Institute of Experimental Botany

The decrease in inorganic phosphate (Pi) content of 10-d-old Phaseolus vulgaris L. plants did not affect rates of photosynthesis (PN) and respiration (RD), leaf growth, and adenylate concentration. Two weeks of phosphate starvation influenced the ATP content and leaf growth more than PN and RD. The ATP concentration in the leaves of 15- and 18-d-old phosphate deficient (-P) plants after a light or dark period was at least half of that in phosphate sufficient (+P, control) plants. Similar differences were found in fresh and dry matter of leaves. However, PN declined to 50 % of control in 18-d-old plants only. Though the RD of -P plants (determined as both CO2 evolution and O2 uptake) did not change, an increased resistance of respiration to KCN and higher inhibition by SHAM (salicylhydroxamic acid) suggested a higher engagement of alternative pathway in respiration and a lower ATP production. The lower demand for ATP connected with inhibition of leaf growth may influence the ATP producing processes and ATP concentration. Thus, the ATP concentration in the leaves depends stronger on Pi content than on PN and RD.

Parameters of the fast chlorophyll (Chl) fluorescence induction (the O-J-I-P curve) of plants of winter wheat grown in the field canopy were statistically tested for Gaussian distribution. Five different statistical methods showed that the obtained values did not obey the Gaussian distribution law. The presentation of the parameters with the help of the mean and standard deviation masks the information about statistical properties of the values. Thus, we recommend to present the parameters by means of median, quartiles, and minimum and maximum values rather than by means of the mean and standard deviation.

The polarized absorption, photoacoustic, fluorescence emission, and fluorescence excitation spectra of whole cells of cyanobacteria Synechocystis sp. embedded in a polymer film were measured. The bacteria cells, as it follows from anisotropy of absorption and fluorescence spectra, were even in a non-stretched polyvinyl alcohol film oriented to a certain extent. The measurements were done for such film in order to avoid the deformation of cyanobacteria shapes. Part of the samples was bleached by irradiation with strong polarized radiation with electric vector parallel to the orientation axis of cells. The anisotropy of photoacoustic spectra was higher than that of absorption spectra and it was stronger changed by the irradiation. Polarized fluorescence was excited in four wavelength regions characterised by different contribution to absorption from various bacteria pigments. The shapes of emission spectra were different depending on wavelength of excitation, polarization of radiation, and previous irradiation of the sample. The fluorescence spectra were analysed on Gaussian components belonging to various forms of pigments from photosystems (PS) 1 and 2. The results inform about excitation energy transfer between pools of pigments, differently oriented in the cells. Energy of photons absorbed by phycobilisomes was transferred predominantly to the chlorophyll of PS2, whereas photons absorbed by carotenoids to chlorophylls of PS1.

Anthocyanins and nonphotochemical quenching (NPQ) are two important tools that provide photoprotection in plant leaves. In order to understand how plants use these tools for acclimation to changing seasonal conditions, we investigated pigments, antioxidative capacity, and photosynthesis in leaves of an evergreen tree (Acmena acuminatissima) in two contrasting seasons. Young leaves of A. acuminatissima appeared in distinct colors, being light green in summer and red in winter due to the presence of anthocyanins. In the winter young leaves, anthocyanins contributed less than 2% to the antioxidant pool. In the summer, young leaves had higher NPQ than that of mature leaves, but in the winter, they did not derive any NPQ-related advantage over mature leaves. These results suggest that the accumulation of anthocyanins in young leaves in the winter may compensate for the insufficient photoprotection afforded by NPQ and that anthocyanins function as a light attenuator to protect the photochemical apparatus against excess light.

The influence of viral infection caused by two different potyviruses, Potato virus Y (PVY) and Potato virus A (PVA) on plant metabolism and photosynthetic apparatus of Nicotiana tabacum L. cv. Samsun and cv. Petit Havana SR1 was studied. The main stress was focused on the activities of phosphoenolpyruvate carboxylase (PEPC), NADP-malic enzyme (NADP-ME), and pyruvate phosphate dikinase (PPDK). The analysis of the presence of viral proteins, enzyme activities, and different photosynthetic parameters showed the time dependent progress of viral infection and NADP-ME and PEPC activities. PVY caused significant response, while PVA affected both tobacco cultivars only slightly. Viral infection, namely PVY, affected more negatively photosynthetic apparatus of cv. Petit Havana SR1 than cv. Samsun.

In Evernia prunastri, photosynthetic gas exchange was saturated with yellow radiation (SOX) at 400 μmol m−2s−1, and then red (R), far-red (FR), or blue (B) radiations at irradiance of 15 μmol m−2s−1 were added. Because of photosynthesis saturation, any stimulation or decay in CO2 assimilation by any radiation quality could be attributed to the involvement of a non-photosynthetic photoreceptor. Thus CO2 assimilation, effective quantum yield, and photochemical quenching were enhanced when R was included, and decreased with FR. Blue radiation completely abolished CO2 fixation. Hence different spectral radiation qualities may activate non-photosynthetic photoreceptors such as phytochrome and blue photoreceptors, which are involved in regulating the photosynthetic activity in E. prunastri.