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The present research was aimed at the foliar biofortification of chard plants with iron and selenium and at determining the influence of this treatment on the accumulation of these elements, as well as proteins and nitrate, in the aerial portion (shoot) of chard. A 3 2 factorial experiment was conducted for the above purpose, and the study factors were the foliar applications of Fe (0, 2500 and 5000 mg L -1 ) and Se (0, 10 and 20 mg L -1 ). The foliar applications were performed every 15 days for a total of four spray applications. The variables evaluated were the accumulations of Fe, Se, proteins, and nitrate in the shoot. Two samples were collected after performing the second and fourth foliar spray applications. The results indicate that increasing application concentrations of Fe and Se promote greater foliar accumulations of these elements. Foliar applications of Se did not affect the accumulation of nitrate; however, a greater foliar accumulation of Se produced a greater accumulation of proteins. On the other hand, after only four foliar spray applications of Fe at a dose of 5000 mg L -1 , there was a statistically significant accumulation of nitrate, which had a positive correlation with the lower accumulation of proteins.

The efficiency of nanoparticles covered with type A gel and loaded with KH2PO4, as a source of P, was evaluated on growth, phosphorus concentration and accumulation, and photosynthesis-related parameters in rice plants (Oryza sativa L. ssp. indica) cv. Morelos A-2010, under greenhouse conditions. Plants were treated for 14 days with P concentrations equivalent to 50 and 100% of those established in the Yoshida nutrient solution. Sources of P were KH2PO4, nano-KH2PO4, and nano-KH2PO4 with trypsin; control treatments were distilled water and nanoparticles with type A gel. The solutions were renewed every 7 d. Rice plants exhibited differential P absorption in function of the P source tested. P supplied by KH2PO4 had a higher uptake rate than P supplied by nano-KH2PO4, alone or with trypsin. Nevertheless, nano-KH2PO4 promoted higher physiological efficiency for P in both roots and shoots, which consequently induced higher biomass accumulation in these organs. P concentration in shoots, as well as P accumulation in shoots and roots, were positively correlated with the photosynthetic rate. Also, nano-KH2PO4 increased instant water use efficiency in rice plants.