**3. Temperature influence on nitrogen nutrition**

Wheat growth can be impaired by heat stress at any developmental stage, and modelling scenarios predict even warmer temperatures in the future [39]. Production of wheat is affected markedly by high temperature [40, 41]. Elevated temperature alters uptake and allocation of N, thus intensifying N deficiency in plants [42]. Wheat shows enormous diversity in canopy architecture, and it has long been proposed that optimised light distribution could improve radiation use efficiency as well as light interception [43]. In heat tolerance, the activity of enzymes has crucial role. Rubisco's affinity for CO<sup>2</sup> decreases with temperatures [44]. Therefore, increasing affinity would simultaneously improve adaptation to warmer conditions, the proof of concept coming from C4 species, in which it is achieved by concentrating CO2 [45]. High temperature not only degrades Rubisco but also accelerates its inactivation by addition of inhibitory sugars to its active site. Moreover, Rubisco has a relatively low turnover number as compared with the other Calvin cycle enzymes. Activity of Rubisco is mainly regulated by a catalytic chaperone—Rubisco activase—which catalyses removal of inhibitory sugars from its active site, switching the enzyme to active mode [46]. Among cereals wheat's Rubisco has one of the best CO2 affinities. Models where wheat's substrate specificity factor of Rubisco is replaced from *L. gibertii* predicted increases of 12% in net assimilation [47]. Combined stress of high temperature and low nitrogen affected both the abundance and mode of regulation of Rubisco, which catalyses CO2 fixation and is one of the primary determinants of photosynthetic rate [48].
