Abstract
Physiology of potted carnations under low light intensity was evaluated in order to improve their postharvest quality. Light compensation points of single leaves were estimated at photosynthetic photon flux density (PPFD) of 10.3 and 12.9 μmol·m−2·s−1 for ‘My fair lady’ and ‘Scarlet’, respectively. Fv/Fm, φPSII and chlorophyll concentration in the leaves remained high under 120 μmol·m−2·s−1 PPFD (16 h of light) but were significantly decreased under 10 μmol·m−2·s−1. Under 10 μmol·m−2·s−1 PPFD, concentrations of sugars and anthocyanin in petals decreased. Moreover, development of flower buds and unfolding of flowers were suppressed and thus potted plant longevity was short at a low light intensity. These findings suggested that low light intensity less than light compensation point resulted in a low photosynthesis rate, shortage of sugar accumulation, and reduced longevity of potted plants and florets. In ‘Scarlet’ maintained under 10 μmol·m−2·s−1, treatments with 30 ppm 5-aminolevulinic acid (ALA) alleviated the decrements of chlorophyll concentrations and φPSII, and thereby slightly improved the numbers of unfolded flowers, and longevity of florets and potted plants. In ‘My fair lady’, treatments with 30 and 150 ppm ALA significantly prolonged the longevity of potted plant under 5 μmol·m−2·s−1 (24 h of light). In ‘My fair lady’, treatments with 30 ppm ALA alleviated the decrease in chlorophyll concentration but did not affect either the photosynthesis rate or light compensation point under 15 μmol·m−2·s−1 (12 h of light).
