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The effect of considering cultivar differences in stomatal conductance (g s) on relative air humidity (RH)-related energy demand was addressed. We conducted six experiments in order to study the variation in evapotranspiration (ET c) of six pot rose cultivars, investigate the underlying processes and parameterise a g s -based ET c model. Several levels of crop ET c were realised by adjusting the growth environment. The commonly applied Ball–Woodrow–Berry g s -sub-model (BWB-model) in ET c models was validated under greenhouse conditions, and showed a close agreement between simulated and measured ET c. The validated model was incorporated into a greenhouse simulator. A scenario simulation study showed that selecting low-g s cultivars reduces energy demand (≤5.75%), depending on the RH set point. However, the BWB-model showed poor prediction quality at RH lower than 60% and a good fit at higher RH. Therefore, an attempt was made to improve model prediction: the in situ -obtained data were employed to adapt and extend either the BWB-model, or the Liu-extension with substrate water potential (Ψ; BWB-Liu-model). Both models were extended with stomatal density (D s) or pore area. Although the modified BWB-Liu-model (considering D s) allowed higher accuracy (R2 = 0.59), as compared to the basic version (R2 = 0.31), the typical lack of Ψ prediction in greenhouse models may be problematic for implementation into real-time climate control. The current study lays the basis for the development of cultivar specific cultivation strategies as well as improving the g s sub-model for dynamic climate conditions under low RH using model-based control systems. • Relative air humidity control is a key but costly aspect of greenhouse climate. • Accurate estimation of evapotranspiration (ET c) is essential for relative air humidity regulation. • Six pot rose cultivars and several cultivation regimes were used. • ET c estimation was improved using cultivar-specific stomatal conductance parameters. • The use of low-stomatal conductance cultivars secures energy saving (2.5–5.75%). [ABSTRACT FROM AUTHOR]

Due to new electricity generation and supply schemes, optimising cost and return in greenhouse production could be achieved with interruptive schemes for supplementary lighting (SL). We analysed the effect of interrupted SL (ISL) on both the cost of electricity and crop yield of tomato cultivation during a winter in Brandenburg, Germany (LAT 52°N). We applied SL for 60 days to a tomato crop (cv. Komeett) with two nighttime regimes of nine hours using high pressure sodium lamps (HPSL; 400 W and 210 μmol m–2 s–1) resulting in equivalent daily light integral (DLI, mol m–2 day–1). CO 2 assimilation of the crop stand was measured either continuously in four airtight gas exchange greenhouse compartments (28.8 m2 each) or from a sampling of total dry mass. Measurements were used to evaluate the predictions of an existing deterministic photosynthesis model. Results indicate: 1) continuously measured crop net photosynthesis (Pn) overestimated the total CO 2 assimilation when measured as crop dry matter at only 1.7%, and 2) an ISL regime had only a low influence on total dry mass formation, presenting 7.6% higher total dry matter in comparison to the model results. It is concluded that 1) continuous measurements of Pn in a daylit environment can be used as a dry mass increase indicator, 2) ISL can be applied without losses in tomato yield, and 3) the existing tomato crop photosynthesis model was not suitable for ISL control. Thus, price optimised ISL can be applied with no negative effect only by looking at electricity prices. • Analysis of dynamic crop net photosynthesis for two lighting regimes at night. • Long term crop photosynthesis model validation using gas exchange measurements. • Correlation between explanatory photosynthesis model and the biomass accumulation. • Interrupted supplemental lighting presents low influence on the total dry mass. • Cultivation practises related to crop net photosynthesis. [ABSTRACT FROM AUTHOR]

The Xenopus Eleutheroembryonic Thyroid Assay (XETA) was recently published as an OECD Test Guideline for detecting chemicals acting on the thyroid axis. However, the OECD validation did not cover all mechanisms that can potentially be detected by the XETA. This study was therefore initiated to investigate and consolidate the applicability domain of the XETA regarding the following mechanisms: thyroid hormone receptor (THR) agonism, sodium-iodide symporter (NIS) inhibition, thyroperoxidase (TPO) inhibition, deiodinase (DIO) inhibition, glucocorticoid receptor (GR) agonism, and uridine 5′-diphospho-glucuronosyltransferase (UDPGT) induction. In total, 22 chemicals identified as thyroid-active or -inactive in Amphibian Metamorphosis Assays (AMAs) were tested using the XETA OECD Test Guideline. The comparison showed that both assays are highly concordant in identifying chemicals with mechanisms of action related to THR agonism, DIO inhibition, and GR agonism. They also consistently identified the UDPGT inducers as thyroid inactive. NIS inhibition, investigated using sodium perchlorate, was not detected in the XETA. TPO inhibition requires further mechanistic investigations as the reference chemicals tested resulted in opposing response directions in the XETA and AMA. This study contributes refining the applicability domain of the XETA, thereby helping to clarify the conditions where it can be used as an ethical alternative to the AMA. • The Xenopus Eleutheroembryonic Thyroid Assay (XETA) was recently developed to screen for thyroid activity of chemicals. • XETA results were compared to Amphibian Metamorphosis Assay (AMA) outcomes for the detection of thyroid-active chemicals. • Results were concordant for all selected mechanisms, but the XETA did not detect inhibition of the sodium-iodide symporter. • Thyroperoxidase inhibition requires further mechanistic investigations due to equivocal responses in the XETA. • The XETA and the AMA consistently identified uridine 5′-diphospho-glucuronosyltransferase inducers as thyroid-inactive. [ABSTRACT FROM AUTHOR]