Accumulation of phenolics and growth of dioecious Populus tremula (L.) seedlings over three growing seasons under elevated temperature and UVB radiation.

Accumulation of secondary metabolites may exhibit developmentally regulated variation in different plant organs. Moreover, prevailing environmental conditions may interact with development-related variations in plant traits. In this study, we examined developmentally regulated variation in phenolic accumulation in the twigs of dioecious Populus tremula (L.) and how the effects of elevated temperature and ultraviolet B (UVB) radiation on growth and phenolics accumulation varied as the plants get older. In an open-field experiment, six female and six male genotypes were exposed to single and combined elevated temperature and UVB radiation treatments for three consecutive growing seasons. The concentrations of low molecular weight phenolics and condensed tannins did not show age-dependent variation in the twigs. In temperature-treated plants, diameter growth rate decreased, and concentration of condensed tannins increased as plants aged; there were no cumulative effects of elevated UVB radiation on growth and phenolic accumulation. Females maintained a higher concentration of low molecular weight phenolics throughout the experimental period; however, growth and phenolic concentration did not vary over time in females and males. Our results suggest that phenolic accumulation in perennial plants may not necessarily always exhibit age-dependent variation and the effects of elevated temperature on growth and phenolic may diminish as plants get older.

Contribution of honeybees towards the net environmental benefits of food.

Beekeeping provides honey, protein-containing drone broods and pollen, and yield-increasing pollination services. This study tested the hypothesis that beekeeping can result in net-positive impacts, if pollination services and protein-containing by-products are utilised. As a case example, Finnish beekeeping practices were used. The study was performed using two different approaches. In both approaches, the evaluated impacts were related to climate change, land use, and freshwater use, and were scaled down to represent one beehive. The first approach considered honey production with pollination services and the replacement of alternative products with co-products. The impacts were normalised to correspond with planetary boundary criteria. The second approach evaluated the impacts of the different products and services of beekeeping separately. In the first approach the honey production system moved towards a safe operational space. Freshwater use was the impact category with the largest shift towards a safe operational space (39% shift). The second approach caused a global warming potential of honey production of 0.65 kgCO2-eq kg-1, when pollen and drone broods were considered as by-products and the influence of pollination services were not included. When honey, pollen, and drone broods were considered as co-products and pollination services were included, the impacts regarding land use and climate change were net-positive. The impact of freshwater use was relatively small. For honey, the impacts on the climate change, land use, and freshwater use were -0.33 kgCO2-eq kg-1, -7.89 m2 kg-1, and 14.01 kg kg-1, respectively. The impact allocation with co-products and pollination services was conclusive. A lack of consideration for the impact reduction of pollination led to beekeeping having a negative impact on the environment. Based on these results, beekeeping enhances food security within planetary boundaries, provided that pollination services and protein-containing by-/co-products are utilised.

Screening bioactivity and bioactive constituents of Nordic unifloral honeys.

The objective of this study was to screen the antibacterial and antioxidant activity of thirty nine honey samples from Finland, Sweden, Norway and Denmark. Their physicochemical properties were analysed, antioxidant activity was evaluated by DPPH assay and antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus was assessed by microdilution assay. The honey samples obtained were buckwheat, caraway, clover, dandelion, fireweed, heather, lime tree, lingonberry, rape, raspberry, sweet clover, willow, mire, honeydew and polyfloral. Eleven honey samples showed high antioxidant activity. With 15% honey dilution, three unifloral honeys had over 85% inhibition against growth of P. aeruginosa and ten honey samples against S. aureus. The buckwheat, raspberry and honeydew honeys showed the highest antibacterial and antioxidant activity. An unexpectedly high amount of methylglyoxal was found in mire and forest honeys. Some phenolic compounds are shown to be plant species-specific floral markers due to their appearance in specific unifloral honey samples.