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Mechanism of Plant Growth Stimulation by Naphthenic Acid: II. Enzymes of CO₂ Fixation, CO₂ Compensation Point, Bean Embryo Respiration

D. James Wort
Plant Physiology
Vol. 58, No. 1 (Jul., 1976), pp. 82-86
Stable URL: http://www.jstor.org/stable/4264496
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Mechanism of Plant Growth Stimulation by Naphthenic Acid: II. Enzymes of CO₂ Fixation, CO₂ Compensation Point, Bean Embryo Respiration
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Abstract

Potassium naphthenate, 20 mM, was applied to the foliage of 14-day-old plants of bush bean, Phaseolus vulgaris L, cv Top Crop, maize, Zea mays L, cv Golden Bantam, spring wheat, Triticum vulgare Vill., cv Neepawa, and a 2 mM solution to 21-day-old plants of sugar beet, Beta vulgaris L, cv CS-43. Seven days after application, the activities of ribulose diphosphate carboxylase and phosphoenolpyruvic carboxylase in leaves of naphthenate-treated bean and maize were greater than in the leaves of untreated plants. The increase in activity of the carboxylases in treated spring wheat lacked statistical significance. At the same time after treatment, the CO2 compensation point of bean was smaller than that of control plants, as was the average CO2 compensation point of sugar beet measured at intervals up to 21 days after spraying. Respiratory rates of embryos of bean seeds soaked for 12, 24, and 48 hours in 43.5 μM K naphthenate were greater than those of seeds soaked in water. Ascorbate oxidase activity in bean leaves, determined 7, 14, and 21 days after K naphthenate application, was also stimulated. Foliar application of 10 mM cyclohexanecarboxylic acid to bean was followed in 7 and 14 days by a greater activity of catalase than in control plants. Higher activity of the enzyme, measured 6, 7, 12, and 14 days after spraying, also resulted from K naphthenate application. The results indicate that the higher rates of photosynthesis in naphthenate-treated plants may be due in part to increased rates of CO2 fixation, and that greater photosynthetic efficiency, together with a more plentiful supply of ATP arising from increased electron flow in respiration, is involved in the greater growth of plants to which naphthenate has been applied.

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