Impact of Drought and Salinity on Sweetgum Tree (Liquidambar styraciflua L.): Understanding Tree Ecophysiological Responses in the Urban Context

Abstract

Understanding urban tree responses to drought, salt stress, and co-occurring stresses, as well as the capability to recover afterward, is important to prevent the cited stresses’ negative effects on tree performance and ecological functionality. We investigated the impact of drought and salinity, alone and in combination, on leaf water potential, gas exchange, chlorophyll a fluorescence, xanthophyll cycle pigments, and isoprene emission of the urban tree species Liquidambar styraciflua L. Generally, drought had a rapid negative impact, while the effect of salt stress was more long lasting. Both stressors significantly decreased photosynthesis, transpiration, and stomatal conductance, as well as the maximum quantum efficiency of photosystem II (Fv/Fm) and the photochemical efficiency of PSII (ΦPSII), but increased nonphotochemical quenching (NPQ). Under stress conditions, a strong negative correlation between the PSII efficiency and the xanthophyll cycle pigment composition indicated a nocturnal retention of zeaxanthin and antheraxanthin in a state primed for energy dissipation. Drought and salt stress inhibited isoprene emission from leaves, although its emission was less responsive to stresses than stomatal conductance and photosynthesis. Full recovery of photosynthetic parameters took place after rewatering and washing off of excess salt, indicating that no permanent damage occurred, and suggesting downregulation rather than permanent impairment of the photosynthetic apparatus. Sweetgum trees were capable of withstanding and surviving moderate drought and salt events by activating defense mechanisms conferring tolerance to environmental stresses, without increasing the emission in the atmosphere of the highly reactive isoprene.

Effects of Slag-Based Fertilizer to Mitigate Salinity Stress on Greenhouse Durum Wheat (Triticum Durum Desf.) Cultivars

“…Indeed, the osmotic stress induced by salinity, which can lead to a reduction of CO2 assimilation by the plant and consequently an inhibition of photosynthesis (Ezquer et al 2020;Yang et al, 2020). In addition, salinity is a constraint that disrupt photochemical reactions of photosynthesis, especially at the PSII level (Baraldi et al 2019;Zahra et al, 2022). This study also showed that the decrease in stomatal conductance was related to a reduction in chlorophyll fluorescence (Fv/Fm) in plants subjected to salt stress.…”

The importance of prenol lipids in mitigating salt stress in the leaves of Tilia × euchlora trees

“…Resistance can include avoidance, tolerance and a combination of these two methods of defense against the stress factor (Blomqvist 1998). The following methods can be used to relieve salt stress by trees: inhibition of Cl and Na uptake and redistribution of elements from leaves to other parts of plants (Shelkeet al 2019), the storage of Na + and Cl − in cell structures (Baetz et al 2016), the induction of antioxidant enzymes and hormones (Zhao et al 2019;Sarker and Oba 2020), the presence of ectomycorrhizal fungi (Zwiazek et al 2019;Olchowik et al 2021), the accumulation of compatible compounds, the increased conversion of xanthophyll pigments (Baraldi et al 2019), and the presence of genes that can increase salt tolerance (Parihar et al 2015).…”

Physiological analysis reveals relatively higher salt tolerance in roots of Ilex integra than in those of Ilex purpurea

“…Salt tolerance of annual crops can be assessed by comparing biomass production by the plant growing in saline conditions to that when grown in control conditions over a certain time. However, for woody plants, usually with a relatively slower growth rate, other ways than biomass comparison, e.g., simple and quick physiological variables may be employed to compare salt tolerance (Baraldi et al 2019).…”