Three different pigments - chlorophyll, flavonoids, and carotenoids - mixed in different proportions, give color to plants. By mixing and matching the three pigments, an endless variety of colors can be created. E.g. most reds are the result of mixing orange carotenoids with magenta flavonoids. Cellular pH (not to be confused with soil pH) has a profound effect on plant color.

Even most experienced gardeners think that lowering soil pH produces blue blooms in hydrangea. Technically, it is only a part of the equation. Lowering soil pH makes aluminum ions more readily available for plant uptake. The aluminum is then available to bond with pigment compounds (anthocyanin, the colored component of flavonoids) changing the way color is reflected. Our perception is blooms changing from pink to blue.

The anthocyanidin group is what makes apples, autumn leaves, roses, strawberries, and cranberries red. They make blueberries, cornflowers, and violets blue. They also make some grapes, blackberries, and red cabbage purple. One of the things that changes the color of anthocyanins
is the level of acid or alkali (the pH) in the cell surrounding the pigment. As cellular pH increases, the pigment changes structure and reflects different wavelengths of light. The anthocyanin reflects bright pink in acid cell environments, reddish-purple in neutral and green in more alkaline cells.

Since actual nutrient availability and possible nutrient "lock-up" or overload due to soil pH can also have an impact on cellular pH, it's a good bet that having your soil professionally tested for pH and to see what nutrient problems there might be would be a good first step to definitively identifying the cause of the changes you observe.

Al

Thanks very much, Al. Very helpful and I will try to get my soil tested - though I´m not sure if that is very easy out here. I might try to do it myself with one of those kits that I can get from garden centres when I am next over in the UK.
I am particularly interested in why I seem to be losing "the reds". Am I right in thinking that true reds are quite difficult to find...or am I perhaps just biased against those pinky reds that seem to be everywhere...?!
Thanks again and happy gardening.
Almeria

Al, I have question for you after reading ( very analytical)
your posting. Will feeding plants with of some of the vitamins in form of
powder or solution help color of flowers ?

Soil pH effect flower color in only a few plants. More likely you are seeing a response to different light levels that are either degrading or increasing pigments depending on the how the exposure you provide differs from that of the nursery.

Don't really know what caused it, but I have my own color change experience. When I was a kid, my Mom had some run-of-the-mill red roses. We lived near a lake and one day I came home with some Sunnies (fish) that I had caught, and my mother and i planted them in the rose garden. Wouldn't you know that those roses to changed to a rich, deep, salmon color! We liked the new color better.

windchime,

you mean they changed colors forevermore or only that season?

windchime,
Fish bones,scales etc. contain calcium phosphate.As the fish parts bio-degrade in the soil they release phosphate that plant can consume.In turn this will help plant to produce healthy flowers.
Your observation is correct.

I have the same thing going on in my Yellow Roses they are blooming and the Flowers have red edged petoles, could this just be pests? or More pigment, (sorry using more lamen terms). and i allways thought of The Reder color being like a suntan? Is that a false statment?
Cheers

Akheadbanger,

Red or purple is an anthocyanin pigment. Anthocyanins are often produced in cold temperatures (or as in autumn for deciduous tree leaves become apparent when other pigments are reduced).

Have your roses experienced cool or cold temperatures, cloudy rather than sunny skies?

admmad I have to disagree with you. Anthocyanins are generally known to be stress related pigments. Both cold and hot temps play a role in their expression. Salty coditions as well as too much light will affect them as well, pH will too. Moreover in the case of a stress they are expressed in leaves and stems rather than in flowers.
Carotenoids on the other side range from yellow to reds. And in this case, it is not impossible that the red edge (red as in tomato-red not red as red maple) is just other carotenoids, either because of the cultivar or because of too much light, etc.

Nazanine,

I agree that anthocyanin pigments are affected by various environmental factors, temperature, vacuolar pH, light (for example, that is why I asked about cloudiness), etc, but they are affected by those factors when they are well within normal ranges, that is even when a plant is not under stress and the effects are present in flowers as well as other tissues in those circumstances.

This quote is from research on the anthocyanin levels in aster flowers and is just one of many that investigate the effects of low temperatures on flower anthocyanin levels:
"Temperature is one of the main external factors affecting anthocyanin accumulation in plant tissues: low temperatures cause an increase and elevated temperatures cause a decrease in anthocyanin concentration." from Physiol Plant. 2002 Apr;114(4):559-565.

This quote is an indication of the effect of relatively unstressful temperatures on anthocyanin content: "the leaf anthocyanin content was thirty-five times higher in plants grown at 18 °C when compared to plants grown at 23 °C." from http://www.springerlink.com/(lnoqx5ydxmrrch552hxn3kih)/app/home/contribution.asp?referrer=parent&backto=issue,1,13;journal,65,86;linkingpublicationresults,1:100325,1

The tomato red is lycopene and is present in rose hips. However, anthocyanins (and in some plant species the related betalains) are the typical red pigments found in flowers. Rose flowers can have both anthocyanin pigments and carotenoid pigments, unlike many other species which have just one type of pigment.

Unfortunately, lycopene synthesis is inhibited by high temperatures and therefore it may be difficult to distinguish between these two suggestions and these are only two of what may be many possible explanations.

Admmad,
I think I did not make myself clear and I apologize.
When I talked about carotenoids, I talked about them in general. Reading that the rose colour should be yellow, it seems normal to think that anthocyanins are not involved (Otherwise the colour wouldn't be yellow, right?).

When I talked about tomato-red, I didn,t mean lycopene in particular, but since we were dealing with carotenoids, I thought it maybe helpful to mention tomato red, which means sort of an orangish-red as opposed to purple red (anthocyanin).

Asters have anthocyanins in their flowers and although I haven't read the paper I'm pretty sure that those fellows are comparing red asters' anthocyanin levels within different ranges of temperatures. Moreover, by no means should 18 C degrees be considered as a low temperature. It is a perfect normal physiological temperature.

I am not saying it can't be cold temperature (it could be actually very hot days, or drought for ex.), just wondering why the leaves and stems of the plant haven't experienced this redenning if it was some kind of stress.

Nazanine,

Reading that the rose colour should be yellow, it seems normal to think that anthocyanins are not involved (Otherwise the colour wouldn't be yellow, right?).

Ah...that may well be the problem.

Roses are capable of having both carotenoids and anthocyanins as flower pigments. In any particular rose cultivar the visible flower colour might be due only to carotenoids, only to anthocyanins or to any combination of both pigment types in various concentrations. This will depend on what particular alleles are present at the genetic loci in the two pathways.

If there is a mutation in a gene early in the carotenoid pathway such that no coloured pigment is produced then as long as the anthocyanin pathway is functioning normally the flower colour will be determined by anthocyanins alone.

If there is a mutation in a gene early in the anthocyanin pathway such that no coloured pigment is produced then as long as the carotenoid pathway is functioning normally the flower colour will be determined only by carotenoids.

If there were such mutations in both pathways the flower colour should be white or nearly so.

But if both pathways are functional then the colour of the flower will depend on the exact nature of which anthocyanins/flavonoids/carotenoids are produced and their concentrations.

A rose cultivar that produced both pigment types in its flowers might have yellow flowers most of the time. But the yellow could be due to a high concentration of carotentoids with a very low (unnoticeable to the human eye) concentration of anthocyanins. Such a cultivar might have flowers that were yellow with a blush/overlay of red when they opened on cool days in early spring and which then became pure yellow as the temperature increased during the day or as the sunlight became more intense for example. Later in the summer the flowers could open pure yellow during high daytime and nighttime temperatures. That is the balance between the carotenoid concentration and the anthocyanin concentration coul dchange due to temperature (or light), etc.

This is something that actually happens in some daylily cultivars which also have both pigment types in their flowers. Hemerocallis 'Matt' is yellow with a reddish overlay. On hot days the overlay is minor and disappears during the day, if it is present at all. On cool/cloudy days the overlay is enhanced and does not disappear. Daylilies can also have anthocyanin-based petal picotees and other more diffuse coloured petal edges and the intensity and width of such edges is affected by the temperatures during petal development and possibly bud opening.

Flower petal edges seem to have several intrinsic differences in comparison to petal centres as shown by such pigmentation differences. Those may be metabolically based (if there are meristems at the petal edges) or perhaps may be environmentally based (due to edges being more shaded in bud by overlying edges, or less shaded due to sepal edges, etc).

A more complex potential explanation would involve temperature-sensitive alleles. A mutation can have an effect only at permissive temperatures or it can have an affect at all temperatures. The yellow rose, if it is lacking in all anthocyanins could have a temperature-sensitive mutation in its anthocyanin metabolic pathway. That type of mutation would not even need to be related to low temperatures it could be related to high temperatures.

A temperature-sensitve mutation that only knocked-out the anthocyanin pathway at low temperatures would then show anthocyanin overlays at high temperatures but pure yellow flowers at low temperature.

A temperature-sensitve mutation that only knocked-out the anthocyanin pathway at high temperatures would then show anthocyanin overlays at low temperatures but pure yellow flowers at high temperatures.

The concentration of the overlay might depend on the specific environmental temperatures and the effect on the flower colour might be such that low anthocyanin over carotenoids was visible as an anthocyanin blush but high anthocyanin over carotenoids was visible as a yellowish-red or murky yellow-red-purple (brown/dusky?) or perhaps even as an orange.

The 18/23 temperature effects were quoted to indicate that most temperatures have effects on anthocyanin and thus the plant may not be in stress to show anthocyanin coloration.

Each tissue may have its own response to temperatures because it is not necessarily the same gene that determines the production of anthocyanins in different tissues. In this respect the anthocyanin pathways in leaves/stems may be completely independent of those in flowers.

Some species have duplicated at least some of the genes in the anthocyanin pathway such that some are activated in leaves and others are activated in flowers. For some specific species and specific genes there can be as many as five or six slightly different (sequence-wise) genes for the same biochemical function within the pathway.

Yes but do ALL roses have both pigments (yellow, white, etc.)?
I understand what you mean and I totally agree with what you say in the above paragraphs.
But please go back to your second reply on this post. You mention that the red is from anthocyanins and ask if the yellow rose has experienced cool or cold temperatures.

I would like to know why you are ruling out carotenoids, that's all.

Once again I agree with all you said above (different mutations, etc. even overexpression in some genes )

I would like to know why you are ruling out carotenoids

One can never completely rule out anything when living organisms are involved. However, in the vast majority of flower petals, when red colour is involved an anthocyanin pigment is present. A carotenoid pigment may or may not be present in the red flowers of some species.

I do not recall any plant species with red petals that does not have an anthocyanin pigment present and more often than not only anthocyanins are present.

For roses, since they are capable of and often have both pigment classes present in their petals it is possible that a yellow does not and cannot under any circumstances produce an anthocyanin pigment OR it is possible that a yellow can and does produce anthocyanins under some circumstances.

The article referenced below indicates that there is a class of yellow-flowered roses that contain anthocyanin pigments. It also indicates that there are classes of yellow roses that do not contain the anthocyanidins but do contain the precursor flavonols. When the carotenoids were extracted from rose flowers the colour ranged from colourless (0 rating) to very intensive yellow (5 rating).

In trying to narrow down the number of possible explanations for a colour change I begin with the most probable and work to the least probable. Petals that are red are known to typically have anthocyanins, plant tissues are known to have altered levels of anthocyanins based on temperature and light. Some yellow roses have anthocyanins in their petals. The explanation with the highest probability is that Akheadbanger's rose produces anthocyanins that redden the petal edges under some circumstances.

No explanation was ruled out, but no other explanation was ruled in. More information was requested to determine if the circumstances could rule out the most probable explanation. Scientific discovery uses Occam's razor (and modifications of it) as a working method (http://pespmc1.vub.ac.be/OCCAMRAZ.html). That is, until the simplest, most probable explanation is ruled out it is considered the most likely explanation.

Hi,

I think we might not be talking about the same roses. My reference is to akheadbanger's post where it is mentionned that his/her YELLOW roses have started to bloom and they have red-edged petoles(sic) (since akheadbanger has mentionned flowering, I presume he is talking about petals and not petioles).

If you go back to the article you mentionned and look in the table that is provided under Yellow roses, you can notice that in the anthocyanin (pelargonidin and cyanidin) column you see 0. Which means that medium yellow and deep yellow roses do NOT contain anthocyanins and are NOT supposed to have any reds (anthocyanin wise) in the flowers! The yellow blend (which is not supposed to akheadbanger's variety) however does contain anthocyanins.

For me, from this description, there are 2 possibilities :
1- The YELLOW rose that was purchased was mislabelled and akheadbanger bought a YELLOW with RED-edged flowered rose. (Remember that this is supposed to be neither a yellow blend nor orange, nor a red variety, it's supposed to be YELLOW).
In the case that it is a mislabelled rose that is supposed to have red-edged petals, I totally agree with you that it could be anthocyanins.

2- Since the yellow colour means carotenoids, and carotenoids means yellow, the most probable explanation for the 'red' edge is the presence of carotenoids. Either in higher concentrations, or just as a result of an environmental factor (photooxidation for example). Notice that I put the word 'red' in brackets because red can range from bright orange, to brownish red/orange.

So since the plant is not supposed to have reds, and under no circumstance are anthocyanins produced in tissue where the pathway is non existant, for me at least, anthocyanins are not involved.

Nazanine,

Notice that I put the word 'red' in brackets because red can range from bright orange, to brownish red/orange.

You are making a reasonable assumption that red can vary.
Akheadbanger wrote,
I have the same thing going on in my Yellow Roses they are blooming and the Flowers have red edged petoles

But in this case you are not making the reasonable assumption that the colour indicated by the term 'Yellow' can vary.

In my opinion that is inconsistent. The term 'Yellow' as used by Akheadbanger may mean light yellow, cream yellow, lemon yellow, gold, etc. It could just as easily mean yellow-blend. We simply do not know, just as the use of the term red may or may not mean crimson red, orange-red, purple-red, rusty red and so on.

One of the problems associated with flower colours is that the pigments are often present as mixtures of different concentrations which result in different colours to the naked eye. Depending on the ratio of carotenoids to anthocyanins a high carotenoid: very low anthocyanin can be seen as yellow.

Since the yellow colour means carotenoids, and carotenoids means yellow, the most probable explanation for the 'red' edge is the presence of carotenoids.

I do not see the logic to your statement. You seem to be saying since yellow colour means carotenoids then red must be carotenoids. I do see the logic in a statement such as since yellow often means carotenoids and red often means anthocyanins then red is most likely due to anthocyanins.

I did a search for red-flowered species with carotenoids in the petals and found none. Fruits do have 'red' carotenoids but I could not find any species with only carotenoid pigments in its petals that was red-flowered. I imagine that there are red-flowered species with carotenoids only but they must be infrequent in comparison to red-flowered species with anthocyanins.

So since the plant is not supposed to have reds, and under no circumstance are anthocyanins produced in tissue where the pathway is non existant, for me at least, anthocyanins are not involved.

I have indicated above roses have both the carotenoid pathway and the anthocyanin pathway in their petals. One or the other pathway may have a mutation in it that blocks the appearance of its associated pigments in some manner but that cannot delete the entire pathway. This is especially true as the pathway is used in relation to the process of photosynthesis as well as flower pigments in many species (although some species have duplicated genes that function in particular tissues only). The absence of a pigment does not mean the absence of the pathway. We have no way of knowing whether the anthocyanin pigments are truly absent in a flower labelled as yellow without appropriately analyzing the pigments.

In terms of your question about whether all roses have both pathways the question cannot be answered in either way - since no one has examined all roses. Therefore no assumption can be made that there are roses that lack the pathway. Disregarding the cultivated rose varieties and even just considering rose species - even those species with only yellow flowers are likely to have the anthocyanin pathway but possibly blocked by one or more mutations at a position in the pathway that stops the production of coloured pigments in the petals (or possibly reduces their concentration to levels not visible to the human eye). As long as my memory is not playing tricks with me I believe that has been actually found to be the case in another species.

In spring, new rose shoots may be red-coloured (see the web-site below) - normally they are green. If we examine a green leaf or stem we do not see any red colour. That does not mean that we conclude that the anthocyanin pigments are not present and the pathway does not exist in the leaf or stem. In fact anthocyanin pigments are present and the pathway does exist in the leaf and stem at all times. The red colour is not visible since the associated anthocyanin pigment is present in low concentrations and the green chlorophyll pigment is present in high concentrations and masks it.

However, something in the spring causes the anthocyanin pathway to produce more pigment and thus the red is visible.

In the autumn the chlorophyll in the leaves of many species degrades and along with other changes the anthocyanins (and carotenoids) become visible. Other changes may cause an increase in the production of anthocyanins as well.

The colour yellow in flower petals is associated with carotenoids (although yellow can also be due entirely to various pigments associated with the anthocyanin pathway); the colour red in petals is associated with anthocyanins (I have been unable to find a single species with carotenoids only in its petals and red-flowered). Many species, including roses show increases in anthocyanin production and the appearance of red pigment where none was visible before under some conditions. My suggestion is and remains that the red colouration may be due to a similar effect and be an anthocyanin pigment.

There are always many potential explanations for an observation and to find a reasonable (or the correct) one requires much work. In this case, as Akheadbanger has not reposted we have been unable to investigate the changes. For example, anthocyanins are water soluble, carotenoids are fat soluble. Placing a petal in warm water can extract anthocyanin pigments so it would be interesting to know what would happen to the red-edged petals. Warming or cooling the petal may also change the amount of pigment present and it would be interesting to know if the red edge changed in those conditions.

We have different opinions and without more information about this specific red-edged yellow rose we are probably not going to change them.

Please go back to the article you provided, it clearly mentions that yellow flowered roses do not have any anthocyanins (in flowers that is, not in shoots nor stems). I just don't understand why you cited an article that clearly contradicts what you say.

By yellow I mean all the yellows you mentionned: light, dark, creamy. So your theory about anthocyanins being masked by carotenoids does not hold.

To answer your question, or your remark on red carotenoids, I am sure that you are aware that not all carotenoids are yellow. They range from light yellow to brown. pH plays an important role as well as environmental factors.

You are right that we will probably not know until akheadbanger posts again and lets us know. For me this discussion has come to dead end.
Naz

My apologies for not noticing this for the discussion in the previous post.

On the web page for the inheritance of colour in roses (see a previous post above) all the colour classes for all the varieties examined were found to contain flavonols kaempferol and quercetin. Both of these are part of the anthocyanin pathway - they are the 'non-coloured' precursors to the anthocyanidins. This is clear evidence that the anthocyanin pathway is present in all roses but not necessarily producing measureable quantities (for the methods used) of the coloured anthocyanidins under normal circumstances for unknown reasons (which may differ between varieties).

The following quote may also be relevant:
"It is obvious that a working hybridist must find some method by which he can get some idea as to the purity of colour in the strain on which he is working. Two shades of deep yellow are available. The first is a mustard yellow such as Lydia [H. Robinson, 1949], which owes its intensity to its greenish tinge, showing that the red-blue factor is present and active. The other, such as Allgold, is a clear deep yellow with no green shade. By studying the whole flower one can see the difference. In the first case somewhere in the stigma, style, anther, or filament the red or green or both red and green will show. In the second case the pure colour extends through the whole flower; stigma, style, anther, and filament are of the same shade as the petal."

As the author indicates the red-blue factor I would have to assume that this is an indication of an anthocyanin factor as blue is associated with anthocyanins only and not carotenoids. In which case there are two types of deep yellow one with the factor and one without yet they both have deep yellow flowers although of different shades.

Nazanine,

We disagree about whether the term yellow-blend is a yellow or is not yellow. We also appear to disagree about whether a large amount of one pigment can hide a low amount of another.

Perhaps the rose cultivar shown below will bring the discussion to a focus. There are three flowers of Masquerade and the web-site indicates
"Some flowers seem to stay completely yellow, others stay cherry red, and many take on a mixture of the two"
{{gwi:432830}}

I would suggest that Akheadbanger's rose is perhaps an example of a similar effect (but less extreme and perhaps less obvious) as shown in the Masquerade rose - the flower can show completely yellow or the flower shows a mixture of the two colours as in the photo and perhaps never shows as completely red.

We have two alternative explanations:

A) The yellow pigment is a carotenoid and so is the cherry red pigment.

B) The yellow flower has a high carotenoid pigment concentration and a very low anthocyanin pigment concentration. The cherry-red flower has a high anthocyanin pigment concentration with carotenoid pigment present in some concentration.

You consider A as the most likely and I consider B as the most likely.

Admmad, the major problem here is that you are not talking about pure yellow roses. The examples you are giving are all either red / pink or red /pink with yellow, or yellow with red pink. In these of course there are anthocyanins, either masked or not.

I am talking about PURE yellow, plain yellow with no other colours than yellow. Go back to your first article and read it. The yellows contained no anthocyanins. So why do you want them to be masked when they're non-existant????
Another point, there are protocols for extracting anthocyanins . You can not just put a tissue in warm water and expect the anthocyanins to be expelled from cells because . If is was this simple there would'nt be so many red-coloured flowers in the tropics.

The presence of kaempferol and quercetin does not necessarily mean that red pigments are present. Just as the presence of some of the anthocyanins does not necessarily mean that delphinidin (TRUE blue pigment) is present.

Nazanine,

"Admmad, the major problem here is that you are not talking about pure yellow roses"

You are making the assumption that when Akheadbanger used the term 'yellow' that 'pure yellow' was meant. That is inappropriate. One cannot know that any yellow flower is pure yellow unless one examines the flower for all its pigments. One would have to show that there were no other pigments present in any concentration in such a flower with any absorption at any other wavelengths other than those that are labelled 'yellow'. I consider that the human eye is inadequate to label a flower colour as being pure.

The examples you are giving are all either red / pink or red /pink with yellow, or yellow with red pink. In these of course there are anthocyanins, either masked or not.

A masked pigment is not visible, by definition. Therefore, when an anthocyanin is masked because it is at very low concentration by a carotenoid at high concentration it is not visible as pink or any other shade.

You are making the assumption that a rose that can make anthocyanins will show at least some red colouration all the time. I am not making that assumption. It clearly is not reasonable to assume that the human eye can identify all concentrations of one pigment included with another or that plants that obviously have different concentrations of red pigment cannot have low enough concentrations that are not visible to the human eye. In my personal experience, with other plant species, cultivars that show varying amounts of red over yellow pigments are clearly able to produce flowers that show no visible red at some times.

Please re-read the quote regarding the colour of 'Masquerade' - the statement made is 'completely yellow'.

The changing flower colour (Akheadbanger's) was yellow (of some sort that is unknown in exact shade and cannot be assumed to be 'pure yellow') at some point it then had a red pigment develop on its petal edges. That is the flower had both red and yellow in it just as the 'Masquerade' type flower was 'completely yellow' and then had both red and yellow in it.

I am talking about PURE yellow, plain yellow with no other colours than yellow

You are but it is unreasonable to make as narrow an assumption for Akheadbanger. We do not know that Akheadbanger's classification of flower colours is narrow or broad, that is, if an individual classifies flower colours as being white or yellow or orange or red or purple where would the intermediate mixtures be classified by that individual?

You are also making the assumption that a yellow flowered rose that has the ability to develop red colouration will always show red colouration under all circumstances and at all times. That such flowers show different degrees of red colouration from being described as 'completely yellow' to being 'cherry-red' clearly indicates that the amount of red varies widely - but you appear to disallow the possibility that under some conditions there is no visible red in some such flowers (as in 'completely yellow'). It would appear that by your definition of 'yellow' a plant that produced a continuous range of red pigment concentrations had to always produce enough red pigment so that it would be visible to the human eye and therefore the flower colour would never be adequately described as 'yellow'.

As an example, let's say if the red pigment concentration had to be 3% (of the yellow pigment concentration) to be visible in a yellow flower by your definition of yellow-flowered roses such a plant could not produce less than 3% (or the amount that makes the pigment visible to the human eye) red pigment under any circumstances. I do not make such an assumption. I assume that there may be cultivars that are capable of producing concentrations of red pigment below the human threshold of recognition as red pigment (say 0.01% as an example) which can then under other circumstances increase the production of the red pigment to visible concentrations

The yellows contained no anthocyanins.

Your definitition of the term yellow is unreasonably narrow and limited. Examine the table in the article. Yellow-blends contain anthocyanins. You are making the assumption that all yellows that contain anthocyanins show the anthocyanins. You are not considering the possibility that a yellow with less anthocyanin present than a yellow-blend such that it would not show any red in some circumstances would under the appropriate circumstances show red pigment (just as Masquerade does) and have been classified as a 'yellow-blend'. You are not considering the possibility that the methods used in that particular article could not detect very low levels of anthocyanins in all cultivars. You are not considering the possibility that the yellow cultivars chosen to be examined did not include a yellow that would then shade to red (perhaps because such a cultivar would have been automatically placed in the yellow-blend category) or just by chance.

Another point, there are protocols for extracting anthocyanins

Of course there are very sophisticated ones, but that does not mean that simple procedures cannot also provide acceptable results.

You can not just put a tissue in warm water and expect the anthocyanins to be expelled from cells because .

Actually you can, I have and they do. This website describes extracting anthocyanins from red cabbage with boiling water http://chemistry.about.com/library/weekly/aa012803a.htm
One does not need to use boiling water, water from a hot water faucet does work with flower petals. Boiling water destroys the tissue structure, depending on the temperature of the water used the petal structure can survive the treatment and still extract some of the anthocyanin pigment.

If is was this simple there would'nt be so many red-coloured flowers in the tropics.

My apologies, but I did not mean to imply that warm water was rainwater warm. The temperature of the water needs to be high enough that it breaks down some of the epidermal cellular structure (but if you want to save the petal structure not so hot that the petal turns to mush).
The presence of kaempferol and quercetin does not necessarily mean that red pigments are present

You are misinterpreting my statements related to the presence of kaempferol and quercetin. You made the statement "So since the plant is not supposed to have reds, and under no circumstance are anthocyanins produced in tissue where the pathway is non existant, for me at least, anthocyanins are not involved."

Since the presence of kaempferol and quercetin in all rose colour classes indicates that the pathway is indeed present in all rose colour classes then your statement regarding the non-existence of the pathway is not relevant.

Akheadbanger, under your narrow definition of the term yellow and your wide definition of the term red, both as used by Akheadbanger you consider that the red colouration is likely to be a carotenoid pigment.

From the analogy of rose cultivars such as Masquerade and Charleston (which has been shown to have carotenoids when yellow and anthocyanins when red Phytochemistry 12:1783-1786, 1973) I consider that Akheadbanger's flower may have much lower concentrations of anthocyanins than those two examples such that in certain conditions the flower can be described as yellow because of its carotenoids and under other conditions it can show red tinges because of increased anthocyanins. Since it is known that specific roses can have high carotenoid and low anthocyanin pigments sometimes and then produce more anthocyanins at other times I consider that sort of explanation more probable.

Nazanine,

You wrote:

"I am talking about PURE yellow, plain yellow with no other colours than yellow."

How can you persist in describing Akheadbanger's rose as 'pure yellow'? By your own definition they are not pure yellow. Even if the flowers were yellow on one day and yellow and red-edged on another day they would not be "yellow with no other colours than yellow" since there are an unknown number of occasions when they also have red pigment.

Akheadbanger wrote:

"I have the same thing going on in my Yellow Roses they are blooming and the Flowers have red edged"

From this statement we do not know if the 'yellow' roses have bloomed with flowers with only yellow pigment on one day or many days. We do not know if the flowers have only yellow pigment on few days and red-edges on many days or vice versa.

The assumption that the 'yellow' rose is a 'pure yellow' is not supported.

Hi,
I think you are wrong in saying that I am making the assumption that it's carotenoids. Actually, I wanted you to answer the question I asked you earlier, ie, why can't it be carotenoids? You seemed too quick and too certain when you stated that 'red is anthocyanins which are often produced in cool/cold temperatures' (both statements are wrong).

The first article you provided us with states that pure yellow roses do not contain anthocyanins.
Now you say that kaempferol and quercetin are a sign that the anthocyanin pathway is present. (Wrong again)

Pigment extractions of that sort are very common, with cabbage, beet, spinach, carrots, etc. any plant or plant part that has too much of a pigment. To extract those pigments you can either boil the tissues or cut them in pieces, or both. You do this to disrupt cell membranes so that the pigment (be it hydrophilic or -phobic) spills out of the cells. If you put this plant tissue in water,without any treatment, theoretically you should not have any pigment spills since no cell membranes are ruptured. These experiments are usually done in class to give the students a chance to work with pigments. All the plants listed above are good candidates since they have lots of one pigment, so each student is able to get tons of pigments without no trouble.

In our case, it is different. Because we don't know what pigment we are dealing with. Even if the pigment IS anthocyanin, it will not readily cross membranes. You'll have to boil the petals or cut them into pieces. Once you do that, nothing proves that it can not be carotenoids. Since the membranes are disrupted, pigments will spill out (be it hydrophobic or -philic). Once again there are specific protocols (and not necessarily sophisticated) that help determine the nature of pigments without making false assumptions.

Once again it is not that I don't agree that it may be anthocyanins, yes it can, but I think you were too quick on assuming that it was anthocyanins and nothing else.

All summer my roses had been colored Yellow, sence we purchased it this year. The color was yellow up until recently it was only on a few sets of blooms, and yes it had started getting cloudyer and colder, and more rain. Could the dye in the Mulch have ne thing to do with it? (we have red mulch). Sry i dont konw what the name of the plant is.

Cheers

'red is anthocyanins which are often produced in cool/cold temperatures' (both statements are wrong).
I have provided references above indicating that low temperatures do indeed cause increases in anthocyanins in plants - there are dozens of research papers indicating this and here is another:
THE EFFECT OF TEMPERATURE AND LIGHT ON GROWTH AND FLOWERING OF ROSA 'BACCARA' IN GREENHOUSES from Acta Hort 14
The abstract states the following "Low temperature has generally resulted in higher anthocyanin content in the plants (Harborne 1967)."

I have undertaken several searches looking for any plant species that has been found to have only carotenoids in its flower petals and is red - I have found none in the scientific literature. As I mentioned previously I fully expect that since living organisms are so varied that there probably are some but they are obviously very infrequent. All other species with red flower petals contain anthocyanins (or the related betalains).
Here is just one of many quotes regarding red and anthocyanins in plants "Almost any flower, fruit, or plant part that is red, blue, or purple contains a class of chemical compounds called anthocyanins that change color with pH" and is taken from http://antoine.frostburg.edu/chem/senese/101/acidbase/faq/household-indicators.shtml

kaempferol and quercetin are a sign that the anthocyanin pathway is present. (Wrong again)

Below is a copy of the anthocyanin pathway from a course at Purdue University. Note from http://www.intl-pag.org/4/abstracts/p269.html that "Chalcone synthase is a key enzyme in anthocyanin biosynthesis."

Note that both kaempferol and quercetin are indeed members of the anthocyanin pathway and therefore their presence indicates that the pathway is present. Kaempferol is produced from dihydrokaempferol and quercetin is produced from dihydroquercetin. Cyanidin is also produced from dihydroquercetin with intermediate steps. The fact that the pathway is present does not necessarily mean that all enzymes in the pathway are functional, but even if not switched-on it does mean that they may be able to be switched-on.

At this point I am going to review the potential explanations.

A yellow flower may be yellow because it contains carotenoid pigments only. Or it may be yellow because it contains chalcone pigments, aurone pigments or various other yellow pigments only. Or it may contain any of those pigments in mixtures along with various non-coloured or light cream coloured flavonoids. There are species that have been found with these pigments in the petals of their flowers.

The most frequently found pigment in yellow petals are carotenoids.

A red flower may contain only anthocyanin pigments, or only betalain pigments or it may contain anthocyanin pigments and carotenoid pigments in mixture. I have been unable to find research that indicated that any species has red petals and only has carotenoid pigments.

The most frequently found pigment in red flowers are anthocyanins.

In those flowers which can be yellow at some time and in some conditions, and red or red and yellow at some other time and other conditions (such as various roses) the yellow pigments have been identified as carotenoids and the red pigments have been identified as anthocyanins.

In my opinion it is highly unlikely that the red pigment that appeared in Akheadbanger's roses was a carotenoid - I have been unable to find any plant species that has red petals and contains carotenoids without also containing anthocyanins. In my opinion it is highly likely that the red pigment was an anthocyanin.

Since there appear to be no red flowers with carotenoid pigments only and since the scientific literature indicates that flowers that can be yellow and red do contain anthocyanins, especially roses, I am unlikely to consider that the red pigment in the rose petals is a carotenoid simply because there are reddish carotenoids present in some fruit.

We had yellow dalihas last year that are now white this year.
This has happened before.WHY