The influence of irradiance on phenolics contents and rooting of Ilex paraguariensis cuttings was studied. Results of the first experiment with stock plants under controlled-irradiance conditions show that when the irradiance level increased from 1.5 to 100 % PPFD, the oxidation of cuttings raised from 19 ± 11 to 88 ± 4 % (r² = 0.64). At the same time, a strong correlation was observed between total phenolics content and irradiance (r² = 0.7). In consequence, adventitious rooting diminished from 67 ± 5 to 3 ± 3 % under full radiation (r² = 0.7). In the second experiment with stock plants subjected to field conditions, the results showed that the rooting process is strongly affected by the genotype (P < 0.0001), while the statistical analysis did not show a correlation between rooting and age of the donor plant. Season had a variable effect and depends on genotype. Although we did not find correlations between the rooting ability and the canopy structure of the stock plants, the position of the branches in the mother plant affected rooting and depended on season in addition to genotype. Concomitantly, the levels of soluble phenolics compounds were higher from leaves subjected to high-irradiance conditions than samples collected from inner canopy; which was coincident with the pattern of cuttings oxidation. In conclusion, our results provide evidences which support the hypothesis that the physiological status of the stock plant at the time that cuttings are excised is of utmost importance for the subsequent rooting of I. paraguariensis cuttings. The influence on soluble phenolics content of different irradiances given to the stock plants negatively affect the rooting process since the product of its oxidation cause the browning and death of the cuttings.
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