S03 - Session P2 - Impact of wide range of light spectra and intensities on grafted cucumber seedlings during healing and acclimatization

Authors: Farzaneh Bekhradi *, Mohamad Mohammadian, Sasan Aliniaeifard, Mahmoud Lotfi

Nowadays there is a high tendency for using grafted transplants. Since the newly-grafted seedlings have no vascular connections during the healing period; therefore, they are extremely susceptible to desiccation. Keeping the newly-grafted seedlings under favorable environmental conditions is of vital importance for the successful production of grafted seedlings. The present study investigates the effects of light spectra and intensities on performance of grafted cucumber scion on squash seedlings. The newly-grafted seedlings were placed in 29 cabinets in a large LED-equipped vertical systems under different light spectra including Red, Blue, Green, White, Red:Far red, Red:Blue (in two ratios of 50:50 and 70:30). Each spectrum was applied in four intensities [25, 50, 100, and 200 µmol m -2 s -1 photosynthetic photon flux density (PPFD)] together with a darkness treatment in the research laboratory of Sepahan Rooyesh Company. Results showed that there was no significant difference among PPFDs lower than 200 µmol m -2 s -1 for graft-taking trait of the grafted seedlings exposed to different light spectra except for the white- and darkness-exposed seedlings. The grafted seedlings were spoiled under dark condition. The highest root fresh weight was detected under 100 µmol m -2 s -1 Red:Blue (70:30), while the lowest root fresh weight was obtained under 25 µmol m -2 s -1 PPFD in all light spectra. Under sole Red light and Red:Far red spectra, the highest root fresh weight was achieved under the highest light intensity (200 µmol m -2 s -1 ). The longest roots we recorded under 200 µmol m -2 s -1 of sole Red light, while the shortest roots were detected under 200 µmol m -2 s -1 Green and 25 µmol m -2 s -1 Red:Far red light treatments. The longest stems and highest stem fresh weights were observed under Red:Far red light. There was a negative effect of light intensity on stem fresh weight and length under most light spectra. In all light spectra, the thinnest stem in the scion part was detected under lowest light intensity (25 µmol m -2 s -1 ), whereas the thickest stems were detected in 200 µmol m -2 s -1 Red:Blue (70:30) and 100 µmol m -2 s -1 Red:Far red. In all light spectra, the thinnest stem in the rootstock part was detected under 200 µmol m -2 s -1 of Green light. whereas the thickest rootstock stems were detected in 25 and 100 µmol m -2 s -1 Red:Blue (70:30), 25 and 50 µmol m -2 s -1 Red:Far red and 50 µmol m -2 s -1 Blue. In all of the light spectra (except for the sole Red light), the lowest leaf area was recorded under 25 and 200 µmol m -2 s -1 PPFDs. In conclusion, since elongated seedlings are not desirable and enough leaf areas are desirable for the grafted seedling production, spectra containing Blue spectrum yielded better results, since some negative effects of high PPFDs were detected and due to energy saving aspects, both 50 and 100 µmol m -2 s -1 PPFDs can be recommended for production of grafted cucumber seedlings.