We evaluated the effects of phosphate (Pi-deficiency: 0.1 mM; Pi-sufficiency: 0.5 mM), phosphite (low-Phi: 0.1 mM; medium-Phi: 0.5 mM; and high-Phi: 2.5 mM), and two mean daily photosynthetically active radiations (lower PAR: 22.2 mol ⋅ m -2 ⋅ d -1 ; higher PAR: 29.7 mol ⋅ m -2 ⋅ d -1 ), as well as their interactions, on flavonoid, nitrate and glucosinolate (GL) concentrations and growth characteristics in hydroponically grown Brassica campestris cv. Mibuna Early and Brassica juncea cv. Red Giant. As expected, higher PAR increased dry matter and contrariwise decreased number of leaves but only in B. campestris . Total flavonoid and individual flavonoid compounds increased with the higher PAR value in B. campestris . Pi-sufficiency resulted in a lower quercetin concentration in both species, the isorhamnetin and total flavonoid concentrations in B. campestris , and the cyanidin concentration in B. juncea , in comparison to Pi-deficiency. Similarly, Pi-sufficient plants exhibited lower GL concentration, especially alkyl-GLs in B. campestris and alkenyl-GLs and an aryl-GL in B. juncea . Pi did not affect the nitrate concentration in either species, and nor did Phi influence the flavonoid concentrations in either species. In B. campestris , medium Phi (0.5 mM) increased the 1-methoxyindol-3-ylmethyl GL concentration by 28.3%, as compared to that observed at low Phi. In B. juncea , high Phi level increased the but-3-enyl-GL concentration by 18.9%, in comparison to values recorded at medium Phi. B. campestris plants exposed to higher PAR increased total flavonoids concentration. In both Brassica species, higher PAR stimulated the alkyl-, alkenyl-, and indole-GLs. The interaction of lower PAR and increasing Phi significantly decreased flavonoid concentration in B. juncea , whereas increasing Phi at higher PAR increased such concentration in this species. The same combination reduced the concentration of 2-phenylethyl- and indol-3-ylmethyl-GL in B. juncea . The highest indol-3-ylmethyl-GL concentration was observed when Pi was deficient combined with medium Phi in B. juncea . Thus, PAR, Pi and Phi may modulate flavonoid, GL and nitrate concentrations in Brassica species, which may be a useful tool to improve the nutraceutical quality of these leafy vegetables if properly managed.

Phosphite (H 2 PO 3 -; Phi) has been shown to increase fruit quality and activate plant defense mechanisms in plants when provided in a nutrient state with sufficient phosphorous. In this study, five solutions containing different percentages of Phi (0, 20, 30, 40 and 50%) in Steiner's solution were evaluated during the flowering and fructification stages; the Steiner' s nutrient solution was kept al 50% during the flowering stage and at 75% from the beginning of the fructification stage on. The objective was to determine the effects of phosphite on total P concentration in leaves, yield, pH, electrical conductivity (EC), anthocyanin concentration, and fruit size of strawberries (cv. Festival). The experiments were performed in a tunnel-type greenhouse using drip irrigation and volcanic rock (volcanic gravel) as substrate. In the fruit development phase, the concentration of P in the leaves was proportional to the level of Phi used. Although no significant differences were observed when compared to the control, the addition of 20% Phi slightly improved yield and fruit size. The highest pH, EC and anthocyanin concentration were identified in the fruit of plants treated with 30% Phi. Our findings suggest that supplying Phi at 30% or less in the nutrient solution does not significantly affect yield but does affect fruit quality and activates plant defense mechanisms by producing a higher concentration of anthocyanins.

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