Who demonstrated that the extract of the infected plants of tobacco could cause infection in healthy plants?

$T$.$O$. Diener discovered a

Lichens are ecologically important as they

Assertion $A$: Viruses are considered as a link between living and non-living organisms.
Reason $R$: Viruses are non-living,but they are obligate parasites in living cells.
Which option is correct for Assertion $A$ and Reason $R$?

Lichens grow at a very slow rate ($1 mm$ per year). In how many years does a lichen mature?

Select the correct statement.