Controlling the opening/closing of flowers.

[OsedaxMucofloris]

Hi
I'm unsure where to post this, so I've started a new topic. Sorry if it's covered elsewhere, but I must have missed it if that is the case.

I am wondering if anyone knows what it is that a cactus responds to that makes it open and close its flowers. Is it temperature or light? If light (as I expect) what part of light is the active factor - visible light, ultraviolet, infra-red?
- and 'how much' light is necessary?

I hope to be able to manipulate my cacti to open their flowers at my bidding. This is not just a perversely human desire to control nature, although it is partly the curiosity present in most horticulturalists that leads me to ask.

My main motivations are:
- to be able to show the splendid flowers to some people that are never able to see them open naturally;
- I also intend to do some time-lapse photography of the opening, closing and withering of the flowers, but I repeatedly miss the start of the process.

The time of day that the flowers open is irregular, so I'm presuming it is a reaction to external influences, rather than an internal clock, and it seems that light is the more variable factor than temperature. Particularly here in the UK, where cloudcover is a significant restriction to the "amount" of light available.

The particular cacti that i have currently flowering, in case it makes a difference, are of the Notocactus genus, but I am unsure of the species. (One of them is yellow not pink, so I'm not even certain that it's a notocactus).

Sorry for the long post, but if this sort of control is possible, I thought it might be of general interest to the cacti-growing community, especially those who are always out when their flowers open!

Any help with this would be very much appreciated.

Regards, Simon.

[SkyClan Cat]

This is an interesting subject. My tiny Gymnocalycium's had the same bud since February and it still hasn't done anything, and that cactus has been in my room the whole time. My Rebutia minuscula, on the other hand, grew two big buds and flowered in the cool, perpetually dark basement, about a week or two after I got it.

[OsedaxMucofloris]

@SkyClan Cat:

Thanks for your reply.
Does the bud on your Gymnocalycium look ready to flower? - is it in effect a complete flower that never opens, or a bud that hasn't developed to maturity? The first situation could relate to my query certainly.. if it never receives the particular catalyst that prompts its opening, perhaps. Is it possible it has opened but you've never seen it happen? In my limited experience, I would've expected it to have withered and dried up by now.

Nocturnally flowering plants confound my ideas as well. Certainly some species do, and exploit the pollenating effect of nocturnal moths etc. But I had been approaching the conclusion that my flowers respond to ultraviolet radiation in sunlight, when it reaches a certain intensity. This cant be the case for your Rebutia if it is isolated from sunlight..

Another thing, perhaps it is signifiacnt that the flowring took place soon after you acquiring the plant. I'm very new to cacti growing, but I know that sometimes other plants will be prompted to flower and fruit/seed as a sort of panic reaction. Change to there environment such as relocation, might have made your Rebutia 'think' it was under threat, so 'felt' the need to produce progeny.

I'm going to pursue this one with some experimentation...

Simon

[iann]

Heat and light are both important, and how much is needed varies from plant to plant. Many Gymnocalyciums need a lot of heat, most Rebutias don't.

I haven't had any open their flowers in the dark but then I don't keep my cacti in the dark. There are some nocturnal species but other than that they mostly open during the day and then close at night. Some open earlier in the day than others, but it isn't always easy to separate timing from temperature.

[OsedaxMucofloris]

Hi again

I see from the number of views logged that there has been some interest in the idea, even if no one can yet offer an answer. - sorry Ian didnt see your post

Surely if you enjoy cactus flowers, and I assume most of you do, then it would be great to be able to display them when you chose? Or is that too much a 'human' attitude? does it take some of the joy of nature's transient beauty away from your fascination? A big part of my enjoyment comes from trying to understand it...

Perhaps you are reading this and thinking "Fool! it's obvious.."

Anyway, I am going to pursue this through experimental observation, and report my findings here. This is actually more interesting to me than finding an answer via Google!

My hypothesis is that the necessary ingredient for the flowers to open is ultra-violet light. However, before I go and buy a UV lamp to test that, I'm first going to eliminate other possibilities.

1st step: I covered the cacti with boxes, excluding most light. Checking a short while later revealed that the flowers had closed up tight, having been approx 1/4 open. This suggests that it is indeed light that they respond to, not temperature (and therefore probably not infrared light).

2nd step: Exposing the cacti, outside, to sunlight.
I have done this, but during the late afternoon under an overcast sky, in England, so the intensity of sunlight is fairly minimal. There was some reaction, however. The flowers began to open from their tightly closed "night-time" state, to a looser bud, but didn't pass, say the 1/6 stage of opening (difficult to gauge).

Interestingly (to me), the yellow flowers reacted more than the pink ones. The flowers were equally exposed, and as they are very similar in structure, I speculate that the difference may have to do with pigment. I don't know what chemical function takes place that causes the opening

and closing, but I know that there is a difference in the efficiency of different shades of green leaves at absorbing useful light (to do with chlorophyll concentration). Perhaps yellow flowers are more responsive than pink for similar reasons. Certainly they are reflecting - and therefore absorbing - different colours of the visible spectrum.

I believe that performing the same experiment in the late morning under clearer skies will yield a more complete "opening" of the flowers.
That certainly will enable me to do the (clichéd) time-lapse photography I intend, as and when I am ready to make the flowers open.

Yet, I particularly want to display the flowers in the evening, for the benefit of people who are unable to see them during the day. I must therefore have to simulate sunlight, exposing the plants to the correct wavelength(s) of radiation from the spectrum.

We know that ambient home-lighting doesn't work, or the flowers would be open half the night. All my lights are "energy-saving" bulbs, which emit much more limited wavelengths than the old incandescent bulbs. (Incandescent bulbs emit a much broader continuous spectrum, inlcuding a high intensity of infra-red - which is why they get hot. That is why they are much less energy efficient). The reason I say this is that, whilst the extra wavelengths produced by an incandescent (tungsten) bulb are superfluous to the purpose of lighting a room, the broader spectrum might yield more reaction in the cacti flowers, but not with the intensity/energy that ambient room-lighting offers. My next experiment is to concentrate the light of an incandescent bulb on a cactus flower, through an aperture and lenses, and observe the effects. This probably all seems an absurd waste of time to anybody reading it. Especially as I expect to see no reaction from the incandescent light. It will help me to confirm that it is probably UV radiation that the flowers respond to. Then I can go and buy a UV lamp, feeling more confident that I'm not wasting money. Hopefully I'll not find that I need to produce gamma-waves or something to find an answer!!

At this point, may I thank anybody that has bothered to read this far. I'll try and give you a conclusive answer in due course. I apologise for my verbose approach, and amateurly scientific pretentions!

A further question that arises from contemplation and the reply by SkyClan Cat...
Some cacti (and other plants) flower only at night. If the flower opening is a response to sunlight, what is the trigger for nocturnal flowering, when there is NO (or very little)sunlight available to them? It might suggest that I'm way off the mark with my hypothesis.

hmmm...

I can speculate that perhaps nocturnal flowers are still light depenmdent, but there reaction is converse: they react to the removal of a light source. But that would not apply in the case of SkyClan Cat's Rebutia - because it is in isolation from sunlight, and presumably also experinces minmal temperature change...


I, please, welcome any input, critical or otherwise.

Regards, Simon.

[OsedaxMucofloris]

Ian

Thanks for your reply.

I agree that both heat and light are important, and that there are significant differences between various cacti species. I cant assume that my current observations can necessarily be applied to other species.
Certainly temperature is important over the longer-term - the micro-climate, as it were, of the plant's location, whether greenhouse, window-sill or basement.. however, I'm not convinced that slight changes in temperature have a bearing on the flower opening.
The flowers I'm currently playing with open for only a few hours, during which time I doubt much change in room temperature occurs. This is further supported by my "box" test. The flowers reacted to being deprived of light, yet I can assume that ambient temperature change was neglible. However, direct heating by absorption of infrared radiation from the sun would no longer have taken place.

I have conducted another test involving an incandescent light bulb. I used the yellow flower, as it showed most reaction in the previous test (whether the colour is significant or not). There was no reaction. The light was focused on the cactus, using a small aperture, parabolic mirror and lens, and the experiment was housed in a <badly> insulated, translucent enclosure, which excluded some of the extraneous ambient light, and contained the heat from the lamp. The bulb produces quite considerable infrared light, reaching the cactus directly and warming the air within the enclosure. It didn't occur to me to put a thermometer in, but the change in temperature was certainly noticeable.

As the flowers didn't react, I'm inclined towards the idea that temperature change, infrared light, and the visible spectrum of light are not a factor in the opening and closing of the flowers. This suggests that the ultraviolet radiation in sunlight may be the "active ingredient." But that isn't congruent with the evidence of nocturnal flowering. I don't know where to go from here, other than acquiring a UV lamp and testing its affect in isolation.

Anyone any suggestions?

Thanks, Simon

[apfire]

I am in no way a scientific expert. I have read about people raising hylocerus undus in Vietnam using 100 watt bulbs at night during certain times of the year to make the plants flower and produce fruit when it does not normally produce fruit. I also remember reading that certain amounts of light trigger a hormonal response in the plants to make them flower. Then there are studies of using various amounts of Gibberellic acid to make plants flower. It seems there is no magic bullet for all plants and they are so varied in the requirements for blooming of each species you could read the different studies almost forever. I look forward to reading your findings.

[luddhus]

If UV was the triggering factor then the flowers should not open much when behind glass. They do, so UV is not important.

I have made some experiments with this. Nothing systematic, but I have noted that different species react very differently, some species refuse to open if the time is wrong, at night for example.
Many cactus flowers can be forced to open by placing them under a strong light source, like a photo studio light. I have used a 250 W incandescent lamp with a reflector.

Something else: that your cactus has yellow flowers does not prove that it is not a Notocactus, yellow is a very common flower colour in that (sub)genus.

[Loph]

my money is on light. heat sure, but if the heat is right, and its sunny day vs cloudy day for some day bloomers, it means the difference between open or not. cant say much as all plants differ, but i really notice this here with day bloomers like Lophophora, Frailea, Gymnos. then other day bloomers seem to like certain photoperiods to start flowering, and once they begin to flower they may try and hold out for opening, but will still open on dark conditions...astros, arios, strombo, turbs etc...at least for me.

there are some local studies using light at night for Hylocereus crops to try and get longer fruiting season (they are very seasonal), and it has shown success. it has little to do with opening flower, as they always open once they grow at night and die once the sun is out for a few hours (regardless of temps, but dark days i see them open past noon).

i personally feel, at least for a lot of species, photoperiod and intensity is pretty important. i kind of think maybe like heat is opening the door and the light level dictates who walks outside.

[Peterthecactusguy]

Funny thing, but I have a Thelo, T. hexaedrophorus and both times it has bloomed it has rained the next day. Weird I know but its got a neat flower

As for what makes the flowers open, I would say are 2 factors. Amount of light and heat.

I am no expert but it seems that the heat is a factor as much as the amount of light.