Effects of abscisic acid on content and biosynthesis of terpenoids in Cannabis sativa at vegetative stage

The influence of abscisic acid (ABA) on plastidial and cytosolic terpenoids and on two key enzymes for terpenoid biosynthesis was determined in vegetative stage of Cannabis sativa L. Low concentration of ABA (1 μM) increased 1-deoxy-D-xylulose 5-phosphate synthase (DXS) activity in treated plants in comparison to control plants. The amounts of chlorophyll a and carotenoids increased in response to ABA treatment but chlorophyll b content declined. The accumulation of α-tocopherol was stimulated only by 10 μM ABA. The ABA-treated plants showed a decline in 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) activity which was followed by a decrease in squalene and phytosterol content. ABA also decreased tetrahydrocannabinol (THC) and cannabidiol (CBD) contents. The essential oil had higher ratios of monoterpenes to sesquiterpenes as ABA-treated plants had less numbers of sesquiterpenes in comparison with control plants. Influence of ABA on the amounts of sesquiterpenes was different, some of them showed decrease of content and others increase of content.