How does nightflowering cacti knows it’s night?

[Mrs.Green]

This may sound as a silly question, since in nightbloomers natural habitat it will get dark at night. But staying up late last night waiting for the E.subdenuta to open its flower, I began to wonder; what is really the trigger for the flower to open up? Since I live in the northern part of Scandinavia, it doesn’t get dark at night here in summer, the only difference is the lack of sun at night.

Something a wild plant will never experience. So what tells the plant to open the flower, lack of sun, lower nighttemperatures, a mix of these or something else?

If the plant stood under strong artifial lights, would it still know its night and bloom?

[DaveW]

Evidently it is controlled rather like the oscillations in a quartz watch.

See:-

https://www.adonline.id.au/flowers/circ ... 20at%20day.

https://pubmed.ncbi.nlm.nih.gov/12214234/

[7george]

Cacti know what is the time right now most days. My Discocactus also open flowers ~ 7 PM even here is not dark in the summer. Pollinators fly in the dusk already and also in early morning hours. Biological clock, you know.

[DaveW]

Referring to the circadian rhythm and plant flowering times. It can also affect the emission of scent. A friend who is a Botany teacher told me flowers don't always produce scent all the time they are open, many flowers only produce the scent at the time their pollinators are flying. This often accounts for some people saying a flower is scented whilst another can't detect it, simply because they smelt it at a different time of day (or night if night flowering). This is a method of the plant not wasting its energy producing scent when unneeded. Of course some flowers are scented all the time.

https://www.realclearscience.com/journa ... %20evening.

The following link says

"The creation of scent is a balancing act: plants must generate enough smell to induce insects to fertilize their flowers, but not so much that they waste energy and carbon. In fact, for many species, scent emission is not constant; snapdragons decrease scent production 36 hours after pollination."

https://scienceline.org/2013/01/making- ... f-flowers/

[Mrs.Green]

Thank you 7george Interesting, but it does goes dark sometimes during the night, were you live?

DaveW; thank you very much,interesting links! The scent part I am well aware of, not so much from cacti but from garden and wild flowers, the scent will vary from species to species depending on both time of day and temperature in my experience .

[7george]

Thank you 7george Interesting, but it does goes dark sometimes during the night, were you live?

Yes, it gets dark after 10 or 11 but this doesn't change the things as when you do to work night shift you don't look at the sun but your watch only. Maybe plants can measure the angle of the sun rays?

[jerrytheplater]

Referring to the circadian rhythm and plant flowering times. It can also affect the emission of scent. A friend who is a Botany teacher told me flowers don't always produce scent all the time they are open, many flowers only produce the scent at the time their pollinators are flying. This often accounts for some people saying a flower is scented whilst another can't detect it, simply because they smelt it at a different time of day (or night if night flowering). This is a method of the plant not wasting its energy producing scent when unneeded. Of course some flowers are scented all the time.

https://www.realclearscience.com/journa ... %20evening.

The following link says

"The creation of scent is a balancing act: plants must generate enough smell to induce insects to fertilize their flowers, but not so much that they waste energy and carbon. In fact, for many species, scent emission is not constant; snapdragons decrease scent production 36 hours after pollination."

https://scienceline.org/2013/01/making- ... f-flowers/

Dave

I once had an Echinopsis I lent to a friend at my church who was a perfumer at a local fragrance company. I gave it to him when I knew the flower would open the next night. He brought it in to his work and had one of the technicians stay up all night taking air samples of the fragrance and analyzing it on the Gas Chromatograph. They wanted to get the entire fragrance profile throughout the night. They were careful not to exert to much vacuum pressure as they sampled the air lest they influence the plant. In the end, the fragrance was nothing exceptional that they did not already have. They took photos of the blooming flower and sampling setup, which they placed on the cover of the annual report for the company.

[Mrs.Green]

Hi Jerrytheplater, interesting story

[nachtkrabb]

What an interesting question, and what interesting answers! And from Sweden with the long summers, too.

I have an Echinopsis subdenudata (night-blooming hedgehog). It usually opens its flowers around 2:am, in the middle of the night, and closes them around 2:00pm. I have no idea when it starts smelling as it doesn't do so in the beginning. Somehow, I tend to sleep a bit . But when I check on the flowers in the morning, there is a slight citrussy smell. Lovely.

Also the Selenicereus at my place (donkelaari & grandiflorus) first open their buds and much later begin to smell. It is more an "invading" smell you notice on coming into the room thinking "somebody has baked a cake!".
In a video, Urs Eggli called my attention to the source of the smell: A rose or the E. subdenudata smells from the center of the flower, while a Sel. grandiflorus smells from the thick end of the pedicel near the flower.
N.

[Mrs.Green]

What an interesting question, and what interesting answers! And from Sweden with the long summers, too.

I have an Echinopsis subdenudata (night-blooming hedgehog). It usually opens its flowers around 2:am, in the middle of the night, and closes them around 2:00pm. I have no idea when it starts smelling as it doesn't do so in the beginning. Somehow, I tend to sleep a bit . But when I check on the flowers in the morning, there is a slight citrussy smell. Lovely.

Also the Selenicereus at my place (donkelaari & grandiflorus) first open their buds and much later begin to smell. It is more an "invading" smell you notice on coming into the room thinking "somebody has baked a cake!".
In a video, Urs Eggli called my attention to the source of the smell: A rose or the E. subdenudata smells from the center of the flower, while a Sel. grandiflorus smells from the thick end of the pedicel near the flower.
N.

Thank you Nachtkrabb A slight ‘correction though; I am from Norway, not our neighbour country Sweden.. Ah, I would love to see and smell the Selenicereus flowers! I do have a Selenicereus ( not sure about the species) but it hasn’t graced me with flowers yet. Interesting that the origin of the smell varies from species to species .

[7george]

Talking about the smell: Escobaria vivipara flowers have real aroma of roses and often one can feel that smell before seeing a plant itself, especially if several ones open that time...

Cacti can feel many things: I even think they can hear the thunder and prepare to take the shower soon...

[Mrs.Green]

Talking about the smell: Escobaria vivipara flowers have real aroma of roses and often one can feel that smell before seeing a plant itself, especially if several ones open that time...

Cacti can feel many things: I even think they can hear the thunder and prepare to take the shower soon...

Ah, that sounds lovely! Or should I say ‘smells’ lovely? That cacti and other plants can hear or rather feel? changes in weather sounds very likely, we do, so why shouldn’t plants do?