S08 - Session O3 - Photosynthetic characteristics of grafted cucumber seedlings following healing and acclimatization under different light spectra and intensities

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

Utilization of grafted seedlings as the starting plant material for production of cucumber is attracted lots of attention during the last two decades. Good photosynthetic functionality is an important parameter determining the quality of grafted seedlings. In the current study, analysis of biophysical photosynthetic traits as well as the photosynthetic pigments were carried out on grafted cucumber scion on squash seedlings that were exposed to wide ranges of light spectra and intensities. To do so, grafted seedlings were exposed to different light spectra including Red, Blue, Green, White, Red:Far red, Red:Blue (in two ratios of 50:50 and 70:30) and four light intensities [25, 50, 100, and 200 µmol m -2 s -1 photosynthetic photon flux density (PPFD)] in the research laboratory of Sepahan Rooyesh Company. Based on obtained results, exposing grafted seedlings to the highest light intensity (200 µmol m -2 s -1 PPFD) was harmful for survival rate of the grafted seedlings except for the seedlings exposed to the combination of Red:Far red light. Accordingly, the lowest maximum quantum yield of photosystem II (Fv/Fm) was also obtained in grafted seedlings exposed to highest light intensity (200 µmol m -2 s -1 ). The maximum Fv/Fm was detected in grafted seedlings under lighting regimes which had blue light in their overall spectrum. Energy dissipation per reaction center was the highest in grafted seedlings under lighting regimes having sole or more than 75% red light in their overall spectrum. By increasing blue light in overall spectrum lower Energy dissipation per reaction center was detected. In combinational light regimes (e.g., white, 70Red:30Blue, and 50Red:50Blue) and green light, the highest chlorophyll a and b content was detected under the highest PPFD. Carotenoid content in the light regimes containing blue light in their overall spectrum was the highest under 200 µmol m -2 s -1 PPFD, while in light regimes containing sole red light the lowest carotenoid content was detected under 200 µmol m -2 s -1 PPFD. In conclusion, combinational red and blue light with an intensity of 50 µmol m -2 s -1 PPFD can result in best graft taking and photosynthetic performance of grafted cucumber seedlings.