Detection of Chemicals Inhibiting Photorespiratory Senescence in a Large Scale Survival Chamber

Abstract

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.

Mass screening of rice mutant populations at low CO2 for identification of lowered photorespiration and respiration rates

“…This suggests that chlorophyll retention under low CO 2 stress and increased pigmentation under greenhouse conditions are controlled by distinct pathways and thus any improvements to rice photosynthetic performance under low CO 2 do not necessarily translate to improved performance at ambient levels. Manning et al (1984) found that the cytokinin, N 6benzyladenine (BA) reduced mortality under low CO 2 but without an extended greenness phenotype in soybean, contrary to previous results in snapbean (Fletcher and Adedipe, 1970). BA is known to maintain RNA and increase protein synthesis.…”

“…In contrast, rice leaves typically do not have large intercellular air spaces, although it is possible that mutations impacting leaf cellular anatomy could provide a route to enhancing photosynthetic productivity (Lehmeier et al, 2017;Lundgren et al, 2019). Manning et al (1984) illustrated that the prolonged greenness in soybean seedlings under low CO 2 could be due to the effect of plant hormones or other synthesised compounds, with 2-(4chlorophenoxy)-2-methyl-propanoic acid (CPMP) reducing leaf chlorophyll loss. CPMP is reported to function in an antagonistic manner to auxin, triggering chloroplast formation and retarding leaf senescence under low CO 2 conditions as well as increasing leaf chlorophyll content per unit leaf area under non-stressful glasshouse conditions (Wittwer and Murneek, 1946;Burstrom, 1951;Manning et al, 1984).…”

“…Manning et al (1984) illustrated that the prolonged greenness in soybean seedlings under low CO 2 could be due to the effect of plant hormones or other synthesised compounds, with 2-(4chlorophenoxy)-2-methyl-propanoic acid (CPMP) reducing leaf chlorophyll loss. CPMP is reported to function in an antagonistic manner to auxin, triggering chloroplast formation and retarding leaf senescence under low CO 2 conditions as well as increasing leaf chlorophyll content per unit leaf area under non-stressful glasshouse conditions (Wittwer and Murneek, 1946;Burstrom, 1951;Manning et al, 1984). However, whilst CPMP extended greenness under both control and reduced CO 2 conditions, another compound, 3-butyl-2-hydroxy-4H-pyridol (BHPP) protected against low CO 2 only (Manning et al, 1984).…”

“…CPMP is reported to function in an antagonistic manner to auxin, triggering chloroplast formation and retarding leaf senescence under low CO 2 conditions as well as increasing leaf chlorophyll content per unit leaf area under non-stressful glasshouse conditions (Wittwer and Murneek, 1946;Burstrom, 1951;Manning et al, 1984). However, whilst CPMP extended greenness under both control and reduced CO 2 conditions, another compound, 3-butyl-2-hydroxy-4H-pyridol (BHPP) protected against low CO 2 only (Manning et al, 1984). This suggests that chlorophyll retention under low CO 2 stress and increased pigmentation under greenhouse conditions are controlled by distinct pathways and thus any improvements to rice photosynthetic performance under low CO 2 do not necessarily translate to improved performance at ambient levels.…”