Question

In Cycas, fertilisation occurs through
A. Isogamy
B. Siphonogamy
C. Zoidiogamy
D. Both B and C

Answer 1

Hint: Cycas tree belongs to an ancient lineage that exhibits both Siphonogamy and Zoidogamy type of fertilization. Cycas belongs to Gymnosperms. Its taxonomy hierarchy includes Kingdom: Plantae, Family: Cycadaceae; Pers.
Class: Cycadopsida.

Complete answer:
Cycas belongs to the genus the Cycadophyta of the family Cycadaceae that belongs to a very ancient lineage. Cycas is a gymnosperm but not closely related to palm trees or fern trees or any other group of plants.
It is observed that the fertilization in Cycas occurs through both siphonogamy that is the formation of the pollen tube and zoidiogami that is the participation of ciliated male gametes.

Siphonogamy is a type of reproduction in plants in which pollen tubes get developed for the transfer of the male cells into the eggs. After pollination, pollen upon germination forms a pollen tube that is developed for the transfer of male cells to the eggs. It is a characteristic of all spermatocytes.

In Zooidogamy male gametes or antherozoids swim through a path of the water to the female gametes or archegonium. Found to take place in members of Algae, Bryophytes, Pteridophytes, and some Gymnosperms.

Hence in Cycas, fertilization occurs through. both siphonogamy and zoidiogami.
Hence, Both B and C are the correct answer.

So, option D is the correct option.

Note:
Isogamy is a type of sexual reproduction where male and female gametes show similar morphology.
The seed plants are siphonogamous whereas in the lower plants male cells swim to the egg through water film. So why the spermatocytes are sometimes called siphonogamous.