Elevated CO2 Modulates Plant Hydraulic Conductance Through Regulation of PIPs Under Progressive Soil Drying in Tomato Plants
Shenglan Li, Liang Fang, Josefine Nymark Hegelund, Fulai Liu
Abstract
Increasing atmospheric CO 2 concentrations accompanied by abiotic stresses challenge food production worldwide. Elevated CO 2 ( e [CO 2 ]) 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 [CO 2 ] and drought stress. Results showed that e [CO 2 ] 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 [CO 2 ], AC leaf and root hydraulic conductance ( K leaf and K root ) decreased at e [CO 2 ], 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 [CO 2 ] on plant water relation characteristics. In both genotypes, drought stress resulted in decreased E , K leaf , and K root accompanied by transcriptional responses of PIPs and OST1. However, under conditions combining e [CO 2 ] and drought, some PIPs were not responsive to drought in AC, indicating that e [CO 2 ] 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 2 -enriched environment.