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A prokaryotic autotrophic nitrogen fixing symbiont is found in
A
$Pisum$
B
$Alnus$
C
$Cycas$
D
$Cicer$
Detailed Solution
A prokaryotic, autotrophic nitrogen fixer is a cyanobacterium (blue-green alga) such as $Anabaena$ or $Nostoc$, which is photosynthetic.
$Cycas$ has specialised coralloid roots that are associated with nitrogen-fixing cyanobacteria ($Anabaena\ cycadae$, $Nostoc$).
$Pisum$ (pea) and $Cicer$ (gram) are legumes whose root nodules contain $Rhizobium$, which is prokaryotic but heterotrophic.
$Alnus$ root nodules contain $Frankia$, an actinomycete, which is also heterotrophic.
Hence the prokaryotic autotrophic nitrogen-fixing symbiont is found in $Cycas$.
$Cycas$ has specialised coralloid roots that are associated with nitrogen-fixing cyanobacteria ($Anabaena\ cycadae$, $Nostoc$).
$Pisum$ (pea) and $Cicer$ (gram) are legumes whose root nodules contain $Rhizobium$, which is prokaryotic but heterotrophic.
$Alnus$ root nodules contain $Frankia$, an actinomycete, which is also heterotrophic.
Hence the prokaryotic autotrophic nitrogen-fixing symbiont is found in $Cycas$.