Influence of vapour pressure deficit and photoperiod on growth, productivity and mineral composition on greenhouse tomato.

The objective of this study was to determine the effect of four vapour pressure deficits (VPD) and three photoperiods on growth, yield and mineral composition of tomato plants. A factorial experiment was conducted from 28 July 1993 to 30 May 1994 in a greenhouse at Laval University Envirotron in Quebec, Canada. Four day/night VPD treatments were compared: 1) 0,4/0,4 kPa, 2) 0,97/0,4 kPa, 3) VPD adjusted to a transpiration rate of 800 mL d(-1) plant(-1) and 4) 0,97/0,97 kPa. For each VPD treatment, three photoperiods were used: 1) 12 h, 2) 14 h and 3) seasonal progressive photoperiod of 12 to 16 h. The highest VPD significantly increased total and marketable yield, biomass and Ca, Mg, K, N and P contents of the leaves. Results obtained with adjusting the VPD to transpiration needs showed no significant differences with those obtained with the highest VPD. Photoperiod effects were not significant.