Leaves change color in the fall, because the chemical changes in the leaves, as their nutrients drain into the tree’s branches, trunk, and roots for winter storage, cause the leaves to stop producing the green pigment chlorophyll. When the pigment chlorophyll departs, secondary pigments, substances that also absorb light, emerge to take its place, and change the leaves’ colors to theirs.

Example:

Yellow and Orange leaves contain the Pigment Carotene, the same Pigment that gives carrots their Bright Orange color.

Sunlight affect the following factors there by color change will occur in leaves and flowers

Carotenoids

Anthocyanis

Flavonols

Carotenoids:

With all pigments, the more pigment the flower produces in the bud, the brighter its colors will be. With carotenoids, a little bit of pigment makes a soft yellow flower. As the pigment levels increase, flowers become increasingly vivid yellows, oranges, and reds. This is the progression that a tomato follows as it ripens, gradually increasing production of carotenoids until it is fully ripe and red. Carotenoids increase production in response to heat and lots of sun. The hotter and sunnier the weather gets, the more carotenoids a plant produces, the brighter the oranges and reds will get. When weather cools off, carotenoid production decreases, and colors become softer oranges and yellows.

Anthocyanins:

Anthocyanins are best known as the red pigment in fall leave. They are much less stable than carotenoids. The least little change in the environment or health of the plant affects the sap, which means it also affects the anthocyanins. Some anthocyanins are very sensitive to heat. Enzymes in plant sap completely destroy several of the anthocyanins in hot weather and bright sunlight.

Flavonols:

Flavonols are in the flavanoid family with anthocyanins, and have all the same characteristics of anthocyanins - they degrade in heat and lots of bright light, and they increase in a healthy plant and in cold weather.

Indeed interesting research, especially the relation to human behavior.

Dr. Gupta,

I seem to recall some early work by Japanese researchers suggesting that it was not just pH that led to the difference in color. I believe that they associated some of teh blue color to divalent cations, especially calcium and magnesium. Of course, as the pH changes with the efflux of K+ and Na+ and the increase in H+, the divalent metal dissociates from the anthocyanin leading to the bathochromic shift (reddening). Is the blue in Ipomoea related to divalent cations?

Mr.Joe Olechno,

I agree with your opinion of color change due to K+ and Na+ divalent cations and the increase in H+ along with that one more factor is " inactivation of single gene"

Violet-blue flowers of Ipomoea purpurea are based on a Cyanidin backbone, while red-purple blowers are based on the pelargonidin backbone. The difference between Pelargonidin and cyanidin is the Hydroxyl Group in the 3'-position of the B-ring of the Flavonoid backbone, and this is also the necessary requirement for the Methylation to Peonidin. The hydroxylation is carried out by a cytochrome P450 enzyme, a Flavonoid 3'-Hydroxylase also known from many other plants, and the destruction of this gene activity is the most important factor in color changes in the flowers

The major anthocyanin in blue morning glory flowers, Peonidin 3-(Dicaffeylsophoroside)- 5-Glucoside, is stable in a neutral aqueous solution and is solely responsible for the color of the flowers. Co-ocurring flavonols based on quercetin at the pH's of epidermal cells have no effect on the color of the anthocyanin. Deep or strong Reddish-Purple buds change to moderate or light blue open flowers within a 4 hr period, and during this time the pH of epidermal tissue increases from 6.5 to 7.5

How does sun light effect in changing colour of leaf, flower colour?

Leaves change color in the fall, because the chemical changes in the leaves, as their nutrients drain into the tree’s branches, trunk, and roots for winter storage, cause the leaves to stop producing the green pigment chlorophyll. When the pigment chlorophyll departs, secondary pigments, substances that also absorb light, emerge to take its place, and change the leaves’ colors to theirs.

Example:

Yellow and Orange leaves contain the Pigment Carotene, the same Pigment that gives carrots their Bright Orange color.

Sunlight affect the following factors there by color change will occur in leaves and flowers

Carotenoids

Anthocyanis

Flavonols

Carotenoids:

With all pigments, the more pigment the flower produces in the bud, the brighter its colors will be. With carotenoids, a little bit of pigment makes a soft yellow flower. As the pigment levels increase, flowers become increasingly vivid yellows, oranges, and reds. This is the progression that a tomato follows as it ripens, gradually increasing production of carotenoids until it is fully ripe and red. Carotenoids increase production in response to heat and lots of sun. The hotter and sunnier the weather gets, the more carotenoids a plant produces, the brighter the oranges and reds will get. When weather cools off, carotenoid production decreases, and colors become softer oranges and yellows.

Anthocyanins:

Anthocyanins are best known as the red pigment in fall leave. They are much less stable than carotenoids. The least little change in the environment or health of the plant affects the sap, which means it also affects the anthocyanins. Some anthocyanins are very sensitive to heat. Enzymes in plant sap completely destroy several of the anthocyanins in hot weather and bright sunlight.

Flavonols:

Flavonols are in the flavanoid family with anthocyanins, and have all the same characteristics of anthocyanins - they degrade in heat and lots of bright light, and they increase in a healthy plant and in cold weather.

It's really interesting for all, especially for somebody like me, who discovers the world of plants.

I thank you. My students, too, off course!

I just wanted to follow-up on the impact of polyvalent cations on the color of anthocyanins. While in Ipomoea, the purple and blue colors may be a simple matter of pH, in other flowers the case is a little different. Cornflowers (Centaurea cyanus) are a beautiful sky blue. But the anthocyanidin responsible for the color is cyaniding, the same compound that makes roses, cherries and cranberries red. In cornflowers, six molecules of anthocyanin (an acylated cyaniding diglucoside) associate with six flavone molecules, one molecule of ferric ion, one magnesium ion and two calcium ion to form the beautiful blue pigment (see oregonstate.edu/instruction/bb317/flowercolor.pdf).

I wanted to point out that while anthocyanins should be colorless when the pH is between 4 and 5 (when they are in the carbinol pseudo-base structure), they are often colored because polyvalent cations in solution stabilize the other structures. You can also see the impact of the aluminum cation on anthocyanins at www.demochem.de/p26_anth-e.htm . The ethanol extract of the rose petals is very faint but becomes deep red with acid, deep blue with base (but at even higher pH they turn yellow) but when aluminum chloride is added, the solution becomes a deep violet. So, while pH has a significant effect, other flavonoids and various cations can also impact color.

Concerning carotenoids, the concentration of the various carotenoids will affect the depth of color but the individual carotenoids can affect the actual hue. For example, lycopene is a deep red (see http://en.wikipedia.org/wiki/File:Lycopene_powder.jpg), zeaxanthin is orange (http://plant-extracts.en.alibaba.com/product/392271412-211945829/Natural_Color_Zeaxanthin_Marigold_Extract_Lutein.html) and phtyoene is colorless. Low concentrations of both lycopene and zeaxanthin will appear yellow—zeaxanthin gives maize its characteristic yellow color.

Thanks a lot Mr.Joe Olechno for giving detailed information.

I would like to know about role of Flavonols in plants.

Hi! Could any of you (for instance, Dr Gupta) send a paper of concern to me via researchgate firstly?

I will thereafter personally reply to him (to her) for thanking. I would especially like to know how to cite his (her) work in our future papers, my collaborators and me. I am a chemist and teacher in Algeria but I really discover the world of plants and natural colors. We try to know which components are exactly present in the cacti and in the oxalis (excluding the potassium or sodium or ammonium oxalates), like the ascorbic acids, the other vitamins, anthocyanins etc. Unfortunately, we have no working HPLC device, neither Soxhlet apparatus. We have just the matter (invader plant, oxalis), the vessels and the shaker, and the UV and IR for the characterization of the liquid and solid part but you know that it is "dramatically" unsufficient.

Many thanks and good following

Happy New Year and Merry Christmas for the Christians and for all.

Amar Mecherri

PS1: I am not so sweet at 59 years old, but Amar means (amazingly) love in Spanish. Such a luck!

PS2: I apologize for my "poor" English, as I am not a native speaker.

Mr.med-oimar Mecherri,I would like to know what are all the factors involved in color of a flowers,leaves?

In response to the question about components in both Oxalis and the cacti, let me mention only those components associated with color.

Oxalis is often tinted purple due to malvidin-based anthocyanins. See Acylated anthocyanins from leaves of Oxalis triangularis by Torgils Fossen, Saleh Rayyan, Maya H Holmberg, Håvard S Nateland, Øyvind M Andersen (http://www.mendeley.com/research/acylated-anthocyanins-leaves-oxalis-triangularis/ ) and Anthocyanins from Oxalis triangularis as potential food colorants by E. Alexandra Pazmiño-Durán, M. Mónica Giusti, Ronald E. Wrolstad, M.Beatriz A. Glória (http://www.sciencedirect.com/science/article/pii/S0308814601002011).

Malvidin

Cacti, like many other plants in the Caryophyllales, use a completely different set of compounds for their colors, the betalains. These compounds (also found in beetroot, amaranth and chard) are completely unrelated to anthocyanins. Rather than coming from the amino acid, phenylalanine, via the phenylalanine-ammonia lyase pathway they are derived from tyrosine and contain an indole structure.

Betalain

Common wisdom in the past suggested that plants had either anthocyanins or betalains but some research suggests that some plants may have both (Identification of Anthocyanins? in Cactaceae by LC-ESI-MS-MS by Charles A. Johnson, Paul A. Campbell, Mindy Walker, Chad M. Scholes, and James M. Chapman (http://www.rockhurst.edu/academic/chemistry/documents/IdentificationofAnthocyaninsinCactaceaebyLCESIMS-MS.pdf)

Sorry, the images did not transfer in the earlier message. I have attached malvidin here..

And betalain is here.

I thank you so much, dear Sir. I see that things are so complex and I have to learn the minimum for digesting it all. There is no doubt that the references you give me so kindly will help me to get a clearer picture and your thoughtful comments will be very useful before further reading. You are an angel!

Is the following malvidin structure correct, Sir?

Yes, that is the correct structure.

Thanks a lot, Sir. I will surely keep you informed of my work in progress.