In heat stressed genotypes of Triticum aestivum L. (Sever and Golia) and Triticum turgidum subsp. durum (Acalou and TE 9306), chosen according to its genetic background diversity, Ca and Mg accumulations were correlated with its photosynthetic performance. It was found that with high temperatures the concentrations of Ca increased in the shoots, whereas the accumulation of Mg augmented only in bread wheat genotypes. Under heat stress, the pattern of electrolytes release in Golia and Acalou remained similar, but the extrusion rates became higher in Sever. During grain filling, the levels of total chlorophylls decreased in the heat stressed genotypes (excepting in Sever). In all the Triticum genotypes, stomatal conductance and the net carboxilation rate displayed similar trends. After anthesis, the net carboxilation rates did not vary in Acalou and TE 9306 but changed significantly in the heat stressed bread wheat, being found antagonistic patterns in both genotypes. During grain filling, the mean internal CO2 concentration only increased significantly in the heat stressed Golia. In Golia and TE 9306, the transpiration rates didn't vary between the control and heat stress treatments, but in Sever and Acalou, significant increases were found. Our data identified synergistic patterns among Ca, Mg, chlorophylls accumulation, and stomatal conductance, whose implications on photosynthesis are discussed.

The interactions between Fe/Mn accumulation and the photosynthetic light reactions were investigated in heat stressed bread and durum wheat genotypes (Triticum aestivum L. and Triticum turgidum subsp.durum). Four genotypes were chosen according to its genetic background diversity. Plants were grown in a greenhouse at two different day/night temperatures regimes (control - 25/14ºC and heat stress - 31/20ºC), during the grain filling phase. The contents and uptake/translocation of Fe and Mn were evaluated on booting, grain filling and maturity and correlated with chlorophyll a fluorescence parameters. It was found that, under heat stress, the concentrations of Fe in the culm and leaves diminished in bread wheat, but increased in durum wheat. An opposite trend was found on the contents of Fe in the spike, being this effect higher in Sever. During grain filling, the concentrations of Mn in the heat stressed plants raised significantly in the shoot for all genotypes (excepting Golia). After anthesis, the proportion of Mn translocated also augmented with high temperatures. At maturity, the same trend was found in the translocated proportion of Fe. During grain filling, all the studied fluorescence parameters did not vary significantly except qP and qE that decreased in the heat stressed Golia and F V and Fv/Fm that increases in Acalou. It was concluded that under heat stress, during the grain filling period, Fe and Mn translocation to the shoots accelerates, eventually to overcome the negative effects on several photosynthetic physiological traits.

Brazil is the largest world producer of papaya and the third largest exporter despite of only 1.5 to 2.0% of its production is exported. Such an underexplored exportation potential highlight the necessity for physiological studies on new cultivars and hybrids to verify their agronomic and commercial viability. Two Brazilian states, Bahia and Espirito Santo, are responsible for 80% of national production. Papaya can also be an agricultural alternative to north / northeast of Rio de Janeiro, because the region is close to consumer centers and have similar environmental conditions of the most productive regions. Nevertheless, it is worth to develop cultivars that can express the highest yield potential in this region. The aim of this work was to characterize physiologically two hybrids developed for the north/northeast of Rio de Janeiro (UENF/Caliman 01 and JS12) in comparison with three top commercial genotypes (Golden, Sunrise Solo 7212 and Tainung) of Caricapapaya L. The cv. Golden presented the lowest shoot and root growth, the lowest height, shrunk diameter, specific leaf weight, less efficiency in electrons transport per sample area and show the lowest ability to synthesized total chlorophylls in comparison with the others genotypes. At noon, this genotype showed higher stomatal conductance, related to the leaf-air vapor pressure deficit, which lead to higher transpiration rate and intrinsic water use efficiency. No differences were detected in the photosynthetic rates among the five genotypes suggesting that the UENF`s hybrids are endowed with similar photosynthetic capacity and morphological characteristics to the top commercial genotypes. The relevance of this characterization to drive future successful genetic improvement programs will be discussed.