TITLE:
Physiological Performances of Temperate Vegetables with Response to Chronic and Acute Heat Stress
AUTHORS:
Cheng-Hsiang Lai, Jie He
KEYWORDS:
Chlorophyll Fluorescence, Heat Stress, O2 Evolution, Photosynthetic CO2 Assimilation Rate, Stomatal Conductance, Thermotolerance
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.7 No.14,
October
19,
2016
ABSTRACT: In face of climate change
catastrophes, understanding the thermal limits and optimal physiological
thermal window food crop is of particular urgency. This research aims to evaluate:
1) how physiological performances of plant will change with increasing chronic
and acute heat stress; 2) if the examined parameters form a hierarchy in terms
of thermal tolerance; and 3) the optimal thermal window and critical
temperatures of the examined plants with response to chronic and acute heat
stress. Six temperate vegetables were subjected to chronic and acute heat
stress and a suite of physiological parameters were evaluated. Dose responses
were observed in shoot fresh weight, photosynthetic gas exchange,
photosynthetic oxygen evolution, electron transfer rate, photo- and
non-photochemical quenching with significant drop in performance as early as 28°C
for selected species. Conversely, ratio of variable to maximum fluorescence (Fv/Fm)
was not affected by heat stress until 46°C in chronic heat stress.
Examining the temperature at which a measured parameter’s performance dropped
by 50% compared to control (LT50), a distinct hierarchy of the
indices was observed for Canasta, recombinant inbred line 141, Lactuca serriola and Lactuca sativa (L. “Salinas”): shoot fresh weight, representing the highest
integrated level of photosynthesis was the most sensitive to thermal stress (28°C
- 30°C), followed by oxygen evolution (35°C - 45°C)
while non-photochemical and photochemical quenching which is subcellular function of stress alleviation had a
much higher capacity failure temperature (47°C - 60°C). It is
expected that Fv/Fm ratio, a measurement of sub-cellular
structural integrity, will approach that of non-photochemical and photochemical
quenching, if not exceeding it. By examining the photosynthetic parameters via
their hierarchy of biological organization, it can be inferred that plants like
Arugula and recombinant inbred line 192 are already operating near their
thermal limit and have less energetic investment into heat stress mediation
whereas L. serriola prioritizes
thermal tolerance at the expense of photosynthesis efficiency.