Mitigation of ammonium toxicity by silicon in tomato depends on the ammonium concentration

Abstract

Ammonium toxicity in hydroponically grown crops can affect tomato development. However, it has been shown that the silicon (Si) attenuates ammonium toxicity in plants depending on the plant species, the stage of development and the ammonium concentration in the nutrient solution. Thus, in order to investigate how Si attenuates stress caused by ammonium in tomato, a study was carried out involving plants cultivated up to 40 days after seed germination using nutrient solutions containing ammonium concentrations (1, 2, 4, 6 and 8 mmol L −1 ), in the absence or presence of Si (1 mmol L −1 ). The accumulation and efficiency of nitrogen and Si use, as well as the concentrations of chlorophyll, carotenoids, malondialdehyde, hydrogen peroxide and growth parameters was assessed. At a concentration of 1 mmol L −1 ammonium, Si increases the accumulation of nitrogen and Si, the nitrogen use efficiency, the root area and dry biomass of the shoot. At concentrations of 1 and 2 mmol L −1 ammonium, Si increases the leaf area and root dry biomass, and in higher concentrations, there was no effect of Si after the supply of ammonium. It was observed that the addition of Si mitigates ammonium toxicity by 1 mmol L −1 ammonium, and we can recommend its use in the nutrient solution (Si = 1 mmol L −1 ) to grow tomato cropsthat employs ammonium concentration of 1 mmol L −1 .

Silicon mitigates ammonium toxicity in plants

“…However, few studies have investigated how the effects of N forms can affect the development and partition of root biomass. The high NH 4 + ratios decrease the total N accumulation in the dry matter of species considered as sensitive to excess ammonium, such as Brassica napus L. (Madsen & Pan, ; Pan et al., ) Cucumis sativus (Campos et al., ; Roosta et al., ), Vicia faba L. (Pan et al., ) Triticum aestivum ( Horchani et al., ; Pan et al., ), Solanum lycopersicum (Barreto et al., ), and Oryza sativa and Spinacia oleracea (Silva, Mello Prado, & Ferreira, ), as well as in tolerant species, such as Saccharum spp . (Ishikawa et al., ) and Passiflora edulis (Silva Júnior et al., ).…”

“…plants cultivated with high ammonium, thus increasing leaf and stem dry matter production. Studies on the interaction between silicon and excess ammonium in Zea mays (Campos et al., ), Cucumis sativus (Campos et al., ), Solanum lycopersicum (Barreto et al., ), and Brassica oleracea (Barreto et al., ) indicated that the use of the beneficial element alleviated the ammonium toxicity, with an increase in the N and Si accumulation and the photosynthetic activities, thus providing higher plant dry matter accumulation.…”

Response of radish seedlings ( Raphanus sativus L.) to different concentrations of ammoniacal nitrogen in absence and presence of silicon

“…After 5 d of emergency, thinning was made leaving four plants in each pot, allowing adequate distance for root growth. Substrate mixture of (1:1, v/v) medium vermiculite (90 to 100% of the particles between 1.19 and 1.50 mm) and superfine (90 to 100% of the particles between 0.21 and 0.30 mm) was used, allowing for adequate porosity and aeration (Sarasketa et al, 2014;Barreto et al, 2016).…”

“…A recent study in the cultivation of Solanum lycopersicum verified a linear decrease of dry matter with the use of ammonium concentrations higher than 1 mmol L -1 in the nutrient solution (Barreto et al, 2016). In other research on different species, the effect of NH 4 + toxicity can also be verified, and its critical concentration of toxicity in plants such as Lemna minor, with 3.3 mmol L -1 of NH 4 + (Huang et al, 2013), and Solanum tuberosum, with 4.1 mmol L -1 of NH 4 + (Zebarth et al, 2012).…”

“…In recent studies (Barreto et al, 2016) on the strengthening of silicon in the nutrient solution in tomato plants under excess of ammonium, researchers have found an increase in the accumulation and the efficiency of use of nitrogen in the leaf area and the dry biomass of roots. However, there are not studies on ammoniacal toxicity in radish crop and its relationship with silicon nutrition.…”