Plants can detect the quality, quantity and direction of light and use it as a signal to adapt their morphogenesis and growth. Thus according to their light transmission, coloured nets used to protect plants from pests and limit irradiance can also affect plant growth and production.
Scientists at Yezin Agricultural University (Myanmar), Kasetsart University (Thailand), INRA and CIRAD (France) have determined the importance of the light spectrum on plant growth, reproductive characteristics and fruit chemical composition in tomato plants, grown under blue or red nets transmitting similar photosynthetic yield from transplanting to the end of harvest.
Results showed that the morphological traits, organ physiology and fruit composition were strongly influenced by net colour. Plants under the red net were taller with a greater leaf area and a shoot to root ratio. An increased blue to red ratio slightly enhanced the reproductive development (visible bud development and 1st flowering) of tomato plants. An increased red to blue ratio enhanced the tomato glucose (17%) and fructose (6%) contents, while the citric (5%) and malic acids (4%) contents decreased, triggering a higher sugar/acid ratio. A high blue to red light limited organ growth and plant light interception was reduced despite a higher photosynthetic yield and a slight enhancement of the organ appearance rate.
"A low blue to red light increased fruit weight at harvest and even if it did not significantly improve fruit yield, it favoured fruit quality as it enhanced the tomato sugar/acid ratio," explain the scientists.
Source: Aye Aye Thwe, Poonpipope Kasemsap, Gilles Vercambre, Frédéric Gay, Jessada Phattaralerphong, Hélène Gautier, 'Impact of red and blue nets on physiological and morphological traits, fruit yield and quality of tomato (Solanum lycopersicum Mill.)', 2020, Scientia Horticulturae, Volume 264, 109185.