Abstract
Male (staminat) flower development, being separated in 8 phases, was investigated in Laurus nobilis (Lauraceae) through the usage of histological sections and scanning electron microscopy (SEM) analysis. Flower development starts when apical meristem differentiates, followed by the conversion of this structure to floral meristem. Initial development phases comprise incidents similar to the ones of the female flower. 4 tepals and 8-10 stamens primordia develop through floral meristem in turn. In early stages of the development, sexual dimorphism occurs when the carpel primordium arrests. Filaments carry 2 nectaries in stamens which arise in 3 whorls. Anther wall consists of epidermis, endothecium, 2 or 3 middle layers and a single-layered glandular tapetum. Anthers are bisporangiate. Meiotic division is regular in pollen mother cells, and pollen grains do not contain aperture. Beside the pollen scattered individually within the pollen sacs, groups which contain some pollen tied to each other are rarely observed, as well. Pollen grains seldom germinate within microsporangium. Anthers are opened with 2 valves which widen from the base through the top. Accumulation of polysaccharides, lipids and proteins were identified by histochemical methods in stamens. These organic substances are greater within and around the vascular bundle compared to other tissues.
Highlights
Sex determination mechanism in dioecious species, which contain approximately 10% (Dellaporta and Calderone-Urea, 1993), appears analogous to the system in animal species, significantly
Dioecious plants and animals are considered as remarkable examples of parallel evolution
Apical meristem differentiate from vegetative meristem is transformed into floral meristem in male flower, and flower sex organ primordia develop from floral meristem in turn
Summary
Sex determination mechanism in dioecious species, which contain approximately 10% (Dellaporta and Calderone-Urea, 1993), appears analogous to the system in animal species, significantly. Unisexual flower development is categorized in 2 main types (Mitchell and Diggle, 2005). In male and in female flowers, in frequent Type I development, stamen and pistil begin to be formed; in one flower, only androecium or gynoecium reaches functional maturity. In Type II development, only one of the sex organs of unisexual flowers develops. In this sort of development, mature flowers do not carry rudimentary organ. This development is documented in Mercurialis annua L. This development is documented in Mercurialis annua L. (Durand and Durand, 1991), Spinacia oleracea L. (Sherry et al, 1993), and Thalictrum dioicum L. (Di Stilio et al, 2005)
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