The effects of two mineral and two organic acids, four organic solvents (methanol, ethanol, 2‐propano and acetone) and three inorganic metal salts in combination with temperature regimes 0 and 22C on the yield and resolubility of potato tuber proteins were studied. Using acids, the yield of precipitated protein ranged from 22.3% (citric acid, 0C) to 54.5% (acetic acid, 22C) of total protein; however, the resolubility was generally very low. The precipitation with organic solvents resulted in significantly higher yield as well as resolubility (P < 0.05) when precipitated at low temperatures. The yield ranged from 23.4% (ethanol, 22C) to 64.5% (2‐propanol, 0C) of total protein. The use of the salts resulted in precipitates with high resolubility regardless of the temperature regimes. The yield of precipitated protein ranged from 25.8% (ZnCl2, 0C) to 86.4% (FeCl3, 0C) of total protein. PRACTICAL APPLICATIONS The work studied the possibility of isolation of native potato proteins from potato fruit juice (PFJ) resulting from starch manufacturing process. Ethanol and FeCl3 were evaluated as the most promising precipitators for the recovery of potato tuber proteins from PFJ. However, ethanol usage for industrial isolation of potato proteins is strongly limited by the temperature regime in contrast to FeCl3, which could be used in a much wider range of temperature regimes without significant difference in protein yield and resolubility.

The effect of the type of leaf tissue selected for the study of green fluorescent protein (GFP) fluorescence intensity was investigated here using the T(1) generation of transgenic tobacco expressing the m-gfp5-ER gene. The fluorescence of GFP was detected by fluorescence binocular microscope coupled with the CCD camera and quantified by means of image analyses using the Lucia((R)) software. Mean brightness values from various leaf tissues were compared. First, an original data revealing the significant differences in the fluorescence intensity between the abaxial and adaxial surfaces are given. Stronger signal was detected on the abaxial side. Subsequently, the effect of the tissue location within the leaf surface was investigated and higher fluorescence was detected on the samples detached from leaf tips. Finally, the effect of the physiological age of leaves was studied using the in vitro clonally propagated plants. Leaves from the analogous positions within the plant body of three clones were investigated. The decrease in the fluorescence towards the plant top (youngest leaves) was observed in all studied plants. Surprisingly, the variability of the fluorescence within the clones of studied genotype was high enough to conclude, that the fluorescence of each individual is unique and affected by particular genotype and environment. Our study showed that the origin of leaf tissue selected for the GFP quantification is crucial and that the fluctuations in the fluorescence intensity should be taken into account when comparing the GFP fluorescence patterns of different plants. Moreover, the degree of fluorescence variability seems to be individually affected.