Effects of HgCl2 stress on the upper leaf necroses and water use efficiency of oriental hybrid lilies

Some of the oriental hybrid lily cultivars are prone to upper leaf necrosis (ULN), which has become a major threat to the quality of cut and pot lilies. The ULN of oriental lily is believed to relate with water metabolism. In order to explore the relationship between ULN of lilies and the aquaporin, we used three different concentrations of aquaporin inhibitor HgCl2 (50, 100 and 200μmol/L) to irrigate two lily cultivars which are different in sensitivity to ULN. The result showed that with the increasing concentrations of HgCl2, the ULN indexes of the cultivar ‘Sorbonne' were increased by 13.56%, 36.06% and 42.19%, respectively, compared with the contrast; for the cultivar ‘Siberia', the ULN indexes were increased by 7.20%, 12.15% and 18.00%, respectively. The height, stem diameter, leaf area, root length, activity of stem shooting roots, net photosynthetic rate and transpiration rate of ‘Sorbonne' and ‘Siberia' were inhibited to varying degrees, especially for the root activity. The root activities of ‘Sorbonne' were reduced by 41.9%, 54.7% and 67.5%, respectively, compared to the contrast after treated with three concentrations of HgCl2; for ‘Siberia', the root activities were reduced by 4.8%, 33.5% and 38.2%, respectively. The WUEs of ‘Sorbonne' were decreased by 14.00%, 19.23% and 46.06% after HgCl2 treatment, while those of ‘Siberia' were decreased by 8.62%, 17.60% and 28.71%, respectively. The following conclusions could be drawn: with different levels of HgCl2stress, the water transportation of ‘Sorbonne' and ‘Siberia' was inhibited, and the ULN indexes were increased. We initially speculate that the degree of ULN of lilies is related to the expression of plant aquaporins.