DO TOMATOES ON THE PLANT BEHAVE AS CLIMACTERIC FRUITS

I considered the possibility that changes in fruit photosynthesis obsc ure the occurrence of the climacteric rise in respiration in tomato fr uits attached to the plant. Internal CO2 and ethylene concentrations i n tomatoes (Lycopersicon esculentum Mill. cv. OH 7814) were analyzed a fter direct sampling through polyethylene tubes implanted in the exter nal pericarp. Fruits which were shaded with aluminium foil contained u p to 60 ml l(-1) CO2, until the internal ethylene concentration exceed ed 1 mu l l(-1), when CO2 concentration declined to below 40 ml l(-1); the CO2 concentration in fruits exposed to light only occasionally ex ceeded 40 ml l(-1). The internal CO2 concentration of detached fruits first declined and then increased along with ethylene concentration, a s expected for the climacteric. Detached green fruits under continuous low photosynthetic photon flux density (100 mu mol m(-2) s(-1)) conta ined almost no internal CO2 and produced no CO2. Changes in photosynth esis and an associated CO2-generating system in green fruits are thoug ht to obscure the climacteric rise in tomato fruits developing on the plant.