Larvae and imagos of bees rely exclusively on floral rewards as a food source but host-plant range can vary greatly among bee species. While oligolectic species forage on pollen from a single family of host plants, polylectic bees, such as bumblebees, collect pollen from many families of plants. These polylectic species contend with interspecific variability in essential nutrients of their host...

Seasonal variation in the antioxidant activity and content of phenolic compounds was studied for the 70% methanol extracts of Sorbus aucuparia leaves harvested monthly over the full course of the growing season. The antioxidant potential of the extracts was evaluated using two complementary in vitro tests: the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical-scavenging assay and the AAPH [2,2'-azob...

Tree seedling flooding tolerance for 22 species was assessed under controlled field condi­ tions. Initial heights under control (freely draining soil, n = 20 per species) and flooded (stand­ ing water, depth = 10 cm, n = 20 per species) conditions were measured in March 1990. Sur­ vival, height and diameter growth were determined after 120 days. Recovery from flooding effects was assessed in th...

BACKGROUND AND AIMS The low-temperature range limit of tree species may be determined by their ability to produce and disperse viable seeds. Biological processes such as flowering, pollen transfer, pollen tube growth, fertilization, embryogenesis and seed maturation are expected to be affected by cold temperatures. The aim of this study was to assess the quality of seeds of nine broad-leaved tr...