The physiological acclimation and growth response of Populus trichocarpa to warming

Abstract

Plant metabolic acclimation to thermal stress remains underrepresented in current global climate models. Gaps exist in our understanding of how metabolic processes (i.e., photosynthesis, respiration) acclimate over time and how aboveground versus belowground acclimation differs. We measured the thermal acclimation of Populus trichocarpa, comparing aboveground versus belowground physiology over time.Ninety genetically identical ramets were propagated in mesocosms that separated root and microbial components. After establishment at 25 C for 6 weeks, 60 clones were warmed +4 or +8 C and monitored for 10 weeks, measuring photosynthesis (A), leaf respiration (R), soil respiration (R s ), root plus soil respiration (R s+r ), and root respiration (R r ). We observed thermal acclimation in both A and R, with rates initially increasing, then declining as the thermal photosynthetic optimum (T opt ) and the temperature-sensitivity (Q 10 ) of respiration adjusted to warmer conditions. Photosynthetic acclimation was constructive, based on an increase in both T opt and peak A.Belowground, R s+r decreased linearly with warming, while R s rates declined abruptly, then remained constant with additional warming. Plant biomass was greatest at +4 C, with 30% allocated belowground. Rates of mass-based R r were similar among treatments; however, root nitrogen declined at +8 C leading to less mass nitrogenbased R r in that treatment. The Q 10 -temperature relationship of R r was affected by warming, leading to differing values among treatments. Aboveground acclimation exceeded belowground acclimation, and plant nitrogen-use mediated the acclimatory response. Results suggest that moderate climate warming (+4 C) may lead to acclimation and increased plant biomass production but increases in production could be limited with severe warming (+8 C).

Temperature responses of photosynthesis and respiration in evergreen trees from boreal to tropical latitudes

“…A timescale of c . 1 month (Smith & Dukes, 2017) to 8–10 wk for photosynthesis (Hogan et al ., 2021) has been suggested. We need to better understand the timescale over which acclimation occurs, the mechanisms that control this timescale and how this varies amongst PFTs.…”

“…When models have included acclimation mechanisms, implementation is assumed to continue indefinitely with future warming. However, it is likely that there is a limit to the acclimation potential of plants with the temperature optimum unlikely to shift much beyond this limit (Crous et al ., 2013; Hogan et al ., 2021). More research is needed to investigate where potential limits to the shift in T optA may lie.…”

Substrate and adenylate limit subtropical tree fine‐root respiration under soil warming

“…Second, we lacked synchronous aboveground warming. This may indirectly affect root respiratory acclimation by altering photosynthesis and plant C allocation (Hogan et al, 2021). Finally, although tissue N concentrations are intimately correlated with respiration rates (Han et al, 2021; Lambers et al, 2005; Reich et al, 2008) and can serve as surrogate for enzyme capacity, it should be noted that enhanced presence of N storage compounds in some roots, such as under chronic N additions, could complicate the tissue respiration to N relationship (Burton et al, 2012; Frey et al, 2014).…”

Populus root exudates are associated with rhizosphere microbial communities and symbiotic patterns

“…The growth and development of Populus are partially dependent on the functional microbial communities in the rhizosphere, which is the critical root-soil interface for plant growth ( Song et al, 2020 ). Research on Populus has focused on plant aboveground traits, such as photosynthetic characteristics, carbon and nitrogen storage, and circulation, or focused on single factor on the belowground traits ( Hogan et al, 2021 ; Wu X. et al, 2021 ; Wang et al, 2022 ). While research on the belowground traits, including dominant combined keystone taxa in the rhizosphere of Populus and the regulatory effects of differential root exudates on dominant and keystone taxa is lacking.…”