Effects of grapevine fanleaf and stem pitting viruses on the photosynthetic activity of grapevine plants grown in vitro

Abstract

The effects of viral diseases on the photosynthetic activity of grapevine (Vitis rupestris var. Rupestris du Lot) leaves were investigated. The third and sixth leaves used for measurements were obtained from in vitro grown healthy plants and plants affected by grapevine fanleaf and rupestris stem pitting viruses. The induction curves of prompt and delayed chlorophyll fluorescence, as well as the temperature characteristics of steady-state, prompt, and delayed emissions, were investigated. Age-dependent changes were found, which were related, on the one hand, to the acceleration of electron transport and the enhancement of thylakoid energization and, on the other hand, to a smaller extent of transmembrane ΔμH+ in the younger sixth leaf compared to that in the third leaf. The infected plants characteristically showed faster electron transport, an elevated energetic efficiency of photosynthesis, and the suppression of CO2 fixation owing to a presumable activation of the adenylate metabolism. An analysis of the thermograms of prompt and delayed fluorescence revealed the shifts in the position of the M1 peak and a half-inhibition temperature T50 towards a higher temperature in infected plants, which indicates a certain increase in the thermal tolerance of thylakoid membranes. The data suggest that the viral metabolism affects the functional activity and stability of thylakoid membranes.