Artificial lighting treatments for seedlings

Transcription

1 Artificial lighting treatments for seedlings Luke Suonenjoki/Kuopio Johanna Riikonen (

2 Use of artificial light in forest nurseries In Nordic countries, seedlings of forest tree species are traditionally grown under natural light conditions Artificial light is used for photoperiod control Night is interrupted by light pulses to prevent premature growth cessation and bud set LED technology is developing -> new possibilities also for silvicultural applications?

3 How plants are using light? nm UV Blue Green Yellow Red Far-red Defence compounds Photosynthesis, growth regulation Sign of photosynthetically unfavourable conditions Not well known Photosynthesis, growth regulation Sign of photosynthetically unfavourable conditions Red-to-far-red ratio!

4 Custom light regimes from seed to senescence?

5 1. Improved seed germination by red light exposure Red light is known to stimulate germination => activates phytochrome => seeds are able to germinate in darkness In preliminary tests, exposure to red light combined with seed pre-soaking enhanced seed germination energy by percentage points depending on the mulching material used Photo: Markku Nygren/Luke Nygren, M Itääkö männyn siemen pimeässä. Taimiuutiset 3/

6 2. Could blue light be used as a growth retardant? Growth in continuous light containing high proportion of blue light reduces height growth Could blue light pulses at the end of the day be used as growth retardants Light source could be mounted to a watering boom No significant height growth reductions under the treatments Exposure to elevated blue light might be needed throughout the day Height growth reduction by blue light is possible in growth chambers, but probably not in traditional nurseries

7 3. Far-red radiation in supplemental light? Photo: Markku Keinänen

8 3. Far-red radiation in supplemental light? + FR R:FR modifies characteristics related to drought tolerance and post-planting growth 50 Water use efficiency Pn/gs NO FR 0 +FR -FR The responses were related to the different growth habit and physiological stage of the seedlings Riikonen, J. Forest Ecology and Management 390 (2017) 8 14

9 4. Different light spectra in producing transplant seedlings Seedlings are pre-cultivated in mini-containers under optimal conditions for a few weeks => transplanted to larger containers when the root system bounds the peat plug => Containers are moved directly outside Aim of the transplant method is to: - enhance the homogeneity of germination and reduce height variation - increase flexibility in seedling production - reduce the need for greenhouse and storage

10 4. Different light spectra in producing transplant seedlings - Four different light spectra were used - Norway spruce and Scots pine seedlings were grown 6 weeks under the LEDs or HPS in conrolled conditios - Transplanted into bigger containers - Outplanted in autumn

11 4. Different light spectra in producing transplant seedlings - Different growth and morphology at the time of transplanting - Growth light rich in red and deficient in far-red seems to enhance root growth => shorter rotation time? High proportion of blue light ( nm) Hight proportion of far-red light ( nm) HPS 55% blue + 45% red

12 Conclusion: Different light spectra during the early growth did not affect the quality of the end product, but they might affect the rotation time in the growth facilities 12 Riikonen, J. 2016: New Forests (2016) :

13 5. Ongoing research: UV-C in disease control - Grey mould (Botrytis cinerea) is a harmful disease in forest tree nurseries worldwide - There is a general pressure to reduce the use of fungicides - frequent use of fungicides can lead to the development of pathogen resistance - There is a general pressure to reduce the use of fungicides

14 5. Ongoing research: UV-C in disease control - UV-C ( nm) radiation has effective antimicrobial properties - Direct impact of UV-C radiation on the pathogen, and an indirect effect through enhanced host-resistance - The aim is to determine an effective UV-C dosage for controlling grey mould infection without causing damage to the seedlings, and to examine the potential risks - Research group: Marja Poteri, Johanna Riikonen, Hanna Ruhanen, Anne Uimari Photos: Hanna Ruhanen/LUKE

15 Thank you! 15 Jaana Luoranen