Evaluation of physiological responses and tolerance to low-temperature stress of four Iceland poppy (<i>Papaver nudicaule</i>) varieties

<p>Iceland poppy (<i>Papaver nudicaule</i>) is a boreal flowering plant and native to subpolar regions of Europe, Asia and North America, and the mountains of Central Asia. To investigate response and tolerance to low-temperature stress, the four varieties of Iceland poppy, Champagne Bubbles (CB), Domestic Variety (DV), Wonderland (WL), and Garden Gnome (GG), were subjected to low-temperature treatment from 0°C to −9°C. The relative electrical conductivities in four varieties increased along with the decrease in temperature. Treated by −3°C, the morphological changes of seedlings at different time points were investigated. Four varieties were differentially injured by freezing temperature. The dynamic accumulations of malondialdehyde (MDA), free proline (FP), soluble proteins (SP), and activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) during low-temperature treatment were measured and compared. A minor change in SP content during treatment was found, whereas MDA and FP were significantly induced. Complex patterns of activity alternations of SOD, POD, and CAT were found. Based on the calculation of semi-lethal temperature and comprehensive physiological parameters investigation, the tolerance of four varieties was evaluated as CB > GG and DV > WL.