Effects of photosynthetic photon flux density and inorganic nutrient salts on post-harvest flower bud opening of tight bud-cut carnations

Abstract

SummaryThe effects of photosynthetic photon flux density (PPFD) and inorganic nutrient salts (INS) on flower bud opening (FBO) of the standard red carnation ‘Francesco’ cut at the ‘tight bud’ stage were investigated. For each treatment, seven bud-cut ‘Francesco’ carnations were placed in a ventilated transparent cylindrical-container (25° ± 1°C) under continuous light with a PPFD of 30 µmol m–2 s–1 (P30) or 150 µmol m–2 s–1 (P150) with the cut ends in flower opening solution (25 mg l–1 AgNO3, 200 mg l–1 8-hydroxyquinoline citrate and 30 g l–1 sucrose) with (INS) or without (N) the addition of INS recommended for hydroponic carnation culture. A PPFD of 150 µmol m–2 s–1 and addition of INS to the flower opening solution reduced the time required for FBO. The mean times to reach full FBO from the ‘tight bud’ stage (beginning of emergence of petals) of carnations were 7.0 d for P30-INS, 5.0 d for P150-INS, 7.5 d for P30-N, and 6.0 d for P150-N in the Summer Experiment (A). Total sucrose uptake in the P150 treatments was greater than in the P30 treatments during FBO, and hourly average sucrose uptake in the P150 treatments was twice that in the P30 treatments. Carbon from net CO2-exchange (CNCE) and carbon from gross photosynthesis (CGP) per stem under P150 was higher than under P30, but there was no difference between the INS and N treatments. Hourly average CGP in P150 was 2.2- to 2.5-times that in P30 during FBO. The results indicate that higher PPFD was effective in reducing the time required to achieve FBO for carnations cut at the ‘tight bud’ stage. Acceleration of FBO of tight bud-cut carnations by higher PPFD may be attributed to increased rates of sucrose uptake and net CO2-exchange during FBO.The addition of INS to the flower opening solution also stimulated bud opening.