Question

Select one of the following pairs of important features distinguishing gnetum from cycas and pinus and showing affinities with angiosperms.
A. Perianth and no integuments.
B. Embryo development and apical meristem.
C. Absent of resin duct and leaf venation.
D. Presence of vessel elements and the absence of archegonia.

Answer 1

Hint: Important features distinguishing gnetum from cycas and pinus and showing affinities with angiosperms are in the structure of their xylem and in their reproductive structure.

Complete answer:
• Gymnosperms- these are the plants whose seeds are not enclosed in an ovary.
• Gnetum belongs to the order Gnetales of gymnosperms. They have vessels elements in the xylem unlike the other gymnosperms
• The leaves of the gnetum show reticulate venation which is the character found in the angiosperms
• Gnetum has no archegonia. Some free nuclei present as eggs. The female gametophyte initially is partially developed and developed fully after fertilization.
• The presence of short apices is the characteristic of gnetum which is also found in angiosperms.
• The ovules of the gnetum are also enclosed.
• The resin duct is present in both gymnosperms and angiosperms but the best commercial resins are extracted from gymnosperms.

Hence, the correct answer is option (D).

Additional information:
Gnetum belongs to gymnosperms but it also has some characteristics similar to those of angiosperms and thus due to such characters gnetum is considered as the connection link between gymnosperms and angiosperms. Also, the wood of angiosperms is called hardwood due to the presence of fibers whereas gymnosperms do not have fiber thus their wood is called softwood.

Note: Cycas, pinus, and gnetum all belong to the class of gymnosperms. This characteristic of gnetum separates itself from the gymnosperms but also it shows affinities towards angiosperms. Gymnosperms do not have an enclosed ovary.