Double fertilization outcome in flowering plants: What is the usual ploidy of the endosperm in angiosperms after fertilization?

Introduction / Context:
Angiosperms exhibit double fertilization, a hallmark of the group that yields both a zygote and nutritive tissue called endosperm. Recognizing endosperm ploidy is central to understanding seed development and the unique reproductive biology of flowering plants.

Given Data / Assumptions:

• One sperm fertilizes the egg cell.
• A second sperm fuses with the central cell containing two polar nuclei.
• Standard angiosperm condition is two maternal plus one paternal genome in endosperm.

Concept / Approach:
Endosperm typically forms when one sperm nucleus fuses with two polar nuclei, creating a primary endosperm nucleus with 3n ploidy. Although exceptions exist in a few species, the textbook norm is triploid endosperm.

Step-by-Step Solution:

Verification / Alternative check:
Botany texts and seed biology references present 3n endosperm as the usual result of double fertilization in angiosperms.

Why Other Options Are Wrong:

• Haploid or diploid: do not match the canonical fusion event of two polar nuclei with one sperm.
• Tetraploid: not the standard outcome.
• Variable in all cases: exceptions exist but the typical case is triploid.

Common Pitfalls:
Confusing gymnosperm nutritive tissue (haploid from female gametophyte) with angiosperm endosperm (usually triploid).

Final Answer:
Triploid (3n)