Carbohydrates, minerals and free amino acids in Triticum aestivum L kernels during early embryony

Culture procedures for zygotic and somatic embryos can be improved by simulating the nutrient and hormone levels observed in ovules during zygotic embryogenesis. To meet this objective, we identified potentially important nutrients in wheat Triticum aestivum L. kernel fractions that contained ovule fluids, which were collected by centrifugation. Malate dehydrogenase assays suggested that these samples contained apoplastic and cytoplasmic fluids. Kernel fractions were analyzed for minerals, free amino acids, and water soluble carbohydrates. On a mole percentage basis, K, P, Mg, and S accounted for 85% of the minerals in the ovule solutions while Ser, Ala, NO3-, NH4+, Gly, Glx and Pro accounted for 81% of the free amino acids, NO3-, and NH4+ fraction. Sucrose, fructose, and glucose in these solutions ranged from 30 to 160 mmol kg(-1) fresh mass (FM) in sucrose equivalents. These solutions also contained high concentrations of short and longer-chain fructans. Loosely-joined endosperm cells, collected through centrifugation, comprised about 10% of kernel FM at 6 d past anthesis (DPA), but less than 1% of kernel FM by 18 DPA. Concentrations of maltose, sucrose, neokestose and 1-kestose in the pelleted endosperm increased to high levels by Is DPA, which is evidence that stored fructans and amylopectins in the endosperm are hydrolyzed and used as nutrients by the growing embryo. The liquid fraction of younger kernels may closely approximate ovule fluid, and embryo culture procedures have been improved by incorporating the nutrient analysis information obtained therefrom.