Abstract <p>Our knowledge of photosynthesis in non-foliar tissues is still limited, especially about the tolerance of photosynthetic apparatus in these tissues to unfavorable environmental factors. Here we monitored the activity of photosystem II in leaves and vine chlorenchyma in grapevine (<i>Vitis vinifera</i> L.) during the period of active vegetative growth. Both tissues maintained high values of effective quantum yield of photosystem II (Y(II)) over the whole period of hot sunny weather, while Y(II) values were consistently higher in vine. No significant correlation between Y(II) and environmental conditions was found, and there was no influence of phenological phases on this parameter. Laboratory measurements demonstrated a high tolerance of photosynthetic apparatus in vine chlorenchyma to high temperatures (up to 50°C). Non-photochemical quenching and the contribution of different components, including the energy-dependent component, associated with transthylakoid pH gradient and functioning of the violaxanthin cycle (<i>q</i>_E); quenching due to redistribution of excitation energy between the reaction centers of photosystems (<i>q</i>_T); and quenching induced by photoinhibition (<i>q</i>_I) at different light intensities were estimated. The contribution of <i>q</i>_I was high at all light intensities, and it increases with increasing light intensity, while the contribution of <i>q</i>_E and <i>q</i>_T was smaller and reached maximal values at low light intensities. The analysis of carotenoids showed that compared to the leaf, vine chlorenchyma is characterized by high lutein and xanthophyll content with antheraxanthin being a dominant xanthophyll, a lower violaxanthin-to-zeaxanthin ratio, but higher xanthophyll de-epoxidation index. This work contributes to our understanding of photosynthetic processes in non-foliar tissues under various environmental conditions.</p>