Nocturnal sap flow as compensation for water deficits: an implicit water-saving strategy used by mangroves in stressful environments

Abstract

As part of the plant water-use process, plant nocturnal sap flow (Qn) 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 Qn 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 (En) and nocturnal stem water refilling (Rn). 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 Qn while stem recharge of the Avicennia marina mainly occurred in the daytime and the high salinity environment inhibited the Qn. The diversity of stem recharge patterns and response to sap flow to high salinity conditions were the main reasons for the differences in Qn/Q among species. For Kandelia obovata and Aegiceras corniculatum, Rn was the main contributor to Qn, 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 Qn, driven by vapor pressure deficit, and the Qn mainly used for En, which adapts to high salinity conditions by limiting water dissipation at night. We conclude that the diverse ways Qn properties act as water-compensating strategies among the co-occurring mangrove species might help the trees to overcoming water scarcity.

Nocturnal Water Use Partitioning and Its Environmental and Stomatal Control Mechanism in Caragana korshinskii Kom in a Semi-Arid Region of Northern China

“…However, in arid and semiarid regions, the influence of high wind and strong solar radiation brought great challenges to the complete sap flow velocity data continuity and stability. The thermal dissipation probes (TDP10) method has recently been used to measure the sap flow velocity for plants with small DBH, such as bamboo species [40], Populus adenopoda [41], Aegiceras corniculatum [42] and so on. Compared with an induced hydraulic pressure and sap flow changing device and a whole-culm pot weighing method, the 10 mm long TDP was proven to be a valid means of measuring the sap flow of Phyllostachys pubescens [43].…”

The dynamics of nocturnal sap flow components of a typical revegetation shrub species on the semiarid Loess Plateau, China

“…These two components of En have different effects on plant growth and survival ( Wu et al., 2023 ). Qn can enhance nutrient supply to distal parts of plant crowns ( Scholz et al., 2007 ), and transport O 2 to cells and nutrients to plants ( Daley and Phillips, 2006 ).…”