Effect of 5-aminolevulinic acid on the pigment content of darkgrown hypocotyls of Phaseolus vulgaris

5-Aminolevulinic acid (ALA)-treatment of sections of dark-grown hypocotyls of kidney beans from the hook and downwards resulted in an additional biosynthesis of the protochlorophyll(ide) complexes Pchl(ide)_628-633, and Pchl(ide)_636-642, approximately proportional to the concentration originally present. A short light pulse given to sections treated with ALA for 6 h phototransformed the Pchl(ide)_650-657 originally present to chlorophyllide.
When the sections were kept in light for 6 h without ALA, chlorophyll was formed and only traces of protochlorophyll(ides) were left. The pigment concentration (weight per fresh weight) in different sections of the hypocotyls was compared with their cell volume. The concentration decreased towards the roots and this decrease is mainly a dilution effect due to a gradual increase of the cell volume downwards, but a change of the pigment concentration per plastid also takes place.