Morphological and metabolic responses of four Iris germanica cultivars under salinity stress

Salinity stress poses a serious challenge to plant growth and development and degrade visual quality of ornamental plants. Iris germanica (bearded iris) are important perennial plants in demand for landscape and garden plants. In this study, four popular cultivars of I. germanica were subjected to salinity treatments (created by 0, 35, 70, 105, 140 and 175 mM NaCl) for 28 days. Plant visual quality, photosynthetic characteristics, activities of antioxidant enzymes and mineral concentration were investigated. The results showed most metabolic responses including photosynthetic characteristics, activities of antioxidant enzymes were affected by the interaction between salinity treatment and cultivar. Salinity stress was accompanied by a clear increase of Na+ concentration. Foliar damage was observed in all the cultivars with 70 mM NaCl or higher saline solution treatments. characteristics including net photosynthetic rate and transpiration rate generally showed a decreased trend with increasing NaCl concentrations, while the specific changes were different in four iris cultivars. After 14 days of treatment, Na+ concentration in rhizomes were lower than those in roots or leaves under certain salinity treatments in general. Among the different cultivars, the cultivar 'Memories of Harvest' showed better salinity tolerant performances than other cultivars.