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Re: HYB: Lycopene color(s)

Some thoughts re lycopene red iris. This is a problem I have given some thought to and done some research. Why can't we have tomato red irs.

First look at the cell structure.

Bearded iris can have papillae of various heights on top of falls but not elsewhere and beard hairs may even be an extreme expression of this. The petals have three cell layers and top and bottom epidermis are very thin and join at edge , sandwiching a thick mesophyll layer. Epidermis layers are 90% vacuole. the mesophyll layer is mostly plastids with comparatively small vacuoles.

(So what is the structure of the beards? Any one have any ideas? I havenbt run across any info.)

Thus the water soluble pigments are primaily in the upper and lower epidermis and the oil soluble are primarily in the mesophyll.  The absence of anthocyanin or carotene give  us white flowers. Not transparent flowers. They still have considerable prto-anthocyanin of various types. There have been discovered some mutant forms in some flowers ( I would have to look it up). This proto-anthocyanin is colourless but do provide something, perhaps structure , that makes them appear white. You can take a white flower petal and extract the colourless chemicals. After drying our the flower petal it is transparent. Thus when we are looking at the oil soluble pigment like lycopene we are looking through this proto-anthocyanin. It has to be muting the colour to some extent.

The next problem is what is the constitution of the colour of tomatoes. It is not all lycopene but a primarily a combination of lycopene and carotene, varies from tomato variety to variety. Usually around 60% lycopene. There are also a number of xanthophylls (carotene derivatives). The yellow tomato varieties are almost all xanthophyll pigments. There are some red xanthophylls but I don't know all the names of the xanthophylls and their associated colours so I can't say for sure how much of a role they play. I think they play a role with red peppers, I'll have to look it up again.

I have extracted the pigments from some red beards this year and extracted quite a bit of carotene  with methyl hydrate and the beard then looked pale pink. Its also possible that  there was some xanthophylls extracted at same time. They may be soluble in alcohol.

Another problem is in the structure of the cells. There is only so much pigment that can be stored in the cells. Green tomatoes actually have a fair bit of beta-carotene in their skins. Actually almost all green plants do. It protects the chlorophyll from being damaged by the sun (so I understand). Lycopene doesn't develop if the temperature is above a ceratin temperature ( about 93F if I remember correctly) so a tomato ripening at a high temperature doesnbt produce lycopene and is a light yellow when the lycopene can't develop. Tomatoes have a special ripening  process. A change occurs (transition point) and at that time the chloropyll undergoes a special transformation into lycopene. It is this change from chlorophyll to lycopene which increases the amount of lycopene beyond what the cells can normally hold. 
Thus we need to first get the chlorophyll into the iris flowers and then get it converted into lycopene. Not a very promising  or likely scenario. 

We also need to get rid of the proto-anthocyanin so cell walls are more transparent.

There has been a significant increase in the amount of carotenoids in iris flowers. The intense orange flowers are examples of this. My pigment extractions of orange flowers gave me both lycopene and a carotene ( probably beta-carotene).  I'm still puzzling over this. Orange iris are tttt yet there is still considerable carotene in addition to the lycopene. So a lot of lycopene is being converted to carotene, almost as if there is an overflow. An even more puzzling result is an analysis of Chariots of Fire. It has pink standards with an orange rim. An extraction of the standards seemed to show the carotenoid distributed into a rim around the standards while lycopene was distributed evenly over the standards, as if their distribution were being controlled by separate factors. I have no idea what to make of this but will need to do some other extractions to confirm this.

Gene transfer is a shotgun approach to changing genetics. Not figuratively, but reality. Once the relevant gene structure is identified it is packaged into tiny bullets and shot into the nucleus of the recipient , and it is hoped it lands in the right place. Then lots of these modified plants are grown to  see if the gene got into the right place. With iris being tetraploid it would take a lot of work to get these recessive genes all lined up and to grow  enough generations of enough attempts to see what you had produced. Many thousands of plants over several generations. This is were the time and expense really adds up  Is the iris industry big enough to justify this expense? 

I would also think that the anthocyanin approach would be more feasible.

Another possible approach could be the xanthophylls. Look for a nice red one. Perhaps we should be looking at red peppers for some possibilities. Xanthohylls in bearded iris hasnbt been studied very well. the pigment extractions as published in World of Iris had a number of unidentified xanthophylls and the right ones can produce good strong hot colours (yellows, and perhaps red and orange). Many xanthophylls are nearly colourless.

Chuck Chapman 

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