R. Stelzer et al., X-RAY MICROANALYTICAL STUDIES ON MINERAL CONCENTRATIONS IN VACUOLES OF NEEDLE TISSUES FROM LARIX-DECIDUA (L) MILL, Botanica acta, 106(4), 1993, pp. 325-330
Elemental concentrations in the vacuoles of mesophyll, endodermis and
transfusion parenchyma cells were determined by means of electron prob
e microanalysis on bulk frozen hydrated needles of an out-door-grown l
arch tree. The investigations were done routinely throughout a life cy
cle of the deciduous larch needle, starting with bud burst in March an
d ending with leaf abscission in November. It could be shown that the
endodermal vacuoles preferentially accumulate S, Cl and Ca while the t
ransfusion parenchyma vacuoles transiently store Mg, K and S. Between
May and September the inorganic ion level of mesophyll cells is consta
ntly lower than in the endodermal and transfusion parenchyma vacuoles.
In autumn, when the degradation of chlorophylls becomes detectable, t
he elements Mg, S, Cl and Ca are found increasingly in the vacuoles of
the mesophyll cells. It is concluded that, in mature and intact larch
needles, the vacuoles of the endodermis in cooperation with the trans
fusion parenchyma vacuoles act as efficient ion storage buffers which
maintain a constant low ion level in the vacuoles of mesophyll cells.