Mineral nutrition in white spruce (Picea glauca [Moench] Voss) seeds and somatic embryos. I. phosphorus, phytic acid, potassium, magnesium, calcium, iron and zinc

The mineral nutrient storage reserves in white spruce (Picea glauca [Moench ] Voss) somatic embryos and various parts of white spruce seeds were invest igated. Somatic embryos are embryos produced in tissue culture. A single so matic embryo or zygotic embryo contained similar amounts of P and both type s of embryos had similar amounts of the total P present in phytic acid (PA) . The large female gametophyte tissue, which is absent in a somatic embryo, contained 86% of the total P and 95% of the total phytic acid-phosphorus ( PA-P) in a single seed. The female gametophyte of a single seed contained a pproximate to 7 times more P and approximate to 22 times more PA-P than a s ingle zygotic embryo. Somatic and zygotic embryos had significantly less of their P present in PA than did the female gametophyte tissue, which has ov er 87% of its P present in PA. A single somatic embryo or zygotic embryo co ntained similar amounts of K, Mg, Ca, Fe and Zn. The female gametophyte tis sue contained 59% of the K, 85% of the Mg, 28% of the Ca, 69% of the Fe, an d 65% of the Zn in a single seed. The seed coat of a single seed contained the majority of a seed's Ca (71%) and also contained significant levels of K, Fe and Zn. On a dry weight (DW) basis, differences were found in the amo unts of all the mineral nutrients studied here because somatic embryos are larger than zygotic embryos. Overall, a white spruce somatic embryo has equ ivalent amounts of all these nutrients as found in a natural white spruce z ygotic embryo. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.