Effect of photosynthetic photon flux density on postharvest flower bud opening of cut carnations with reference to carbon balance

摘要

Postharvest flower bud opening (FBO) was studied in cut shoots of the standard red carnation 'Nelson'. For each FBO treatment, six carnations harvested at Stage V were placed under photosynthetic photon flux density (PPFD) of 32 (P32), 123 (P123) or 225 (P225) Rmol m(-2) s(-1), with individual stem cut-ends in flower opening solution containing 30 g l(-1) sucrose (S30) or without sucrose (SO). The flower-opening angle in all the treatments increased rapidly for the first 12 h period, and increased steadily thereafter. The time required for FBO was reduced by increasing PPFD in the S30 treatments (60 h in P32-S30 (control), 48 h in P123-S30, 36 h in P225-S30). The time for FBO in P225-S0 was 120 h. There was no difference in flower quality score among the S30 treatments at the end of the FBO treatment whereas flower quality in P225-S0 was significantly (P<0.05) lower than in the S30 treatments. The results indicate that PPFDs of 123 and 225 mumol m(-2) s(-1) each combined with 30 g l(-1) sucrose in flower opening solution were effective for reducing the time required for FBO compared with the control, and that 30 g l(-1) sucrose in the flower opening solution cannot be eliminated for FBO treatment even when PPFD is increased to 225 mumol m(-2) s(-1). There was no marked difference in carbon-base integrated sucrose uptake from the flower opening solution per stem during FBO (CS) among the S30 treatments, and hourly average CS became greater with increasing PPFD. In the S30 treatments carbon-base integrated net CO2 exchange per stem during FBO (CNCE) increased with increasing PPFD, and hourly average CNCE in P225-S30 was greater than those in P32-S30 and P123-S30. Acceleration of FBO by an increase in PPFD among the S30 treatments may be attributed directly to increased rates of sucrose uptake and net CO2 exchange during FBO.