Effect of pollination success on floral longevity in the orchidCalypso bulbosa(Orchidaceae)

Abstract

The lifespan of an individual flower is often affected by pollination success. Species differ regarding whether male function (pollen removal), female function (pollen deposition), or both trigger floral senescence. We studied senescence in the singleflowered, deceptive orchid Calypso bulbosa by manipulating the degree of male and female reproductive success. We found that deposition of any amount of pollen resulted in dramatic changes in shape and color within 4 d, whereas unmanipulated flowers and those that had had pollinia removed remained unchanged for 8‐11 d after treatment. Selection may favor the reproductive function that is less easily satisfied as the trigger for senescence, because a flower that senesces after accomplishment of this function is likely to have already succeeded at the more easily satisfied one. Deceptive (i.e., rewardless) flowers are more likely to satisfy male than female function since the latter requires that a pollinator be fooled twice, first to pick up pollen and second to deposit it. A survey of naturally pollinated Calypso showed that male function, pollinium removal, was more likely to occur than female function, deposition (95% vs. 66% of visited flowers); thus floral senescence in Calypso is triggered by achievement of the function less likely to succeed. Studies of senescence triggers in species in which female function is more likely to be achieved than male are necessary to further test this hypothesis.

Notes on fine-scale spatial distribution of three Cephalanthera species (Orchidaceae) that grow in sympatry in Korea: Implications for maintenance of species boundaries

“…This percentage of pollinia removal was considerably lower than those observed in E. palustris (60− 67%, Nilsson, 1978) and E. helleborine (up to 85%, Ehlers et al, 2002) in Sweden. Unlike the present work, previous studies in other orchids revealed that the rate of pollinia removal is higher than the fruit set (Schemske, 1980;Proctor and Harder, 1995). The low rate of pollinia removal observed in the present study would be attributable to only a 2-day survey and/or rarity of pollinators during the study period.…”

Intrafloral phenology of Trifolium polymorphum Poir. (Leguminosae) aerial flowers and reproductive implications

“…This recorded period was obtained in cultivated experimental conditions (without environmental factor control) in which the pollination effect was not considered. Pollination usually reduces floral longevity by means of ethylene production (Stead 1992;Proctor & Harder 1995;van Doorn 1997;Arathi et al 2002), and it is a way to minimize the invested female resources and assure male fitness by reducing pollen-grain competition once the grains reach the stigmatic surface (Lankinen et al 2006). It is likely to assume that some variation in flower longevity found in T. polymorphum could be explained by this cause.…”

Is the pollination efficiency of long-lived orchid flowers affected by age?

“…(Pijl & Dodson, 1966). In these plants, greater longevity is observed in non-pollinated flowers; pollination promotes rapid changes that induce floral senescence (Proctor & Harder, 1995;Martini et al, 2003;Abdala-Roberts et al, 2007). The long-lived orchid flowers have been interpreted as an adaptation to low pollinator activity (Stpiczynska, 2003), increasing the chances of pollination and thus the reproductive success (Pijl & Dodson, 1966;Martini et al, 2003).…”