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Drop of leaves at structurally defined abscission zones is a typical feature of dicotyledonous angiosperms. It is rare in monocots including the grass family (Poaceae). Some grass species have an odd, yet poorly studied pattern of leaves disarticulating regularly between the leaf sheath and the leaf lamina. Using species of three distantly related genera, such disarticulation zones were anatomically...
The taxonomic composition of the vascular epiphyte flora at the Río Changuinola, Panama, was examined and complemented with an analysis of biogeographic affinities and physiological parameters related to plant water and nutrient relations. In an area of ca. 1000ha, we found a total of 476 species of vascular epiphytes. This marks a new diversity record among lowland rainforest sites. Species composition...
The paper reports on hitherto largely neglected discriminative characters in Polypleurum stylosum, P. elongatum, P. minus, as well as the problematic P. munnarense (Podostemaceae, subfam. Podostemoideae) from India and Sri Lanka. The characters discussed include dimorphism of floriferous and vegetative shoots, leaf dimorphism, presence of peculiar floating trichomes on vegetative leaves, and presence...
We analysed the long-term development of limestone grasslands in West- and Central Europe (Mesobromion: Gentiano-Koelerietum) under conditions of restoration comparing vegetation changes with the composition of its corresponding soil seed bank over a time period from 1992 to 2005. Because of optimal climatic, edaphic and geomorphologic conditions restoration of vegetation developed gradually into...
In the semidesert of Namaqualand and adjacent regions of the former Cape Province, South Africa, there occurs an assemblage of geophytes belonging to eight monocot families and some Oxalis species that exhibit special morphological adaptations of their aerial parts to harvest and absorb water from dew and fog, the main source of moisture in this region. Most of them pass their vegetative phase in...
A comparative embryological study on two Spanish cultivars and one growing in Bulgaria of Olea europaea was carried out. The embryo sac develops according to Allium (bisporic)-type. The critical phases during the development of male and female gametophyte that lead to sterility and abortiveness of the embryo sacs and ovules are reported. The embryogenesis follows the Asterad-type. The endosperm passes...
Norway spruce (Picea abies (L.) Karst.) exhibits strong ecotypic variation along altitudinal gradients in morphological traits, e.g. slenderness of crowns or arrangement of second-order branches. We were interested whether montane and lowland morphotypes differ in a key trait for the survival in cold environments, i.e. frost hardiness, and asked: (i) are montane morphotypes more resistant to frost...
Past taxonomic treatments have classified Euterpe espiritosantensis as a synonym of E. edulis. However, both continue to be identified as two distinct species and are enumerated in the threatened species list. The goal of this study was to compare the reproductive biology of sympatric populations of these two morphs so as to identify morphological characters and mechanisms of reproductive isolation...
The establishment and survival of young individuals of five desert phreatophytes that form dominant or codominant stands round river oases at the southern rim of the Taklamakan Desert was studied to explain the patterns observed in the established vegetation. We hypothesized to find differences between species in the rates of establishment and survival as well as in the susceptibility to grazing....
Capsella bursa-pastoris (L.) Medik. is a self compatible tetraploid annual species which has successfully spread to most continents and is mostly confined to man-made habitats. The colonising success may be associated with fine-scaled ecotypic differentiation, and regional adaptation. Seeds of 377 individuals from 40 provenances were collected over a distance of more than 2500km from the Kola Peninsula...
Little is known about the variation in demographics, flower number, fruit set, and summer dormancy in Allium species native to the Intermountain West region of the United States. The purpose of this study was to investigate demographic patterns, summer dormancy traits, and variation in reproductive characteristics among habitats. Three populations of each of three species, Allium acuminatum, A. brandegei,...
The performance of seeds and seedlings in relation to the age of the mother plant was studied in Carex secalina. Seeds of this sedge can differ substantially in size. We planted 100 C. secalina individuals from three populations in a common garden and followed them for four years. We found that mean seed mass varied with plant age, but the pattern of variation was population-specific, with only one...
Alpine treelines at medium high mountains are less abundant and thus have been less frequently studied than at high-elevation mountain ranges of the world. We studied mature Norway spruce stands along an extended elevation transect at Mt. Brocken (Harz Mountains, Central Germany) to analyse the altitudinal changes in climate-related growth conditions, and to evaluate the prevailing climate conditions...
Epiphytic lichens are an important part of the vegetation of northern coniferous forests of Eurasia and North America. Much progress has been made during recent decades at disentangling relevant site factors, which control the diversity and distribution of epiphytic lichens in boreal and oroboreal forests. The present paper aims at summarizing the present state of knowledge. Relevant site factors...
The potential natural distribution of deciduous forests in Central Asia is the subject of ongoing discussions. Ulmus pumila (Siberian elm) is the only tree species occurring in southern and south-eastern Mongolia. In the semi-arid Mongolian Gobi, the species is restricted to ravines and beds of semi-temporary rivers. Compared to zonal occurrences in moister northern Mongolia, elm trees in the Gobi...
This work consists of an extensive study of soil properties and floristic composition of the Paraguayan Chacoan forests. The role of the soil factors was determined conditioning the classical landscape differentiation between the dry western Chaco and the wet eastern Chaco. Soil horizon A best explains the previous classification of the forests. It highlights the soil differences between the eastern...
Rare plant species can be divided into naturally, ‘old rare’ species and anthropogenically, ‘new rare’ species. Many recent studies explored genetic diversity of ‘new rare’ species. Less is, however, known about genetic diversity of ‘old rare’ species. We examined isozyme genetic variability of 20 populations of an ‘old rare’ plant species, Ligularia sibirica (Asteraceae) in the Czech and Slovak Republic...
Inflorescence and floral organogenesis and development of the bushy perennial legume Astragalus lagopoides of the section Hymenostegis were studied by means of epi-illumination light microscopy. Based on our observations, the primordia of lanceolate racemose inflorescences are born in the axils of leaves. Each inflorescence apex initiates acropetally bracts and floral apices for some time and then...
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