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Water-use strategies play a crucial role in the adaptive capabilities of mangroves to the saline intertidal conditions, yet the intricacies of daily water-use patterns in mangrove species, which are pivotal for maintaining water balance, remain poorly understood. In this comprehensive study, we aimed to clarify the water use strategies of three co-occurring mangrove species, Avicennia marina , Aegiceras corniculatum and Kandelia obovata , through stem sap flow monitoring, leaf gas exchange and stem diameter change measurements. Our findings revealed that the daily sap flow density of Avicennia and Aegiceras reached the peak about 1 h earlier than that of Kandelia. When transpiration was strong, Kandelia and Aegiceras used stem storage to meet water demand, while Avicennia synchronized stem water storage. These three mangrove species adopted cross-peak water used and unique stem water storage to regulate their water balance. In Kandelia , the daily sap flow in per sapwood area was significantly lower, while water-use efficiency was significantly higher than those of Avicennia and Aegiceras , indicating that Kandelia adopted a more conservative and efficient water-use strategy. Sap flow in Avicennia was the most sensitive to environmental changes, while Kandelia limited water dissipation by tightly controlling stomata. Meteorological factors (photosynthetically active radiation, vapor pressure deficit and air temperature) were the main driving factors of sap flow. The increase of soil temperature can promote the water use of mangrove species, while the increase of salinity resulted in more conservative water use. Our results highlight the diversity of daily water-use strategies among the three co-occurring mangrove species, pinpointing Kandelia as the most adaptive at navigating the changing conditions of intertidal habitats in the future climate. In conclusion, our findings provide a mesoscale perspective on water-use characteristics of mangroves and also provides theoretical basis for mangroves afforestation and ecological restoration. [ABSTRACT FROM AUTHOR]

This study examines the effects of light emitting diodes (LEDs) on tissue culture proliferation of Acacia melanoxylon plantlets among five different clones (FM1, FM2, FM4, FM5, and FM10). Shoot bud apex cuttings were transplanted onto Murashige and Skoog basal medium containing 0.1 mg L-1 6-benzyladenine and 0.5 mg L-1 naphthalene acetic acid and cultured in vitro for 40 days. Root growth was studied under different light intensities and photoperiods ex vitro. The bud proliferation coefficient was greatest under a light intensity of 45 μmol m-2 s-1 photosynthetic photon flux and photoperiod of 16 h light, but decreased as the light intensity increased. However, the greatest light intensity was beneficial for the growth of robust plantlets. Plantlets exposed to red and blue LED combinations grew tall and green, with a small number of roots. Plantlets also grew taller and some roots expanded under the longer photoperiod. Increased light intensity had positive effects on root number and rooting rate, and prolonged light greatly increased root number. Therefore, lower light intensity and a short photoperiod were beneficial for bud proliferation, while red/blue LED combinations, increased light intensity, and longer light illumination were beneficial for plantlet growth and root growth of Acacia melanoxylon.

As part of the plant water-use process, plant nocturnal sap flow ( Q n ) has been demonstrated to have important ecophysiological significance to compensate for water loss. The purpose of this study was to explore nocturnal water-use strategies to fill the knowledge gap in mangroves, by measuring three species co-occurring in a subtropical estuary. Sap flow was monitored over an entire year using thermal diffusive probes. Stem diameter and leaf-level gas exchange were measured in summer. The data were used to explore the different nocturnal water balance maintaining mechanisms among species. The Q n existed persistently and contributed markedly over 5.5%~24.0% of the daily sap flow ( Q ) across species, which was associated with two processes, nocturnal transpiration ( E n ) and nocturnal stem water refilling ( R n ). We found that the stem recharge of the Kandelia obovata and Aegiceras corniculatum occurred mainly after sunset and that the high salinity environment drove higher Q n while stem recharge of the Avicennia marina mainly occurred in the daytime and the high salinity environment inhibited the Q n . The diversity of stem recharge patterns and response to sap flow to high salinity conditions were the main reasons for the differences in Q n / Q among species. For Kandelia obovata and Aegiceras corniculatum , R n was the main contributor to Q n , which was driven by the demands of stem water refilling after diurnal water depletion and high salt environment. Both of the species have a strict control over the stomata to reduce water loss at night. In contrast, Avicennia marina maintained a low Q n , driven by vapor pressure deficit, and the Q n mainly used for E n , which adapts to high salinity conditions by limiting water dissipation at night. We conclude that the diverse ways Q n properties act as water-compensating strategies among the co-occurring mangrove species might help the trees to overcoming water scarcity., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Wu, Gu, Zheng and Chen.)