Anatomical Features on the Sieve Elements and Sorbitol Content in Various Organs of Rosaceae Fruit Trees

Abstract

The development of the nacreous cell wall in the sieve tube of the petiole, fruit stalk, and root in four Rosaceae fruit trees: loquat (Eriobotrya japonica Lindl.) ; peach (Prunus persica (L.) Batsch.) ; apple (Mains domestica L. Borkh.) and Japanese pear (Pyrus pyrifolia Nakai) was observed. In addition, the soluble carbohydrate contents in these organs and in the leaves and fruits were determined.
The organelles in the cytoplasm of the sieve tube elements in petioles of young, unexpanded peach leaves were observed. As the nacreous cell wall enlarged into the cytoplasm, the organelles began to degenerate and virtually disappeared when the cell wall of the sieve tube ceased to elongate. At the beginning of the nacreous cell wall formation in peach petioles, the p-protein body appeared in the cytoplasm of the sieve tube, then the p-protein body dispersed into cytoplasm during the cell wall thickening.
Ingrowth of the cell wall occurred in the sieve tubes of the petioles in all species examined. Its degree of development in the fruit stalk was species dependent; the ingrowth was thickest in the loquat, it was moderately thick in the peach and least thick in the apple and Japanese pear. The nacreous cell wall in sieve tubes of the loquat root was moderately thick; it was less thick in apple roots. Only a narrow nacreous cell wall in roots of the peach and Japanese pear was observed.
By examining the morphology of the phloem tissue, we hope to establish a relationship between the ingrowth degree of the nacreous cell wall in the sieve tubes of the petiole, fruit stalk, and root of Rosaceae fruit trees, which differed among species and organs, and the soluble carbohydrate transported therein.