Question

Select the mismatch.
A. Equisetum-Homosporous
B. Pinus- Dioecious
C. Cycas- Dioecious
D. Salvinia- Heterosporous

Answer 1

Dioecious is used for organism which have male and female sex organs in male and female organisms respectively. Heterosporous refers to the occurrence of two different types of spores: mega and microspores on the same plant while homospore produces identical cells.

Complete answer:
A. Equisetum are Pteridophytes which are known to be the first terrestrial vascular plants. They mainly live in the moist and shady places. Some of the pteridophytes have large leaves and some contains small leaves. Plants are seedless as well as flowerless. Equisetum belongs to the class of Sphenopsida of Pteridophytes where the stem contains distinct nodes and internodes. Branches are arranged in whorls. Equisetum is homosporous in which the spores are formed only of single type and the gametophyte is photosynthetic.
B. Pinus is the largest group of the gymnosperms known as conifers. The body of Pinus is differentiated into true roots, stem and pointed needle like stems. Pinus is a monoecious gymnosperm having both male and female cones on the same plant and male and female strobilus are borne on separate strobili. C. Cycas is a gymnosperm plant that belongs to the Cycadaceae family. It has unbranched stems. It has a small specialized root called a coralloid root which has an association with the nitrogen fixing Cyanobacteria. The male and female strobili are present on different trees so it is a dioecious plant. D. Salvinia belongs to the phylum Pteridophyta. They are heterosporous plants, which means they produce two different types of spores. They represent a significant step towards the evolution of seed habit because the embryo develops into the female gametophyte which is retained on the parent sporophyte.

Hence, the correct answer is option (B).

Note: The two different kinds of spores are microspores and megaspores. Microspores are the small sized spores that give rise to the male gametophyte or the antheridium. Megaspores are quite larger than microspores that give rise to the female gametophyte or the archegonium. The male and female gametes fuse and zygote is formed. The zygote further develops into an embryo and it takes place within the female gametophyte. This female gametophyte is retained on the parent sporophyte for a considerable period of time.