Catalyzes the reduction of geranylgeranyl diphosphate to phytyl diphosphate, providing phytol for both tocopherol and chlorophyll synthesis. 3 NADP(+) + phytyl diphosphate = geranylgeranyl diphosphate + 3 H(+) + 3 NADPH Porphyrin-containing compound metabolism; chlorophyll biosynthesis. Cofactor biosynthesis; tocopherol biosynthesis. Part of the FLU-containing chloroplast membrane complex composed of FLU, CRD1, PORB, PORC, CHLP and HEMA1. Expressed during deetiolation and during chloroplast to chromoplast transformation. Belongs to the geranylgeranyl reductase family. ChlP subfamily. Extended N-terminus.