Differences in the effects of flooding the soil early and late in the photoperiod on the water relations of pot-grown tomato plants

The water relations of potted tomato plants (Lycopersicon esculentum Mill. cv INCA 9(1)) submitted to two flooding/recovery cycles imposed at the begi nning and at the end of photoperiod were studied under controlled condition s. Tn both experiments, flooding induced stomatal closure due to leaf dehyd ration linked to a lowered root hydraulic permeability. Thus. during the ea rly hours of flooding there was an effective negative hydraulic message fro m O-2 deficient roots. However, when the soil was drained stomata did not r e-open until some time after leaf water potential and leaf turgor potential returned to normal: supporting the view that chemical messages predominate , Flooding imposed at the end of photoperiod induced a delay in g(1), Psi ( 1), and Psi (p). recovery. (C) 2001 Elsevier Science Ireland Ltd. All right s reserved.