In protected growing systems, plant requirements are usually fulfilled by fully or partially automated systems. Even in such an environment, however, undesirable cross effects among the various factors (e.g. components of the nutrient solution, temperature, ventilation, insolation) can perturb the development of plants. This can lead to yield losses caused by nutrient deficient fruits in most cases. In our experimental setup, data collected from six tested plant groups representing various climatic conditions under the plastic tunnel greenhouse revealed that shading had a more significant impact on plant water usage and transpiration than ventilation. Lack of shading could lead to even a 2°C higher temperature on the leaf surface. The tested plant groups, irrespective of their position, responded with intensive transpiration to the drastic increase in temperature. Rising outside temperature resulted in the increase of air and root zone temperatures in the forcing facility. Due to the high temperature, relative humidity increased in the plastic-covered growing facility thus influencing transpiration and nutrient transport. The long-lasting root zone temperature of 29°C hindered Ca2+ ion uptake. Cells of young pepper fruits set in this period required higher amounts of Ca2+ ions thus the formation of blossom end rot started already in this period. White areas around the fruit tip caused by irreversible epidermis damage (sunscald) were formed in summer due to sudden exposure to intense sunlight. In our experiment fruits situated at the lower arc of the tunnel ribs, out of the shade of the shading net were exposed the most to the burning effect of sun. To determine the exact difference between the two pepper fruit surface damages, besides visual diagnosis microscopic examination was also necessary.