Physiological Performances of Temperate Vegetables with Response to Chronic and Acute Heat Stress

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 (F v /F m ) 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 (LT 50 ), 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 F v /F m 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.

Quality of supplementary LED lighting effects on growth and photosynthesis of two different Lactuca recombinant inbred lines (RILs) grown in a tropical greenhouse

“…Using HR-RIL and HS-RIL, our team has reported that shoot and root FM of HR-RIL were significantly higher than that of HS RILs that were grown in the tropical greenhouse under ambient conditions due to their lower photoinhibition of PSII reaction center during midday (He et al 2013). Recently, we have confirmed further that HR-RIL grown in the tropical greenhouse showed lesser photoinhibition as compared to HS-RIL (Lai and He 2016). Thus, we hypothesised that the two different genotypes, HR-RIL and HS-RIL, may exhibit different responses to supplemental light quality when they were grown in the tropical greenhouse.…”

Root-Zone Heat Priming Effects on Maximum Quantum Efficiency of PSII, Productivity, Root Morphology and Nutritional Quality of Two Aeroponically Grown Leafy Greens in a Tropical Greenhouse

“…The abrupt exposure to severe heat stress of 42 • C-RZT could have resulted in significantly lower F v /F m ratios for non-primed plants (25 • C-RZT → 42 • C-RZT plants), particularly the F v /F m ratio of non-primed Arugula which reached close to 0.6 (Figure 2). This agrees with the findings of Lai and He [32] in which F v /F m ratios of six temperate crops, including Arugula and Canasta, decreased with increasing heat stress. Although F v /F m ratios of 25 • C-RZT Arugula leaves were the highest, there was no significant difference between the F v /F m ratios of RZ heat primed (25 2).…”

The thermal tolerance of photosynthetic tissues: a global systematic review and agenda for future research

“…Adopting more realistic regimes and justifying these with data from relevant natural settings, as well as providing better descriptions of the temperature ranges around set points would enable a more nuanced investigation of the differences between acute and chronic stress responses, and between facultative protective responses and signs of irreparable damage (Lai & He, 2016; Trapero‐Mozos et al ., 2018). At present, the definition and use of ‘stress’ and ‘stressful events’ is somewhat ad hoc and impedes our ability to compare results or derive generalizations (Jansen & Potters, 2017).…”