Polyamines in buds of apple as affected by temperature and their relationship to bud development

Abstract

The time course of changes in the concentrations of arginine and polyamines in spur buds of apple ( Malus domestica Borkh.) was studied. The trees were exposed to six temperature treatments: 13° and 13°C; 13° then 20°C; 20° and 20°C; 20° then 27°C; 27° and 27°C, and 27° then 13°C in two successive periods of 6–7 and 12 weeks, starting at full bloom. Shoot growth and flowering were recorded as well. In the first six weeks, the arginine concentration in spur buds did not differ much between temperatures, but thereafter an increase occurred, especially at the 27–27°C and 20–27°C regimes. The drop in temperature from 27° to 13°C at 6–7 weeks after bloom resulted in an increase of arginine that surpassed the 13–13°C and even the 27–27°C values. In general, the time course of changes in the concentration of total polyamines (PAs) was not pronounced and lacked consistency. The relation to temperature was the inverse of that of arginine; the level became lower with the rise in temperature. More than 80% of PAs were accounted for by spermidine and spermine. The pattern for concentrations for spermidine and putrescine in relation to temperature was generally similar to that for total polyamines, but the reverse holds for spermine. The rise of temperature at 6–7 weeks after bloom reduced the contents of spermidine and putrescine, but did not influence spermine. Conversely, the drop of temperature (27° to 13°C) increased the spermidine and putrescine levels, and produced a decline in spermine. The results are discussed in terms of a `passive' storage function for arginine and a more `active' function for polyamines in modulating bud growth activity. The relationship between polyamines and flower-bud formation is also discussed.