Provide definitions/explanations for the following terms:
$(1)$ Heterocysts
$(2)$ Conidiophores

(N/A) $(1)$ Heterocysts are specialized cells found in certain filamentous cyanobacteria like $Nostoc$ and $Anabaena$. They are the primary sites of nitrogen fixation,where the enzyme nitrogenase functions in an anaerobic environment.
$(2)$ Conidiophores are specialized hyphal branches found in $Ascomycetes$ (sac fungi). They produce asexual spores called conidia exogenously (externally) at their tips. Upon germination,these conidia give rise to new mycelia.