Spatiotemporal photosynthetic physiology responses of remnant Myricaria laxiflora populations to regulated water level fluctuations

Abstract

The construction of the Three Gorges–Gezhouba Dam cascade hydropower station has changed the water level fluctuation pattern of the habitats for remnant rare and endangered Myricaria laxiflora populations downstream of the dam. The present study utilized biochemical markers of photosynthetic physiology to evaluate the spatiotemporal responses of remnant populations to human-regulated water level fluctuations. The results showed that the photosynthetic physiological activities of remnant M. laxiflora populations underwent a period of rapid growth, followed by a gradual decline in the growth recovery phase after flooding. During the entire experimental period, photosynthetic physiological activities of remnant M. laxiflora populations changed with prolongation of emergence time: specifically, net photosynthetic rate and stomatal conductance initially decreased and then subsequently increased, intercellular carbon dioxide concentrations peaked at mid-phase and transpiration rate continuously increased. The maximum net photosynthetic rate, apparent photosynthetic quantum efficiency and dark respiration rate in the light–response curves of the plants continuously increased during growth. The water level gradient also significantly affected the photosynthetic physiological activities in the remnant populations, i.e. the photosynthetic physiological activities of high-altitude plants were significantly higher than the middle- and low-altitude plants. The changes in photosynthetic pigment content of plants in remnant populations during the growth recovery phase and the entire growth period were similar to those occurring in photosynthetic activities in plants. Further, canonical correspondence analysis showed that photosynthetic physiological activities in the plants were significantly correlated with changes in water levels, emergence time, elevation gradient, soil water and soil nitrogen contents. Therefore, the artificial regulation of water level fluctuations by large hydropower stations will inevitably affect the photosynthetic activities and growth of remnant M. laxiflora populations.

Branches and Leaves Growth Patterns in Myricaria laxiflora Remnant Populations Are Affected by Human-altered Water Level Fluctuations

“…An investigation on the M. laxi ora remnant populations by Bao et al (2010) revealed that the remnant population structure had an extremely low ratio of young seedlings, indicating a population degradation caused by the hindered population regeneration. In our recent study on the growth and reproduction characteristics of M. laxi ora remnant populations, sexual reproduction, photosynthetic activity and seedling establishment were signi cantly reduced due to the changes in the water level uctuation pattern (Chen et al, 2019;Guan et al, 2020a;Guan et al, 2020b). This study further elucidated the effects of regulated water-level uctuations on the formation and changes in M. laxi ora branch and leaf growth traits.…”

“…Because M. laxi ora have extremely small leaves, their young branches (green-colored) are also important photosynthetic organs. A decrease in the number of branch and leaves will affect the photosynthetic capability and the accumulation of organic matters of plants (Guan et al, 2020b), which further in uences the plant growth and sexual reproduction after ood (Chen et al, 2019: Guan et al, 2020a. This could explain why M. laxi ora populations continue to degenerate under the regulated water level uctuation pattern (Bao et al, 2010).…”

De novogenome assembly ofMyricaria laxifloraprovides insights into its molecular mechanisms under flooding stress

“…M. laxiflora can be an ideal plant for studying the molecular mechanism of plant flooding tolerance [6,7]. In recent years, many studies have been conducted to investigate the effects of flooding stress on the physiological response of M. laxiflora [2,8,9]. However, little is known about the molecular mechanism of waterlogging tolerance in M. laxiflora , partly due to a lack of high-quality reference genome.…”

Integrated Transcriptomic and Proteomic Analyses Uncover the Regulatory Mechanisms of Myricaria laxiflora Under Flooding Stress

“…M. laxiflora has been regarded as an ideal plant to study the ecological restoration of Yangtze River (Chen and Xie, 2009;Chen et al, 2019). To date, many studies have been performed to investigate the influences of flooding on the seedling survival and physiology responses of M. laxiflora (Chen and Xie, 2009;Guan et al, 2020;Zhou et al, 2020); however, the molecular mechanisms underlying the flooding stress remain elusive.…”