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The role of ice nucleation active bacteria in supercooling of citrus tissues
Author(s) -
Constantinidou H. A.,
Menkissoglu O.,
Stergiadou H. C.
Publication year - 1991
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1991.tb05098.x
Subject(s) - ice nucleus , pseudomonas syringae , nucleation , supercooling , frost (temperature) , bacteria , chemistry , ice crystals , population , pseudomonas , botany , bacterial growth , horticulture , biology , materials science , organic chemistry , thermodynamics , physics , demography , sociology , optics , composite material , genetics
The frost sensitivity of Citrus sinensis in relation to the presence of biogenic ice nuclei was studied. In commercially managed citrus groves the ice nucleation active (INA) bacterium Pseudomonas syringae reached 6 × 10 4 colony forming units (CFU) leaf −1 , a population sufficiently high to catalyze ice formation. However, a transient loss of bacterial nucleation activity was noticeable at subzero field temperatures, followed by resumption as temperatures rose. This loss was apparently due to a temporary transition of INA to ice nucleation inactive (INI) bacteria. Field application of Bordeaux mixture, copper hydroxide, streptomycin, and 2‐hydroxypropylmethanethiolsulfonate (HPMTS), resulted in reduction of INA bacterial populations to detectability (≤ 10 2 CFU leaf −1 ) limits. However, the corresponding reduction in ice nucleation events in treated samples as compared to controls at nucleation temperature ≥−3°C was not as dramatic. It ranged from approximately 7% in samples treated with the bactericide HPMTS, to 35% in samples treated with chemicals possessing combined bactericidal ‐ fungicidal action (coppers). Since a quantitative relationship exists between ice nucleation events on individual leaves and the INA bacterial populations harbored by these leaves, these results suggest the co‐existence of a bacterial and a proteinaceous, yet non‐bacterial ice nucleating source in citrus, both active at ≥−3°C.