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Nitrate reductase (NR) is the first enzyme in the nitrogen assimilation pathway. The determination of its activity requires modifications for each plant species. The goal of this work was to evaluate the variation of NR activity throughout the day and the optimization of assay conditions in foliar and radicular tissues of Physalis angulata. The analysis was done in plants cultivated in a hydroponic system at two months of age. The NR activity was based on the in vivo assay method. Enzyme activity was observed on leaf and root, indicating two sites of nitrate assimilation with a higher activity in the daylight in leaf. The NR activity in leaf was increased after 4h of luminosity. In the root, we observed a high activity during most of the day, especially in periods of higher solar radiation and temperature. To obtain the highest activity of NR in both tissues we suggest 1% n-propanol, 50mM of KNO3- in pH=7 phosphate buffer for 75 min incubation in water bath.

Exogenous application of nitric oxide (NO) may play an important role in drought-tolerant plants in large crops or underexploited species. Sodium nitroprusside (SNP, 0, 25, 50, 75 and 100 μM), an exogenous NO donor, was used in this study to evaluate the potential of NO in water deficit mitigation in Physalis angulata plants. This species is a genetic resource underexploited in Brazil, but that has uses in traditional medicine and potential for growing of small fruits. Gaseous exchanges, chlorophyll content, water relations, sugar accumulation and growth parameters were evaluated in this work. Despite water deficit influence on all variables, exogenous application of nitric oxide promoted attenuation of symptoms on photosynthetic performance, notably carbon assimilation, water use efficiency and chlorophyll content. Relative water content seems not to be influenced by exogenous supply of NO. While, direct relationship between sugars accumulation and leaf water potential promoted by exogenous NO was observed. Similarly, NO reversed and/or attenuated symptoms of water deficit on plant growth, especially plant height, dry matter accumulation and leaf area. Low concentrations of SNP have shown to mitigate negative effects of water deficit in Physalis angulata plants, improving photosynthetic rates, maintenance of leaf water potential and growth.

Despite the use of chemical priming as a promising tool for the study of plant stress physiology and the management of field crops, little is known of its importance when studying adult plants, especially in unexploited species. The aim of this work was to evaluate the use of sodium nitroprusside (SNP), hydrogen peroxide (H2O2) and proline (Pro) as possible chemical priming inducing agents in Physalis angulata plants exposed to water deficit. For this, plants in well-watered conditions were sprayed with different concentrations of SNP (25 and 50 μM), H2O2 (10 and 20 Mm) and Pro (10 and 20 mM) and evaluated after exposure to water deficit. Although the parameters of water relations, gas exchange, growth and dry matter accumulation were reduced with the imposition of water deficit, pretreated plants showed significant improvements in the same variables. Plants sensitized with Pro and SNP doses showed improvement in relative water content and water leaf potential, contributing to the maintenance of plant water status when exposed to water deficit. The attenuation of the effects of reduced water availability on gas exchange was significantly promoted with SNP spraying, notably carbon assimilation, stomatal conductance and transpiration, parallel to an increasing in the photosynthetic pigment content. The pretreatment also influenced the growth (with Pro 10 and 20 mM; SNP 50 μM) and biomass accumulation of plants exposed to water deficit (especially with SNP 50 μM), contributing to tolerance increase to this abiotic stress. Pretreatment with hydrogen peroxide had a reduced priming effect. The pretreatment of plants with sodium nitroprusside and proline contribute to the attenuation of water deficit effects in Physalis angulata plants, acting as potential chemical priming.

Choosing an appropriate nitrogen source is of utmost importance, since it affects the plant development and fruit and seed yield. This study aimed to evaluate the quality of Physalis angulata fruits and seeds obtained from plants grown in a hydroponic system, under different concentrations of nitrate and ammonium. The treatments consisted of four NO3-:NH4+ ratios (100:0, 75:25, 50:50 and 25:75). After full grown, the fruits were collected for biometric and chemical analyses, and seeds were removed for the germination test. The germination test was conducted in a germination chamber and the parameters evaluated were the germination rate, mean germination time, speed, germination uniformity coefficient and relative frequency. Fruits with lower weight and diameter were obtained at doses above 50 % of ammonium; however, there was an increase for ºBrix and soluble solids/titratable acidity ratio. Such dosage also reduced the rate, speed and uniformity of germination. The combined use of nitrogen sources (50:50 of NO3-:NH4+) is recommended, because it produces larger and sweeter fruits with vigorous seeds. RESUMO A escolha da fonte nitrogenada adequada é de suma importância, pois afeta o desenvolvimento da planta e a produção de frutos e sementes. Objetivou-se avaliar a qualidade de frutos e sementes de Physalis angulata obtidos de plantas cultivadas em sistema hidropônico, sob concentrações de nitrato e amônio. Os tratamentos consistiram de quatro proporções de NO3-:NH4+ (100:0, 75:25, 50:50 e 25:75). Ao final do cultivo, os frutos foram coletados para a realização de análises biométricas e químicas e para a retirada de sementes utilizadas no ensaio de germinação. O teste de germinação foi conduzido em câmara de germinação e os parâmetros avaliados foram a porcentagem, tempo médio, velocidade, coeficiente de uniformidade e frequência relativa. Os frutos de menor massa e diâmetro foram obtidos com doses acima de 50 % de amônio; entretanto, houve aumento para ºBrix e relação sólidos solúveis/acidez titulável. Essa dosagem também reduziu a porcentagem, velocidade e uniformidade de germinação. A utilização combinada das fontes nitrogenadas (50:50 de NO3-:NH4+) é aconselhável, pois produz frutos maiores, mais doces e com sementes vigorosas.