Soil Contamination in Forest and Industrial Regions of Bulgaria

Based on systematic data from 1988 to 2015, the main sources of soil contamination in forest and industrial areas of Bulgaria were presented. The processes of soil acidification and eutrophication as well as accumulation of heavy metals in forest and industrial soils were analysed. The content of heavy metals in soils, pasture grasses and medicinal plants from two National Parks—Central Balkan and Pirin, as well as from two Natural Parks—Bulgarka and Strandzha was also reported. Data on heavy metals accumulation in leaves of tree species in some industrial areas of the country were presented as well. Soil and plant contamination with heavy metals were estimated according to the applied criteria of ICP Forests

Effect of wastewater sludge treatment on early growth and physiological responses of willow (Salix spp.) and poplar (Populus spp.) pot-grown plants

Combining biomass production from fast-growing woody species with wastewater treatment is an attractive concept from the economic, energy and environmental points of view. A pilot experiment on study-ing the effect of wastewater treatment on the early growth and initial physiological responses of willow and poplar plants was carried out in greenhouse conditions. The survival, height growth, net photosyn-thesis, stomatal conductance and transpiration of two hybrid clones of black poplar (Populus x euroameri-cana (Dode) Guinier) (I-214 and I-45/51) and white willow (S. alba L.) pot-grown plants treated with different doses of agrochemically characterised wastewater sludge were studied during the establishment year. The height growth and number of resprouted willow shoots were also measured during the second year after cutting, at the end of the vegetation season. While the early growth height of poplar clones was markedly affected by the clone origin and wastewater sludge treatment, the latter did not considerably influence the height of the willow plants either during the establishment and the following year, but essentially increased the number of resprouted shoots during the second vegetation season. The rate of CO2 assimilation of willow plants was significantly influenced by the wastewater sludge treatment, with plants grown at the higher doses displaying higher photosynthetic performance. The application of wastewater sludge had no essential impact on the values of the physiological parameters of the poplar plants, but particular responses were found among the clones

Evaluation of response of lettuce (Lactuca sativa L.) to temperature and light stress

The aim of the study was to assess the effect of irrigation water temperature and shading on the rate of photosynthesis and transpiration in four varieties of lettuce (Lactuca sativa L.) – green foliage (‘Salakis’ and ‘Estony’) and red foliage (‘Lollo Rossa’ and ‘Nika’). During the production of seedlings in the greenhouse, two irrigation water temperature regimes (12 and 20°C) were applied. After transplanting in the field plants were grown under three lighting systems (100, 70, and 50% of lighting in the open). The rates of photosynthesis and transpiration were measured at the end of the greenhouse period and 14 days after shading in the field using a Li 6400 infrared gas analyzer. In most varieties, cooling of the irrigation water was not found to have an effect on the rate of photosynthesis. Plants of all the varieties responded to the decrease in irrigation water temperature and to strong shading by reducing transpiration and increasing the water use efficiency. The ‘Salakis’ and ‘Estony’ plants have shown the best adaptability to the changing conditions and therefore they could be used successfully in the practice of extending vegetative growth