The threshold concentration of ethylene causing sleepiness of freshly cut carnations was 125 ppb when the blooms were exposed for 24 hr at 20°C. The threshold decreased to 30 to 60 ppb when the blooms were held for 2 days at 5° prior to exposure. High partial pressures of CO2 in the atmosphere prevented ethylene-induced sleepiness. With 10% CO2, the blooms were not damaged by 250 ppb ethylene, and 20% CO2 provided protection against 500 ppb ethylene. Blooms with stems previously placed in water were as susceptible to ethylene damage as those held dry before exposure to ethylene.
Storage atmospheres with 2-1/2, 5 or 10% CO2 caused a physiological injury to lettuce almost identical to the brown stain observed in lettuce from rail cars and trailers in which CO2 concentrations exceeded 2% at destination. Carbon dioxide injury, or brown stain, was not always evident when lettuce was removed from the controlled atmosphere, after 7 days at 38°F, but became more evident during a subsequent 4 days at 50° in air. About 16% of the heads held at 2–1/2% CO2 developed brown stain while 38% and 86% of the heads developed the disorder in lots held at 5% and 10% CO2, respectively.
Significantly more heads developed brown stain when the CO2 was combined with 3% oxygen than when combined with 21% Ο2 Decay, pink rib, and tipburn were not significantly influenced by the O2 or CO2 level.
Increased levels of CO2 reduced the severity of butt discoloration in lettuce examined immediately after storage in the controlled atmosphere, but after an additional 4 days at 50°F in air, the differences were not evident. The danger of physiological injury from 2-1/2 to 10% CO2 during storage or shipping outweighs the small improvement in butt color and general appearance.
Added CO (1½%) or low O2 (3%) increased the susceptibility of head lettuce (Lactuca sativa L., ‘Great Lakes’ type) to CO2 injury (brown stain). The combination of low O2, added CO, and high CO2 (2½ − 10%) was particularly damaging.
Lettuce (Lactuca sativa L.) held in an atmosphere of 3% O2 plus 1.5% CO for 7 days at 3.3°C had a better appearance before and after the wrapper leaves were removed, than lettuce held in atmospheres with various other combinations of CO, CO2 and O2. Butt discoloration and pink rib also were inhibited by this atmosphere. These effects were no longer apparent after an additional 4-day holding period in air at 10°. Rusty brown discoloration was not affected by any of the atmospheres tested during the initial 7 days, but after 4 additional days in air, the incidence of objectionable rusty brown discoloration was higher in lettuce previously held in atmospheres with CO2 than in those without CO2.
The Aspergillus flavus group was associated with both sound and insect damaged kernels of almond Prunus dulcis (Mill.) D.A. Webb during 1972 and 1973. About 1 of 2,000 sound kernels and 1 of 200 insect damaged kernels were colonized. Surface contamination was common on sound and damaged kernels. In orchard plots, spores inoculated on the fruit colonized hulls, shells, and kernels of maturing almonds. Aflatoxins were detected in harvested kernels and hulls. Almond fruits were susceptible to colonization from the time of hull-split, when rapid drying of the fruit began, until after harvest when moisture of the kernel dropped below about 5% based on the fresh weight of the kernel. Infestations by the navel orangeworm, Paramyelois transitella (Walker), increased colonization of the kernels by A. flavus from experimental plots.