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Spray applications of 3.49 millimolar 2-(4-chlorophenoxy)-2-methylpropanoic acid (CPMP) significantly decreased leaf chlorophyll loss, compared with the control, after 72 hours of subcompensation-point stress. Treatment with CPMP also consistently increased leafchlorophyll per unit area under nonstress greenhouse conditions. These effects may be due to increases in specific leaf weight produced by CPMP although the compound did not consistently act as a height retardant. The compound, 3-butyl-2-hydroxy4H-pyridoll,2-alpyrimidin4-one (BHPP), inhibited senescence under low CO2 conditions but did not decrease leaf light transmission at ambient CO2 levels. The cytokinin N'-benzyladenine (BA) retarded low CO2 stress senescence although greening effects were not observed. Neither 2-hydroxy-3-butynoic acid (HBA) nor its butyl ester, inhibitors of glycolate oxidase, influenced low CO2 survival. Cyclohexanecarboxylic acid (CHCA) and sodium naphthenate had no effect upon subcompensation-point senescence.Antisenescence effects of CPMP, BHPP, and BA do not appear to be directly attributable to effects upon the competing carbon paths of photosynthesis and photorespiration. Protection against low CO2 stress and increased chlorophyll synthesis under nonstress conditions may represent separate effects upon plastids by some of the compounds. This screen will identify compounds which inhibit photorespiratory senescence without decreasing the CO2 compensation point. (21) provided HBA. The nuclear magnetic resonance and IR absorption spectra of all of the above compounds were in agreement with the published data and confirmed the assigned structures.Cyclohexanecarboxylic acid (CHCA) and N6-benzyladenine (BA) were purchased from the Aldrich Chemical Co., Inc. and 3 Abbreviations: CPMP, 2-(4-chlorophenoxy)-2-methylpropanoic acid; BHPP, 3-butyl-2-hydroxy4H-pyrido[1,2-a]pyrimidin-4-one; BHB, butyl 2-hydroxy-3-butynoate; HBA, 2-hydroxy-3-butynoic acid; CHCA, cyclohexanecarboxylic acid; NaNAP, sodium naphthenate; T, transmission value; SLW, specific leaf weight; r, C02 compensation concentration.4 CPMP(2-(4-chlorophenoxy)-2-methylpropanoic acid) has been generally referred to as p-chlorophenoxyisobutyrate or CPIB in publications dealing with its effect upon animal peroxisomes and with its hypolipidemic activity.

Compared with anion-activated cell lysis of oral bacteria damaged with either lysozyme or trypsin, cells which were treated with both of these enzymes showed a far greater degree of lysis. This was true regardless of whether turbidimetric, DNA release, or electron microscopic assays were used to monitor the lytic process. At an acidic pH of 5.2 and an NaHCO3 concentration of 100 mM, the kinetics of lysis for two different serotype c strains of Streptococcus mutans were similar. At 0 to 100 mM bicarbonate, however, differences in the lytic susceptibilities of the two strains were evident. At pH 5.2, NaHCO3, but not NaSCN, NaCI, or NaF, was effective in promoting cell lysis of the oral bacteria. At apparent sublytic concentrations of NaHCO3, lysis was achieved by adding appropriate concentrations of NaSCN, NaCI, or NaF to the lysozyme-protease-damaged cells. In in vivo studies, hamsters given a combination of NaHCO3, NaCl, and NaSCN were found to have significantly reduced levels of S. mutans on their molar teeth compared with that found in controls or animals exposed to any one of the salts alone or to a combination of chloride and thiocyanate only. The results suggest that bicarbonate is an essential anion which, together with the other major salivary inorganic monovalent anions, plays an active role in the lysis and ultimate elimination of cariogenic bacteria. X 108 cells per ml; Petroff-Hausser counting chamber) immediately before lytic assays were performed.Actinomyces naeslundii I and virulent and avirulent strains of Actinomyces viscosus T14 were obtained from Sigmund Socransky, Forsyth Dental Center, Boston, Mass. Lactobacillus casei DSM 20011 was provided by Karl Schleifer, University of Munich. After the organisms were grown in brain heart infusion broth, dilutions (1:100 or 1:1,000) were made into FMC synthetic medium as de-610

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