Question

In Cycas male cone and __ (A) ___ are borne on ___ (B) ___ tree
A. A = Megasporophyll, B = different
B. A = Female cone, B = different
C. A = Megasporangia, B = same
D. A = Female cone, B = same

Answer 1

Hint: Cycas plants are the exceptional group of cycads which do not form female cones and are dioecious.

Complete answer:
- Cycads are slow-growing gymnosperm species with individuals that are either male or female (Dioecious). Gymnosperms are characterized as trees with naked seeds. They produce haploid gametes known as microspores for male gametes and megaspore for female gametes. These spores are produced within sporangia known as microsporangia and megasporangia that are present on sporophylls (microsporophyll and megasporophyll). The sporophylls are arranged spirally to form compact strobili or lax or cones.
- But Cycas plants are the exceptional genus of Cycads. Cycas plants are Dioecious and are sporophyte (2n). They reproduce both by vegetative propagation and sexual reproduction. In sexual reproduction, the microsporophylls are arranged spirally to form a male cone, and megasporophylls are produced at the apex of the stem in succession with the leaves and do not aggregate to form a cone.

Hence, in Cycas male cones and megasporophyll are borne on different trees.

Additional Information:
- The eggs of Cycas are the largest among all species of the plant kingdom, with a size of about 1/2mm in diameter in Cycas circinalis.
- Also, the sperm of Cycas revolute is largest among all the plants, with a size of 200 to 300m in diameter.
- In Pinus belonging to gymnosperm has the male and female cones borne on different plants.

Note: Genus Cycas is an exceptional species in the Cycad Family when considering their reproductive organs. Siphonogamy refers to the formation of the pollen tube for the transport of male gamete into the female gamete to undergo fertilization (oogamy).