Responses to Drought Stress in Poplar: What Do We Know and What Can We Learn?

Abstract

Poplar (Populus spp.) is a high-value crop for wood and biomass production and a model organism for tree physiology and genomics. The early release, in 2006, of the complete genome sequence of P. trichocarpa was followed by a wealth of studies that significantly enriched our knowledge of complex pathways inherent to woody plants, such as lignin biosynthesis and secondary cell wall deposition. Recently, in the attempt to cope with the challenges posed by ongoing climate change, fundamental studies and breeding programs with poplar have gradually shifted their focus to address the responses to abiotic stresses, particularly drought. Taking advantage from a set of modern genomic and phenotyping tools, these studies are now shedding light on important processes, including embolism formation (the entry and expansion of air bubbles in the xylem) and repair, the impact of drought stress on biomass yield and quality, and the long-term effects of drought events. In this review, we summarize the status of the research on the molecular bases of the responses to drought in poplar. We highlight how this knowledge can be exploited to select more tolerant genotypes and how it can be translated to other tree species to improve our understanding of forest dynamics under rapidly changing environmental conditions.

Ecophysiological response of Populus alba L. to multiple stress factors during the revitalisation of coal fly ash lagoons at different stages of weathering

“…Stomatal closure as a common response to drought reduces CO2 uptake and fixation, but also reduces transpiration, limiting the cooling of the leaf’s surface, resulting in thermal stress that has negative effects on metabolic processes, primarily photosynthesis. Thermal stress also causes changes in chlorophyll pigment and carotenoid content in leaves, thus affecting photoinhibition, which results in a reduced quantum yield of PSII (lower Fv/Fm), enhanced peroxidation in the leaf cell membrane (an increase in MDA), and reduced membrane thermostability ( Yoon et al., 2014 ; Stojnić et al., 2016 ; Pilipović et al., 2020 ; Rosso et al., 2023 ). Increased salinity limits plant growth by inducing osmotic stress, impairing the uptake of ions leading to their imbalance or toxicity, inhibiting metabolic processes and enzyme activity, damaging thylakoid membranes, reducing photosynthetic pigments, and disrupting photosynthetic activity ( Chen and Polle, 2010 ; Zhang et al., 2019 ).…”

“…At L3, P. alba was found to have lower vitality, but significant differences in the content of Chl a, Chl b, Tot Carot, Anthoc, Ph Free, Ph Bound, and MDA compared to control individuals were not found. This may be the result firstly of NPK fertilisation, as N application improves the drought tolerance of poplars ( Song et al., 2019 ), secondly of the higher Mn content in leaves compared to the other two sites as one of the mechanisms for overcoming stress ( Della Maggiora et al., 2023 ), and thirdly the higher total antioxidant capacity of P. alba at this lagoon (<IC 50) as an indicator of the activation of enzymatic and non-enzymatic antioxidant systems ( Zhang et al., 2019 ; Rosso et al., 2023 ). Also, the localisation of high concentrations of accumulated B in chlorotic and necrotic tissues in the tips and marginal parts of leaves is another adaptive mechanism of plants, which thus ensures a significant proportion of photosynthetic tissue remains functional ( Rees et al., 2011 ).…”

Adaptation Mechanisms of Olive Tree under Drought Stress: The Potential of Modern Omics Approaches

“…However, these strategies are not widely investigated in woody/tree crops, with a few exceptions such as the Populus sp. [39,40]. To thoroughly investigate these drought management strategies, the entire range of functions of olive plants that are exposed to drought and/or recovery should be considered.…”

Spatiotemporal Metabolic Responses to Water Deficit Stress in Distinct Leaf Cell-types of Poplar

“…While poplar species are good targets for carbon sequestration (Wullschleger et al, 2005) and production of feedstocks for biofuels and biomaterials (Bryant et al, 2020), they have also been widely used in physiological studies to understand how perennial trees respond to environmental changes (Li et al, 2014). Whole tissue responses to WD stress have been investigated in Populus at epigenome (Sow et al, 2021), transcriptome (Robertson et al, 2022, Rosso et al, 2023, Lee et al, 2021, Yang et al, 2023, Jia et al, 2017, Cossu et al, 2014, Wilkins et al, 2009), proteome (Plomion et al, 2006, Gao et al, 2022, Li et al, 2014, Xiao et al, 2009, Durand et al, 2011), and metabolome (Jia et al, 2020, Barchet et al, 2013, Hamanishi et al, 2015, He et al, 2022, Law, 2020, Tschaplinski et al, 2019b, Barchet et al, 2014) levels. However, spatiotemporal molecular mechanisms controlling plant responses to WD stress is not yet thoroughly understood in Populus and similar perennial trees.…”