Aim Increases in annual mean temperature in the course of current climate change are expected to facilitate mass species migration towards higher altitudes and latitudes. However, this migration may be slowed, or even temporarily reversed, by infrequent and unpredictable episodes of low winter temperatures. Iran experienced a severe cold wave in January and February 2008, giving an opportunity to observe the effects on a large number of woody plant species, many growing further north than their natural ranges. LocationThe study was carried out in the National Botanical Garden of Iran (35°44′20.06″ N; 51°10′25.66″ E). MethodTo estimate the damage caused to each individual woody plant in the garden, we adopted the following protocol; at the start of the growing season, at the end of March and beginning of April 2008, all woody species were inspected for damage. In the case of evergreens this took the form of obvious damage to foliage, usually manifested as severe browning. In the case of deciduous species, damage was recognized by the failure of all or part of the plant to produce new leaves; all affected individual plants were labelled. In July all labelled plants were rechecked and, based on whole or partial above-ground die-back, a final list of damaged individuals was produced. ResultsAs expected, the majority of native and exotic species introduced from cold temperate habitats showed no freezing injuries. Many woody species in the garden were damaged or killed, despite their previous survival and growth, in many cases for up to 40 years. The majority of taxa (101 out of a total of 145) that suffered freezinginduced damage were evergreens. Main conclusionsThe results indicate that despite an increase in mean annual temperature, unpredictable lethal cold waves may retard the expansion of plants towards higher altitudes and latitudes. Broadleaved evergreen species from warm climates were particularly badly affected, with many species suffering high rates of mortality.

and M. Hasani-Nejad, Research Inst. of Forests and Rangelands, PO Box 13185-116, Tehran, Iran. Scutellaria L. in Lamiaceae subfamily Scutellarioideae is a subcosmopolitan genus with about 360 species. According to the latest subgeneric classifi cation, two subgenera are recognized: S. subgen. Scutellaria and S. subgen. Apeltanthus . We studied pollen grains from 29 species of Scutellaria belonging to both subgenera and from both the Old and the New World to evaluate their taxonomic importance for the infrageneric classifi cation of the genus. Pollen grains were acetolysed and studied by scanning electron microscope (SEM) and light microscope (LM). All examined pollen grains are isopolar, tricolpate, suboblate, oblate spheroidal, prolate spheroidal to subprolate. Th e exine is mainly bireticulate perforate, but with variations in lumina shape and size as well as perforation size and uniformity. Based on the exine sculpturing, two subtypes are recognized within the bireticulate pollen type. In subtype I the primary reticulum of the exine consists of angular muri; the lumen has an irregular polygonal shape and the perforations of the secondary reticulum are more or less uniform and of the same size. Th is pollen subtype was observed in species of subgenus Scutellaria , sectt. Scutellaria p.p., Anaspis , Perilomia and Salazaria . In subtype II the primary reticulum of the exine consists of a more or less curved murus; the lumen is rounded or obtusely angular and the secondary reticulum consists of one or more large central perforations surrounded by some smaller ones. Th is pollen subtype was observed in species of subgenus Scutellaria sectt. Scutellaria p.p., Salviifoliae and in all members of subgenus Apeltanthus . Th e results of this study reveal that the exine ornamentation is a diagnostic character useful for the infrageneric classifi cation of Scutellaria .

In this survey, the chromosome counts of eight Nepeta L. species were investigated and the karyotypic diversity among these species was studied. The examined species belong to N. cephalotes Boiss. species group, namely N. eremokosmos Rech.f., N. gloeocephala Rech. f., cephalotes Boiss., N. pungens (Bunge) Benth., N. ispahanica Boiss., N. mahanensis Jamzad & Simonds, N. hormozganica Jamzad and N. denudata Benth. collected from different habitats in Iran. The ploidy levels, karyotype formula, chromosome length range, total karyotype length, several karyotype asymmetries values and Stebbins classification were determined in this study. Results showed the same chromosome number, 2n = 2x= 18 for all studied species. The basic chromosome number for the above mentioned species are x = 9. Also, the smallest chromosome length is 1.02 μm in N. mahanensis. The largest chromosome length is 2.3 μm in N. ispahanica. The chromosomes of species were metacentric or submetacentric. According to the Stebbins classification, these species were located into three classes 1A, 2A and 3A. The chromosome numbers for six of studied species are reported here for the first time.

Botanical gardens, as one of the most important urban forests to any region, play an important role in the ecology of human habitats in many ways (e.g., air filtering). The National Botanical Garden of Iran, with an area of 145 ha, includes various woody species with a predominance of oaks (Quercus spp.). The size of acorns, fruits of oaks, varies in different species, which can affect their biomass. The biomass and carbon content of acorn components (endocarp, pericarp, and cupule) of four native oak species (Q. castaneifolia C.A. Mey., Q. libani Oliv., Q. infectoria Oliv., and Q. brantii Lindl.) and one exotic oak species (Q. ilex L.), planted in the National Botanical Garden, were studied to obtain detailed comparative results. Regarding the biomass of acorn components, Q. libani and Q. ilex showed the highest and lowest values among the study species, respectively. The ranges of carbon content of acorn components were 53.5% (pericarp of Q. brantii) to 58% (cupule of Q. castaneifolia). These results confirm the variation of biomass and carbon content of acorn components among the oak species studied.