AUTHOR=Li Shenglan , Fang Liang , Hegelund Josefine Nymark , Liu Fulai 

TITLE=Elevated CO2 Modulates Plant Hydraulic Conductance Through Regulation of PIPs Under Progressive Soil Drying in Tomato Plants

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.666066

DOI=10.3389/fpls.2021.666066

ISSN=1664-462X

ABSTRACT=<p>Increasing atmospheric CO<sub>2</sub> concentrations accompanied by abiotic stresses challenge food production worldwide. Elevated CO<sub>2</sub> (<italic>e</italic>[CO<sub>2</sub>]) affects plant water relations <italic>via</italic> multiple mechanisms involving abscisic acid (ABA). Here, two tomato (<italic>Solanum lycopersicum</italic>) genotypes, Ailsa Craig (AC) and its ABA-deficient mutant (<italic>flacca</italic>), were used to investigate the responses of plant hydraulic conductance to <italic>e</italic>[CO<sub>2</sub>] and drought stress. Results showed that <italic>e</italic>[CO<sub>2</sub>] decreased transpiration rate (<italic>E</italic>) 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 [CO<sub>2</sub>], AC leaf and root hydraulic conductance (<italic>K</italic><sub>leaf</sub> and <italic>K</italic><sub>root</sub>) decreased at <italic>e</italic>[CO<sub>2</sub>], 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 <italic>flacca</italic> during soil drying. Severe drought stress could override the effects of <italic>e</italic>[CO<sub>2</sub>] on plant water relation characteristics. In both genotypes, drought stress resulted in decreased <italic>E</italic>, <italic>K</italic><sub>leaf</sub>, and <italic>K</italic><sub>root</sub> accompanied by transcriptional responses of PIPs and OST1. However, under conditions combining <italic>e</italic>[CO<sub>2</sub>] and drought, some PIPs were not responsive to drought in AC, indicating that <italic>e</italic>[CO<sub>2</sub>] might disturb ABA-mediated drought responses. These results provide some new insights into mechanisms of plant hydraulic response to drought stress in a future CO<sub>2</sub>-enriched environment.</p>