Abstract
The Ca 2+ content of Globodera rostochiensis egg-shells was investigated by X-ray microanalysis. When intact eggs were treated with 5 mM sodium 1, 2-di (2-aminoethoxy) ethane- N,N,N',N',-tetra-acetate (EGTA) only part of the egg-shell Ca 2+ was removed. Similarly treated opened egg-shells lost almost all their Ca 2+. We think that Ca 2+ of intact egg-shells which is accessible to EGTA is in the outer part of the shell and that the inaccessible Ca 2+ is in the inner lipoprotein layer. Much Ca 2+ was removed from opened egg-shells by the hatching agents Zn 2+, La 3+ and decationised potato-root exudate, but none by dilute acetic acid or Mg 2+. Hatching agents, by binding to or replacing Ca 2+, may change lipoprotein membrane structure. Eggshells treated with potato-root exudate contained about 3 times as much Ca 2+ as untreated shells, because the treatment makes additional binding sites available. Our results suggest that three types of Ca 2+ -binding sites occur in the egg-shell.
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