Control of photosynthesis, glutathione and amino acid metabolism by light quantity and quality in wheat

Photosynthesis, glutathione and amino acid metabolism are adjusted to changes in the light conditions which is important for the appropriate growth of plants because of their central role in the control of various physiological and biochemical processes. Increase in light intensity was accompanied with a simultaneous increase in the photosynthetic activity and fresh weight of shoots in wheat. Modification of the ratios of blue, red and farred spectral components also affected the photosynthetic electron transport rate which was inhibited by farred light. However, the growth of the seedlings was not influenced by spectrum. Alterations in photosynthesis affected the redox environment since the total glutathione content and the ratio of the glutathione disulphide was greater at higher light intensity compared to the lower ones. In farred light the total glutathione content was smaller compared to the other spectral conditions. The altering availability of reducing power from photosynthesis also influenced the accumulation of free amino acids which was greatly induced by the increase in light intensity and by the blue light. The concentration of most amino acids was much lower in pink light compared to blue light and farred light. However, the lowest contents of proline (Pro) and methionine were observed in blue light. The spectrum had the largest influence on Pro which was shown at both metabolite and gene expression level. Taking into account the role of Pro in the maintenance of the osmotic and redox environment, this amino acid may have a key function in the adjustment of metabolism to the light conditions. The expression of several genes related to redox system and amino acid metabolism increased with increasing light intensity and a few of them was also affected by spectrum. The observed light-dependent alterations in the metabolism of glutathione and free amino acid levels may contribute to the appropriate growth of wheat if the intensity of illumination or its spectral composition changes