Variations in sugars and cyclitols during development and maturation of seeds of brazilwood (Caesalpinia echinata Lam., Leguminosae)

Abstract

Seeds of Caesalpinia echinata are tolerant to desiccation, keeping their viability up to 0.08 g H2O g-1 DM. When stored under laboratory conditions they lose their viability within one month, while under low temperatures germination ability is maintained during two years of storage. Here, we report on the variations of soluble carbohydrates, cyclitols and cyclitol galactosides in seeds of C. echinata during development and maturation, aiming for a better understanding of the involvement of these compounds in the maturation process and seed quality. Individual flowers were tagged on the day of anthesis and pods were collected directly from the branches from 32 to 59 d after anthesis (DAA). Seeds were also collected after shedding. The physiological maturity of C. echinata seeds occurred 60-65 DAA, immediately before shedding, when seeds had 0.43-0.67 g H2O g-1 DM. Soluble carbohydrates made up about 10% of the seed dry mass. Gas chromatography and mass spectrometry allowed the identification and quantification of 12 soluble carbon compounds present in both the axis and cotyledons of developing C. echinata seeds. These included fructose, glucose, sucrose, raffinose, the cyclitols myo-inositol, D-chiro-inositol, D-pinitol, and the cyclitol galactosides, galacto-pinitol A, galacto-pinitol B and ciceritol. Sucrose was present in high proportions in both tissues during seed development. Traces of raffinose were also detected, mainly in immature seeds. D-chiro-inositol and myo-inositol were found in low amounts and pinitol transiently increased in both axis and cotyledons. Ciceritol, galacto-pinitol A and galacto-pinitol B accumulated from 40 DAA to the end of seed maturation, representing along with sucrose the major carbon reserves of C. echinata seeds. These results allowed us to conclude that variations in soluble carbon reserves of C. echinata seeds were related to the maturation process and seed quality.