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.
ANNALES HISTORICO-NATURALES MUSEI NATIONALIS HUNG AR ICI ïomus 64. 1972. Some Observations on the Dynamism of Structural Development in the Stem-borne Root of Lithospermum purpureo-coeruleum L. By D. KOVÁTS and J. STIEBER, Budapest Morphological Observations It is known that the vegetative shoots of Lithospermum purpureo-coeruleum Lelongate so extensively by the summer that they become recumbent and take to roots (SZUJKÓ-LACZA & FEKETE, 1971. The authors have shown also the high potassium requirements of the plant). Prior to the emission of the roots, and before the root apices had broken through the primary cortex of the shoot, the apex of the recumbent shoot arises from the ground (Plate,L, Fig. 1-6). We think it probable that the pressure of the energetically advancing roots (often not yet piercing the cortex) may play also a mechanical role in the recurving of the shoot apex (Plate II. Fig. 13). According to our observations made hitherto, shoots developing in more favourable conditions may emit roots already in June and that this rooting process may continue — naturally depending principally on the climate — until the end of November or till the middle of December; indeed, it seems that in favourable circumstances it may continue during the winter and spring. The shoot apex lignifies, its xylem ring strengthens and produces more and more roots (Plate IL, Fig. 15, 16). By the beginning of winter, roots of varying, length and development appear (Plate I., Fig. 5, 6). The effective taking to roots is often mechanically hindered or obstructed by the other plants (competition), or the litter cover, the compactness of the soil and many other factors. The vegetative shoots of plants grown in gardens in favourable conditions (regular watering, decreased competition, etc.; had taken to roots not only at the shoot apices but at several other intermediate points (Plate I., Fig. 8, Plate II., Fig. 10), indeed, on one occasion a shoot had ramified in several places and the resultant adventitious shoots had all taken to roots according to MEUSEL (ex verb.), we have to deal here with an increase in vegetative shoots induced by favourable light conditions). The stem-borne roots, overwinter together with their shoot apices. According to our observations, the major part of the shoot apices also get underground, or overwinters underneath the litter. By the next spring, the vegetative shoot of the previous year becomes a rhizome, it is w T holly hypogeal and develops vegetative and reproductive shoots (Plate I., Fig. 7, 8; Plate II., Figs. 9-12). We have found on the investigated roots that the young, recumbent shoot apex contains preponderantly still primary tissues, and it has collateral open bundles and the interfascular cambium just being formed when the root apices already appear. These root apices originate from the primary medullary ray (Plate II.,.
