Flower Color in Daylilies by Tom Hart

Flower color in daylilies has been discussed for quite some time. This discussion may not be warranted for the knowledgeable today. Here I will try to present a simplified version for the non-scientists among us. Please allow me to throw in a few terms. You need not remember them unless you are really interested.

Flowers tend to be brightly colored to attract pollinators. We often think of bees as being major pollinators of flowers and while this is true in general, this is may not be the case in all of our daylilies. Small bees will collect pollen from the anthers and by mistake will they transfer the pollen to the stigma. This does happen but more often bee pollination is unsuccessful. The structure of many daylily flowers is one that lends itself to pollination by moths. This can be easily seen in the trumpet shaped nocturnal species. When the stigma is close to the position of the anthers and the flowers are diurnal, then bees are likely to be important pollinators. We have attempted to eliminate the trumpet shape and produce flowers that have the corolla come out at nearly right angles. This makes the actions by moths and nectar collecting bees much less efficient because it is unlikely that the insects will come into contact with the stigma and stamens.

Daylilies are colored as a means of attracting insects to see and get nectar and/or pollen from the flowers. All the major colors seen in today’s daylilies can be produced by variations in only five different color producing pigments. The colors are green, melon, yellow, red and violet. Green, melon and yellow colors are produced by flower pigments inside structures called plastids in the cytoplasm of some of the plant cells. Plastid are passed on by the pod parent and are not found in the sperm. The last two colors are water-soluble pigments dispersed within the cell (actually in very large structures called vacuoles). There are a number of other pigments such as flavonoids and flavonols, which may be visible to insects but not to us. These pigments may also affect the color of the anthocyanins, which we see.

The green pigment in leaves and the throats and some of our daylily edges is called chlorophyll. It is localized within the plastids and is responsible for the production of sugars from sunlight, which is called photosynthesis. This is the source of all the energy we consume to keep us alive. Also in the plastids and necessary for photosynthesis to occur are the carotenoids. Plastids, with chlorophyll and carotenoids, are not normally found in the outermost layer (epidermis) of the flower parts. One of the yellow pigments is beta-carotene (one molecule can be split by the human body to produce two molecules of Vitamin A). There are a number of other yellow carotenoids besides beta-carotene. In daylilies, zeaxanthin and violaxanthin appear to be the most important. A precursor is lycopene, which is melon colored or orange in higher amounts. Tomatoes are orange or red due to high concentrations of lycopene. We have not yet found high enough concentrations of lycopene in daylilies to produce a red flower color.

No carotenoids/xanthophylls or chlorophyll		Carotenoids present but NO chlorophyll

The other important pigments found in daylilies are water-soluble anthocyanins. Anthocyanins are located in the cell sap, not in the cytoplasm or plastids. They may be found anywhere in the petals or sepals but they are often concentrated in the epidermis, thus a cross section of a flower part will often appear to have layered colors. Cyanidin and delphinidin have been found in Hemerocallis. The colors of both will vary depending on the pH or acidity of the cell sap. In a test tube they both tend to be red under acid conditions and blue under alkaline conditions. Cyanidin in daylilies tends to be red in color while delphinidin appears purple or violet. Some daylilies have only cyanidin, some have only delphinidin, some have both, and some have neither.

Green– Chlorophyll

Yellow/orange – Carotenoids and xanthophylls

Orange – Carotenoids, xanthophylls and Cyanidin (yellow and red)

Melon – Lycopene or carotenoids and some Cyanidin

Red/pink –Cyanidin (red)

Purple/violet – Delphinidin (purple or violet)

Red violet –Delphinidin and Cyanidin (purple or violet and red)

Brown – Delphinidin (or Delphinidin and Cyanidin) and Beta-carotene (purple or violet and yellow)

White – no pigments

Variations in the amount of pigment produced will change the intensity of the color. The appearance of red or purple colors over yellow or orange is not imaginary. Remember that it is common for the water-soluble anthocyanins (cyanidin and delphinidin) to be found in the upper epidermis while the yellow and orange carotenoids are located in the internal cells of the flower. The presence of lycopene or beta-carotene in red, pink or purple flowers may be the reason that some flowers have a drab or muddy appearance.

Blue Daylilies

Much discussion has occurred about delphinidin and why it doesn’t show a blue color in the flower as one might expect. This may be due to the pH of the cell sap or the presence of other compounds in the cell, which might modify the color produced. The compound quercetin (a flavonol) is often stated to be an important co-pigment with delphinidin to produce a blue color. Kasha, et.al hypothesizes that the daylily might be similar to the sweet pea as far as flower color is concerned. In the sweet pea, the blue pigment is due to malvidin (similar to delphinidin) combining with quercetin and another compound called kaempferol to produce the blue pigment.

It is interesting to note that particular daylilies like Grace Stamile’s Hemerocallis 'Got the Blues’ and Modavan’s H. ‘Piece of the Sky’ have a definite blue color to the eye. The photograph of ‘Got the Blues’ shows both the blue and red pigments in the flower. If the carotenoids could be eliminated the blue might be even brighter.

Steve Moldovan crossed a reddish patterned-eyed ‘Digital Imagery’ (Moldovan) times a purple-eyed ‘Vertical Horizon’ (Moldovan) resulting in the first blue-eyed daylily named ‘Piece of the Sky’. The blue of the eye is noticeably variable under different environmental conditions. This cross supports the idea that both cyanidin and delphinidin should be involved. The question remains, is the blue color of the eye due to delphinidin complexed with another compound or is delphindin the only pigment in the eye and the blue color due to a decrease in pH? If, as has been theorized, a quercetin/delphinidin complex is what causes the blue color, then in the eye of ‘Piece of the Sky’ and ‘Got the Blues’ quercetin may be produced instead of or in addition to cyanidin. What is different about the daylily eye? What must be done to transfer the blue color to the rest of the flower? Is it purely a matter of pigment concentration or is there more to it?

Chromosomal mutations may occur when one or more genes are transferred from one location on a chromosome to another or from one chromosome to another. Particular portions of the chromosomes are active in enzyme production at different times. For example, cells of the throat may be producing particular pigments while cells of the eye, leaf, root, etc. may be synthesizing completely different enzymes. Specific genes may be moved by a process called crossing over from an inactivechromosome location to an active location and visa versa. Hence, genes responsible for the production of eye pigments may be relocated to locations, which are inactive or even active for some other function like the color of the stamen filament, self or throat. In time, with hybridizing, the chromosomal mutations will rearrange the genes on the chromosomes so that the blue pigments we now have in the eye of some of our daylilies will be found in other parts of the flower as well. The speed with which this will occur depends on the rate of chromosomal mutations in daylilies, how close the involved genes are on the chromosome, if they are on the same chromosome, the number of blue-eyed times blue-eyed flowers that are crossed and probably other factors as well.

Today we have bluish daylilies and we have whitish daylilies. The problem is the flowers are not really blue or white enough to satisfy us. Few will argue that the some flowers have no blue pigment of are almost lacking pigments making them nearly white.

Distribution of colors in the Daylily flower.

H. fulva (wild Daylily)	‘Lady Betty Fretz’

Note the eye in H. fulva. Many of our modern daylilies have the eye color extended to the edge of the petals giving the petals a dark edge, which extends towards or to the tip of the petals. Even throat colors may be seen on the very edge of the petals. In ‘Lady Betty Fretz’ (Petit), the edge is red (from the eye) and outside that is yellow (from the outer throat). In time we might expect the very outer edge to show colors from the inner portion of the throat as well. This can be seen in some of the green edged daylilies such as ‘Leslie Renee’ (Stamile). More desirable might be varieties, which show the edge on the sepals as well as the petals. Two examples of new daylilies with teeth on both petals and sepals are ‘Puffer Fish’ and ‘Heavenly Pink Fang’ by Jamie Gossard.

Certain edges such as in ‘Mort Morss’ (Salter) may be produced in a different manner. The edge and teeth here does not appear to be as easily associated with eye or throat colors. Here the edge and associated teeth are found on both the sepals and the petals and are white while the outer throat is yellow. If 'Mort Morss' is examined closely it appears that there is very little yellow pigment in the self. It may be this lack of color on the extreme outer region of the throat that is carried over to the teeth. ‘Fortunes Dearest’ (Morss) and ‘Face of the Stars’ (Lambertson) are similar but lack the teeth on the sepals. Velvet appearance to the corolla Most upper epidermal cells are rounded on the top. In some cases, more common on red flowers at the present time, there are extensions on the surface (I won’t tell you what my wife calls them). These give the impression that the flower is covered with velvet. One of the reasons that ‘Ashwood Dark Side’ (Norris) has the appearance it does is because of the extensions on some of the epidermal cells. There is probably no reason that flowers of other colors are or will eventually also be covered with this "velvet" surface. The development of longer extensions through time may drastically change the appearance of the flowers

Diamond or Gold Dusting

Diamond dusting has been theorized by some to be due to crystals located in the upper epidermis. Many plants do have crystal of various kinds (druses and raphids) in some of the cells but none would be expected to reflect light as seen with diamond dusting. Microscopic examination of the cells has failed to show the presence of any crystals in the epidermis of daylilies. Some cells do show a domed surface and are slightly larger and extend deeper than others. These larger cells might reflect more light than normal to cause the diamond-dusted appearance in some of the daylilies. Corn has somewhat similar large (much larger) cells called bulliform cells. In corn leaves the cells are in rows and cause the leaf to curl during drought conditions. The "bulliform" cells of daylilies appear to be scattered and their function, if any, is probably unknown. Also seen are fairly large depressions in the epidermis. These may be associated with reflecting light but typically such depressions in the outer layer of cells contain glands.

Light Midribs

With the anthocyanin pigment being concentrated in the epidermal regions of the flower parts and the carotenoids being located internal, coloring may vary depending on the thickness of the different tissues. A thin epidermis may cause a decrease in the storage of the red and violet pigments, while the lack of photosynthetic tissues above the major veins will decrease yellow pigments.

Decrease epidermal thickness causing a light midrib	Darker midrib caused by a thicker epidermis	Spots on 'Sprinkled With Paprika'

Colored Dots on the flower

Barbara McClintock was basically isolated from the scientific community in 1951, when she hypothesized that the genes responsible for particular characteristics could move from one location to another in corn. It wasn’t until thirty years later that she was able to convince everyone that she had been right. We may have an example of this in Holley’s, 2005, ‘Sprinkled with Paprika’. Maybe there is another explanation for the small-scattered spots on the petals of daylilies. Spotting is not unusual in many of today’s other daylilies such as ‘Connect the Dots’ (Jerabek) and ‘Stippled Tapestry’(Lambertson).

Our understanding of the pigments, the way they act and the genetics behind them will change as we learn more about what is going on.

Determination of Anthocyanin Presence

Pigments according to Bisset

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