title: ent-kaurene biosynthesis is enhanced by long photoperiods in the long-day plants Spinacia oleracea L. and Agrostemma githago L.
abstract: The effect of photoperiod on ent-kaurene biosynthesis was determined in the long-day (LD) plants spinach (Spinacia oleracea L.) and Agrostemma githago L. Further metabolism of ent-kaurene was blocked by application of the growth retardant tetcyclacis, and ent-kaurene accumulation was measured by isotopic dilution using gas chromatography-selected ion monitoring (GC-SIM) (E. Grosselindemann, J.E. Graebe, D. Stöckl, P. Hedden [1991] Plant Physiol 96: 1099-1104). In spinach, the rate of ent-kaurene accumulation in shoots grown under LD conditions was 3 times higher than in shoots grown under short-day (SD) conditions. ent-Kaurene also accumulated in fully expanded leaves, but at a lower rate than in shoots (15 and 55 pmol g-1 dry weight h-1, respectively). In Agrostemma, ent-kaurene accumulated at a rate 2.5 times higher in plants grown under LD conditions than in those grown under SD conditions. In spinach, enhanced ent-kaurene accumulation was detectable after 1 long day, and with exposure to additional long days, the rate of ent-kaurene accumulation increased further. Conversely, when plants were exposed to LD conditions and then returned to SD conditions, the rate of ent-kaurene accumulation decreased. Following tetcyclacis application, ent-kaurene accumulation was observed in all parts of spinach that were analyzed, but there were large quantitative differences between organs of different ages. As the leaves matured, ent-kaurene biosynthesis declined. Petioles accumulated more ent-kaurene than the corresponding leaf blades. It is concluded that stimulation of ent-kaurene biosynthesis by LD conditions leads to a higher rate of gibberellin biosynthesis, which is essential for stem elongation in rosette plants.
authors.affiliation: Michigan State University-Department of Energy Plant Research Laboratory, East Lansing 48824.
authors.forename: J A
authors.initials: JA
authors.lastname: Zeevaart
authors.forename: D A
authors.initials: DA
authors.lastname: Gage
mesh_terms: D003624:Darkness; D004224:Diterpenes / Q000378:metabolism*; D045786:Diterpenes, Kaurane; D007536:Isomerism; D008027:Light; D017440:Photoperiod; D010944:Plants / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects*; D014018:Tissue Distribution; D014230:Triazoles / Q000494:pharmacology; D014675:Vegetables / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects
chemical_list: D004224:Diterpenes; D045786:Diterpenes, Kaurane; D014230:Triazoles; C002627:kaurene; C053723:tetcyclacis