Propolis is the substance used by bees as a draught excluder and general purpose sealer for their hives. It usually consists of a mixture of pop­ lar bud exudate and beeswax [1]. Propolis balsam (a 70% alcohol extract of propolis which contains the bud exudate components) is a popular herbal medicine [2-4] containing a number of phenolic constituents with antimicrobial activity [4-6], Bees appe...

Despite many studies of the percent loss of hydraulic conductivity in excised branches, there is doubt as to whether cutting stems in air introduces unnatural embolism into the xylem at the cut surface. To address this question, hydraulic conductivity was measured in seedlings of northern red oak (Quercus rubra L.) and rooted scions of eastern cottonwood (Populus deltoides Bartr. ex Marsh.) tha...

The rapid juvenile growth of eastern cottonwood (Populus deltoides Bartr. ex Marsh.) makes it a desirable hardwood species for revegetation of disturbed sites. In addition, revegetation may be facilitated by improved root growth in response to endomycorrhizal colonization. An experiment was conducted to identify the effect of inoculation with a mix of three Glomus spp. isolates on the root grow...

Abstract The water use by short rotation coppices (SRC) has been a focus of ongoing research in the last decades. Nevertheless, investigations that consider site factors and present long-term monitoring components balance are rare. This quantified tree-based transpiration 4th growing season uncoppiced 1st rotational hybrid poplar stands ( Populus deltoides Bart. ex Marsh × P. nigra L . “AF2”) w...

Intersectional crosses between species of sections Aigeiros (Populus deltoides, P. X euramericana or P. nigra) and Leuce (P. alba or P. tremuloides) are known to be reciprocally incompatible. The site of pollen tube arrest is on the stigma surface in pollinations between pistils of section Leuce and pollen of section Aigeiros; tubes failed to penetrate the stigma surface. In reciprocal matings,...

We compared the physiological and morphological responses of rooted cuttings of Populus trichocarpa Torr. & Gray and P. trichocarpa x P. deltoides Bartr. ex Marsh. grown in either near-ambient solar ultraviolet-B (UV-B; 280-320 nm) radiation (cellulose diacetate film) or subambient UV-B radiation (polyester film) for one growing season. Midday biologically effective UV-B radiation was 120.6 and...

Diseases of poplar caused by the native fungal pathogen Sphaerulina musiva and related species are of growing concern, particularly with the increasing interest in intensive poplar plantations to meet growing energy demands. Sphaerulina musiva is able to cause infection on leaves, resulting in defoliation and canker formation on stems. To gain a greater understanding of the different responses ...