Flowers can open at different times to increase attractiveness. For example, moth-pollinated flowers open at night :)

Several studies found that display span are related with the production of fruits and seeds. In addition, the anthesis in each plant species denpending on which are the effective pollinators. Thus, the duration and time of day of anthesis (could be diurnal, nocturnal or crepuscular) partially depends on the activity of the associated pollinators (also it could depends on exposition, light, humidity, etc.).

Regards,

Cristian

Based simply on observations over time, once a flower has been pollinated, at least in most cases the pollinator-attracting features are of less significance and will start to shut down. Often times this means that corolla will start to wither or fall off, fragrance production will diminish, etc. If the flower is one of many on an inflorescence, then other flowers not yet pollinated, as well as bracts in many cases, will continue to attract the pollinator to visit. Those with inflorescences pollinated by one of the trap-line pollinators have typically evolved in such a way that bracts or other advertising/attracting features will continue to show off through the life of the inflorescence, but the first flowers, once pollinated, pretty quickly start to go towards fruit development even while the later flowers are still forming and opening. I hope that all this speaks to the question's intent.

After the pollinisation of flower it is not good to keep this one opend,

so the time of aromatic attraction is finished too.

Generally, flowers that have not been pollinated tend to have a longer receptivity period than pollinated flowers. See, for example, the papers below.

Devlin B, AG Stephenson 1984 Factors that influence the duration of the staminate and pistillate phases of Lobelia cardinalis flowers. Bot Gaz 145:323-328.

Richardson TE, AG Stephenson 1989 Pollen removal and pollen deposition affect the duration of the staminate and pistillate phases in Campanula rapunculoides. Am J Bot 76:532-538.

Here is a good example: Lupinus pilosus (see the attached picture) is pollinated mainly by bees. It starts open its flowers from the lower ones and proceeds toward the upper flowers. The lower pollinated flowers stay open and don't wilt for few more days, but change their flag color from white to pink and to dark red. This behavior may be interpreted as a contribution to far bees' attraction and directing then to the not pollinated upper flowers while getting closer. There are more Lupinus species that behave similarly.

Dear Gad,

Thank you very much for your response, it is just that I was looking for...do you know any publication about this (Lupinus or any other species)?

Thank you all for your interest. Actually, all that you replied is indeed broadly known, I am especifically wanted to know if there is any publication reporting that pollinated flowers remain still open to increase individual-level pollination attractiveness.

Best.

Dear Alberto, there are many publications dealing with this interesting topic: pollinated flowers remain still open to increase individual-level pollination attractiveness. Here are three of them:

Floral color change in Lupinus argenteus (Fabaceae): why should plants advertise the location of unrewarding flowers to pollinators?‏

DF Gori - Evolution, 1989‏ - Wiley Online Library‏

Floral color change: a widespread functional convergence‏

MR Weiss - American Journal of Botany, 1995‏ - JSTOR‏

Floral color change and insect pollination: a dynamic relationship‏

MR Weiss, BB Lamont - Israel Journal of Plant Sciences, 1997‏ - Taylor & Francis‏

Alberto,

Another possible similar scenario occurs with the tropical shrubs in the genus Brunfelsia. Several species within this genus are commonly referred to as "Yesterday, Today, and Tomorrow" because the flowers open deep purple and gradually fade to white over a three to four day period. I have not looked into papers on this, but had understood that it was to gradually go from one possible pollinator to another, giving the flowers the best chance for getting pollinated. Certainly the color change in some fruits serves to attract one potential disperser and then another. I mentioned the idea of bracts in my response above with trap-line pollinators. It may be that in the case of the Lupinus flowers that once pollinated they are starting to shut down but the color shift does serve, in a way similar to bracts and with less energy consumption as the pigments shift (?) to act more as bracts do. Several different possible angles for study here. Good luck with it.

Dear Gad and Johnatan, once again, thank you very much.

Indeed it is quite fascinating. Actually I am not interesting on color change over time, but rather only whether there is any study reporting whether pollinated flowers remain still open to increase individual-level pollination attractiveness, independently of color change or whatever. I thoroughly think that there are few studies reporting this pattern, but so far I am only aware of the one I posted before (Ishii and Sakai 2001).

Thank you both very much.

Dear Alberto, think about this: pollinated flowers that remain open usually reduce their reward amount, sometimes to zero. If they remain open to increase pollinator attractiveness they have to change some signal, to direct the visiting pollinator to the not pollinated flowers. Visit again the pollinated flowers don't help the plant, and may even damage the pollinated flowers. Therefore all the cases I know of "pollinated flowers remain still open to increase individual-level pollination attractiveness" are connected with color change, or flower shape change. The Lupinus case is a classic one. Its flowers contain only pollen, and no nectar. The pollinated flowers are mostly empty of pollen. The white flag of the young flowers is attractive to the bees, its main pollinators, while the old flowers' red flag is accepted as black and not attractive for the bees. The only reason for keeping the pollinated flowers open is to increase attractiveness to the bees, and the flag color change help the visiting bee to distinguish between the pollinated and the not pollinated flowers, which is in favor of both the plant and the bee.

Protogynous flowering sequence is another option for flowers that stay open and active after being pollinated. Many hermaphrodite flower species are dichogamous, separating the time of their male and female organs' activity. Most dichogamous species expose first their male organs (pollen releasing) and later their female organ (receptive stigma), which is termed proterandry behavior. These species' flowers finish their life cycle and wilt after (a) pollen releasing and then (b) pollination of the female stage. However, this is not the case for the protogynous species. They first expose the stigma, and then, after being pollinated, they move to the male stage, which may last few hours or up to few days. The avocado is an example. Each avocado flower opens twice, on two successive days. On the first day the flower exposes a receptive stigma and the stamens are attached to the petals with no pollen releasing. After about half a day the pollinated flowers close, and open again on the next day functioning as a male. The stigma is not receptive any more, but the stamens rising and releasing pollen. Only after another half day the flower close, and wilt gradually on the coming days.