Abstract
The objective of this study was to evaluate the effects of combinations of nitrate and ammonium in the medium, on the accumulation of nitrogen compounds and carbohydrates, in the presence and absence of salinity in sorghum plants. CSF 20 genotype sorghum seeds, were grown in the greenhouse and supplied with a nutritive solution at three different concentrations of nitrate and ammonium (100% NO3-: 0% NH4+, 75% NO3-: 25% NH4+ e 0% NO3-: 100% NH4+) both in the presence and absence of NaCl. Salinity reduced the nitrate concentration in both leaves and stalks in treatments at 100:0 and 75:25. The accumulation of ammonium was higher in those plants, in both leaves and stalk, in the presence of NaCl. The levels of free amino acids in the leaves showed no change, whereas those in the stalk increased in the presence of salt and with the increase of ammonium. The concentration of free proline in both leaves and stalk was higher in plants under salinity. The total nitrogen content was higher in the leaves without, however, showing much change in the presence of salt. The concentration of total soluble carbohydrates was higher in those plants treated with salt, except in the stalk 0:100. Sucrose levels in the leaves were lower in the presence of NaCl and the increase in ammonium, while they were higher in the stalk at 75:25 NaCl. The starch content did not alter much with the different levels of nitrogen and salinity. It is concluded that NO-3 and NH4+ combinations in the medium affect the accumulation of nitrogen compounds and carbohydrates in the leaves and stalks of sorghum plants, both in the presence and absence of salinity.
Highlights
The objective of this study was to evaluate the effects of combinations of nitrate and ammonium in the medium, on the accumulation of nitrogen compounds and carbohydrates, in the presence and absence of salinity in sorghum plants
Foram utilizadas para esse experimento sementes de sorgo forrageiro [Sorghum bicolor (L.) Moench], genótipo CSF 20, cedidas pelo Banco de Germoplasma da Empresa Pernambucana de Pesquisa Agropecuária (IPA)
A salinidade aplicada reduziu a concentração de nitrato tanto nas folhas como no colmo em todos os tratamentos, exceto o que contêm apenas amônio na solução, onde não houve diferença significativa entre os tratamentos - NaCl e + NaCl (FIG. 1A, 1B)
Summary
Foram utilizadas para esse experimento sementes de sorgo forrageiro [Sorghum bicolor (L.) Moench], genótipo CSF 20, cedidas pelo Banco de Germoplasma da Empresa Pernambucana de Pesquisa Agropecuária (IPA). A solução foi filtrada para obtenção de um extrato, onde foram realizadas as determinações de solutos inorgânicos. O material congelado (folhas e colmo) foi liofilizado, macerado, pesado (50 mg) e transferido para tubos de ensaio onde foram adicionados 5 mL de água destilada. Posteriormente, a solução foi filtrada para obtenção de um extrato, onde foram realizadas as determinações dos solutos orgânicos. 50 mg do material liofilizado e 1,5 mL de solução MCW (solução de metanol, clorofórmio e água 12:5:3 v/v) foram colocados em eppendorfs e ficaram sob agitação a 25 oC, por 30 min. Após o resfriamento foram adicionados aos tubos 3 mL de antrona (antrona 0,2% em ácido sulfúrico), e os tubos posto em banho-maria a 40 °C, por 20 min. Os dados foram analisados segundo análise de variância (ANOVA) e as médias comparadas pelo teste de Tukey ao nível de 5% de significância
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