The past, present and future tasks of Hungarian dendrological research.
Hungarian dendrological research (research of living woody plants) has more than 200 years old history; the first general work by János Keresztély Grossinger was published in 1797. Further basic works in our time yet are: Forest Botany by Lajos Fekete and Sándor Mágócsy-Dietz (1896); and the chorological work, Distribution of trees and shrubs of sylvicultural importance in the region of Hungarian State by Lajos Fekete and Tibor Blattny (1913). A few dendrologists and many botanists have helped to get better knowledge of Hungarian dendroflora. From the point of view of taxonomy, chorology and habitat - which are interested by field botanists - it can be said that knowledge is fairly heterogeneous. There are sufficient information about most of the rare (protected/endangered) woody plants (an about 50 species) and the important adventives, above all invasive trees and shrubs (an about 10 species). From these two groups beyond there are only few taxa which can be said thoroughly worked up and known (e.g. Castanea sativa, Cornus mas, Fraxinus spp., Quercus spp.). List of the dendrotaxa, hardly known in the above-mentioned point of view is rich in species that are important for forestry or horticulture (e.g. Alnus glutinosa, Acer spp., Betula pendula, Corylusavellana and most of Salix spp.), supplemented with other species (e.g. Clematis vitalba, Colutea arborescens, Lonicera xylosteum, Padus avium, Sambucus nigra, Staphylea pinnata, Viburnum spp.).Followings can be asked from our field botanists: i) look for a specialist in cases of critical dendrotaxa; ii) a circumspect identification is necessary - especially in the case of leaves - by right of great number of samples from the adequate part of shoot; iii) keep in view frequent hybridization (e.g. in the case of Betula, Crataegus, Pyrus, Tilia), and frequent appearance of hybrids (e.g. Betula × rhombifolia, Cerasus × eminens, Salix × rubens); iv) appearance of interim forms are usually typical in the cases of species classified into aggregate species (e.g. Quercus petraea agg., Qu. pubescens agg.); v) take intraspecific taxa according to various ecological demands, area, morphological differences into consideration; vi) culture variations cannot be treat as an equal with the species (e.g. Populus spp., Salix spp.); vii) natural ↔ artificial area have to be separated; viii) lend a helping hand in getting taxonomical knowledge of hardly known dendrotaxa.
Tree of heaven Ailanthus Altissima (Mill.) Swingle: The weed of urban environment
This paper shows the analysis of overall abundance and population structure of species Ailanthus altissima in the period 2000 - 2002, on the territory of Mirijevo, one of the suburbs of Belgrade. The total census of populations of Ailanthus altissima showed presence of 3909 individuals of this species. It was recorded that in the researched area Ailanthus altissima is most distributed in ruderal habitats, as well in old orchard groves and vineyards that are not exploited.
Diurnal dynamics of photosynthetic parameters of Norway spruce trees cultivated under ambient and elevated CO2: the reasons of midday depression in CO2 assimilation
Diurnal courses of net CO2 assimilation, non-assimilatory processes, electron transport rate, photosystem (PS) II photochemical efficiency, and pigment composition were investigated during summer days for sun exposed needles of Norway spruce trees grown under ambient (AC) and/or elevated (EC; 700 mu mol (CO2) mol(-1)) atmospheric carbon dioxide concentration ([CO2]). Daily courses of net CO2 assimilation (AN c,) documented significantly higher values for trees cultivated under EC conditions at irradiances above 250 mu mol m(-2) s(-1). In comparison with the AC variant, EC treatment led to the diminution of midday photosynthesis depression that was predominantly caused by stomatal closure and subsequent decrease of intercellular [CO2] (Ci). A partial recovery of assimilation ability of AC shoots correlated with the partial restoration of stomatal conductivity during the afternoon hours. On the contrary, maximum depression of light-saturated assimilation rate (A(Nmax)), permanent decrease of assimilation capacity (A(Nsat)) over the day and an atypical daily course of gross photosynthesis (P-act) suggested an increased contribution of non-stomatal processes in a down-regulation of carboxylation efficiency in EC shoots during the noon and afternoon hours. The relatively high potential quantum yield of PS II photochemistry (F-V/F-M >= 0.8), estimated on both AC and EC dark adapted needles throughout the day, confirmed that PS II photoinhibition was not the primary reason of the midday depression of photosynthesis. However, the feedback effects of enhanced down-regulation of photosynthesis under EC induced: (a) slight inactivation of PS II and reduction of PS II electron transport rates, (b) enhanced demand on xanthophyll dependent non-radiative dissipation of excess light energy (accumulation of deepoxidized antheraxanthin and zeaxanthin), (c) adjustment of the light harvesting complexes (increase of chlorophyll a/b ratio). (c) 2005 Elsevier Ireland Ltd. All rights reserved.