Anatomical features of leaves of sweet pepper (Capsicum annuum L.) fed with calcium using foliar nutrition

The effect of three foliar-applied Ca-containing preparations on the anatomical features of leaves of sweet pepper (Capsicum annuum L.) was studied. The following preparations were used: Ca(NO3)2, Librel Ca and Wapnowit, applied at the respective concentrations of 0.5%, 1%, 1%, which corresponded to a content of 2000 mg Ca × dm-3. Light and scanning electron microscopy were used in the study. It was demonstrated that in amphistomatic bifacial pepper leaves numerous specialised cells occurred which accumulated calcium oxalate crystals in the form of crystalline sand. Anisocytic stomata were found with a much greater density in the abaxial epidermis. They were characterized by very well-developed outer cuticular ledges. It was found that in the leaves of the plants sprayed with the nutrient supplements with increased Ca content there was a much smaller number of epidermal cells per 1 mm2 than in the control plants. These cells were distinguished by an increased size. In the case of the application of the nutrient supplements Librel Ca and Wapnowit, the number of stomata also decreased. However, the application of the calcium supplements resulted in an increase in the value of the stomatal index compared to the control, which is attributable to a significant reduction in the number of epidermal cells not belonging to the stomata. The plants additionally supplied with Ca were marked by a larger number of colenchyma layers and an increased volume of leaf parenchyma cells. In the case of pepper leaves, the thin cuticle and the outer cell wall are not a major barrier to the Ca-containing preparations applied for spray treatment. Nevertheless, the decrease in the number of stomata may restrict the possibility of Ca uptake by this way, which compensates the increase in surface area of particular epidermal cells that will be the main way of Ca penetration into the internal leaf tissues.