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

This study was conducted to assess the effects of red-light irradiatio n at low photosynthetically photon flux density (20 mu mol m(-2) s(-1) PPFD) during storage at 15 degrees C for 15-16 days on the growth of new leaves, chlorophyll and carbohydrate levels, and photosynthetic ra tes of strawberry seedlings (Fragaria X ananassa Duch, var. 'Nyoho'). Petiole length of new leaves that elongated under red-light irradiatio n for 8 h photoperiod at 15 degrees C was shorter than that of those e longated under metal halide lamps for 8 h photoperiod (400 mu mol m(-2 ) s(-1) PPFD) at 27/15 degrees C or in continuous darkness at 15 degre es C, Red-light irradiation effectively inhibited the decrease in chlo rophyll levels of the leaves that unfolded prior to storage (old leave s), However, the decrease in both reducing sugar and sucrose levels of the roots, crown and old leaves was not inhibited by red-light irradi ation, 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 lev els and lower photosynthetic rates compared to those grown under red-l ight irradiation when measured at the end of storage. The values for p lants 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 dif ference between treatments on days 2 to 5. (C) 1997 Elsevier Science B .V.