Transpiration and canopy resistance of greenhouse soilless roses: Measurements and modeling

Abstract

Measurements of transpiration (TR) of a rose crop (cv. First Red) grown on perlite were recorded during the winter of 1998 in a glasshouse located on the coastal area of Eastern Greece. Simultaneously, measurements of solar radiation (Rs), air temperature and vapour pressure deficit (VPD), and leaf temperature were carried out. These measurements were used for the calibration of a regressive model of the type: TR = Ao f1 (LAI) R s + B0 f2 (LAI) VPD. This model was compared with a similar one proposed by Gonzalez-Real (1995) for cv. Sonia grown on rockwool. Although the parameters A0 and B0 were different from those obtained by these authors, the two models give very similar estimations of TR and a satisfactory agreement with respect to measured values. The determination of the canopy resistance rc was deduced from the measurements of TR and leaf-to-air VPD. The calculated values of rc were further modelled using the multiplicative model of Jarvis. Significant differences in the values of rc and model parameters were found in our case when compared with the values reported by Baille et al. (1994) for cv. Sonia. These differences can be ascribed to the cultivar or to the different growing conditions. These results seem to confirm that, in greenhouse conditions, the physiological resistance of the canopy does not appear to play a significant role in determining the canopy transpiration. Then, simplified models of TR that include the assumption of a constant stomatal resistance can probably be considered as sufficiently robust and realistic for greenhouse applications such as climate control and irrigation scheduling.