Limestone quarry did not affecred the intensity of photosynthesis in the species analyzed, compared to the same species, from an reprezentativ area, except the specie Trifolium sp., in which d = 2.90> 2.57, p = 0.01, that caused the rejection of the null hypothesis. At the other species (Taraxacum sp.: D = 1.52 <1.96, p = 0.05), (Plantago sp.: D = 0.73 <1.96, p = 0.05), (Fragaria sp .: d = 1.46 <1.96, p = 0.05), the null hypothesis can be accepted, the differences between mediums not being significant (in case 1). At the two working mode, the differences between average, in all cases, were significant, with probability levels of 0.001 and 0.01. 22 The only explanation of these differences consisted in calcareous dust deposits on the leaves of species in the quarry area, which explains the rejection of the null hypothesis (in case 2). And also at assimilating pigments null hypothesis is accepted,the difference between average not being significant in both casis of work, case 1 and case 2: Trifolium sp.: D = 0.38 <1.96; p = 0.05; Taraxacum sp.: d = 0.58 <1.96; p = 0.05; Plantago sp.: d = 0.98 <1.96; p = 0.05; Fragaria sp.: d = 0.46 < 1.96;p=0.05.