ENERGY-DISPERSIVE X-RAY-MICROANALYSIS OF BORAGINACEAE SUBFAM BORAGINOIDEAE NUTLET SURFACE - ARE SI-DEPOSITIONS OR CA-DEPOSITIONS CHARACTERSOF SYSTEMATIC RELEVANCE

The mericarpids (''nutlets'') of the four Boraginaceae subfam. Boragin oideae tribes, the Anchuseae, Cynoglosseae, Eritrichieae, and Lithospe rmeae are known to possess anatomical differences aside from the morph ological ones. They differ in the shape of sclerified outer and inner epidermis (exocarp and endocarp) and the presence or absence of a meso carpal stone cell layer. With its three-layered mesocarp, the Lithospe rmeae exhibit the most elaborate pericarp anatomy. The stability of th e fruit wall is increased by additional deposition of calcium and/or s ilicon compounds. The exact location of deposition has not yet been id entified. The aim of this investigation was to localize these elements within the pericarp and to test whether the depositions are of any sy stematic relevance within the Boraginoideae (tribal demarcation). Ener gy dispersive X-ray microanalysis (EDX) was used to investigate the su rfaces and inner fruit walls of Boraginoideae nutlets. Silicon is pres ent in large amounts on the nutlet surface. Protuberances and glochids in the Eritrichieae and Cynoglosseae tribes contain a particularly hi gh amount of this element. In contrast, calcium is found mainly in cel l walls of both meso- and endocarp. Only within the Lithospermeae the lumina of the sclerenchymatic mesocarp are filled with calcium compoun ds. Potassium always occurs with calcium. The deposition of Ca, K, and Si takes place shortly before nutlet maturity. The distribution of th ese elements on the nutlet surface does not allow assignment of a spec ies to a particular tribe. Nutlet morphology, pericarp anatomy, and su rface sculpturing are better suited for this purpose.