Abstract
Distylium chinense is an evergreen shrub used for the vegetation recovery of floodplain and riparian areas in Three Gorges Reservoir Region. To clarify the morphological and physiological responses and tolerance of Distylium chinense to off-season flooding, a simulation flooding experiment was conducted during autumn and winter. Results indicated that the survival rate of seedlings was 100%, and that plant height and stem diameter were not significantly affected by flooding. Adventitious roots and hypertrophic lenticels were observed in flooded seedlings after 30 days of flooding. Flooding significantly reduced the plant biomass of roots, net photosynthetic rate (P n), stomatal conductance (g s), transpiration rate (T r), maximum photochemical efficiency (Fv/Fm), photochemical quenching (qP), and electron transport rate (ETR) in leaves, and also affected the allocation and transport of carbohydrate and nutrients. However, D. chinense was able to maintain stable levels of P n, Fv/Fm, qP, ETR, and nutrient content (N and P) in leaves and to store a certain amount of carbohydrate in roots over prolonged durations of flooding. Based on these results, we conclude that there is a high flooding tolerance in D. chinense, and the high survival rate of D. chinense may be attributable to a combination of morphological and physiological responses to flooding.
Highlights
Flooding is a common environmental stress; natural phenomena such as rainfall, snowmelt, or tides and human activities such as the construction of tidal water conservancy and hydropower can result in flood-prone environments [1,2]
The formation of adventitious roots and hypertrophied lenticels was observed in flooded seedlings after 30 days of flooding, and the number of adventitious roots and hypertrophied lenticels was 6.10 and 33.2, respectively, by day 60 (Table 1)
Similar results have been reported by Peng et al [27], who found that the survival rate of D. chinense seedlings was 100% when faced with 30-days summer flooding, with no symptoms of severe injury
Summary
Flooding is a common environmental stress; natural phenomena such as rainfall, snowmelt, or tides and human activities such as the construction of tidal water conservancy and hydropower can result in flood-prone environments [1,2]. Some plant species can sense low oxygen levels via the posttranslational regulation of key hypoxiaresponsive transcription factors by the N-end rule pathway to enhance plant responses to hypoxia and flooding [7,8,9] and bring about various morphological, physiological, and biochemical changes that improve flood tolerance [10,11] These changes include alteration of the light absorption efficiency of plants through changes in leaf morphology with a reduction of light intensity [12], the formation of adventitious roots and hypertrophic lenticels at the stem base [13], the reopening of stomata [14], the formation of a complex antioxidant defense system [15], and reductions in carbohydrate consumption and changes in nutrient partitioning [16]
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