The International Journal of Plant Reproductive Biology 3(2) pp. 133–140, 2011 Correlation Between Sexual Reproduction in Phragmites australis and Die-back Syndrome 1 Lara Reale , Daniela Gigante, Flavia Landucci, Roberto Venanzoni, Francesco Ferranti Department of Applied Biology, Borgo XX Giugno 74, 06121 Perugia, Italy 1 e-mail: citolabo@unipg.it Received: 02.05.2011; Accepted: 12.06.2011 ABSTRACT The common reed Phragmites australis (Cav.) Trin. ex Steud. (syn. P. communis Trin.) is a member of Poaceae with a widespread distribution in both the hemispheres, in different habitat types from river/lake shores, wetlands, coastlands and estuarine habitats, to ruderal, disturbed and even urban areas, hence it is considered a sub-cosmopolite species (Bjork 1967, Haslam 1973, Ostendorp 1993, Brix 1999a) In the last decades, reeds are dying back at a fast rate in sizeable areas of Europe, with significant impacts on important wetland functions (biodiversity, stability of river and lake margins, water quality) and local economy (Den Hartog et al. 1989, Van Der Putten 1997, Brix 1999b). Similar symptoms have been detected even in central Italy (Gigante et al. 2011). Besides ecological, morphological or anatomical parameters studies concerning some reproductive aspects might also be interesting in order to detect the health condition of reed-dominated ecosystems. In all the plant species the flower biology can be a good indicator of the health condition as the seed production and the seed viability. In plants exhibiting both vegetative and sexual reproduction, the energy allocation can be shifted from one to the other strategy in response to environmental stress; it is well known that sexual reproduction decreases the vulnerability of a population to disturbances and biotic stresses by increasing the genetic variability (Lei 2010). On this ground, we took into account the reproductive features of a declining reed stand in central Italy, where the die-back syndrome was recently detected (Gigante et al. 2011), with the aims to extend knowledge on sexual reproduction in P. australis and to highlight links between sexual reproduction and die-back symptoms. In this frame, cyto-histological analyses of inflorescences at different developmental stages were carried out in permanent plots where morphological investigation and histochemical analyses were also carried out to verify pollen and seed viability. An interesting link between some decline symptoms and the rate of spikelets containing at least one viable seed was observed. In detail, it appears that higher rates of viable seeds are recorded in the declining reed stands. Keywords: Phragmites australis, die back, flower development, pollen and seed viability . INTRODUCTION The common reed Phragmites australis (Cav.) Trin. ex Steud. (syn. P. communis Trin.) is a member of Poaceae with a widespread distribution in both the hemispheres, in different habitat types from river/lake shores, wetlands, coastlands and estuarine habitats, to ruderal, disturbed and even urban areas, hence it is considered a subcosmopolite species (Bjork 1967, Haslam 1973, Ostendorp 1993, Brix 1999a). The reed has annual cane-like shoots, reaching heights of between 80 and 350 (1000) cm, usually simple, and an extensive perennial rhizome system (Tutin et al. 1980). The leaves are arranged alternately and attached to the stem by a smooth sheath, bearing prominent wing-like extensions at the leaf base, with a fringe of fine hairs next to the stem. Flowers, usually purple in colour, are borne on branched inflorescences 20-60 cm in length that is composed of spikelets. Each spikelet, 10-15 mm in length, consists of a short axis, the rachilla, bearing two overlapping bracts, commonly called glumes; the lowermost glumes bear no flowers in their axis and are called empty glumes. Above the empty glumes there are from 3 to 5 flowers subtended by two bracts: the lower or abaxial called “lemma” and the upper or adaxial called “palea”. The small branches between the flowers bear long white silky hairs. The reproductive part of