Alleviation of Oxidative Stress by Photosynthetic Modulations in Rice Plants Simultaneously Stressed with Salt and Heat1
A. Bonifacio2, M. O. Martins3, M. C. Lima Neto4, F. E. L. Carvalho5, A. K. M. Lobo5 & J. A. G. Silveira6
Abstract: Plants in the field are exposed to multiple stresses, such as salinity, drought, high light, heat and others, and exhibit different physiological responses. To evaluate the consequences of some of these stresses to the photosynthetic apparatus and antioxidative metabolism, rice plants were submitted to the following treatments: control (without NaCl and at 27 °C), heat stress (without NaCl and at 42 °C), salt stress (100 mM NaCl and at 27 °C) and combined stress (salt and heat stress together). At the end of experimental period, gas exchange, chlorophyll fluorescence and electrolyte leakage were measured and leaves were collected for biochemical determinations. Isolated salt and heat stresses were not sufficient to cause damage in the photochemical apparatus and heat stress only modified stomatal aperture. The results indicate that the photosynthetic processes was affected in CO2-assimilation and quantum efficiency levels in combined stress. Lipid peroxidation was elevated in combined stress, but in isolated heat stress decreased. All enzymes evaluated were differently modulated in all treatments. Taken together, the data indicates more intense impairment of photosynthesis in rice plants at combined stress; however, the effective modulation of antioxidative system was effective in establishing a new redox homeostasis and providing tolerance to abiotic stress.
Key word: photosynthesis, photochemical efficiency, salinity, multiple stresses
1 Part of the Thesis of the first author presented to Federal University of Ceará, Fortaleza, CE, Brazil
2 Adjunct Professor, UFT, CEP 77402-970, Gurupi, TO, Brazil. (63) 33113530. E-mail: firstname.lastname@example.org
3 Postdoctoral student, UFC, Fortaleza, CE, Brazil
4 Postdoctoral student, University of Manchester, Manchester, England
5 Doctoral student, UFC, Fortaleza, CE, Brazil
6 Full Professor, UFC, Fortaleza, CE, Brazil. e-mail: email@example.com
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