Response to carbon monoxide by geographic variants in Acacia farnesiana.
A B S T R A C T Differences in degree of defoliation in CO-air mixtures were shown by geographic variants in Acacia farnesiana (L.) Willd., a widespread, weedy, pantropic, leguminous tree. Laboratorygerminated seedlings from MazatlAn (MAME-1), Sinaloa, Mexico, showed greater sensitivity to a CO gradient than plants from Point Tuna (PORO), Puerto Rico. Seedlings of both strains grown under a light intensity of 200 ft-c showed greater sensitivity to CO than those grown under 1,800 ft-c. When intact plants of 17 geographic variants grown at low-light intensities were exposed to 2%Fo CO in air, 11 strains (Mexico,8; Texas, 1; California, 1; Guatemala, 1) showed almost complete defoliation. The other six strains-from Brazil, Hawaii, Puerto Rico, 1Ttaly, Algeria, and Michoac4n, Mexico-showed defoliation averaging from 23 to 70%. The significance of the CO-defoliation response is difficult to explain in terms of the natural distribution of A. farnesiana. It is suggested that this response may be correlated with some biochemical process of adaptive significance. GEOGRAPHIC variants in Acacia farnesiana (L.) Willd. being studied at the Plant Ecology Research Laboratory differ in several parameters, but the most bizarre difference is one shown by exposure to low concentrations of carbon monoxide. While certain strains show nearly total leaf loss after 24-hr exposure to CO, other strains show little or no defoliation. First observed as a result of accidental exposure to CO, the geo
Stem Orientation in Two Populations of Acacia farnesiana from Mexico Under Controlled Environmental Conditions
The orientation of stem growth in upright plants from an inland population at Saltillo, Coahuila, and in prostrate plants from a beach population at Mazatlan, Sinaloa, was examined under several conditions of photoperiod, temperature, and light intensity. Prostrateness is enhanced by lower temperatures, shorter photoperiods, and higher light intensities in both populations but is induced to a greater degree and over a wider range of conditions in the naturally prostrate form. Under longer day lengths, 16 hr, and higher temperatures, 32-24 C, the prostrate form develops almost upright and is not significantly more prostrate than the naturally upright form. Regenerated stems produced under high light intensities were significantly more prostrate in the beach population than were stems of the inland population, but under low light intensities both populations produced upright stems. The results suggest that niche plasticity of the prostrate population offers selective advantage in a subtropical beach ecosystem.
Synergistic Effect of High Temperature and High pH on the Destruction of Salmonella enteritidis and Escherichia co1i O157:H7.
This study was undertaken to determine if high temperature and high pH interact synergistically to enhance the rate of destruction of two important gram-negative foodborne pathogens, Escherichia coli O157:H7 and Salmonella enteritidis . The rates of destruction in NaHCO3-NaOH buffers at pH 7.0, 10.0, and 11.0 were determined at 35, 40, 45, 50, 55, 60, and 65°C. Use of an improved heating protocol eliminated a "tailing effect" at longer exposure times. The present study demonstrated that the combination of high pH and high temperature resulted in a highly significant synergistic interaction (P > F = 0.0001), which caused rapid death of both E. coli O157:H7 and S. enteritidis . This "alka-therm" technology might be used commercially to destroy gram-negative foodborne pathogens on various raw agricultural commodities.