C 4 photosynthesis consists of the coordinated function of two cell types in the leaves, usually designated mesophyll cells (MC) and bundle sheath cells (BSC), because enzymes of the C4 pathway are located separately in these morphologically distinct cell types. In C4 leaves, atmospheric CO2 enters through stomata and is first accessible to MC, where it is fixed by phosphoenolpyruvate (PEP) car...

We examined the effects of atmospheric vapor pressure deficit (VPD) and soil moisture stress (SMS) on leafand stand-level CO2 exchange in model 3-year-old coppiced cottonwood (Populus deltoides Bartr.) plantations using the large-scale, controlled environments of the Biosphere 2 Laboratory. A short-term experiment was imposed on top of continuing, long-term CO2 treatments (43 and 120 Pa), at th...

change, CO2 concentrations, and refixation of respired CO2 in stands of Populus tremuloides Michx., Pinus banksiana Lamb. and Picea mariana (Mill.) B.S.P. at the northern and southern boundaries of the central Canadian boreal forest. Midsummer gas exchange rates in Populus tremuloides were over twice those of the two conifer species, and Pinus banksiana rates were greater than Picea mariana rat...

The oxygen isotope composition of CO2 respired by Ricinus communis leaves (d OR) was measured under non-steady-state conditions with a temporal resolution of 3 min using a tunable diode laser (TDL) absorption spectrometer coupled to a portable gas exchange system. The SD of d 18O measurement by the TDL was 0.2‰ and close to that of traditional mass spectrometers. Further, d OR values at isotopi...

When sprayed on plant leaves, several compounds, notably phenylmercuric acetate (PMA), can induce stomatal closure (16, 17). Most of these investigations with PMA were carried out on detached leaves with petioles dipping in water; it was found that the stomatal closing markedly reduced transpiration, whereas photosynthesis was reduced to a lesser extent. In these experiments it was demonstrated...

Our understanding of the effects of elevated atmospheric CO2, singly and in combination with other environmental changes,on plant-soil interactions is incomplete. Elevated CO2 effects on C4 plants, though smaller than on C3 species, are mediated mostly via decreased stomatal conductance and thus water loss. Therefore, we characterized the interactive effect of elevated CO2 and drought on soil m...

The modulation of guard cell function is the basis of stomatal closure, essential for optimizing water use and CO2 uptake by leaves. Nitric oxide (NO) in guard cells plays a very important role as a secondary messenger during stomatal closure induced by effectors, including hormones. For example, exposure to abscisic acid (ABA) triggers a marked increase in NO of guard cells, well before stomat...