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. 1. Schematic cross-section figures of 3-40 mm long, young stem-borne roots of Litho spermum purpureo-coeruleum L., at subsequent levels a—

k. K—

1 show considerably longer and older roots, with temporally more advanced and developed structures wherein secondary elements predominate. Relationships to one another of root diameters, and diameter increase by secondary thickening at higher levels were accounted for in the drawings. The central cylinder is stressed in eveiy cross-section picture. Size proportions of the cortex, insignificant for the present study, were left out of consideration. a. only phloem bundles (f> in all) present at subapical levels; central cylinder oval, medially with a parenchymatous pith, endoderm Caspary-punctate (-striata), rhizoderm externally j >resent ; I), two xylem bundles differentiating along longer axis of oval in upper levels; c. already 4 xylem bundles present among existing phloem bundles; d. 6 asymmetrically arranged xylem bundles present, number of phloem bundles increased to 8; c. already 7 xylem bundles present ; I. 8 xylem and phloem bundles present, arranged alternating with each other; g. 10 xylem and phloem bundles each present, radial row of xylem bundles turning to tangential, hence frequently forming an apparently contiguous ring; waved cambium often developed, endoderm usually still Caspary-punctate (-striate), externally with rhizoderm, inside with pith; h. waved cambium closed into a ring, thus forming a uniseriatc xylem ring; number of phloem bundles increasing, endoderm still usually Caspary-punctate (-striate), externally with rhizoderm, internally with pith; i. owing to function of waved cambium secondary xylem increasing, xylem ring strengthening, pith sclerotizing, Caspary-punctate (-striate) endoderm and rhizoderm still often present ; j. a structure as before, but xylem even more robust, pith wholly sclerotized, endoderm still often Caspary-punctate (-striate), cortex that of vegetative shoot; k. a temporally later and more developed stage than the preceding ones: primary cortex already shed, root enveloped by secondary endodermal cells, outer circumference of xylem ring wholly rounded, centrally with oval and sclerotized pith, marginally primary xylem bundles still discernible

1 ; 1. multiannual xylem with annual rings, externally with multiseriate periderm 1. primary xylem, 2. secondary xylem, 3. phloem, 4. cambium, 5. primary Caspary-punctate (-striate) endoderm, 6. secondary endoderm, 7. rhizoderm, (8. exoderm left out). 9. periderm, 10 sclerotic pith. 7 Termeszeiludományi Múzeum Evkönyve 1972.