THE EFFECT OF BACTERIAL-CONTAMINATION ON THE GROWTH AND GAS EVOLUTIONOF IN-VITRO CULTURED APRICOT SHOOTS

Shoots of ''San Castrese'' and ''Portici'' apricots (Prunus armeniaca L.) Gee of cultivable bacteria, shoots of the same origin exhibiting b acterial contamination after repeated subcultures, and contaminated sh oots treated with cefotaxime were compared for gas exchange, prolifera tion rate, and fresh and dry weight. Cultures of San Castrese contamin ated by Bacillus circulans and Sphingomonas paucimobilis, and of Porti ci contaminated with Staphylococcus hominis and Micrococcus kristinae, including those treated with cefotaxime, showed comparable shoot weig hts and lower proliferation rates than healthy cultures. Bacteria, eve n if not visible until the end of subculture, markedly influenced the gaseous composition of the jar headspace. Healthy cultures clearly sho wed photosynthetic activity at 60 mu M . m(-2). s(-1) photosynthetical ly active radiation; in contrast, oxygen quickly decreased and carbon dioxide increased in contaminated cultures, including those treated wi th cefotaxime, in which bacteria became visible in the culture medium only after repeated subcultures.