Ethylene biosynthesis, carbohydrate metabolism and phenylalanine ammonia-lyase activity in gravireacting Kniphofia flower stalks.
Woltering, E. J.; Somhorst, D.; Beekhuizen, J. G.; Spekking, W. T. J.;
Acta Horticulturae Year: 1991 Issue: No. 298 Pages: 99-109 Ref: 24 ref.
1991
บทคัดย่อ
Cut Kniphofia flower stems were recut to 45 cm length and placed in 30 ml plastic tubes filled with tap water. Between 80 and 100 stems were kept vertically and another group was kept horizontally, at 20 deg C, 60% RH and continuous light (15 micro mol m-2 s-1). Stem bending was monitored and the increase in length of a 10 cm stem section just beneath the flower head was regularly measured. Ethylene production, total ACC content and ethylene-forming enzyme (EFE) and PAL activities of this 10 cm stem section were measured in both intact and longitudinally halved sections. In a further experiment, inflorescences were treated with ethylene, 2,5-norbornadiene, CO2, water, aminooxyacetic acid or silver thiosulphate for 20 h, after which the increase in length of the 10 cm stem section in vertically placed inflorescences was measured and the degree of bending was measured in horizontally placed inflorescences. CO2 production and starch and sugar contents of the 10 cm stem sections were measured. Gravistimulation-induced bending of Kniphofia flower stems was due to an approximately 85% growth inhibition of the upper side of the stem and a slightly increased growth rate of the lower side. ACC synthase activity (calculated from data on ethylene production and total ACC content) and ethylene production increased in the lower half of the gravistimulated stems, whereas no changes were observed in the upper halves or in the vertical stems. EFE and PAL activities, CO2 production and the contents of starch and soluble sugars were similar in upper and lower halves. All chemical treatments significantly inhibited the growth of vertically placed flower stems but had no effect on the gravitropically induced bending of the stem. The results indicate that changes in ethylene production or carbohydrate metabolism play no role in flower stem gravitropism.