Technical and control methods to optimise health-promoting plant compounds in various plant species
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Beschreibung
The investigations in this thesis are focussed on the application and development of technical and control methods to optimise health-promoting plant compounds in various plant species. Based on the knowledge that climate change will lead to an excessive change in climatic conditions in greenhouses (GH), new climate control strategies for semi-closed and closed greenhouses were developed and applied to avoid plant damage and the reduction of secondary plant compounds in tomatoes.
The prevailing climatic conditions in semi-closed and closed GH were sufficient to accelerate the plant growth. In this context, comparisons between leaf area growth per plant, depending on different climate control strategies in greenhouses, were realised using a leaf area estimation model, which was developed and applied during the experiments. Furthermore, the changing climate conditions caused by cooled GH increased the dry matter in leaves and promoted the formation of fruit set per truss, in comparison with those grown under conventional climate conditions. The applied algorithm for semi-closed and closed GH led to a maximum total yield increase of 20% and 32%, respectively, to a reduction of blossom-end rot in tomatoes and to a pronounced increase in fruit size during the spring experiments. Compared with conventionally treated tomato plants, a maximum increase in contents of lycopene (by 49%), ß-carotene (by 35%), phenolic compounds (by 16%) and associated antioxidant activity in the water-insoluble (by 19%) and water-soluble (by 35.%) fraction of tomatoes grown in semi-closed GH, was observed. Comparable maximal increases were also determined in closed GH regarding concentrations of lycopene (by 30%), ß-carotene (by 40%), and phenolics (by 25%) but also of titratable acids (by 8%) and soluble solids (by 15%). Therefore, the agronomic approaches in terms of the application of new control mechanisms for semi-closed and closed GH can be appropriate to increase the total yield and to improve the fruit quality, especially the health-promoting properties and flavour attributes of tomatoes (cv. Pannovy).
Another agronomic approach was to apply electricity in pre-harvest and post-harvest processes, based on the knowledge that electricity can activate the biosynthesis of substances with antioxidant activity in different plant species. Compared with untreated plants, the maximum increase in total phenol content was determined in radish roots (by 46%) treated with 1000 milliampere (mA) for one hour per day, followed by that in radish tubers (by 13%). The associated antioxidant activity in radish tubers was affected to a smaller extent, where this level was elevated by 4.5% compared with those treated with 600 mA. Anthocyanins as chromophoric phenolic compounds were increased by 28% in radish tubers, whereas no differences existed between IDC treatments with 600 mA and 1000 mA. In contrast, a further IDC increase to 1400 mA, applied for one hour, was sufficient to promote the levels of phenolic compounds and associated antioxidant activity in garden cress sprouts by 16% and 18%, respectively. Other plant physiological responses, such as increasing contents of total chlorophyll (by 17%) and proteins (by 33%) in garden cress, were achieved with the same IDC intensity (1400 mA).
Different intensities of DC (100–500 mA) with various application times (15–60 min) were applied to tomatoes in post-harvest processes. Almost all DC treatments significantly affected the secondary metabolism, resulting in an accumulation of carotenoids, phenolic compounds and antioxidant activity in tomatoes compared with the reference.
Autor*in
Dennis Dannehl
Themen in »Technical and control methods to optimise health-promoting plant compounds in various plant species«
carotenoids climate change closed greenhouse cooling system phenolic compounds secondary plant compounds tomato