Diversity of the floral nectaries surface of four Crataegus L. species

Abstract

The performed studies focused on the surface structure of floral nectaries of four species from the following genus: <i>C. coccinea</i> L. , <i>C. crus-galli</i> L., <i>C. curvisepala</i> Lindm and <i>C. prunifolia</i> (Poiret) Pers. The observations of the epidermis area were made in a scanning electron microscope (SEM). A nectary appears to be shaped like a slightly curved disk situated between the pistil style and the basal part of the stamens filaments. The nectary area of the studied species differed substantially as regards the cuticle sculpture and stomata number. The nectary secretion in <i>Crataegus</i> flowers proceeds through the stomata located below a level of the other epidermis cells, in the deep indents of the secretory tissue. The highest stomata number in 1 mm<sup>2</sup> nectary epidermis was recorded in <i>C. crus-galli</i>, <i>C. coccinea</i>, <i>C. prunifolia</i> and finally, <i>C. curvisepala</i>. Analyzing the nectary cuticular structure in respect of its increasing complexity (absence or presence of stripes), the investigated taxons can be ordered as following: <i>Crataegus curvisepala</i>, <i>C. coccinea</i>, <i>C. crus-galli</i> and <i>C. prunifolia</i>.