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How is fertilization in angiosperms different from fertilization in other types of plants?

Published in Plant Reproduction 2 mins read

Angiosperm fertilization is uniquely characterized by a process called double fertilization, which is absent in other plant types.

Double Fertilization: The Angiosperm Advantage

The primary difference lies in the phenomenon of double fertilization. According to provided resources, double fertilization, or two fertilization events, is unique to angiosperms and does not occur in any other type of plant or other organism. This process involves two sperm cells from a pollen grain fertilizing two different cells within the female gametophyte (also known as the embryo sac) inside the ovule.

What Happens During Double Fertilization?

After pollen is deposited on the stigma, it germinates and grows through the style to reach the ovule.

  1. One sperm cell fertilizes the egg cell, forming a zygote, which develops into the embryo of the seed.
  2. The other sperm cell fuses with the central cell (containing two polar nuclei) to form a triploid (3n) endosperm. The endosperm acts as a food-rich tissue that nourishes the developing embryo.

Significance of Double Fertilization

The evolution of double fertilization is a key factor in the success and diversification of angiosperms. Here’s why:

  • Efficient resource allocation: The endosperm is only formed after fertilization, ensuring resources are not wasted if fertilization fails. This provides a highly efficient method of nourishing the developing embryo.
  • Rapid seed development: The process contributes to quicker seed development compared to other plant groups.
  • Genetic diversity: The involvement of two sperm cells potentially enhances genetic diversity within the endosperm.

Contrast with Other Plants

In other plant groups, such as gymnosperms, ferns, and mosses, fertilization involves a single fusion of gametes (sperm and egg). There is no equivalent to the angiosperm endosperm. Instead, food reserves for the developing embryo are derived from the megagametophyte tissue, which is already present before fertilization.

Feature Angiosperms Other Plants (e.g., Gymnosperms)
Fertilization Type Double Fertilization Single Fertilization
Endosperm Formation After fertilization (triploid) Before fertilization (haploid)
Efficiency High resource efficiency Lower resource efficiency

In conclusion, the double fertilization process, creating both a zygote and a nutritive endosperm, is the defining difference in fertilization between angiosperms and other plants.