Variation in nocturnal stomatal conductance and development of predawn disequilibrium between soil and leaf water potentials in nine temperate deciduous tree species

Abstract

It is widely acknowledged that many plant species can keep stomata open during night. We examined how nocturnal stomatal conductance differs among potted saplings of nine temperate tree species from diverse native habitats in wet and dry soil conditions, and how it affects plant predawn water status. Nocturnal stomatal conductance in dry soil conditions was low in all the species (with a maximum value of 14.6 mmol m–2 s–1); in wet conditions, it was the highest in Populus tremula L., a fast-growing and anisohydric pioneer species, and the lowest in Quercus robur L., a late-successional and isohydric species. Relatively high nocturnal stomatal conductance in wet conditions in P. tremula compared with the other species resulted in the highest difference in water potential values between the leaves and soil at predawn. As drought progressed, different species tended to keep stomata almost closed at night, and the observed differences between anisohydric and isohydric species disappeared. At an ample soil water supply, nocturnal stomatal behaviour was species dependent and varied according to both the water-use and the life strategies of the species. Keeping that in mind, one should therefore be careful when using predawn leaf water potential as a proxy for soil water potential, sampling different species.

Contrasting sap flow characteristics between pioneer and late-successional tree species in secondary tropical montane forests of Eastern Himalaya, India

“…Under controlled conditions, Chu et al (2009) demonstrated a significant positive correlation between wind speed and nocturnal sap flux up to a threshold when stomatal closure is assumed to limit transpiration. Similar to our observations, in a garden experiment involving temperate broadleaved species, Kangur et al (2021) found significant nocturnal (pre-dawn) stomatal conductance in anisohydric pioneer species in comparison to isohydric late-successional species under hydrated conditions, and they attributed this to contrasting life-history traits dictating stomatal control. Kumar et al (2021) observed a significant diel cycle in summer precipitation, starting from around noon and leaving a short 5–6 h window conducive to plant productivity and transpiration.…”

“…For C. hystrix , previous reports from higher latitudes in China have been significantly lower (4% of daily V ) than our observations ( Chen et al , 2018 ; Wang et al , 2018 ). In contrast to a study by Wang et al (2018) , the observed intraspecific variability in nocturnal sap flow was less than the interspecific variation in late-successional C. hystrix However, in agreement with Kangur et al (2021) , higher intraspecific variability in nocturnal sap flow was seen in the pioneer species S. racemosa and E. acuminata , indicative of a broader range of responses to similar environmental stressors. According to the literature, the ecophysiological mechanisms driving nocturnal sap flux can be broadly categorized into refilling of the stem, facilitating night respiration, and endogenous stomatal controls.…”

Leaf and tree responses of young European aspen trees to elevated atmospheric CO2 concentration vary over the season

“…watered between 5:00 h and 6:00 h with an automatic irrigation system and the amount of water supplied was individually adjusted per pot throughout the season to avoid drought stress. Soil water content was periodically (varying from once fortnightly to twice per week) measured using a ML3 ThetaKit (Delta-T Devices, Burnwell, UK) and maintained above 30 % and below 60 % to avoid negative effects of drought stress and water-saturation, respectively (Kangur et al 2021). Due to the limitation in the number of available chambers (one per treatment), pseudo-replication issues cannot completely be discarded.…”

Nocturnal Transpiration May Be Associated with Foliar Nutrient Uptake

“…During the night, water loss via stomata is reduced, but stomata often do not close completely, allowing for gas exchange with the environment [ 17 , 18 , 19 ]. Nocturnal stomatal conductance (g sw ) has been observed in plants of different species and environments [ 20 , 21 , 22 , 23 ], and the results point to nocturnal water loss, implying some advantages for plants under certain circumstances [ 24 ].…”

“…x nigra ) were chosen to avoid genetic variability [ 51 ]. Poplars, which have a fast-growing capacity, have been used as bioindicators of atmospheric trace elements [ 52 , 53 , 54 ] and are known to have high nocturnal transpiration rates [ 19 ]. We used plants growing in P-poor soil and compared greenhouse plants under normal ambient conditions with those under filtered air, with leaves grown within an almost aerosol-free greenhouse.…”