H.L. Xu, Q.C. Xu, F.F. Qin, F.L. Du, A. Gosselin, B. Dansereau, Y. Zhang
Many plant species respond to strong light intensity and low humidity with the stomatal oscillation to adjust the balance between root water uptake and transpiration water loss. In the present study, tomato and hibiscus were grown in pots under greenhouse conditions and stomatal oscillation was confirmed. Net photosynthesis rate (PN) in leaves of hibiscus showed oscillations under photosynthetic photon flux densities (PPF) of 550 and 350 µmol m-2 s-1. Only tomato plants grown under salinity stress showed hysteresis in PN. It was speculated that the leaf lost its tissue water when the transpiration water loss surpassed the root water uptake and consequently closed its stomata to reduce further water loss and opened its stomata again when the leaf was recharged by the root water uptake. The phenomenon of cyclic changes in PN or stomatal conductance (gs) is called photosynthetic or stomatal oscillation. The oscillation of PN or gs was analyzed using an equation as
PN=[PA+PAcos(ωt+τ)](1+αt)+PR(1+βt) or
gs=[gA+gAcos(ωt+τ)] (1+αt)+gR(1+βt),
where PA or gs is oscillation amplitude; α is a constant associated with cycle period (T) as T=2Π/α; t is the time from beginning of the oscillation; ω is the angular frequency; τ is the phase of the oscillation; β is a constant associated with the oscillation decay or decline; and PR or gA is the residual value of PN or gs when stomata are closed at the oscillation bottom. The results showed that PN oscillation in tomato was much weaker than in hibiscus. The mathematic approach to analysis of photosynthetic oscillation is of reference to plant scientists.
Xu, H.L., Xu, Q.C., Qin, F.F., Du, F.L., Gosselin, A., Dansereau, B. and Zhang, Y. (2011). PHOTOSYNTHETIC OSCILLATION IN LEAVES OF TOMATO AND HIBISCUS UNDER HIGH LIGHT INTENSITY. Acta Hortic. 907, 343-347
DOI: 10.17660/ActaHortic.2011.907.56
hibiscus, light, mathematic model, oscillation, photosynthesis, stomata

Acta Horticulturae