Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 64. (Budapest 1972)

Kováts, D. ; Stieber, J.: Some observations on the dynamism of structural development in the stem-borne root of Lithospermum purpureo-coeruleum L.

Fig. (5. Schematic, long-section picture of seedling root at a given point of time. Xylem situated inside (hatched), external endoderm indicated by pecked line, dermal part represented by contiguous line outwardly. Arabic numerals refer to primary (1) or secondary (2) state of the respective tissues. Lower part of figured root with all three tissues primary (1, 1, 1), its upper part with both xylem and exoderm secondary (the corresponding lines thickening), but endoderm still primary (2, 1, 2). On a black ground, temporal changes of the three tissues at a single cross-section level, expressed in numbers, from above to below, arrow showing sequence of temporal phases. — Fig. 7. Schematic long-section picture, at a given moment, of stem-borne roots. Similarly to the preceding figure, xylem situated inside (obliquely hatched), pith present near shoot (horizontally hatched), endoderm indicated by pecked line, outer dermal part marked by contiguous line. Arabic numerals denote primary and secondary state of tissues. All three tissues primary in lower level of root (1, 1, 1), xylem and rhizoderm still primary but endoderm already secondary at upper levels (1, 2, 1) (line representing endoderm thickened). As in preceding Figure, on a black ground first vertical column of numbers marking changes in xylem, second one those of endoderm an third column those of rhizoderm. Groups of three numbers in a downward sequence indicate a temporal phase each. Summary The essence of the physiological function of the root is the water and ion exchange abilities of living matter. The maximum of liquid flow is largely determined by the anatomical structure (eventually forming also a mechanical resistance against the increasing flow). The knowledge and study of changes concerning anatomical development are important also from this point of view. By our investigations and observations some significant moments in the devel- opment of stem-borne roots of Lithospermum purpureo-coeruleum L. are presented herein. Some features of development dynamism are also discussed. Initially, the root developing stem-borne has several characteristics common with the shoot. Among others, the xylem bundles (or their procambial bundles) tend to occupy a tangential, annular position in the simple-bundle root system. Directional changes can also be observed in the primary differentiation (cf. the various positions of the metaxylem). Meanwhile, a significant central pith evolves. Later the initially polyarchal structure becomes tetrarchal owing to the omission