Vitamin E and defense-related phytohormones are reliable markers of embryo growth in macaw palm fruits exposed to various storage conditions

The fruit of the macaw palm ( Acrocomia aculeata ) may be used for biofuel production, but its exploitation as a crop is currently limited by its low germinability. Therefore, obtaining plantlets in vitro is an excellent way to solve this problem. Here we aimed to identify the optimal conditions for storing the fruit before obtaining plantlets and testing to what extent vitamin E and defense-related phytohormones are good indicators of embryo growth in vitro. We tested the effects of four storage conditions (nursery, laboratory, cold chamber and freezer) on seed germinability and embryo growth, and evaluated endogenous levels of vitamin E and defense-related phytohormones (abscisic acid, salicylic acid and jasmonic acid) in the endosperm and embryos. Low temperatures [both cold chamber (5 °C) and freezer (−18 °C) methods] killed the embryos, while storing the fruit in the laboratory was the most efficient method of obtaining plantlets, even after a year. Vitamin E and abscisic acid turned out to be good indicators of embryo growth. Enhanced vitamin E and abscisic acid levels had a strong positive correlation with successful embryo growth, thus indicating that these compounds are needed to protect the embryo during fruit storage. Furthermore, abscisic acid levels had a negative correlation with the percentage of contaminated embryos, thus suggesting that the endogenous physiological stage of the seeds affects subsequent contamination in in vitro cultures. We concluded that (1) storing fruit under laboratory conditions is the most efficient means of obtaining plantlets successfully, and (2) vitamin E and abscisic acid can be used as reliable indicators of embryo growth during in vitro culture.