Light quality affects shoot regeneration, cell division, and wood formation in elite clones of Populus euramericana

The effect of light (blue, red, and/or green) generated by light-emitting diodes on shoot regeneration was examined in selected clones, 'I-476' and 'Dorskamp', of Populus euramericana. We found that a combination of red and blue light produced the highest percentage of shoot regeneration in comparison to monochromic or fluorescent light. Further studies of light quality and in vitro growth of Dorskamp'' plantlets demonstrated the suitability of combinations of red and blue light to improve most of the characteristics studied. Flow cytometry of the leaves showed that 50 % red + 50 % blue light treatment was the most effective for inducing cell division in Dorskamp'', whereas monochromic red and blue were more effective in I-476''. Histological studies found that secondary xylem formation increased with the monochromic blue light treatment in the stem of I-476'', whereas in Dorskamp'', a combination of red and blue light (70 + 30 %, respectively) was more suitable. Our study demonstrated that combinations of red and blue light increase shoot regeneration and development by stimulation of cell division, although the response may vary among genotypes of the same species. The results of this study can contribute to mass production of the selected clones for forest establishment on reclaimed land and serve as an efficient protocol for genetic transformation of this species.