Ultrastructure of receptive stigma and transmitting tissue at anthesis in two pear species

The ultrastructure of stigmatic and stylar secretory tissues was studied in one cultivar of Pyrus communis and six cultivars of Pyrus pyrifolia var. culta (the so-called Nashi pear) using standard light, scanning, and transmission electron microscopy methods. Although both tissues secreted an extracellular fluid necessary for the development of male gametophyte, they differed markedly in the ultrastructure of the extracellular matrix and in the distribution and ultrastructure of organelles. The difference was most evident in regard to the endoplasmic reticulum, which represented the rough, smooth, and vesicular type in stigmatic papillate epidermis and distal stigmatoid tissue cells and occurred mainly as the rough type in form of expanded cisternae filled with fine-fibrillar content in the transmitting tissue of the style.