High Temperature Acclimation of Leaf Gas Exchange, Photochemistry, and Metabolomic Profiles in <i>Populus trichocarpa</i>

Author(s): Dewhirst, RA; Handakumbura, P; Clendinen, CS; Arm, E; Tate, K; Wang, W; Washton, NM; Young, RP; Mortimer, JC; McDowell, NG; Jardine, KJ | Abstract: High temperatures alter the thermal sensitivities of numerous physiological and biochemical processes that impact tree growth productivity. Foliar root applications methanol have been implicated in plant acclimation to high temperature via C1 pathway. Here, we characterized at 35 °C leaf gas exchange, chlorophyll fluorescence, extractable metabolites potted Populus trichocarpa saplings examined potential influences mM concentrations added during soil watering over a two-month period. Relative plants grown under low (LGT), (HGT) showed suppression water use carbon cycling including transpiration (E), net photosynthesis (Pn), an estimate photorespiration (Rp), dark respiration (Rd), attributed reductions stomatal conductance direct negative effects on exchange photosynthetic machinery. In contrast, HGT upregulation nonphotochemical quenching (NPQt), optimum for ETR, isoprene emissions 40 °C. A large number (867) were induced HGT, many flavonoid biosynthesis highlighting potentially protective role these compounds. Methanol application did not significantly but slightly reduced Rd Rp by while impairing Fv′/Fm′, qp. However, unable determine if was sufficiently taken up effect foliar processes. small extracted tissue (55 out 10 015) altered abundances LGT treatments relative controls, this increased compound (222) HGT. The results demonstrate impacts poplar seedlings highlight enhancement ETR as rapid mechanism. Although no physiology observed, are consistent with both photochemistry light reactions formaldehyde toxicity stimulating through formate oxidation CO2.