Abstract
Increasing atmospheric CO2 concentrations accompanied by abiotic stresses challenge food production worldwide. Elevated CO2 (e[CO2]) affects plant water relations via multiple mechanisms involving abscisic acid (ABA). Here, two tomato (Solanum lycopersicum) genotypes, Ailsa Craig (AC) and its ABA-deficient mutant (flacca), were used to investigate the responses of plant hydraulic conductance to e[CO2] and drought stress. Results showed that e[CO2] decreased transpiration rate (E) increased plant water use efficiency only in AC, whereas it increased daily plant water consumption and osmotic adjustment in both genotypes. Compared to growth at ambient [CO2], AC leaf and root hydraulic conductance (Kleaf and Kroot) decreased at e[CO2], which coincided with the transcriptional regulations of genes of plasma membrane intrinsic proteins (PIPs) and OPEN STOMATA 1 (OST1), and these effects were attenuated in flacca during soil drying. Severe drought stress could override the effects of e[CO2] on plant water relation characteristics. In both genotypes, drought stress resulted in decreased E, Kleaf, and Kroot accompanied by transcriptional responses of PIPs and OST1. However, under conditions combining e[CO2] and drought, some PIPs were not responsive to drought in AC, indicating that e[CO2] might disturb ABA-mediated drought responses. These results provide some new insights into mechanisms of plant hydraulic response to drought stress in a future CO2-enriched environment.
Highlights
The atmospheric carbon dioxide concentration ([CO2]) has been constantly increasing, and it is predicted to reach ca. 800 ppm at the end of this century (Pan et al, 2018)
It is widely believed that abscisic acid (ABA) could alter plant hydraulic properties (Parent et al, 2009; Rosales et al, 2019), our results demonstrated that hydraulic response to severe drought could be ABA-independent and might be attributed to decreased leaf turgor as reported in our previous study (Wei et al, 2020)
Here we found that the root plasma membrane intrinsic proteins (PIPs) of flacca still responded to e[CO2] though those effects were only shown in stressed plants, which was consistent with slight changes in hydraulic conductance of flacca (Figures 3, 6; Supplementary Figure S1; Table 2)
Summary
The atmospheric carbon dioxide concentration ([CO2]) has been constantly increasing, and it is predicted to reach ca. 800 ppm at the end of this century (Pan et al, 2018). It is well known that e[CO2] could induce stomatal closure, alleviating the negative effect of drought stress (van der Kooi et al, 2016). Plants benefit from e[CO2] due to an increase in photosynthetic rate, and decreases in stomatal conductance (gs) and transpiration rate (E), resulting in improved water use efficiency (Wullschleger et al, 2002; van der Kooi et al, 2016). Another possible mechanism is the enhanced osmotic adjustment. The increased leaf area of plants grown under e[CO2] might increase water consumption, leading to a fast depletion of soil water, causing severe drought stress to plants (Manea and Leishman, 2015)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
