INTRAMOLECULAR RESPIRATION OF TOMATO FRUITS

These experiments on intramolecular respiration have been conducted as a part of a general study of the development of tomato fruits. Nitrogen and in two experiments hydrogen have been used to replace air. These gases were first passed through a wash bottle containing NaOH which absorbed the CO2 and then through three bottles of chromous chlorid which absorbed any oxygen that was in the gas. The CO2and 02-free gas was then passed through the respiration chamber by the pressure in the tank and reduction of the pressure in the system by suction. As it came from the chromous chlorid the gas was frequently tested for oxygen by passing it over phosphorus, always with negative results. The respiration chamber was always kept at atmospheric pressure and was immersed in a constant temperature bath held at 25? C. A control in air otherwise similarly treated was run simultaneously. The fruits were usually picked during the afternoon and put into the chamber through which air was drawn over-night in order to establish an equilibrium, before any collection for analysis was made. The CO2 was collected in o.i M Ba(OH)2 contained in modified Pettenkofer tubes, and titrated with o.i M oxalic acid. Further detail may be obtained from a previous paper (5) 2 In the present experiments the Pettenkofer tubes had a diameter of only 9 mm. in the main portion, with both ends enlarged somewhat, to facilitate the insertion of stoppers. The use of tubes with a small diameter made it possible to utilize a volume of only sixty cubic centimeters of Ba(OH)2 and yet the gas passed through a column of liquid long enough to absorb the CO2 completely. With such a small volume of liquid the time of the individual collections could be shortened to one hour in some instances. In all but one experiment the length of time for collection of each sample was from one to three hours. Such short periods enabled one to follow more closely the changes in the rate of CO2 production. In the early experiments three hour periods were used almost exclusively, but in the later experiments several fruits were used and the time could be shortened to one hour when the gas production was at its maximum. After some preliminary trials an experiment with a ripe fruit weighing