ABSTRACT
Silicon mitigates ammonium toxicity in yellow passionfruit seedlings

Gabriel B. da Silva Júnior1*, Renato M. Prado2, Cid. N.S. Campos3, Flávia B. Agostinho4, Sylvia L. O. Silva5, Luiz C.N. Santos2, and Leónidas. C. González6
 
Ammonium (NH4+) toxicity in yellow passionfruit (Passiflora edulis Sims f. flavicarpa O. Deg.) may be mitigated by Si application. This study aimed to evaluate the interaction effect of Si and high level of NH4+ on yellow passionfruit seedlings nutrition, physiology, growth, and DM production. Pots were filled with pinus bark and nutrition solution was applied. Treatments were arranged in a completely randomized design, with five replicates, in a 2 × 2 factorial scheme: two ratios of NH4+ and nitrate, NO3+ (40/60%, without high level of NH4+; and 75/25%, with high level of NH4+) at N concentration of 13 mmol N L-1, in the absence and presence of Si (2.0 mmol L-1). Sixty days after seedling transplant it was evaluated: N, Si, K, Ca and Mg root and shoots accumulation, leaf green color index (GCI), electrolyte leakage index (ELI), intracellular CO2 concentration (Ci), transpiration rate (Tr), stomatal conductance (gs), net photosynthesis rate (Pn), stem diameter, leaf area, root length, N use efficiency (NUE) and root and shoot DM content. Plants cultivated with Si had 19.1% and 16.3% lower Tr and gs, respectively, regardless NH4+ concentration. Moreover, Ci and Pn were 13.2% and 16.4%, respectively, higher in plants that received Si. Plants cultivated under high NH4+ concentrations, with Si application had 17% bigger stem diameter and 15.4% bigger root length than plants without Si application. Si application in yellow passionfruit seedlings cultivated with high level of NH4+ increased accumulation and NUE, root length, root DM, and GCI. In addition, Si application reduced ELI, which resulted in higher stem diameter. These results prove that Si application mitigates NH4+ toxicity in yellow passionfruit seedlings.
Keywords: Abiotic stress, beneficial element, NH4+, nitrogen, Passiflora edulis, toxicity.
1Universidade Federal do Piauí, Centro de Ciências Agrárias, Departamento de Fitotecnia, Campus Ministro Petrônio Portella, Ininga, CP: 64049-550, Teresina, Piauí, Brasil. *Corresponding author (gabrielbarbosa@ufpi.edu.br).
2Universidade Estadual Paulista “Julio de Mesquita Filho” Departmento de Solos e Adubos, Faculdade de Ciências Agrárias e Veterinárias, via de acesso Prof. Paulo Donato Castellane, CP: 14884-900, Jaboticabal, São Paulo, Brasil.
3Universidade Federal de Mato Grosso do Sul, Campus Chapadão do Sul, Rodovia MS-306, Zona Rural, CEP 79560-000, Chapadão do Sul, Mato Grosso do Sul, Brasil.
4Louisiana State University, School of Plant, Environm