Variations in storage protein and carbohydrate levels during development of avocado zygotic embryos

Variations in carbohydrates and proteins were monitored during avocado (Persea americana Mill.) zygotic embryo development and correlated with growth parameters in order to define specific markers characterizing distinct embryogenic phases. Hexose (glucose and fructose) levels were initially high and declined as embryo development advanced reaching the lowest levels in completely mature embryos. Sucrose and starch evolution showed an opposite trend with a progressive increase during embryo growth. The beginning of the maturation phase could be identified by a switch in the carbohydrate status from high hexose/sucrose ratio to low hexose/sucrose ratio. Storage protein accumulation began at early cotyledonary stages (7–8 mm), increasing significantly in the maturation phase where they represented 83% of total proteins. Mature embryos (38–40 mm) contained albumins, globulins and glutelins, albumins being the predominant and most heterogeneous fraction. Storage protein accumulation occurred in a sequential and specific way suggesting a possible role as indicators of embryo development. The complete maturation stage could be characterized by the synthesis and accumulation of a 49 kDa albumin.