The objective of the trial was to study the physiological function and potential ecological significance of non-glandular trichomes in red clover based on their relation to the leaf transpiration intensity. The transpiration rate, relative water content and water deficit of the leaves were recorded in field-grown, high and slightly pubescent genotypes. According to results, the presence of non-glandular epidermal trichomes on the leaf surface of red clover was a micromorphological trait related to the regulation of leaf transpiration in stressful conditions. Non-glandular trichomes significantly enhanced water retention of the leaf tissue at high leaf water deficit. In the environmental conditions, limiting leaf evaporation, the pubescent genotypes displayed higher levels of transpiration. It can be suggested that the non-glandular trichomes in red clover are morphological structures supporting the function of leaf stoma apparatus. A positive relation between the degree of pubescence and resistance to powdery mildew was established under natural conditions.