Light quality affects in vitro adventitious rooting and ex vitro performance of cherry rootstock Colt

The effect of light quality on in vitro rooting of cherry rootstock “Colt” was studied to evaluate adventitious root development, ex vitro acclimatization and plant growth performance. Adventitious rooting was dependent on the light quality to which the microcutting were exposed. Highest number of roots per microcuttings was recorded under dichromatic light (blue + red). This response could be ascribed to the control of a strong synergistic interaction between phytochromes and blue light photoreceptors. Red light was more effective on root elongation than blue light. In this response a strong synergistic interaction between phytochromes and blue light photoreceptors was suggested. The effect of light quality on the number of root/explant affected the plant during acclimation, scoring the highest level of plant survival in the blue-, red- and blue + red-exposed plantlets. The light quality effect was also observed under greenhouse culture conditions, as shown by growth parameters at the end of six months in plants growth. No specific role was observed for the photoequilibrium of phytochrome. The results reported in this work show that plantlets exposed to different light quality, during the in vitro rooting phase, retain the light quality effects in the subsequent plant acclimatization and greenhouse plant growth phase.     

Light quality regulates shoot cluster growth and development of MM106 apple genotype in in vitro culture

The interaction between shoot proliferation and regulative action of light quality was investigated in terms of cluster growth and development. In the commercial laboratory, the shoot multiplication procedure is normally conducted by growing clusters of shoots during several sub-cultures. Thus in this work the regulative action of light quality was evaluated by analysing the shoot cluster proliferation rate, the evolution of axillary bud differentiation, the axillary shoot development on both initial explant stem (order 1 axis) and three representative lateral branches (order 2 axes), growing from the lateral buds located at the bottom of the initial explant. Experiments showed that light qualities regulate bud differentiation and interact with apical dominance, leading to strong control of axillary bud outgrowth, and, finally, resulting in a differentiated architectural formation of clusters and type of branching.