INVESTIGATIONS ON PHOTOSYNTHETIC PIGMENTS IN LEMNACEAE .15. INFLUENCEOF THE SELECTIVE HERBICIDE 2,4-DICHLORPHENOXYACETIC ACID ON THE GROWTH AND PIGMENT SYNTHESIS IN MIXOTROPHICALLY, AUTOTROPHICALLY, AND HETEROTROPHICALLY CULTIVATED LEMNA-GIBBA PLANTS

In auto- and mixotrophically cultivated Lemna gibba plants (monocotyle dons) 10(-5) and 10(-6) mol . 1-1 2,4-dichlorphenoxyacetic acid (2,4-D ) cause a concentration-depending inhibition of the division growth, a considerable significant marked strong reduction of the dry weight as well as a biosynthesis inhibition of the photosynthetically active pi gments (chlorophyll a and b, beta-carotene, lutein, violaxanthin and n eoxanthin) in auto-, mixo-, and heterotrophic plants. The ratios betwe en the pigments are hardly influenced. Therefore chlorophylls and caro tenoids are bleached in like manner. Obviously, the frequently describ ed selectivity of 2,4-D does not depend on the systematic category (di cotyledons, monocotyledons) of the experimental plants, but on the her bicide's potential to invade the plant.