2010 Volume 79 Issue 3 Pages 301-307
The indoor display life of potted carnations ‘Annemarie’ is limited to 12 days because of its low flowering ability under low-light conditions (15 μmol·m−2·s−1 PPFD, 20°C). When commercially grown potted carnations were transferred to indoor (low-light) conditions, dry weight and total soluble carbohydrates (TSC) decreased during the first 6 days after transfer (DAT), remained constant until 10 DAT, and then increased at 14 DAT. Glucose, fructose, and sucrose contents decreased markedly during the first 6 DAT and then gradually decreased. Pinitol content was unchanged until 10 DAT and then slightly increased at 14 DAT. After 30 days in indoor conditions, the concentrations of fructose, glucose, and sucrose in leaves declined to barely detectable levels, while the pinitol content was unchanged. By the end of 30 days, pinitol accounted for 79% of TSC. In another experiment, potted carnations were grown under water-stress conditions (0.21 m3 water/m3 soil) for 14 days. Compared with plants grown under ample water conditions (0.41 m3water/m3 soil), water-stressed plants showed lower water potential and increased the contents of pinitol, glucose, and TSC in the leaves; however, the differences in water potential and soluble carbohydrate level disappeared after plants were supplied with ample water. To optimize flowering, we thinned the number of florets to 20, 50, or 80 per plant. Compared with plants with 50 or 80 florets, plants with 20 florets per plant showed higher chlorophyll fluorescence ratio (Fv/Fm) in their leaves and had more flowers per plant. In addition, we evaluated the effects of low-light conditions (15 μmol·m−2·s−1) and high-light conditions (alternate cycles of 15 μmol·m−2·s−1 for 2 days and 150 μmol·m−2·s−1 for 1 day) on flowering. At 20 DAT, flowers in the high-light treatment showed higher TSC than those in the low-light treatment; however, levels of pinitol were significantly higher in plants grown under low-light conditions. These results suggested that thinning flower buds and growing plants under high-light conditions could alleviate the carbohydrate shortage that occurs in indoor conditions, and could improve the quality and display life of potted carnations. We discuss the roles of pinitol in carnation plants under stress conditions.
