Enzyme of the plastid non-mevalonate pathway for isoprenoid biosynthesis that converts 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate into isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). Is essential for chloroplast development. H2O + isopentenyl diphosphate + 2 oxidized [2Fe-2S]-[ferredoxin] = (2E)-4-hydroxy-3-methylbut-2-enyl diphosphate + 2 H(+) + 2 reduced [2Fe-2S]-[ferredoxin] dimethylallyl diphosphate + H2O + 2 oxidized [2Fe-2S]-[ferredoxin] = (2E)-4-hydroxy-3-methylbut-2-enyl diphosphate + 2 H(+) + 2 reduced [2Fe-2S]-[ferredoxin] Binds 1 [4Fe-4S] cluster per subunit. Isoprenoid biosynthesis; dimethylallyl diphosphate biosynthesis; dimethylallyl diphosphate from (2E)-4-hydroxy-3-methylbutenyl diphosphate: step 1/1. Isoprenoid biosynthesis; isopentenyl diphosphate biosynthesis via DXP pathway; isopentenyl diphosphate from 1-deoxy-D-xylulose 5-phosphate: step 6/6. Homodimer. Expressed in roots, stems, leaves, flowers and siliques. Circadian-regulated with a peak in the late period of dark phase and early period of the light phase. Albino phenotype and seedling lethal when homozygous. The phenotype is caused by an early arrest in chloroplast differentiation. Belongs to the IspH family. Truncated N-terminus.