Estimation of water needs of young and aged rose plants with the use of two simplified transpiration models

Water needs of a soilless rose crop during a growing period, may alter significantly depending on plant growth stage and cultivation treatments. However, simplified transpiration (Tr) models, are not tested after rapid change of crop's leaf area (LA) due to specific cultivation treatments. The aim of this work was to estimate the water needs of rose plants ('Miss Piggy') cultivated in a closed hydroponic system, after planting, pruning, harvesting and bending. For this purpose, plants Tr and LA were measured on young plants after planting and on mature plants after pruning, harvesting and bending. At the same time plants Tr was estimated based on simplified models by Penmann-Monteith, according to greenhouse climate parameters and crops leaf area index (LAI). The LA of young plants varied from 0.003 to 0.013 m² plant^‑1 while their Tr from 0.008 to 0.046 g m^‑2 day^‑1 during the two months period. Mature plants LA ranged from 0.16 to 0.37 m² plant^‑1 and their Tr from 0.25 to 1.36 g m^‑2 day^‑1 during the same period. LAI in young plants increased constantly from 0.022 to 0.1, while LAI in mature plants altered depending on the treatments (pruning, harvesting and bending). However even after pruning, both Tr and LA of mature plants increased (more than 10 times) in comparison to those of young plants during the two months' period. The results from the above mentioned measurements show that, young and mature plants Tr was overestimated by model that did not take into account LAI alteration after pruning, harvesting and bending treatments, although it responded efficiently when plants LA remained almost stable during the cultivation period. The model that included LAI, fitted well when plants LA reduced significantly after the above mentioned treatments. None of the transpiration models estimated the Tr of young plants correctly.