The chlorophyll fluorescence parameters response of Fenugreek (Trigonella foenum-graceum L.) landraces to freezing stress

The state of the photosynthetic apparatus is considered as one of the indicators for evaluating the tolerance of plants to environmental stress, including freezing stress. Therefore, the effects of three temperatures (-9, -12 and -15°C) on the cold tolerance of 10 landraces (Azari, Ardestan, Rudsar1, Rudsar2, Shiraz, Shirvan, Mashhad, Neyshabur, Hamedan, Hendi) in four periods (12, 24, 48, and 72 hours) were evaluated in controlled condition using a factorial arrangement in a completely randomized design with three replications. The maximum efficiency of photosystem II (F′v/F′m) was affected by temperature decline from -9 to 12- and -15°C in fenugreek landraces. The greatest decrease of this parameter was observed in most of the landraces at temperatures of -12 and -15°C , respectively, 72 and 48 hours after freezing stress. At temperatures below -15°C the index had a decreasing and irreversible trend, which can be justified due to the dead of landraces at this temperature. Only Rudsar2, Shirvan, Mashhad and Neyshabur landraces had the survival rate of more than 50% at -12°C and the fluctuations of this index were less when faced with temperature stress of -9 and -12 °C, which indicates their less sensitivity to freezing stress and the ability to suitable recovery at this temperature. A significant positive correlation between the maximum efficiency of the potential of photosystem II and the percentage of survival (r2= 0.81**), recovery traits consist of leaf area (r2=0.76**) and dry weight (r2=0.73**) was observed, which indicates the suitability of these landraces for further studies for autumn.