Photosynthetic CO2 Fixation in the Second Leaf of Wheat Seedlings Grown at Different Conditions of Nitrogen Nutrition |
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Authors: | Polesskaya O G Dzhibladze T G Kashirina E I Alekhina N D Bukhov N G |
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Institution: | (1) Faculty of Biology, Moscow State University, Vorob'evy gory, Moscow, 119899, Russia;(2) Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya ul. 35, Moscow, 127276, Russia |
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Abstract: | The rates of photosynthetic 2 assimilation were determined in fully expanded second leaves of 21-day-old wheat (Triticum aestivum L.) seedlings grown on media supplied with nitrate or ammonia and on a nitrogen-free medium (NO3
–- or NH4
+-treatments and N-deficit treatment, respectively). The maximal quantum efficiency of photosynthesis was independent on conditions of nitrogen nutrition. When leaves were exposed to 0.03% 2 and high-intensity light, the lowest photosynthetic rate was noted for N-deficit treatment and the highest rate was characteristic of NH4
+ treatment. The elevation of the 2 concentration in the gas phase to 0.1% stimulated photosynthesis at high-intensity light in all treatments. The rate of 2 uptake by the leaf of N-deficient seedlings increased with 2 concentration to a larger extent than in other treatments and approached the 2 uptake rate characteristic of the NO3
– treatment. In plants grown on a nitrogen-free medium, the leaf accumulated lesser amounts of reduced nitrogen and higher amounts of starch, but the content of chloroplast protein corresponded to that of NO3
– treatment. In the leaf of NH4
+-treated seedlings, the rate of 2 assimilation was higher than in the leaf of NO3
– treated plants, regardless of the composition of the gas mixture. The ammonium-type nutrition, as compared to the nitrate-type nutrition, elevated the amount of reduced nitrogen in the leaf and promoted accumulation of chlorophyll and protein, the chloroplast protein in particular. |
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Keywords: | Triticum aestivum nitrogen status carbohydrate status CO2 assimilation |
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