Leaf age and methodology impact assessments of thermotolerance of Coffea arabica

Abstract

Key message Mature Coffea arabica leaves were more heat tolerant than expanding leaves, longer recovery time yielded more accurate thermotolerance assessments, and photochemistry was more heat sensitive than cell membranes. Abstract Given future climate predictions of increased heatwaves in the tropics, suitable habitat to grow ecologically, economically, and socially valuable Coffea arabica L. is threatened. Accurate assessments of high temperature tolerance or thermotolerance are critical for understanding C. arabica responses to increased temperature. Thermotolerance curves of C. arabica leaf discs were constructed by measuring chlorophyll fluorescence (ratio of variable to maximum fluorescence, F_V/F_M; minimum fluorescence, F_O) across three leaf age classes and two recovery times (15 min, 24 h) after 15 min exposure to temperatures from 25 to 58 °C. Thermotolerance measured with electrolyte leakage after 20 min at 25–65 °C was compared with F_V/F_M thermotolerance curves. The temperature corresponding to 50 % damage (T₅₀) was 49.0 and 58.6 °C for the chlorophyll fluorescence and electrolyte leakage methods respectively. The critical temperature at which the F_O rise began on F_O-temperature curves (T_crit) was 46.0 °C. We found that the 24 h recovery time yielded more accurate estimates of T₅₀, and that thermotolerance based on T_crit increased with leaf age. Differences between the fluorescence and electrolyte leakage methods showed that photosystem II processes were more sensitive to temperatures above 40 °C than cell membrane stability.

Citation

Marias, Danielle E.; Meinzer, Frederick C.; Still, Christopher. 2017. Leaf age and methodology impact assessments of thermotolerance of Coffea arabica. Trees. 31(3): 1091-1099. https://doi.org/10.1007/s00468-016-1476-4.