The temperature dependence of the induction kinetics parameters of chiorophyll (Chl) fluorescence in leaves and isolated chloroplasts of young plants of PhaseoliLt vulgaris L. was studied. Theoretical prerequisites for the influence of fluorescence measuring temperature as well as 3 min pretreatment of leaf discs cn both the photophysical and dark processes in the photosynthetic appaiatus were evaluated. The registration manner of fluorescence kinetics detennined the pattem of temperature dependence curve. The characteristic temperature of sharp changes of induction kinetics parameters, maximal and initial fluorescence and Fq, were in ranges of 45-47 and 55-60 °C, respectively. The fitting of experimental data from thermograms registered at weak exciting iiradiance in thermoinactivated leaf discs allowed to estimate the activation energy (FJ of the intemal energy conversion process in excited Chl molecule as 51.2±0.15 kJ moTT The theoretical analysis of /'q measured by a PAM fluorometer showed that Fq registered even at low inadiances markedly exceeded its ideál dark value. The Fq measured at 25 °C was increased by 125±5.3 % by the herbicide DCMU and diminished by -23.8±1.6 % by the elechon acceptor DCBQ. At the experimental conditions ušed there were about 25 % of 1\ from dosed Qg non-reducing reaction centres in the measured Fq value. Thus the thermoinduced increase in Fq observed within the temperature inteiwal of 45-50 °C might be doně by a transition of PS2 reaction centres from a statě capable of reducing Q3 to a Qg-non-reducing statě.
Silicomolybdate (SiMo) is an electron acceptor that has many characteristics, the ignorance of which makes an interpretation of the results quite troublesome. In photoinhibitíon experiments the photosystem 2 (PS 2) actívity can be best monitored if 1 pM dibromotíiymoquinone (DBMIB) is added after photoinhibitory treatment and SiMo is added in the light. Diuron (DCMU) may complicate interpretation of the results as it is also a competítíve inhibitor of SiMo binding at pH 7.6. The binding niche of SiMo is probably located at the stroma side between the fourth and fifth helix of the Dl and D2 proteins close to Q^- The whole chain actívity was much more affected by the photoinhibitory treatment than the PS 2 actívity itself Uncoupling of electron flow by addition of ammonium chloride accelerated the rate of photoinhibitíon. Photoinhibitory treatment decreased not only the Hill actívity at photon saturation, but also decreased the quantum yield and increased the photon flux density yielding half maximum rate of electron flow (K^). Decrease of quantum yield indicated that the photochemistry of PS 2 was afiected; increase of indicated a coiďormational change of the SiMo binding site. In experiments on PS 2 actívity monitored witíi SiMo, DCMU had no protectíve effect on the damage of the electron transport chain between water and QA.
By examining iron contents, it is demonstrated that the monogenean Ancyrocephalus mogurndae (Yamaguli, 1940) feeds on the blood of its host, the mandarin fish Siniperca chuatsi (Basilcwsky), The iron content and then the quantity of blood necessary to produce this amount of iron are found different in young and fully-matured worms. Young worms contain higher levels of iron and estimated amount of blood. It is suggested that/1, mogurndae may start to feed on host blood as attached on gills, and the amount of blood ingested by young worms may vary from 0.01 to 1.00 μΙ before reproduction. The difference between young and fully-malurcd worms may be accounted for by the elimination of haematin and change of food composition in matured worms and may also be affected by reproduction. Experimental infections of the monogenean may provide supportive information for explaining the difference, and further studies should also examine the effect of immune components in host blood or mucus on the intestines of the parasite.