Optimizing pear micropropagation and rooting with light emitting diodes and trans-cinnamic acid

Abstract

Meta-Topolin riboside was selected as cytokinin for these experiments. The effects of combinations of monochromatic blue, red and far red LED light were compared to fluorescent light during the micropropagation and rooting of a recalcitrant pear (Pyrus communis L.). During the micropropagation phase, red light gave some particular advantages: maximal shoot length and leaf area were obtained. Under blue light, callus weight quadrupled compared to fluorescent light. Although far red was advantageous for shoot number, shoot quality was inferior because of hyperhydricity and chlorosis as indicated by a low Chlorophyll a\u2009+\u2009b and carotenoid content. The smallest leaf area was detected under fluorescent light. Blue\u2009+\u2009red showed significant improvements. Shoot cluster weight and ‘shoot weight/callus weight’ ratio was maximal, as well as shoot number and shoot length. Leaves were also dark green, showing a maximal Chlorophyll a\u2009+\u2009b and carotenoids content. Adventitious rooting of in vitro cultured pear plants was highly affected by different light spectra and the addition of a new rooting compound: trans-cinnamic acid. Without trans-cinnamic acid, limited rooting was observed under red, blue and blue\u2009+\u2009red light. In combination with trans-cinnamic acid, 100% rooting was achieved under red light.