|Authors: ||A. Zaar, H. Dietrich, E. Krüger|
|Keywords: ||primocane raspberry, high tunnel cultivation, plastic films varying in UV B transparency, net photosynthesis, fruit quality|
In 2014, potted primocane raspberry Rubus idaeus 'Erika' was cultivated under open field conditions and under high tunnels with two plastic types (UVB-blocking: transmittance 90% with 0% transparency for UV B radiation and UVB-window: transmittance 90%, with 75% transparency for UV B) to evaluate their impact on net photosynthesis and different plant characteristics like yield and diverse fruit quality traits.
Diurnal photosynthetic response curves displayed a strong midday depression with a partial recovery in the late afternoon and were mostly influenced by air temperature and rel. humidity of ambient conditions but also by varying climatic conditions under the high tunnels (increased air temperature and reduced rel. humidity than in open field). Critical temperature for net photosynthesis in this study was slightly above 20°C. However, the effect of the different plastic materials on photosynthesis was negligible compared to temperature and relative humidity.
At harvest end net photosynthesis was influenced by the treatment as harvest period under high tunnels was 3 weeks earlier in comparison to open field and plant senescence occurred earlier.
Yield was lowest in the open field while fruit weight was lowest under the UV B window plastic film.
The treatments had no influence on fruit firmness, soluble solids, titratable acidity and vitamin C content.
Fruits grown in open field were more intense in their red color (a* value and Hue), corresponding to higher total anthocyanin content.
Individual anthocyanins were inconsistently affected.
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