Flavonoid, Nitrate and Glucosinolate Concentrations in Brassica Species Are Differentially Affected by Photosynthetically Active Radiation, Phosphate and Phosphite

Abstract

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.

Influence of Continuous Spectrum Light on Morphological Traits and Leaf Anatomy of Hazelnut Plantlets

“…Their synthesis is controlled by several factors. It is stimulated by nutrient deficiencies, in particular sulfur and phosphorus, and affected by environmental parameters including temperature and radiation (Trejo-Téllez et al, 2019). Flavonoid accumulation was stimulated by blue light in tomato (Giliberto et al, 2005) or in two lettuce cultivars (Son and Oh, 2013), whereas a decreased R:FR ratio had contrary effects in two tropical species (Ramalho et al, 2002), as well as in potato (Yanovsky et al, 1998).…”

“…It is known that nitrate reductase enzyme, catalyzing the reduction of nitrate to nitrite, is activated by light (Lillo and Appenroth, 2001) and inactivated in darkness conditions (Lillo et al, 2004). The enzyme activation after exposition to high levels of photosynthetically active radiation led to a decrease of nitrate concentration in Brassica juncea leaves (Trejo-Téllez et al, 2019); conversely, its inactivation caused nitrate accumulation in plant tissues. An increase in nitrate ion concentration promoted flavonoid synthesis in tea plant (Huang et al, 2018).…”

The Effect of Supplementary LED Lighting on the Morphological and Physiological Traits of Miniature Rosa × Hybrida ‘Aga’ and the Development of Powdery Mildew (Podosphaera pannosa) under Greenhouse Conditions

“…It is known that nitrate reductase enzyme, which catalyzes the reduction of nitrate to nitrite, is activated by light, and inactivated in darkness conditions [ 53 ]. The enzyme activation after exposition to high photosynthetically active radiation (PAR) led to a decrease of nitrate concentration in Brassica leaves [ 54 ]; conversely, its inactivation caused nitrate accumulation in plant tissues. In our case, it is possible that under a poorly lit environment (control treatment), the nitrate reductase activity decreased, allowing for the accumulation of nitrate that could be used in flavonoid synthesis.…”

Ascophyllum nodosum Biostimulant Improves the Growth of Zea mays Grown Under Phosphorus Impoverished Conditions

“…Low P availability is reported to differentially reduce the amino acid content and increase flavonoid content in Camellia sinensis . P-starvation induces the accumulation of flavonoids and phenolics in plants (Stewart et al, 2001 ; Trejo-Téllez et al, 2019 ). ANE treatment showed a reduction in the P-limitation-induced accumulation of anthocyanin, flavonoids, and phenolics contents in the corn.…”