Determination of the optimum moisture content of purple ipê (Handroanthus heptaphyllus) seeds for biospeckle tests

Abstract

Handroanthus heptaphyllus (botany synonymy Tabebuia heptaphylla) is considered to have very important economical, ornamental and medicinal value. It is included in the Bignoniaceae botanical family, whose multiplication is quite solely carried by seeds. Forest dispersion elements, i.e., the seeds, deserve a deep understanding on their physiological performance. The objective of this research work was to determine the optimum seed moisture content for laser interaction in biospeckle tests, which is based on laser interferometry. Seeds were hydrated to the level of 69% and then divided into four subsamples, i.e., (1) seeds without teguments, (2) seeds with tegument, (3) seeds without teguments frozen at 0 °C and (4) seeds with teguments frozen at 0 °C. The four subsamples were then separated into five moisture level groups (28%, 35%, 54%, 63% and 69%) and exposed to the laser. The biospeckle phenomenon quantification was carried out by means of the moment of inertia (MI) approach. A positive correlation between MI and seed moisture content was obtained. It was also verified that seed moisture content between 28% and 54% showed better interaction with the laser. The results are important for the application of the biospeckle technique as a possible tool to assess the quality of purple ipê seeds.