Nitrogen assimilation and photosynthetic capacity of wheat genotypes under optimal and deficient nitrogen supply

The performance of two contrasting Bulgarian wheat varieties (Slomer, an old tall cultivar, and Enola, a modern semi-dwarf one) to nitrogen deficiency was compared by measuring biochemical parameters characterizing N uptake and assimilation as well as growth and photosynthetic activity of young seedlings. The old genotype displayed better photosynthetic capacity, higher N assimilation expressed by elevated amino acid synthesis and better overall performance under N limitation. This could be explained by the fact that selection of old varieties was performed mostly in environments with low nutrient availability and consequently these genotypes proved to be more suitable for growing on low-input conditions. Upon limiting N supply modern variety preferentially accumulated sugars while the old one retained higher amino acids levels. It was demonstrated that processes involved in N metabolism were tightly interrelated with photochemical reactions and carbon assimilation even at early developmental stage.