Hiroshi Hamamoto

Petiole length, chlorophyll and carbohydrate levels, and photosynthetic rates of June-bearing strawberry plants as influenced by red-light irradiation during storage under cool conditions

Abstract This study was conducted to assess the effects of red-light irradiation at low photosynthetically photon flux density (20 μmol m−2 s−1 PPFD) during storage at 15 °C for 15–16 days on the growth of new leaves, chlorophyll and carbohydrate levels, and photosynthetic rates of strawberry seedlings (Fragaria X ananassa Duch. var. ‘Nyoho’). Petiole length of new leaves that elongated under red-light irradiation for 8 h photoperiod at 15 °C was shorter than that of those elongated under metal halide lamps for 8 h photoperiod (400 μmol m−2 s−1 PPFD) at 27/15 °C or in continuous darkness at 15 °C. Red-light irradiation effectively inhibited the decrease in chlorophyll levels of the leaves that unfolded prior to storage (old leaves). However, the decrease in both reducing sugar and sucrose levels of the roots, crown and old leaves was not inhibited by red-light irradiation, and the values were the same as those for plants in continuous darkness during the entire experimental period. Leaves that were newly grown in continuous darkness had smaller areas, lower chlorophyll levels and lower photosynthetic rates compared to those grown under red-light irradiation when measured at the end of storage. The values for plants in continuous darkness increased rapidly, while those values for plants in red-light irradiation increased gradually under subsequent high temperature and long-day conditions, resulting in no apparent difference between treatments on days 2 to 5.