Question

Pick the correct group of all genera exhibiting homospory.
a. Lycopodium, Psilotum, Selaginella, Equisetum
b. Equisetum, Pteris, Salvinia, Psilotum
c. Salvinia, Pteris, Lycopodium, Selaginella
d. Equisetum, Psilotum, Lycopodium, Pteris

Answer 1

Hint: Homospory refers to the condition where plants produce one type of spore. Heterospory refers to the condition where plants produce two different kinds of spores namely microspore and megaspore. The microspores are small and are male and the female megaspore is large in size.

Complete answer:
Let's see the characteristics of the plants given in the options one by one and understand which of them produce homosporous and which plant produces heterosporous.
First let's see about Lycopodium. Lycopodium is a flowerless plant and they contain kidney shaped sporangia that bear only one kind of spore, hence homosporous and are present on the sporophylls (spore bearing leaves) in a cone shaped strobilus.
• The next option is Psilotum. Psilotum is a fern with synangia formed by the fusion of three sporangia which bear the spores. The spores are of similar structure and hence they are homosporous. The spores germinate to form the gametophyte.
• Selaginella produces two different kinds of spores (microspore and megaspore) and hence they are heterosporous. So as we can see, the options A and C are ruled out.
• Next coming to Equisetum. Equisetum bear spores under sporangiophores in the strobili. In most of the Equisetum species, the spore bearing shoots are not branched. The spores are identical, hence are homosporous.
• Pteris produces spores that are tetrahedral and trilete. When viewed proximally, they look triangular with rounded corners. The spores are identical and hence they are homosporous in nature.
• The last plant to be discussed from the options is Salvinia. The spores in Salvinia are of two different types, microspore and megaspore meaning they are heterosporous in nature. The spores are present in the sporangium. So, even option B is ruled out.

Hence, the correct answer is option (D).

Note: In heterosporous plants, the microspore gives rise to male gametophytic plants which leads to the formation of male gametes in them and similarly the megaspores give rise to female gametophytes which later produce the female gametes. The homospores give rise to bisexual gametophytes which bear both male and female structures on the same plant.