Abstract
Elevated CO2 concentration in the air (e[CO2]) decreases stomatal density (SD) and stomatal conductance (gs) where abscisic acid (ABA) may play a role, yet the underlying mechanism remains largely elusive. We investigated the effects of e[CO2] (800 ppm) on leaf gas exchange and water relations of two tomato (Solanum lycopersicum) genotypes, Ailsa Craig (WT) and its ABA-deficient mutant (flacca). Compared to plants grown at ambient CO2 (400 ppm), e[CO2] stimulated photosynthetic rate in both genotypes, while depressed the gs only in WT. SD showed a similar response to e[CO2] as gs, although the change was not significant. e[CO2] increased leaf and xylem ABA concentrations and xylem sap pH, where the increases were larger in WT than in flacca. Although leaf water potential was unaffected by CO2 growth environment, e[CO2] lowered osmotic potential, hence tended to increase turgor pressure particularly for WT. e[CO2] reduced hydraulic conductance of leaf and root in WT but not in flacca, which was associated with downregulation of gene expression of aquaporins. It is concluded that ABA-mediated regulation of gs, SD, and gene expression of aquaporins coordinates the whole-plant hydraulics of tomato grown at different CO2 environments.
Highlights
Stomata controls the photosynthesis (An) and transpiration rates
It is well known that e[CO2] enhances An while reducing gs, the response may vary among species and different growth environments[4,27]
For the two GEs the change of gs in response to e[CO2] was associated with a similar pattern of change in stomatal density (SD) (Fig. 1c), suggesting that the endogenous abscisic acid (ABA) level exerted an important role in the e[CO2]-induced modulation of SD and gs
Summary
Stomata controls the photosynthesis (An) and transpiration rates. The rising CO2 concentration ([CO2]) in the atmosphere will have profound impacts on plant physiological processes, those related to stomatal control of leaf gas exchange and plant water relations[1]. The influences of CO2 elevation (e[CO2]) on stomatal morphology and physiology have been well documented[1,2,3,4,5]. It has been suggested that reduction in SD caused by e[CO2] could be modulated by abscisic acid (ABA) levels[10,11]. Earlier studies have shown that SD correlates positively with plant ABA level[12,13,14]
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have