Role of Light and Phytochrome on Piper aduncum L. Germination: An Adaptive and Environmental Approach

Abstract

ABSTRACT The influence of light on the germination process of two Piper aduncum ecotypes (SP and PR) were investigated and reported in this paper. This species has been getting special attention because the safrole content in their leaves. Seeds of both ecotypes were exposed to: daylight (DL), red (R), far-red (FR), blue (B), green (G), dark (DK) and reversible (RVB) to determine the light effects. Both ecotypes behaved similarly, except SP ecotype in the green light treatment, which reached an intermediary germination level. Seeds kept under far-red environment acquired light induced dormancy. This dormancy, however, was reversible and the most germination was observed by seeds first exposed to saturated levels of far-red and then exposed to red light (RVB treatment), a light regime consistent with transitional shading to direct sunlight environments (new deforested fields, gaps, and forest borders). Seeds also germinated under daylight and red light, but not far-red light, blue light, and dark treatments. Some seeds of the PR ecotype, but not the SP ecotype, germinated under green light treatment. The seeds do not germinate without light, classifying the plant as positively photoblastic. Daylight and red light treatments started germination on the 14th day for the SP ecotype and on the 14th and 15th day (for daylight and red light, respectively) for the PR ecotype. The fluency accumulated before the initiation of germination was higher than 1 × 103 μmol · m−2, evidence for the necessity of light for seed germination in this species. Apparently, seed germination in P. aduncum will be promoted by sowing under the shade of other commercial crops (15 to 20 days before harvesting).