Growth, Leaf Gas Exchange, and Chlorophyll Fluorescence Responses of Two Cultivars of Salix integra Thunb. to Waterlogging Stress

Salix integra Thunb. is a shrub distributed in China along the Huai River riparian zone, and plays an important role in water and soil conservation. S. integra shrub land is easily submerged during July to October due to the flooding of Huai River. In order to characterize the physiological mechanisms of waterlogging tolerance of S. integra and to help rationally select waterlogging-tolerant species to alleviate the flood damage to agricultural production, we studied the effects of flooding on the growth, leaf gas exchange, and chlorophyll fluorescence of S. integra cuttings during a growth season (from August to October 2011). The biomass production and photosynthesis of S. integra cv. qingpi were promoted under moderate waterlogging stress, whereas its growth, chlorophyll content, net photosynthetic rate, and stomatal conductance were all significantly lower than those of the control group. A significant increase in non-photochemical quenching (NPQ) and a reduction in PSII maximal quantum photochemistry efficiency (Fv/Fm) were observed inflooded seedlings of S. integra cv. hongpi. In the case of S. integra cv. qingpi, however, there were no significant differences in NPQ and Fv/Fmbetween the treatment and the controls. Our results demonstrated that S. integra cv. hongpi exhibited slight damage to its photosynthetic apparatus under flooding. In contrast, a moderate flooding stress promoted the leaf and root production of S. integra cv. qingpi, indicating that S. integra cv. qingpi can tolerate prolonged soil flooding better than S. integra cv. hongpi. Thus, S. integra cv. qingpi is more suitable for afforestation in the riparian zone.