SENSING OF PHOTOSYNTHETIC CAPACITIES OF SEEDLINGS OF LETTUCE WITH CHLOROPHYLL FLUORESCENCE
Seedlings of lettuce were grown on 1.5% agar medium containing 2 x Otsuka fertilizer. The activities of FL of attached leaves were directly measured with a probe of fluorometer SF-20. To stabilize the activities of FL, the dark adaptation of 5 min was necessary. While air temperatures surrounding leaves from 5 °C to 35 °C did not affect the activities of FL, which decreased as the light intensity of the fluorometer strengthened. The activities of FL and the photosynthetic O2 exchange rates in different age of leaves were highly correlated (r=0.902, significant at 1 % level). During hardening of the agar-grown seedlings in a acclimatization unit, the activities of FL increased in accordance with the increment of the photosynthetic O2 exchange rates. These results indicate that FL at room temperature is useful to non-destructively monitor the photosynthetic capacities.