OZONE IN RELATION TO STORAGE OF APPLES 7 



potassium iodide solution constituted the check. The difference in the 



titration values was used for determining the ozone concentration in 



parts per million. Since 1 milliliter of 0.01 N solution of sodium thio- 



jTX112 

 sulfate equals 0.112 milliliter of ozone the formula « — = parts per 



million of ozone (based on volume) was used. In this formula T 

 equals number of milliliters of sodium thiosulf ate required for titra- 

 tion and S equals liters of gas sample used in analysis after correction 

 to standard conditions. 



EFFECT OF OZONE ON FUNGUS SPORES 



Spores on Glass-Slide Cultures 



Spores of Botrytis cinerea Fr., which causes gray mold rot, and of 

 Penicillium expansum (Lk.) emend. Thorn, which causes blue mold 

 rot, were distributed evenly over a gelatin film on microscope slides. 

 A number of such slides were exposed daily for 1-hour periods to the 

 atmospheres of the ozonized and the nonozonized room. Each day 

 three slides from each room were withdrawn after exposure, placed 

 in sterile petri dishes, and flooded with a nutrient agar. The remain- 

 ing slides were placed in moist chambers and stored at 31° F. until the 

 following day's exposure. The petri dishes were held at room tempera- 

 ture, and germination counts on a number of microscope fields were 

 made at definite intervals to determine the effectiveness of the ozone 

 treatments. 



An atmosphere containing 1.95 p. p. m. of ozone caused a definite 

 reduction in germination of the spores. A single 1-hour exposure 

 reduced germination of spores of Botrytis cinerea; it was 18.8 per- 

 cent in the ozonized room (table 1) as compared with 62.8 percent in 



Table 1. — Effect of exposure of glass-slide cultures of Botrytis cinerea 

 and Penicillium expansum to an atmosphere containing 1.95 p. p. m. 

 of ozone on spore gefmination, 19J^l-^2 





Ozonized room 



Nonozonized room 



Fungus and number 

 of 1-hour exposures 



Fields 

 exam- 

 ined 



Spores 

 counted 



Spores 

 germi- 

 nated 



Fields 

 exam- 

 ined 



Spores 

 counted 



Spores 

 germi- 

 nated 



Botrytis cinerea: 



1_ . * __- 



Number 

 30 

 32 

 30 

 30 

 10 



60 



120 



30 



10 



Number 

 1,225 

 1,344 



699 

 1,056 



463 



2,501 



6,223 



1,855 



465 



Percent 



18. 8 



6.8 



1. 3 



1. 6 

 



59. 6 



2. 1 

 16.2 







Number 

 30 

 30 

 10 

 12 

 10 



30 

 30 

 30 

 10 



Number 

 1, 101 

 835 

 163 

 124 

 269 



1,656 



1, 888 



1,594 



650 



Percent 

 62. 8 



2 



55. 4 



3 



4 ! 



58. 9 

 98. 4 



5 



24. 2 



Penicillium expansum: 

 1 



81. 8 



2_ 



81.8 



3 



55.0 



4 __ 



48.0 







1 Only 1 plate showed any germination (4.8 percent) 



