Sheathing the blade: Significant contribution of sheaths to daytime and nighttime gas exchange in a grass crop.
Despite representing a sizeable fraction of the canopy, very little is known about leaf sheath gas exchange in grasses. Specifically, estimates of sheath stomatal conductance, transpiration and photosynthesis along with their responses to light, CO2 and vapour pressure deficit (VPD) are unknown. Furthermore, the anatomical basis of these responses is poorly documented. Here, using barley as a model system, and combining leaf-level gas exchange, whole-plant gravimetric measurements, transpiration inhibitors, anatomical observations, and biophysical modelling, we found that sheath and blade stomatal conductance and transpiration were similar, especially at low light, in addition to being genotypically variable. Thanks to high abaxial stomata densities and surface areas nearly half those of the blades, sheaths accounted for up to 17% of the daily whole-plant water use, which -surprisingly- increased to 45% during the nighttime. Sheath photosynthesis was on average 17-25% that of the blade and was associated with lower water use efficiency. Finally, sheaths responded differently to the environment, exhibiting a lack of response to CO2 but a strong sensitivity to VPD. Overall, these results suggest a key involvement of sheaths in feedback loops between canopy architecture and gas exchange with potentially significant implications on adaptation to current and future climates in grasses.
['Sadok|Walid|W|0000-0001-9637-2412', 'Lopez|Jose R|JR|0000-0003-2487-4258', 'Zhang|Yangyang|Y|', 'Tamang|Bishal G|BG|0000-0003-4991-6354', 'Muehlbauer|Gary J|GJ|0000-0001-9320-2629']
D002245:Carbon Dioxide D018556:Crops, Agricultural D005838:Genotype D001467:Hordeum D008910:Minnesota D008954:Models, Biological D010788:Photosynthesis D018515:Plant Leaves D054046:Plant Stomata D018526:Plant Transpiration D055548:Vapor Pressure D014867:Water
stomatal conductance photosynthesis vapour pressure deficit barley stomata density climate change drought tolerance nighttime transpiration