Anther opening, pollen biology and stigma receptivity in the long blooming species, Parietaria judaica L. (Urticaceae)

• Published in: Flora. Morphologie, Geobotanik, Oekophysiologie Vol. 202; no. 2; pp. 118 - 127
• Main Authors: Franchi, Gian Gabriele, Nepi, Massimo, Matthews, Merran L., Pacini, Ettore
• Format: Journal Article
• Language: English
• Published: Elsevier GmbH 01.01.2007
• Subjects: anthers; Ballistic pollen release; developmental stages; fertilization (reproduction); flowering; flowers; Gynomonoecy; Italy; Parietaria judaica; plant reproduction; Pollen carbohydrate reserves; pollen germination; Pollen hydration and germination; pollination; Protogyny; sexual reproduction; stigma; Stigma receptivity; Italy; Pollen carbohydrate reserves; Stigma receptivity; Ballistic pollen release; Gynomonoecy; Pollen hydration and germination; Protogyny
• ISSN: 0367-2530; 1618-0585
• DOI: 10.1016/j.flora.2006.03.005

This paper is about pollen ecophysiology, anther opening, pollen dispersal and the timing of the male and female phases in Parietaria judaica (Urticaceae). Ecophysiological (effects of different relative humidities (RHs) and osmotic relationships) and cytological methods (stigmatic receptivity, pollen viability, histology and histochemistry) were used to determine pollen and pollination features during the long blooming period of this species. Pollen is dispersed by rapid uncurling of the filament and anther opening. The filament and anther lack cells with lignified wall thickenings, which are usually responsible for anther opening and ballistic pollen dispersal. Instead, dispersal is the result of the sudden movement of the filament. Pollen is of the partially hydrated type, i.e. with a water content greater than 30% at shedding, and readily loses water, and hence viability, at low RH. Pollen carbohydrate reserves differ with season. Starchless grains germinate quickly and are less subject to water loss. Flowers are protogynous, pollen release occurring only after complete cessation of the female phase within an inflorescence. Parietaria has partially hydrated pollen which differs from typical pollen of this type because of its reduced size and the absence of callose. Because of its low water content at the time of shedding it survives better at higher RH. Dispersal and pollination are adapted to pollen features.