respiration at night reached a minimum of I kg CH20 ha -1 h -~ in April.
Only during 2 nights in April were the ambient air temperatures followed in
the plant chambers. The temperatures were between 0.9 and 7°C and the
minimum respiration rate was measured over the range 0.9--4.5 ° C.
B. Laboratory measurements
Photosynthesis. -- The net photosynthesis rate of an individual leaf of a
tulip at 21°C is presented in Fig. 5. The bottom leaf represents