Temporal changes in floral nectar production, reabsorption, and composition associated with dichogamy in annual caraway (Carum carvi; Apiaceae)

Abstract

The dynamics of nectar production were studied in perfect florets of two varieties (Karzo, Moran) of annual caraway (Carum carvi L., Apiaceae). Florets were protandrous and strongly dichogamous, lasting 7-15 d but producing nectar from the stylopodia for 4-12 d, in an interrupted fashion. Nectar secretion began during a floret's phase of stamen elongation and anther dehiscence. After reabsorption of uncollected nectar, at which point nectary surfaces were completely dry, the two styles elongated and a second bout of secretion commenced during the female phase, up to 5 d later, when a floret became receptive to pollination. During the male and female phases, respectively, 0.392 ± 0.064 μL and 1.083 ± 0.261 μL of nectar of similar solute concentration (844 mg/mL) was produced per ten florets. On a daily basis, florets yielded 1.5-fold more nectar in the female than during the male phase. First-time nectar removal throughout the female phase did not match the sum of nectar quantities from male and female phases combined, suggesting that under natural conditions, any uncollected male-phase nectar, once reabsorbed, is not made available to visitors of the same florets when in the female phase. Nectar-sugar composition differed between bouts of secretion; it was hexose-rich (59.6% fructose, 26.9% glucose, 13.6% sucrose) initially, but hexose-dominant (70.2, 26.8, 3.1) during the female phase. A 5.7-fold difference in mean nectar production per floret occurred among plants.

Secretion and composition of nectar and the structure of perigonal nectaries in Fritillaria meleagris L. (Liliaceae)

“…Nectar resorption is a long-known phenomenon, but has rarely been addressed in studies on nectar secretion (Pedersen et al 1958;Southwick 1984;Pyke 1991;Búrquez and Corbet 1991;Nepi and Stpiczyńska 2008). Resorption of nectar has generally been demonstrated (as in Fritillary) during final stages of anthesis as a postpollination phenomenon (Koopowitz and Marchant 1998;Luyt and Johnson 2002) or following the completion of sexual stages in dichogamous flowers (Langenberger and Davis 2002). Its significance was generally recognized as a resource-recovery strategy, and resulted in at least partial recycling of metabolites invested in nectar production (Southwick 1984;Pyke 1991;Búrquez and Corbet 1991;.…”

Pollen morphology and the flower visitors of Chaerophyllum coloratum L. (Apiaceae)

“…Pollination biology of the Apiaceae related to fl ower preferences of insects has also received little attention, and has been studied mostly in economic plants and only a few wild species: Heracleum sphondylium, Seseli farrenyi, Thaspium sp, Zizia sp. and Daucus carota (Bell and Lindsay 1978, Lindsey 1984, Lindsey and Bell 1985, Lamborn and Ollerton 2000, Langenberger and Davis 2002a, b, Rovira et al 2004, Zych 2006.…”

Molecular evidence of polyphyletism in the plant genus Carum L. (Apiaceae)

“…The best known species of this genus is Carum carvi L. (caraway or Persian cumin), which is one of the oldest herbs known (Nemeth, 1998). It is used traditionally as a condiment, oil and drug and, more recently, for the extraction of carvone, a compound which inhibits sprouting in potatoes (Langenberger and Davis, 2002b;Nemeth, 1998). Caraway is also important for honey production (70 to 134 kg ha -1 ) from Canadian behives (Langenberger and Davis, 2002a) and new medicinal uses such as anti-hyperglycemic potential have recently been reported (Eddouks et al, 2004).…”