Loblolly pine (Pinus taeda L.):: stage-specific elemental analyses of zygotic embryo and female gametophyte tissue

Stage-specific analyses for key elements (metals) for full-term seed and across seed development were completed for zygotic embryo and female gametophyte (FG) tissues of loblolly pine (Pinus taeda L.). Tissue was analyzed in replicate for major and minor elements by the use of inductively coupled plasma emission spectroscopy (ICPES). Variation in elemental composition among five full-term seed sources was minimal providing elemental composition targets for somatic embryos. Seed tissues from two open-pollinated families, grown in different locations, were analyzed across the sequence of development. Significant changes in elemental composition occurred over time. Phosphorus, potassium, magnesium, calcium and zinc contents in the FG were highest during early seed development while sulfur and iron were relatively constant. The lowest copper levels were detected during early FG development. Zygotic embryos attained maximum potassium, calcium, manganese and zinc content during early embryo development. Embryo phosphorus, magnesium, and iron generally increased across embryo development. Both seed collections showed minimal values of embryo iron content at stages 4-7 followed by gradual increases until embryos stopped growth. Sulfur and copper were fairly constant; lowest copper occurred during early embryo stages. Patterns for sodium and boron were not consistent in the two open-pollinated families analyzed for either FG or embryo tissues. One family showed peaks in sodium and boron during early embryo development. The second family showed similar levels for sodium and boron through embryo development. These data provide stage-specific targets for somatic embryos and suggest element media composition changes for each step in the somatic embryogenesis protocol. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.