Abstract
Cleistocalyx operculatus and Syzygium cumini possess a certain waterlogging tolerance. However, the comparable and adaptable strategies to waterlogging stress between these two species on the basis of waterlogging adventitious root (AR) regulation were still unclear. In this study, the plant performances in response to AR regulation based on AR removal and exogenous hormone application were investigated in terms of plant morphology, physiology, photosynthesis, and AR traits. Results showed that C. operculatus possesses stronger waterlogging tolerance than S. cumini based on waterlogging tolerance coefficient, which is mainly due to the higher root biomass, root porosity, and length and activity of ARs, and shorter emergence time of ARs in C. operculatus than in S. cumini. The AR-R treatment increased activity and porosity of primary root, and induce a large amount of up-vertical ARs from the primary root systems in C. operculatus, while similar adaptive morphological changes in roots did not occur in AR-R treated S. cumini. Exogenous ABA application had better effects on alleviating waterlogging damages than exogenous IAA in balancing endogenous hormones (ABA and ZR), promoting ARs development (porosity and activity, and the ratio of cortex area to stele area), improving photosynthesis process and antioxidant system (soluble protein, free proline, and peroxidase). Moreover, under waterlogging conditions, exogenous ABA application induced greater increases in net photosynthesis rate (A), stomatal conductance (gs), chlorophyll b (Chl b), and carotenoid (Caro) in S. cumini than in C. operculatus, which suggested that S. cumini responded more positively and efficiently to exogenous ABA application than C. operculatus under waterlogging conditions. Thus, the findings provided new insights into the waterlogging adaptable strategies in waterlogging tolerant woody species on the basis of ARs, and could provide scientific guidance for the application of these two species during revegetation activities in wetlands.