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Pak. J. Bot., 49(1): 57-62, 2017.

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Effects of Exogenous 24-Epibrassinolide on Photosynthesis

and ATP synthase β subunit of Tomato under Low

Temperature / Poor Light

Lirong Cui^a,  Kai Cao^a AND Zhirong Zou^*

College of Horticulture, Northwest A&F University, Yangling 712100, Shaanxi, People’s Republic of China

^*Corresponding author’s e-mail: zouzhirong2005@hotmail.com; Fax: +86-29-87087298; Tele: +86-29-87082613

^a These authors contributed equally to this work

Abstract

We monitored the effects of exogenous 24-epibrassinolide (EBR) on the photosynthesis and ATP synthase β subunit of tomato (Solanum lycopersicum L.). Seedlings of ‘Zhongza9’ and ‘Zhongshu4’ cultivars were pre-treated with foliar sprays of 0.1 μM or 0.0 μM (control) EBR and then grown in an environmental chamber simulating conditions of low temperature (12°C/6°C, day/night) and poor light (80 μmol·m^-2·s^-1). Stressed seedlings that had received EBR showed increases in stomatal conductance and rates of photosynthesis and transpiration over the untreated (0 EBR) control, but had reduced concentration of intercellular CO₂. Exposure to EBR was also linked with smaller, stress-related declines in the maximum photochemical efficiency of Photosystem II, the actual photochemical efficiency of Photosystem II, the photochemical quenching coefficient, and the efficiency of light energy capture by open PSII reaction centers under our combined stresses. We also found that EBR improved plant stress tolerance, and the mechanism was that ATP synthase β subunit was synthesized in a large amount.

Key words: ATP synthase β subunit, Chlorophyll fluorescence, 24-Epibrassinolide, Photosynthesis, Tomato.