Climate Conditions in a Closed Greenhouse Affect Plant Growth and Secondary Plant Compounds of Tomatoes (Solanum lycopersicum L.)

Due to the climate change and increasing prices for fossil fuels, a new climate strategy for closed greenhouses was developed at the Humboldt-Universitat zu Berlin and compared to a conventional climate strategy. One of the main objectives of this study was to investigate the effects of climate conditions in a closed greenhouse on plant growth, fruit yield and quality characteristics of tomatoes. The first results of the start-up phase showed, that the total yield of marketable fruits harvested in the closed greenhouse without CO2 enrichment was significantly increased by 8.6% compared to the reference greenhouse. Compared to the conventional climate strategy, non-marketable fruits yield was significantly decreased by the influence of the closed operation mode. The results of this study have also shown that the climate conditions in the closed greenhouse increased the leaf area per plant, influenced the formation of fruit sets positively, and significantly affected health-promoting properties of tomatoes. It was demonstrated that the contents of lycopene and beta-carotene of tomatoes were increased significantly in the closed greenhouse. The increase of carotenoids also significantly increased the antioxidant activity by 30% compared to the tomatoes harvested in the reference greenhouse.