Effect of light intensity on in vitro introduction and multiplication of Eucalyptus grandis x Eucalyptus urophylla

Micropropagation technique has been recommended for plant tissue rejuvenation/reinvigoration and the improvement of clonal plants production commercially. Concerning the limiting factors on in vitro cultivation of Eucalyptus grandis x E. urophylla hybrid clone, the effects of light intensity on in vitro introduction and multiplication phases were assessed. The experimental tissue was collected from ministumps cultivated in a semi-hydroponic system. The results of light intensity on in vitro introduction and multiplication were evaluated with four treatments (fluorescent lamp/40 mu mol m(-2) s(-1), red/blue LEDs 20 mu mol m(-2) s(-1), red/blue LEDs 40 mu mol m(-2) s(-1), and red/blue LEDs 80 mu mol m(-2) s(-1)). The explants' morphological, anatomical, and genetic characteristics were evaluated at 30 d in the in vitro introduction, and 12 subcultures for in vitro multiplication. Based on the results, the treatments F/L 40 mu mol m(-2) s(-1) and R/B 80 mu mol m(-2) s(-1) are the most suitable during in vitro introduction and multiplication of Eucalyptus grandis x E. urophylla. It provides a higher percentage of responsive explants, shoots per explant, vigor, photosynthetic pigment content, adaxial epidermis thickness, abaxial epidermis, mesophyll, palisade parenchyma, spongy parenchyma, and vascular tissues. Furthermore, it was found that the micropropagated plants are identical clones of the Eucalyptus grandis x E. urophylla selected tree; that is, there was no somaclonal variation during the twelve subcultures on in vitro multiplication.