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

Szujkó-Lacza, J. ; Fekete, G.: A survey of the plant life-form systems and the respective research approaches IV. Taxonomic aspects of the life-form protection of the embryonal and meristematic tissues in the dormancy stage

rest period. According to VENT (1948). ". ..growth is a highly complex process requiring many conditions, and dormancy may he caused by the lack of any of the multitude of factors required for growth, and only in a secondary way is a problem of inhibitors." Besides the factors affecting the cessation of bud growth mentioned above, some authors connect this phenomenon also with the onset of the short-day stage of the photoperiod. In VEGIS'S (1963) opinion: "It is clear that both temperature and day length play important roles in the control of dormancy". OLMSTED (1951) holds the opposite : "The onset of terminal bud rest is not readily related to natural photoperiodic conditions." Ecological experiments and experimental ecological investigations enriched our knowledge with a number of results as regards the connections between the development of plants and photoperiod. The researches were necessarily delimited to the observation of specimens of a given species (OLMSTED I.e. worked with Acer saccharum, NITSCH and his collaborators with Platanus occidentalis (1957, 1958), Pyracantha coccinea etc.). It is rather interesting to note that the relative abundancy of data concerning a given species stands in sharp contrast to the paucity of references as regards comprehensive studies of the shoot-forming stage, preceding dormancy, of the phenophasis and the photo periodicity within a given plant association. Our own investigations made on the community and species, respectively, of an oakwood (Quercus pubescens, Fraxinus ornus, Sorbus torrninalis, Cornus mas) revealed that the appearance and development of the buds, the attainment of preparation for total bud protection, in other words, the completion of bud development and ensuing dormancy do not occur contemporaneously in all species even within the identical, dominant levels of a plant community. Besides the growth regulating role of the external conditions, KASSEN (in SAMISH I.e.) connected the cessation of bud development prior to the onset of the unfavourable season by auxin accumulation and the inhibiting effect of the large amounts of this substance. Some investigations also demonstrated that auxin will gradually disappear and remains by the onset of the favourable season only in quantities instigating growth. Other studies showed the role of quantitative changes in gibberellin in this process (VEGIS, I.e.). References : 1. ANDREÁNSZKY, G. (1954): Az életformafejlődési központokról (Developmental centres of life forms). Bot. Közi., 44: 77-84. — 2. ANDREÁNSZKY, G. (1954b): Ősnövénytan (Paleobotany). Budapest, 1-320. — 3. CROCKER, W. (1948): Growth of plants. New York. — 4. Du RIETZ, G. E. (1931): Life-forms of terrestrial flowering plants. Acid Phyiogeogaphica Suecica, 'A: 1-91. — 5. FEKETE, G.

—SZUJKÓ-LACZA, J. (1970): A survey of the plant life-form systems and the respective research approaches II. Ann. Hist.-nat. Mus. Nat. Hung., 62: 115-127. — 6. FEKETE, G. & SZUJKÓ-LACZA, J. (1971) : A survey of the plant life-form systems and the respective research approaches III. Ann. Hist.-nat. Mus. Nat. Hung., 63: 37-50. - 7. HANSEN, H. M. (195(3): Life forms as age indicators. Copenhagen, 1-50. — 8. NITSCH, J. P. (1963) : The meditation of climatic effects through endogenous regulating substances. In: Evans, L. T.: Environmental control of plant growth, New York-London, 175-193. - 9. OLMSTED, C. E. (1951): Experiments on photoperiodism, dormancy, and leaf age and abscission in sugar maple. Bot. Gaz., 112: 365-393. - 10. RAUNKIAER, C. (1907): The life forms of plants and their bearing on plant geography. Coll. Pap. G. Raunkiaer 1934, 2-104. — 11. RECHINGER. K. H. (1968): Crambe. In: Flora des Iranischen Hochlandes und der umrahmenden Gebirge. Cruciferae, 45-48. — 12. SAMISH, R. M. (1954): Dormancy in woody plants. Ann. Rev. Plant. Physiol. 5: 183-204. — 13. SCHARFETTER, R. (1953): Biographien von Pflanzensippen. Wien, 1-546. — 14. SCHIFFNER, V. (1891): Monographia Hellobororum. Kritische Beschreibung aller bisher bekannt gewordenen Formen der Gattung Helleborus.