We studied how the presence of silicon structures or phytolites and other structural and biochemical properties affect the optical properties of barley (Hordeum vulgare L.) and spelt (Triticum spelta L.) leafs. The measurements were made in two periods, as we were interested in the differences between the leaves at the beginning and in peak growing season, as well as the difference between the leaves of barley and spelt in each period. The reflectance and transmittance were measured in the range of 280 nm to 880 nm. The morphological analysis of the leaves included leaf thickness, upper epidermal thickness, mesophilic thickness and lower epidermal thickness. We also determined the specific leaf surface and examined the size of the leaf stomata and prickle hairs, both in the upper and lower epidermis. Biochemical analyzes consisted of measurements of photosynthetic pigments namely - carotenoids, anthocyanins and UV-absorbing substances. We have found out that the refllectance and transmittance spectra of the selected species differred between the leaves at the beginning and peak growing season. There were also changes among the selected species in the same developmental phase. The results showed that the morphological and biochemical properties of the leaves affected reflectance and transmittance spectra. In barley, optical properties also depent on phytolith concentration, which we did not prove in spelt. The results also showed that leaves of barley and spelt contained different amounts of phytoliths. We also found out that in the case of barley, the content of phytoliths was higher in the peak growing season, which was not the case with spelt.