Plant Process and Function

en Effects of bioactive compounds on chlorophyll fluorescence parameters of Mexican lime seedlings (Citrus aurantifolia Swingle) under cold stress Effects of bioactive compounds on chlorophyll fluorescence parameters of Mexican lime seedlings (Citrus aurantifolia Swingle) under cold stress تنش دما thermal stress پژوهشي Research <div style="text-align: left;">Cold stress is one of the abiotic stresses that leads to most losses in citrus. Mexican lime is one of the commercial citrus cultivars in the world, which is commonly used as a citrus rootstock in the southern regions of Iran. That is one of the most sensitive citrus cultivars to cold stress. In order to investigate the ameliorating effect of some bioactive compounds on chlorophyll fluorescence parameters and electrolyte leakage of Mexican lime seedlings under cold stress, a split-factorial experiment was conducted in the form of the randomized complete block design. The experimental factors included temperature (0 and -6 °C) as a main factor and foliar application of melatonin (0 and 500 μM), mannitol (0 and 50 μM) and acetic acid (0 and 15 μM) as sub-factors. According to the results, the combined application of melatonin + mannitol + and acetic acid, by improving the photosynthetic parameters, reduced the destructive effects of cold stress (0 and -6 ºC) on photosynthetic machinery in Mexican lime seedlings. The highest Area was observed in the treatment of melatonin + mannitol + acetic acid. The treatments of melatonin and melatonin + acetic acid had the highest values of Fv/Fm and Fv/F0 and the lowest values of F0/Fm at both temperatures compared to the control. In this study, the most appropriate parameters to identify the best treatments included Area (total area between initial fluorescence curve and maximal fluorescence), maximum quantum yield of PSII photochemistry (Fv/Fm), thermal dissipation quantum yield (F0/Fm), and an indicator of the activity of the oxygen-evolving complex on the donor side of PSII (Fv/F0). Therefore, the mentioned bioactive compounds, especially melatonin as well as acetic acid, are proposed to manage cold stress in Mexican lime seedlings.</div> Cold stress is one of the abiotic stresses that leads to most losses in citrus. Mexican lime is one of the commercial citrus cultivars in the world, which is commonly used as a citrus rootstock in the southern regions of Iran. That is one of the most sensitive citrus cultivars to cold stress. In order to investigate the ameliorating effect of some bioactive compounds on chlorophyll fluorescence parameters and electrolyte leakage of Mexican lime seedlings under cold stress, a split-factorial experiment was conducted in the form of the randomized complete block design. The experimental factors included temperature (0 and -6 °C) as a main factor and foliar application of melatonin (0 and 500 μM), mannitol (0 and 50 μM) and acetic acid (0 and 15 μM) as sub-factors. According to the results, the combined application of melatonin + mannitol + and acetic acid, by improving the photosynthetic parameters, reduced the destructive effects of cold stress (0 and -6 ºC) on photosynthetic machinery in Mexican lime seedlings. The highest Area was observed in the treatment of melatonin + mannitol + acetic acid. The treatments of melatonin and melatonin + acetic acid had the highest values of Fv/Fm and Fv/F0 and the lowest values of F0/Fm at both temperatures compared to the control. In this study, the most appropriate parameters to identify the best treatments included Area (total area between initial fluorescence curve and maximal fluorescence), maximum quantum yield of PSII photochemistry (Fv/Fm), thermal dissipation quantum yield (F0/Fm), and an indicator of the activity of the oxygen-evolving complex on the donor side of PSII (Fv/F0). Therefore, the mentioned bioactive compounds, especially melatonin as well as acetic acid, are proposed to manage cold stress in Mexican lime seedlings. Chilling, Freezing, Citrus, Photosynthesis, Melatonin, Mannitol, Acetic acid Chilling, Freezing, Citrus, Photosynthesis, Melatonin, Mannitol, Acetic acid 19 32 http://jispp.iut.ac.ir/browse.php?a_code=A-10-503-10&slc_lang=en&sid=1 Alireza Sanie Khatama Alireza Sanie Khatam saniekhatam.alireza@gmail.com No Department of Horticultural Science, Agriculture and Natural Resource College, University of Hormozgan, Bandar Abbas, Iran Department of Horticultural Science, Agriculture and Natural Resource College, University of Hormozgan, Bandar Abbas, Iran Somayeh Rastegar Somayeh Rastegar rastegarhort@gmail.com 0000-0002-0840-9674 Yes Department of Horticultural Science, Agriculture and Natural Resource College, University of Hormozgan, Bandar Abbas, Iran Department of Horticultural Science, Agriculture and Natural Resource College, University of Hormozgan, Bandar Abbas, Iran Abdolhossein Aboutalebi Jahromi Abdolhossein Aboutalebi Jahromi aa84607@gmail.com No Department of Horticultural Science, Agriculture College, Islamic Azad University, Jahrom Branch, Jahrom, Iran Department of Horticultural Science, Agriculture College, Islamic Azad University, Jahrom Branch, Jahrom, Iran Hamed Hassanzadeh Khankahdani Hamed Hassanzadeh Khankahdani hamed51h@gmail.com No Horticulture Crops Research Department, Hormozgan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Bandar Abbas, Iran Horticulture Crops Research Department, Hormozgan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Bandar Abbas, Iran Seyed Ali Akbar Bagherian Seyed Ali Akbar Bagherian sabagherian@gmail.com No Department of Horticultural Science, Faculty of Agriculture, Jahrom University, Jahrom, Iran Department of Horticultural Science, Faculty of Agriculture, Jahrom University, Jahrom, Iran