Anatomical and histological changes in developing silverberry (Elaeagnus multiflora var. gigantea L.) fruit

Abstract

SummaryThe growth of silverberry (Elaeagnus multiflora var. gigantea L.) fruit, including the calyx tube, which becomes edible, and the ovary wall was investigated in relation to their cell structure. Samples of flowers at anthesis to mature fruits were collected each week from mature trees growing in Japan, replicated over two seasons. Anthesis-to-fruit maturity took 6 – 7 weeks. Cell division in the parenchyma of the calyx tube terminated approx. 3 weeks after anthesis in late April, coinciding with the appearance of tannin cells. Cell division in the ovary wall was not observed after anthesis. Examination of transverse sections of the calyx tube revealed that the sizes of the eight vascular bundles, radially distributed at regular intervals, increased as the fruit developed. Vascular tissues in the calyx tube and ovary did not branch into other tissues. Cells in the outer periphery of the vascular bundles in the calyx tube expanded more than cells in the inner portion. Parenchymal cells of the calyx tube that enlarged laterally during fruit growth became succulent, juicy, and coloured. Changes in the overall diameter and weight of fruit over time were sigmoidal, although the adjacent exterior portion of the vascular bundle in the calyx tube formed a hard shell at maturity. Cells in the ovary wall remained soft throughout fruit growth. Hence, growth and development of the edible calyx tube and the well-developed vascular system were distinctive and unique features of fruit of this species.