Plants have these because root nodules<span> are formed when nitrogen fixing bacteria called "rhizobia" start to enter the cells of a host </span>plant<span>. Rhizobia normally live inside of the soil and they </span>can<span> exist without a host </span>plant<span>.</span>
Answer:
No,it is not important that it must be only fire it may be other source also
LOTIC ECOSYSTEMS, CONSISTING OF RIVERS AND MAINSTREAMS, FREE-FLOWING WATER.
