Morphogenesis of fruits in Gladiolus imbricatus and Iris sibirica (Iridaceae)

Abstract

Based on light microscopy investigation of fruits and seeds in Gladiolus imbricatus and Iris sibirica, new data on morphogenesis and histogenesis of the pericarp and seed coat development have been revealed. The inner ovary structure, vascular system and fruit dehiscence were also studied. The ovary of the studied species has trilocular basal part and unilocular upper part with incomplete septae. The vascular system in both species is composed of three dorsal veins and three septal veins. The dorsal veins are each divided into three vascular bundles radially whereas the septal veins are also each divided into three bundles but tangentially. Vascular supply of ovules is provided by septal veins in the central column. In both species, the floral tube falls down with adnate stamens and style at the beginning of fruit ripening. For both species, a dorsiventral (valvate) type of fruit dehiscence is characteristic; however, in I. sibirica, a dorsal (fissuricidal) type, in which valvae are connected at the center, top and base of the capsule, occurs as well. According to our data, capsule in both species belongs to the Lilium-type, with lignified endocarpium. In G. imbricatus, we observed early tissues differentiation in the pericarp as well as earlier and faster dorsal slits formation. The seed coat in G. imbricatus is of endotestal type, while in I. sibirica – of exotestal type. Highly specialized features of the seed coat in G. imbricatus are the following: wing formation by outer integument, few-layered mesotesta and destruction of cellular structure of the inner integument. The obtained data complement our previously suggested consideration about more pronounced morphological adaptations for dissemination of fruits and seeds in G. imbricatus. In this article, we confirm the high level of adaptiveness of fruits and seeds in the anatomy and histogenesis of the pericarp and seed coat in G. imbricatus to external conditions.

Keywords

• fruit dehiscence
• histogenesis
• inferior capsule
• ovary
• pericarpium
• seed coat