The effect of various sapropel concentrations on content and fluorescence of photosynthetic pigments of bean
Tarosiškio lake sapropel impact on beans (Vicia faba L.) photosynthesis parameters (content of chlorophylls and chlorophyll a fluorescence) was investigated in this study. Plants were sown in 1 L volume pots by 5 seeds with light loamy soil and grown in growth chambers. Considering sapropel composition, 2.2; 3.1 and 4 t/ha dry sapropel concentrations were chosen for investigation. Sapropel affected plants were compared with plants grown in unfertilised and with synthetic fertiliser fertilised soils. On 14th day of experiment, when the plants reached two leaves growths stage (BBCH 12), chlorophyll a fluorescence parameters of investigated plants were measured. Then plants were grown for 4 weeks more and at stem elongation stage (BBCH 31) chlorophyll a fluorescence parameters were measured repeatedly and also the content of chlorophylls and carotenoids were investigated. The efficiency II photosystem of bean increased by increasing sapropel concentration in soil, but insignificantly (p>0.05). Photosynthesis performance index was increasing (r=0.91; p<0.05) up to 3.1 t/ha sapropel concentration increase at BBCH 12 growth stage. The same tendency was detected for electron transfer rate of bean (r=0.9; p<0.05) at this growth stage, but at later stage (BBCH 31) it slightly lowered (r=-0.02; p>0.05). At BBCH 12 stage the highest non photochemical quenching (NPQ) value was measured in control beans, while at BBCH 31 stage, opposite trend was noticed (r=0.86; p <0.05). At BBCH 31 growth stage sapropel concentration increase made bean chlorophyll content to decrease, but insignificantly (r=-0.18, p>0.05), and the changes in carotenoid contents were similar to chlorophyll a+b.