Dear Ghose, thanks for your answer. I was not necessarily asking for microbial production of carotenoids, but in general. I mean, do plants in glassland produce more carotenoids than plants in forests? or maybe algae in the ocean produce even more? or maybe the overall microbial production of carotenoids is higher than those of plants or algae in any ecosystem?

In terms of biomes which could foster high carotenoid content we might want to consider the role of carotenoids is as photo protectants particularly in regard to damaging potential of ultra violet light. In this regard the alpine desert and the lowland desert represent environments where ultraviolet protection would be particularly useful. The carotenoids which are oils soluble might be isolated from aromatic extractions which would be looked at for red, yellow and orange constituents. I believe flamingo birds get their coloration from the diet of small plants and their pigments and this would be an example of lowland desert like biome expressing significant accumulation of carotenoid pigment having significance. In Hawaii the algal ponds have been extracted for significant carotenoids. I think there is less work in the alpine desert like environment.

Thanks for your answers guys.

Paul, so can we say that cactuses in a desert, for example, would produce more carotenoids than plants under a forest?

Or why a carrot is said to be so high in carotenoids when other similar plants like potato is not? do alll apiales (like carrot) produce more carotenoids than solanales (like potato)?

And if carotenoids are useful for protection from UV damage, why carrots concentrate those carotenoids in the root, where no UV is suppose to reach?

From my experience in plants the stress environment can induce defensive plant chemistry. High ultraviolet light can stimulate defensive chemistry. Each specific case would need to be investigated. In general many defensive compounds are reduced under non stressful favorable environments and are increased under stressful environments. Some of the functions of carotenoids would include antioxidant properties but I am sure there are many others. Yes I believe stressful environments can stimulate many of these mechanisms but each case would need to investigated. I have found that in many stressful environments the most tolerant varieties are the highly pigmented ones. Certainly in humans the high pigmentation of skin is highly adaptive and beside the defensive against ultraviolet light it can help in making skin more cross linked so the body is less susceptible to tears and cuts.

As said at biome level it is difficult to predict as carotenoids are species specific. The general approch can not give precise as agae in freshwater or cold desert plant or desert biome in general. But agreed these pigments produce more in stress condition.

It's not clear to me why that could be difficult. There are profiles of plant species for most biomes, and if a sample of them in each case can be analyzed then you can have relatively accurate estimations of carotenoids per biome. I just think that the question had not been asked, maybe because it has no big scientific or commercial interest.

Maybe rather that develop golden rice we might want to put a carrot in our rice. Enjoy the wikipedia

Though I've enjoyed the above interaction, I fully doubt the presumptions.

Say the carrot roots, oranges/ many other fruits, spirulina, most flowers and even common foliage & food grain plants of less dark green color support or possess high carotenoids in the common zones of max bio activity and not in the deserts or alpine area alone. From the plant study

angle we may think on such aspects but better think of man & food aspect

Thus it may be serious to think of the staple consumables, like Golden Rice or orphan foods/millets ,to help meet human needs for the important nutraceuticals/antioxidants etc.

Thanks for your input Paul. Well, I can agree with you that those aspects are very important, although they were not the original motivation for my question (but of course we can discuss those issues too of course).

I was interested in an ecological point of view regarding carotenoids, mainly because I have a result that I wanted to understand. Basically I found that in freshwater environments, the microbial communities possess a particular gene, namely "all-trans-zeta-carotene desaturase", which is more abundant than in the microbial metagenomes from other biomes (forest soil, grassland, marine, etc). Now I think this might be related to the fact that agricultural irrigation of crops normally end in rivers.

Yes, genes are v imp but not present due to the biome. If that was the reason, all

plants in a particular biome shall have

the said gene !(?)

Paul, I was talking about the microbial community metagenome associated to different biomes. And yes, all soil and freshwater associated microbial metagenomes have that particular gene, but in rivers that gene has a higher frequency. The majority of metagenomes from rivers that I have analyzed were sampled from the Amazon river. For example this one:

Ghai, Rohit, et al. "Metagenomics of the water column in the pristine upper course of the Amazon river." PloS one 6.8 (2011): e23785.

Just complementing this in case you are interested. Thanks again and best regards.

Birds?

stressed biomes --- like mangrove ecosystem--you can also consult this paper.

Best Regards,

Thank you Abhijit Mitra .. that makes a lot of sense in the context of my work, that was already published:

Article Redox traits characterize the organization of global microbi...

I wish I had received your interesting input before, as I would have discussed a little about that there...

Best regards and thanks again.