Question

The process during double fertilization in which non-motile male gametes are carried through a hollow pollen tube is called:

• A. chalazogamy
• B. porogamy
• C. mesogamy
• D. siphonogamy

Hint:

{Key Exam Tip:}
- {Siphonogamy = Transport mechanism (pollen tube)}
- {Porogamy / Chalazogamy / Mesogamy = Entry routes into ovule}
Always distinguish between \textit{mode of transport} and \textit{site of entry} in such questions.

Answer 1

The Correct Option is D

Concept:
In flowering plants (angiosperms), fertilization involves the transfer of male gametes from the pollen grain to the embryo sac. Since male gametes are non-motile, they cannot move on their own. Instead, they are transported via a specialized structure called the pollen tube. This entire mechanism of transporting male gametes through the pollen tube is known as siphonogamy. It is a defining feature of higher plants and ensures successful fertilization without the need for water as a medium. Different modes of pollen tube entry into the ovule are:

• Porogamy: Entry through the micropyle (most common)
• Chalazogamy: Entry through the chalaza
• Mesogamy: Entry through the integuments or middle region

However, these terms describe the path of entry, whereas siphonogamy refers to the method of gamete transport.
Step 1: Understanding double fertilization.
In angiosperms, double fertilization involves:

• One male gamete fusing with the egg to form a zygote
• Another male gamete fusing with polar nuclei to form endosperm

Both male gametes are delivered via the pollen tube.
Step 2: Identifying the transport mechanism.
Since male gametes are non-motile, they rely entirely on the pollen tube for movement from the stigma to the ovule.
Step 3: Matching with the correct term.
The process of transporting non-motile male gametes through a pollen tube is specifically termed: \[ Siphonogamy \]
Step 4: Eliminating incorrect options.

• (A) Chalazogamy $\rightarrow$ Refers to entry through chalaza, not transport
• (B) Porogamy $\rightarrow$ Entry through micropyle
• (C) Mesogamy $\rightarrow$ Entry through integuments
• (D) Siphonogamy $\rightarrow$ Correct (transport via pollen tube)

Final Answer: \(\boxed{\text{Siphonogamy}}\)