Title: A Light-Sensitive Mutant in Maize (Zea maysL.)
Abstract: Photosynthetic electron transport and CO2 exchange rates were studied in a light-sensitive, chlorophyll b-deficient mutant of maize. Rates were compared for mesophyll chloroplasts or intact seedlings grown at low and high light intensities. The capacity for PSI and PSII transport by mutant chloroplasts is 2 to 3 times that of chloroplasts from wild-type seedlings grown at high intensities. Whole chain transport by mutant chloroplasts is 50% higher. At low light intensities there is very little difference between mutant and wild-type chloroplasts. Divalent cation effects on variable fluorescence yield and light saturation curves for whole chain electron transport indicate a loss of light-harvesting efficiency by mutant chloroplasts grown at high light intensities. Light saturation curves for CO2 exchange by intact seedlings on a chlorophyll basis are similar to those for whole chain electron transport by isolated chloroplasts. The light saturated rate of CO2 uptake by mutant seedlings is higher than by wild-type seedlings and the difference increases with the light intensity under which the seedlings are grown at rate limiting light intensities, CO2 uptake rates for the wild-type exceed that of the mutant when seedlings are grown at high intensities. Light compensation points are higher for mutant seedlings and the difference in light compensation points between mutant and wildtype increases with the intensity under which the seedlings are grown. On a fresh weight basis, light-saturated CO2 uptake rates are identical for mutant and wild-type seedlings regardless of the intensity under which the seedlings are grown. Phosphoenolpyruvate carboxylase activities are higher in mutant seedlings than in wild-type but are not affected by light intensity. These results indicate that the photosynthetic unit size in the mutant chloroplast decreases with increasing light intensity, primarily through loss of the lightharvesting chlorophyll a/b-protein antenna complex. The relationship between this system and adaptation of genetically normal plants to light intensity is discussed.
Publication Year: 1980
Publication Date: 1980-10-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 14
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