Studies revealed that the application of Mo in beans, via seeds, increases the mass of the nodule ; moreover, its foliar spray increases nodule formation, nitrogen contents, the grain number, the grain mass, and overall productivity . The enhanced benefits may be attributed to the acceleration of N absorption and assimilation processes via BNF . Mo is a crucial element for more than 40 enzymes, four of which have been found in plants, including nitrate reductase and nitrogenase synthesis . Thus, plants receiving increased Mo will have increased N productivity levels based on the higher activities of the abovementioned enzymes. Mo bound to a unique pterin compound, named Mo cofactor, binds to diverse apoproteins and aids in anchoring the Mo center at the correct position within the holo-enzyme for its correct interaction with other components of the electron transport chain . Thus, Mo supply can strengthen plant metabolism at different growth stages through an improved enzymatic and non-enzymatic antioxidant defense system and also enhance other pharmacological properties.
Moreover, Mo is also an essential mineral for the human body as it is part of important metabolic enzymes such as xanthine oxidase sulfite oxidase, aldehyde oxidase, and mitochondrial amidoxime reducing component.With this background, we hypothesized that Mo application can enhance the nutritional and pharmacological value of Canavalia species by improving their N content and resulting in primary and secondary metabolite production. Thus, the present study aimed to evaluate the impact of Mo seed priming on three Canavalia species/cultivar sprouts. To the best of our knowledge, no study has been conducted to assess the influence of Mo seed priming on Canavalia ensiformis var. gladiata, Canavalia ensiformis var. truncata Ricker, and Canavalia gladiata var. alba Hisauc. Herein, we evaluated the impacts of Mo treatment on growth, N content, and phenolic metabolism as well as on the concentrations of several phytochemical compounds. We further examined the role of Mo in the enhancement of pharmacological properties of Canavalia species. Overall, our study contributed to an understanding of the biochemical basis of Mo that induces high growth and tissue quality of different Canavalia species/cultivars.
The variations in the concentration of nutrients and phytochemicals were quantified in both Mo-exposed and unexposed seeds of Canavalia. The quantity of total lipids was significantly increased in CA1, a non-significant change was observed in CA2, while a decrease was recorded in CA3. Furthermore, a significant increase in fiber content was recorded in CA1, a decrease was found in CA3, while there was no change in the fiber content of CA2. Upward trends in total proteins, flavonoids, saponins, and glycosides were noticed .The results showed a slight increase in N production in the sproutings of three species, as shown in Figure 2A. Moreover, the quantification of nitrogen reductase activity showed its increase in CA3 and decrease in CA1 and CA2 in Mo-treated plants, as shown in Figure 2B. Next, we studied the effect of Mo on two pathways of glutamate synthesis, i.e., glutamate-dehydrogenase and glutamine synthetase /glutamate synthase pathways. The activities of GDH, GOGAT, and GS were measured . The results showed an increase in GDH and GOGAT activity in the three species. The rise in GDH activity was significant in CA3, while it was non-significant in other species. Inversely, GS activity was decreased after Mo treatment and the differences were highly significant in the three species/cultivars. Further, the impact of Mo treatmenton dihydrodipicolinate synthase and cystathionine γ- synthase activity was explored.
The experiment showed that the activity of DHDPS significantly increased in CA3 and non-significantly in CA1 and CA2 . Moreover, a notable increase in the activity of CGS was measured in sprouts of CA3 . Furthermore, amino acids, i.e., asparagine, glutamine, glycine, glutamic acid, isoleucine, arginine, tyrosine, lysine, serine, alanine, proline, histidine, leucine, isoleucine, valine, cystine, threonine, tryptophan, and methionine, were quantified in Mo-treated Canavalia species and data were compared to untreated controls. The changes in each amino acid content due to Mo exposure are shown in Table 2. Overall, an increase in amino acid production was detected in the three species. The quantity of cystine, isoleucine, leucine, glycine, alanine, and proline was increased significantly in CA1; asparagine, glutamine, glutamic acid, alanine, proline, cystine, and lysine were enhanced in CA2; and asparagine, glutamine, glycine, histidine, methionine, cystine, isoleucine, tyrosine, lysine, threonine, and tryptophan were enhanced in CA3. Variable trends were noticed among different sprouts.