Technologies Protecting the Environment in Urban Areas

Global warming is the leading cause of the extreme meteorological events increase in the last three decades. Increase of annual average air temperature and temperature values during winter and early spring has been recorded in comparison to the (1961-1990) referent period in Plovdiv region. The lettuce development was researched in a greenhouse in the Agricultural University- Plovdiv. During the lettuce growth six different variants were used: no fertilizer, one chemical, and four organic fertilizers. The effect of the different organic fertilizers was studied through specific physiological parameters and productivity. This paper analyzed changes in functional activity of the plant photosynthetic apparatus and productivity of variants with different fertilizers in an unheated greenhouse. The ratio between photosynthetic active radiation (PAR) and quantum yield (qY-Fv/Fm) of PS II was determined to be more optimal in dark-adapted leaves for the organic fertilizer variants, compared to the no fertilizer variant. The lower and significant difference was observed in the values of the minimal fluorescence Fo in reaction centers of PS II after the dark-adaptation of leaves for organic fertilizer variants compared to the no fertilizer variant. Higher values of chlorophyll content index (CCI) were estimated for organic and chemical fertilizers compared to the no fertilizer variant. All variants fertilized with organic and biofertilizers comply with the quality standard from the beginning to the end of harvesting.