Protochlorophyll differs from chlorophyll in lacking

Protochlorophyll differs from chlorophyll in lacking 2 hydrogen atoms in one of its pyrrole rings.
Protochlorophyll is a green magnesium-containing pigment that is present in etiolated leaves and seedlings which develop in the dark and is converted to chlorophyll by reduction under the influence of light.
Photochlorophyll lacks two hydrogens at the 7 and 8 positions at the porphyrin part of the pyrrole ring.
Protochlorophyll has been detected in dark-grown roots of several species of plants from ferns to angiosperms.