Abstract
Top fresh weight of leaf bunching lettuces (Lactuca sativa L. cv. ‘Grand rapids’) in hydroponics were continuously measured under the conditions changing in relative humidity, air temperature and light intensity.
Reversible fluctuations of top fresh weight were observed. The fluctuations started immediately after the changes in environment, and continued within 30 minutes after the changes. Light and air temperature were more effective on the fluctuation than relative humidity.
The fluctuations were distinguished from long-term changes in fresh weight by its reversibility. The transpiration rate showed opposite pattern of the fluctuation caused by environmental change.
These results suggest that short-term fluctuations reflect the balance of input and output of water which may be regulated by transpiration.
