Via Craig D. Idso – July 20, 2022
“So when the next summer heatwave comes with all the negative narratives that CO2 as its cause, I hope you will remember this post and the many scientific studies that prove CO increases2 levels that help plants better withstand and recover from heat-induced stresses. And when you remember this, share it with others! “
It’s summer again in the Northern Hemisphere. And like every summer, expect the occasional heatwave to unleash the fury of hype news stories claiming today’s heatwaves are caused by human-caused global warming. out or get worse.
There is of course no clear evidence to support such claims (sorry, climate model projections are Not evidence!). However, warmer temperatures are finally reaching the frigid part of the country I live in which makes me think about my next post that explores the many biological benefits of increasing atmospheric CO.2. So read on if you want to learn about higher levels of CO2 helps reduce much of the stress that plants experience during heat waves.
Heat stress can pose a multitude of challenges to plant growth and survival, including dehydration and oxidative damage to biofilms due to highly reactive oxygen species (ROS). However, the level of CO is elevated2 has been shown to reduce the severity of this stress. Therefore, it is of interest to determine the interactive effects of thermal stress and atmospheric CO2 on plants makes predictions about future rising temperatures and CO2 concentration.
Pan et al. (2018), in particular, studied the interactive effects of elevated CO2 and heat stress on a wide range of chlorophyll and photosynthetic fluorescence parameters, as well as cellular redox state, of tomato plants. The work was conducted in environmentally controlled growth chambers where tomato seedlings (Solanum lycopersicum cv. Hezuo 903) were exposed to CO2 concentration of 380 ppm or 800 ppm.
Then, after an acclimatization period of 48 h, half of the seedlings in each CO2 the treatment is subjected to thermal stress for 24 h (42°C, compared with unpressurized day/night temperatures of 26/22°C in the control plants), followed by a recovery period 24 hours. After 24 h of heat stress and again after a 24 h recovery period for temperature control, a series of measurements were performed to assess the potential for CO rise.2 to minimize temperature stress. The results are depicted in the two figures below.
Figure 1. Effects of elevated CO2 and thermal effects on the net photosynthetic rate (Pn) of tomato plants. The red text shows the change in Pn due to elevated CO2 during the control, heat and recovery phases. Source: Pan et al. (2018).
Figure 1 CO presentation2– response of tomato plants to photosynthesis during the control, heat and recovery periods. At normal temperature, CO increases2 increase plant photosynthesis by 45%. Not surprising, regardless of CO2 concentration, heat stress reduces net photosynthesis, this parameter increases during recovery but does not completely return to pre-stress condition. However, the CO increased2 induced relative increases in net photosynthesis of 116% and 96% respectively during heat stress and recovery, these values were not significantly different from those observed in the control group. under normal CO conditions2. As a result, CO increases2 were able to completely ameliorate the negative effects of heat stress on photosynthesis in tomato plants.
Figure 2. Effects of elevated CO2 and heat stress on the photosynthetic apparatus of tomato. The left panel shows the maximum photochromic efficiency of photosystem II (Fv/Fm) shown in the pseudo-color image, the pseudo-color code depicted in the image ranges from 0 (black) to 1 (Violet). Right panel shows actual Fv/Fm values, with percentage in red text indicating change in Fv/Fm value due to elevated CO2 during the heat and recovery period. Source: Pan et al. (2018).
A similar finding was recorded in Figure 2describe the effect of elevated CO2 and thermal stress on the maximum photochemical efficiency of photosystem II (Fv/Fm). Even though CO is high2 has no effect on Fv/Fm under normal temperature conditions, it increases this parameter by 60% and 14% respectively in response to thermal stress and upon recovery, compared to the parameter observed in CO around.2 The treatments.
In commenting on these and their other findings, Pan et al. note “heat-induced overproduction of ROS causes damage to the photosynthetic apparatus as evidenced by reduced Fv/Fm, low electron transport rates, and impaired oxidation and reduction states of PSII and PSI.” change. On the other hand, high CO2 significantly reduces heat-induced damage to the photosynthetic apparatus and promotes electron transport in PSII and PSI by maintaining proper redox balance. “
Moving on to another example of this amazing benefit, Chavan et al. (2019) examined the interactive effects of elevated CO2 and thermal effects on photosynthesis, biomass and grain yield of wheat. CO2 The concentrations examined in their study included ambient (419 ppm) and high (654 ppm). The temperature was maintained at 22/15°C (day/night) in the control treatment. Then, thirteen weeks after planting, heat stress was present in half of the plants in each CO .2 treated by increasing the day/night temperature to 40/24°C for five days. The heat-stressed plants were then brought back to the control temperature. Sufficient water was provided for all treatments throughout the experiment to avoid confounding effects due to water stress.
Chavan et al. found elevated CO2 enhanced true photosynthesis by 36% in plants without heat stress, while high temperature stress reduced this parameter by 42%. In synthesis, CO is increased2 and heat stress treatment, true photosynthesis is not reduced because, in the authors’ words, “elevated CO2 Protects photosynthesis by increasing ribulose biphosphate regeneration and reducing photochemical damage [caused by] heat stress. “
Figure 3. Total biomass (a) and grain yield (b) of wheat at harvest in response to elevated CO2 and thermal stress (HS). Representative values for means ± SE using two-way ANOVA. Means sharing the same letter in individual panels were not significantly different according to Tukey’s HSD test at 5%. Statistical significance level (t-test) for eCO2 The effect is expressed as follows: **P < 0.01: *** P < 0.001. Percentage in red text indicates change in biomass or grain yield due to elevated CO2 under controlled or heat-stressed conditions. Source: Chavan et al. (2019).
For biomass and yield, as shown in Figure 3CO increased2 stimulated these two parameters by 36% and 31% respectively in the control treatment. In contrast, heat stress alone caused a small insignificant reduction in total biomass and a 44% reduction in cereal yield. When CO is high2 and heat stress were combined, the total biomass increased by 46% compared to the control treatment (ambient CO2 and non-thermal stress) and is 58% of that of thermal stress treatment under ambient CO2. On the other hand, grain yield was reduced by 23% in total CO increase2 and thermal stress treatment associated with control conditions, but a positive 37% increase compared with heat stress alone at CO ambient2. Therefore, in the future, CO will increase2 can also largely ameliorate the negative effects of high temperature stress on grain yield for the specific wheat variety investigated in this study.
Comment on the important benefits of CO2 observed in their study, Chavan et al. state “heat stress causes irreversible photosynthetic damage in ambient CO .”2while growing at high CO2 minimize the negative effects of heat stress on photosynthesis. In addition, they found that “plant biomass was completely recovered from heat stress under both CO2 dealing with additional late tillering and spasticity; but they do not fully develop and fill the seeds,” which explains the decrease in grain yield observed under thermal stress.
They therefore support more research and breeding programs designed to improve seed filling and transfer vegetative sources to seeds at high temperatures and elevated CO.2 to protect future food production.
Many other studies have investigated the interactive effects of elevated CO2 and heat stress (e.g. see list of articles reviewed on CO2 Science website on this subject under the title Temperature x CO2 Interaction (Plant Growth Response: Agricultural Plants), Temperature x CO2 Interactions (Plant Growth Response: Grassland Species)and Temperature x CO2 Interaction (Plant Growth Response: Plants).
In almost every case, these studies demonstrate an increased amount of CO2 in the air2 The content helps plants cope and tolerate high temperature pressure better. And these benefits are being realized nowdue to an approximately 50% increase in atmospheric CO2 that the world has experienced since the beginning of the Industrial Revolution, the benefits will only continue to accrue in the future as the CO of the air2 content continues to increase.
So when the next summer heatwave comes with all the negative narratives that CO2 as its cause, I hope you will remember this post and the many scientific studies that prove CO increases2 levels that help plants better withstand and recover from heat-induced stresses. And when you remember this, share it with others!
Dr. Craig D. Idso
Presenter
Chavan, SG, Duursma, RA, Tausz, M. and Channoum, O. 2019. CO increased2 alleviated the negative effects of heat stress on wheat physiology but did not reduce grain yield. Journal of Experimental Botany 70: 6447-6459.
Pan, C., Ahammed, GJ, Li, X. and Shi, K. 2018. CO soar2 improves photosynthesis under high temperature conditions by reducing functional limitations for energy fluxes, electron transport and redox homeostasis in tomato leaves. Frontiers in Plant Science 9: Article 1739, doi: 10.3389 / fpls.2018.01739.
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