Plants of Nicotiana benthamiana (Gray) (60 d old) were mechanically inoculated by a spreading of the fourth and fifth leaves with inoculum with or without plum pox potyvirus (PPV). Changes in growth parameters and selected photosynthetic characteristics were followed in control and inoculated plants in the locally affected leaves (LA) during 11 d after inoculation (DAI), in systemically affected leaves immature at time of inoculation (SAI) during 14-25 DAI, and in systemically affected leaves developed after the inoculation (SAD) during 28-39 DAI. The pure mechanical damage caused by inoculation induced a decrease in the net photosynthetic rate (PN) in LA and SAD leaves, and an increase in the steady-state value of the non-photochemical chlorophyll (Chl) fluorescence quenching qN. The qN increase appeared in certain time intervals in all measured leaves on plants, so it could be regarded as indication of a systemic reaction of plant to the local mechanical injury. The viral infection developed in LA leaves and spread to SAI and SAD leaves was documented by the ELISA-DASI method. The plant height and area of SAI and SAD leaves were lower in infected plants. The combined effect of mechanical damage and viral infection caused a decrease in PN only in LA and SAD leaves. In SAD leaves, an increased relative height of the J step (VJ) in the O-J-I-P Chl fluorescence transient together with a lower B/A band ratio of thermoluminescence glow curves reflected a damage to the acceptor side of photosystem 2 (PS2) caused by the viral infection, and a faster kinetics of the induction of the photochemical quenching coefficient qP of Chl fluorescence indicated a faster QA- re-oxidation in the remaining undamaged centres of PS2. and V. Hlaváčková ... [et al.].
Plants of spring wheat (Triticum aestivum L. cv. Saxana) were grown during the autumn. Over the growth phase of three leaves (37 d after sowing), some of the plants were shaded and the plants were grown at 100 (control without shading), 70, and 40 % photosynthetically active radiation. Over 12 d, chlorophyll (Chl) and total protein (TP) contents, rate of CO2 assimilation (PN), maximal efficiency of photosystem 2 photochemistry (FV/FP), level of lipid peroxidation, and activities of antioxidative enzymes ascorbate peroxidase (APX) and glutathione reductase (GR) were followed in the 1st, 2nd, and 3rd leaves (counted according to their emergence). In un-shaded plants, the Chl and TP contents, PN, and FV/FP decreased during plant ageing. Further, lipid peroxidation increased, while the APX and GR activities related to the fresh mass (FM) decreased. The APX activity related to the TP content increased in the 3rd leaves. The plant shading accelerated senescence including the increase in lipid peroxidation especially in the 1st leaves and intensified the changes in APX and GR activities. We suggest that in the 2nd and 3rd leaves a degradation of APX was slowed down, which could reflect a tendency to maintain the antioxidant protection in chloroplasts of these leaves. and M. Špundová ... [et al.].