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3 Acta Physiologiae Plantarum

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High supply of NO3- mitigates salinity effects through an enhancement in the efficiency of photosystem II and CO2 assimilation in Jatropha curcas plants

100%

Aragao R. M. , Silva E. N. , Vieira C. F. , Silveira J. A.

2012

tom 34

nr 6

This study was performed to determine if a high supply of N-NO₃⁻ is capable of mitigating negative salinity effects on photosynthesis and growth through the stimulation of nitrate assimilation, which could act as an sink from photosynthetic electron transport chain and restrict the over reduction in thylakoid membrane in Jatropha curcas leaves. The experiment was arranged in a factorial design with two nitrate concentrations (1 and 10 mM) and two NaCl levels (0 and 100 mM). Salt-stressed plants supplied with high NO₃⁻ demonstrated a higher nitrate uptake rate, nitrate reductase activity and solubleprotein content when compared with plants that presented low nitrate uptake. High nitrate assimilation was associated with higher leaf growth, CO₂ assimilation and lower membrane damage in salt-stressed plants. The superior performance of salt-stressed plants grown with high NO₃⁻ was indicated by a higher effective quantum yield of PSII and electron transport rate and lower energy excess at the PSII level and non-photochemical quenching. Interestingly, a high NO₃⁻ level in the absence of NaCl did not alter the leaf growth, photochemical activity and gas exchange parameters when compared with plants supplied with low nitrate. The proline and glycinebetaine contents were similarly increased in both low- and high-NO₃⁻ saltstressed plants. Our data suggest that the favorable effects induced by high nitrate supply were possibly associated with stimulation in the nitrate assimilatory pathway. This process might have acted as a sink of electrons from the thylakoid membranes minimizing photo-damage and stimulating CO₂ assimilation under salinity in J. Curcas.

Photosynthesis impairment and oxidative stress in Jatropha curcas exposed to drought are partially dependent on decreased catalase activity

88%

Silva E. N. , Silveira J. A. , Aragao R. M. , Vieira C. F. , Carvalho F. E. L.

Acta Physiologiae Plantarum

2019

tom 41

nr 01

High CO2 favors ionic homeostasis, photoprotection, and lower photorespiration in salt‑stressed cashew plants

75%

Souza N. C. S. , Silveira J. A. G. , Silva E. N. , Neto M. C. L. , Lima C. S. , Aragao R. M. , Ferreira-Silva S. L.

Acta Physiologiae Plantarum

2019

tom 41

nr 09

The aim of this study was to evaluate the effects of elevated CO₂ concentration on acclimation mechanisms related to gas exchange, photochemical activity, photorespiration, and oxidative protection in cashew plants exposed to salinity. Thirty-day-old cashew plants were irrigated with nutrient solution without (control) or with supplemental NaCl (100 mM) for 2 weeks in the greenhouse. Afterward, control and salt-stressed plants were transferred to the growth chamber and supplied with atmospheric (380 µmol mol⁻¹) or high CO₂ (760 µmol mol⁻¹) concentrations for 15 days. The results show that elevated CO₂ alone reduced the CO₂ net assimilation rate (PN) without affecting stomatal conductance (gS) and transpiration rate (E), whereas salinity and NaCl + high CO₂ reduced the PN associated with a decrease in gS and E. The potential quantum yield of photosystem II (Fv/Fm) was not altered, but a slight reduction in electron transport rate and photochemical quenching (qP) in response to high CO₂ alone or combined with NaCl occurred. However, non-photochemical quenching increased due to the effects of high CO₂ and NaCl alone and by their combination. High CO₂ alleviated the toxic effects of Na⁺ favoring the K⁺ /Na⁺ ratio under salinity. High CO₂ coupled with salinity decreased glycolate oxidase activity and the contents of hydrogen peroxide (H₂O₂), NH₄⁺, and glyoxylate. Furthermore, we observed increase in membrane damage associated with increased thiobarbituric acid-reactive substances levels under high CO₂. High CO₂ also decreased ascorbate peroxidase activity, but did not affect superoxide dismutase activity. In general, our data suggest that high CO₂ could induce acclimation processes in plants independent of salinity, revealing a set of responses that are more associated with acclimation than with protective responses.