, reflecting how these plant groups have adapted to their environments over time.