The morphological and anatomical studies of inflorescence, flower, embryo and fruit development in Maclura pomifera (Moraceae)

Abstract

Abstract Maclura pomifera, a dioecious tree species, is recognized by its orange-like fruits and has a fascinating history and varied economic uses. The morphology and anatomy of female inflorescence, flower, embryo, fruit and seed development were surveyed by cyto-histological methods. The flowers and fruits were collected at different developmental stages, fixed in FAA fixative, embedded in the paraffin, sectioned using microtome, stained by hematoxylin and eosin and were photographed using light microscopy. There are 60–70 female flowers in each hairy inflorescence. Each young flower has pinkish and tetrameric perianth which surrounds the unicarpellate pistil composing of a unilocular ovary and long style. The perianth becomes fleshy and green during development and surrounds the ovary forming a drupe-like fruit with a permanent long style. The fleshy perianths and the drupes inside them produce a false multiple (accessory fruit or pseudocarp) and pomaceous fruit in which a few filled seeds are formed. Ovule primordium appears in an apical placentation and its growth direction changes during development. The ovule is ana-campylotropous, suspended, bitegmic and tenuinucellate. The embryo passes globular, heart-shaped and cotyledonary steps. Finally, the curved embryo is formed whose cotyledons constitute massive volume of ovule (seed) and endosperm is eventually degenerated. Suspensor is short and multi-celled. Ovule integument makes the membranous seed coat. The middle part of perianth contains secretory cells that is detached during development forming a soft spongy tissue. This study shows the characteristics of inflorescence and fruit architecture during development that can also clarify phylogenetic relationships among genera and in the family.