PROSTAGLANDINS AND RELATED SUBSTANCES IN PLANTS

Prostaglandins (PGs) have been detected in many different plants and c ertain microorganisms. A few prostaglandin-like compounds have also be en shown to occur in plants such as flax, Chromolaena morii, and aquat ic sedge; and direct precursors (arachidonic acid, di-homo-gamma-linol enic acid and eicosapentaenoic acid) have been detected in a variety o f plants and microorganisms, including certain red algae, brown algae, green algae, and saltwater diatoms. Furthermore, arachidonic acid has been found in mosses and a liverwort. It has also been reported that arachidonic acid occurs in certain angiosperms, namely, poplar (Populu s balsamifera), wheat germ oil, Aloe vera, and Allium sativum (garlic) . In our studies on the possible physiological effects of prostaglandi ns we found that a PG possibly has an effect on the flowering of the s hort-day plant Pharbitis nil. It has hastened flower formation by 28 d ays as compared with controls under inductive conditions (short days), and certain inhibitors of PG-biosynthesis inhibited flowering to a gr eater or lesser extent. In other physiological studies of prostaglandi ns, it was found that they have an effect on such aspects as GA(3)-con trolled responses in barley endosperm, inhibition of crown gall tumor formation on potato discs, and certain electron-flow reactions in isol ated chloroplasts. In corn leaf segments it has an effect on photosynt hesis, nucleic acid metabolism, and protein synthesis. The effect on f our plant bioassay systems was negligible. It has also been reported t hat PGs play a role in the regulation of cell membrane permeability.