Characteristics of photosynthesis in maize leaves (С4 plants) upon changes in the level of illuminance and nitrate nutrition

• Published in: Russian journal of plant physiology 2016-09, Vol.63 (5), p.620-625
• Main Authors: Chikov, V. I., Abdrakhimov, F. A., Batasheva, S. N., Khamidullina, L. A.
• Format: Article
• Language: English
• Subjects: Biomedical and Life Sciences; Life Sciences; Plant Physiology; Plant Sciences; Research Papers
• ISSN: 1021-4437; 1608-3407
• DOI: 10.1134/S1021443716050034

We studied assimilation of 14 СО 2 and distribution of 14 С among the products of 3-min-long photosynthesis of maize ( Zea mays L.) leaves. The day before the experiment, half of the plants were fertilized with Ca(NO 3 ) 2 (1 g/L of water) at a rate of 6 L/m 2 . Five days before the experiment, some plants were shaded for adaptation (illuminance was reduced by 50%). On the day of the experiment (before the application of 14 СО 2 ), several shaded plants were exposed to direct sunlight for 3 min, and some plants grown at full light (light plants) were shaded for 3 min (illuminance of 50%). Unfertilized plants adapted for 5 days to shading showed photosynthesis of 75.9% of control level (full light). If light plants were transferred to shading for 3 min, their photosynthesis decreased to 42.1%. In plants shaded for 5 days and then transferred to full light, photosynthesis in 3 min was 96.3% of control level. At full light, fertilization with nitrate boosted photosynthesis to 132.6% as compared with control material, but photosynthesis decreased to 43.5 and 65.4% of control level in plants shaded for 5 days and those shaded for 3 min, respectively. At the same time, the plants shaded for 5 days and then exposed for 3 min to full light restored photosynthesis to almost control level (95.5%). Analysis of 14 С distribution among the products of 3-min-long photosynthesis showed that, the same as in C 3 plants, a decrease in illuminance (especially a sudden one) in maize reduced the ratio between labeled sucrose and hexoses and elevates incorporation of 14 С into malate, which indicated that its consumption in bundle sheath cells was suppressed. A decrease in the ratio between labeled sucrose and hexoses became more pronounced under the influence of nitrates with this effect also occurring in transport products of photosynthesis (20 cm below 14 С-providing leaf area). In plants fertilized with nitrates, radioactivity of sucrose (% of radioactivity of soluble compounds) decreased in all the types of illumination. When illuminance was suddenly reduced for 3 min, incorporation of 14 С into sucrose was 21.5 against 51.2% in light plants, and radioactivity of aspartate and malate sharply rose to 13.7 and 26.1% (against 2.1 and 8.9% in control material). Incorporation of 14 С into compounds of glycolate pathway was low (less than 2.5%), but it was somewhat greater in nitrate plants. We concluded that the same mechanism of interaction between stomatal apparatus of leaf e