Nectary Structure in Dichogamous Flowers of Polemonium Caeruleum L. (Polemoniaceae)

Abstract

The flowers of Polemonium caeruleum are protandrous. The nectary is in the form of a rim encircling the ovary. Secreted nectar accumulates in a chamber located at the bottom of the floral tube and is protected by dense staminal hairs. The nectary tissue is not vascularized, but is supplied by vascular strands that occur near the base of the nectary and which directly supply the stamens. Nectar is secreted via modified stomata located on the upper part of the rim, particularly on the adaxial surface. The number of stomata and the volume and sugar concentration of nectar are greater during the female stage than during the male stage. In both stages, however, the nectar is sucrose-dominant. This paper shows that in P. caeruleum the nectar sugars are not a direct product of current photosynthesis, since plastids of nectary cells are devoid of chlorophyll. The main source of sugars in secreted nectar is the phloem sap, together with starch that accumulates in the nectary cells during the male stage and is then rapidly hydrolyzed during the female stage.K Ke ey y w wo or rd ds s: : Nectar secretion, histochemistry, protandry, Polemoniaceae, red-listed plant.

Floral Nectary Morphology and Proteomic Analysis of Nectar of Liriodendron tulipifera Linn.

“…Although L. tulipifera nectar is secreted through nectarostomata, the L. tulipifera flower nectary structure is very different than that of Brassicaceae flowers ( Kram and Carter, 2009 ) and even that of Magnolia stellata in the same Magnoliaceae family ( Erbar, 2014 ). As an apocarpous gynoecium flower, the nectary of L. tulipifera flowers was located on the modified orange–yellow part of petals, as in flowers of Helleborus and Symphyglossum ( Vesprini et al, 1999 ; Stpiczynska and Davies, 2006 ), whereas in most species, it encircles the ovary ( Brown, 1938 ; Zer and Fahn, 1992 ; Rivera, 2000 ; Konarska, 2010 ; Nocentini et al, 2012 ; Stpiczyñska et al, 2012 ; Lüttge, 2013 ; Stephens, 2013 ). Although this result was consistent with previous findings in plants in the Ranunculaceae family ( Kosuge, 1994 ), it was different from what has been seen in M. stellata in the same family ( Erbar and Leins, 2013 ).…”

Reproductive biology of the Red List speciesPolemonium caeruleum(Polemoniaceae)

“…As shown in the present study, nectar production, concentration and composition may also differ in subsequent sexual phases of the same flower. This is, however, not associated with differences in nectary structure between the male and female sexual phases of a flower, but the greater activity of the secretory tissues during the female phase (Stpiczyńska, Kamińska & Zych, ). Gender‐biased nectar production, reported here for P. caeruleum , has never been found in other members of Polemoniaceae, but has been demonstrated for several other dichogamous plant families (for a review, see Carlson & Harms, ).…”

Breeding system variability, pollination biology, and reproductive success of rare Polemonium caeruleum L. in NE Poland

“…Flowers are protandrous and the anthers open first, then after a few days the 3-lobed stigma open, but these two stages slightly overlap [21,22]. Flowers produce nectar rich in sugar, which is secreted and stored by the ring-shaped nectary located at the base of the ovary [25,26]. Pollinators are mainly bumblebees and honeybees, although the list of potential pollinators of P. caeruleum might be more abundant [20][21][22]25].…”