Analysis of seedlings growth under different led lights

LED lights have a lower environmental impact than traditional lights due to a series of factors such as high energy-conversion efficiency, small volume, longer life, low thermal energy output. Concerning plant growth, the use of LED lights provide specific wavelength as well as the possibility to adjust light intensity/quality. The increasingly need to reduce energy consumption worldwide, raised the necessity to improve LED lights use. The present work aims to 1) examine the effect of different LED light spectra on seedlings growth of different species in order to define a species-specific cultivation protocol under optimal plant growth spectrum 2) compare direct measurements with non-destructive method by optical sensors. The plant species analyzed were Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L.), Holm oak (Quercus ilex L.) and Pomegranate (Punica granatum L.) Seedlings were left to grow in a growth chamber (16 h photoperiod, 120μmol m-2 s-1 PAR, temperature 21-22°C, humidity 80% germination - 55-70% growth) for 4 weeks under G2, AP67, AP67-3L, NS1 LED light (Valoya) and Fluorescent light (FL, control). Direct measurements of shoot height, root length, shoot and root biomass were carried. Non-destructive analysis was carried by measuring Greenness (percentage of shoot cover projected on tray ground) and Plant height. Greenness data were first obtained by a series of manually taken images (Nikon D70s digital camera) analysed with an open source software (ImageJ). Plant height was manually taken during the growth period to find a relationship with plant biomass. Furthermore, plant height was manually taken and compared with data obtained from images acquired by Optical sensors and analysed by uEyeDualcam HeightMap software (ACREO). Seedlings growth under AP673-L and G2 light, for Scots pine and Norway spruce, showed height values higher than values measured under control light and root length and shoot and root dry weight values similar to the values measured under control light. Seedlings growth under NS1 light, for both species, showed significantly lower total biomass and root length than seedlings growth under control light. In conclusion, seedling growth under G2 LED type shows the highest performance, representing the optimal spectrum. Similar values were found for seedling growth under AP67-3L. G2 light has the higher percentage of far-red/red (600-800 nm) wavelength (λ). Hence, it could interfere with optical measurements such as greenness. Therefore, in alternative to G2 type, AP67-3L LED type could represent the best option for a standard cultivation protocol. Results about non-destructive analysis show that greenness value for Scots pine and Norway spruce species in relation to different light type, showed highest values with AP67-3L. Preliminary results showed the same pattern also for Holm oak and Pomegranate species. Highly significant positive relationships between greenness, plant height and seedlings total biomass were found for Scots pine and Norway spruce for all LED light types (0.89< R 2 <0.99). For all considered species tests were carried to relate plant height data obtained by HeightMap Software (ACREO) with plant height manually measured, and a good relationship was found. (Scots pine: R 2 = 0.85; Norway spruce lower relationship R = 0.59; Holm oak R 2 =0.83). Tests are in progress to relate Greenness data obtained by uEyeDualcam software with plant biomass. In conclusion tests about relationship between plant height and greenness, obtained by manual measurements and by Nikon digital camera-Image J software, highlighted that indirect analysis are good parameters for non-destructive quantification of plant biomass.