A rose by any other name..

May 8, 2012 12:15 PM

Are there differences in the energy needed for a plant to produce a certain color flower than a different plant producing a different color?

So, does it take more energy for a plant to produce a red flower versus a white one? I know by varying the pH of the soil will change hydrangia colors.. so what are the components; energy, minerals, etc) that are key to a plant producing its flower colors? Does it take more resources for a plant to produce a color more than a different plant producing a different color?

This could be a red rose versus a yellow rose, or actually different plants, like a red rose versus a white peony... are there any correlations?

posted by rich to home & garden (8 answers total)

The colors of flowers are (usually) produced through different chemical pigments. It costs different amounts of energy for a plant to synthesize different chemicals, so basically, yes. Whether this amounts to a significant difference I'm not sure.
posted by peacheater at 12:37 PM on May 8, 2012

are there any correlations

Recessive alleles can be responsible for less frequent patterns of pigmentation — a mutation in a gene could result in a change in how chemical precursors are metabolized, changing the color phenotype.

While a change in metabolic processes will definitely result in a change in net energy use, the resulting disparity in proportions of colors in a population of flowers could be due to energy costs in synthesis of pigmentation, but there are other probably more significant reproductive costs. For example, pollinators might find certain flower colors easier (or more difficult) to locate and hone in on than others, resulting in increased reproductive success (or failure).
posted by Blazecock Pileon at 12:49 PM on May 8, 2012

It's really difficult to say. You'd have to analyze the enzyme sequences used to synthesize the pigments and calculate how much energy was used at each step. You'd also need to know how much pigment was ultimate created.
posted by Chocolate Pickle at 1:12 PM on May 8, 2012

Blazecock - understanding that reproduction success based on color could be significantly increased (based on a wide variety of factors - pollinators, location, etc), this would certainly be a factor where it would make sense for a plant to spend more energy to create one color than one that would cost less...

So was wondering if there were any studies that looked at the specifics, such along the lines Chocolate Pickle and peacheater started down.

Of course, I'm not a scientist at all. I was just looking out at my garden and started wondering.
posted by rich at 1:30 PM on May 8, 2012

It's hard to say for sure. The actual energy used to construct a rose versus a peony will certainly be different, even when differences in mass have been accounted for. Major sources of difference will be energy storage organs in e.g. roots and stems, relative nectar and pollen mass (both energetically dense and costly to make) and flower pigments. The fact that an individual plant can harness energy from sunlight and store it temporarily means they can run a net deficit at different times in their life cycle and a surplus in others, so how much it has to spend on e.g. flowers isn't constrained completely by the immediate environment to the flower itself. As a result, flower colour can (for example) evolve according to the particular needs of a pollinator rather than immediate energetics across the whole plant.

But in short - yes, colour is expensive and it's precursor chemicals can be rare - this is certainly the case in some birds and insects where carotenoids have to be sourced from the diet and are important limiting resources in nature. Plants have (a generalisation) a more comprehensive synthetic machinery so this might be less true for them. There's even a theory going round that some plants use colour as an energy-dense dump for excess energy from photosynthesis - after all they can't move or turn off the sun.

The key thing is that energetics have to make sense over the life span of the individual, so all aspects of morphology can determined by more ecological and evolutionary factors than just immediate cost.
posted by cromagnon at 2:54 PM on May 8, 2012

Along the lines of what Blazecock Pileon was saying, there can be an evolutionary cost to certain colors in terms of pollinators. Orange flowers in particular are less visible to bees, this was displayed in a study of snapdragon genetics that made it into a popular science article:

"The team found something remarkable around the floral boundary: there was plenty of mixing between genes of the yellow and magenta plants but much less mixing when it comes to the genes controlling pigment colours. The scientists concluded that the orange-flowered snapdragon was not a new species in the making but the equivalent of a mule, the dead-end cross of a donkey and a horse.

What was it about this particular colour? Orange varieties of flowers do, of course, exist: plant breeders have selected them. But it turns out that although an orange snapdragon can make seed, this colour is not very visible to bees, the insects which pollinate the plants and enable them to reproduce. This is not a problem for other orange flowers which appear bright at ultraviolet frequencies (which bees are sensitive to, unlike us), as is the case with poppies; or which are pollinated by humming birds (which can see orange.) But this is a problem for the snapdragons, which depend on bees."

In terms of the actual energetic cost of the different pigments, I work with plant metabolite pathways as part of my research, and I doubt that there are significant differences in creating red pigment vs. purple pigment or anything like that. The cost would be mostly in terms of pollination recognition.
posted by permiechickie at 2:55 PM on May 8, 2012 [1 favorite]

it would make sense for a plant to spend more energy to create one color than one that would cost less...

Plants don't "pick" colors for flowers, generally. They accumulate mutations (through chance or environment) that predispose them to different pigmentation, which subjects them to selective pressures which determine how many plants might get those genes in the next generation.

But if any given chemical pathway takes less energy, then the "savings" allow breathing room for other metabolic pathways to use resources. An example would be defense mechanisms, such as poisons that discourage insects or foragers from eating the plant.

On the other hand, a chemical pathway that uses more energy leaves less for other things the plant needs to do. But even with the extra burden, there could possibly be greater reproductive benefit — the plant becomes more visible to pollinators, for example, or through mimicry it looks more like a poisonous plant (even though it isn't) and foragers tend to stay away. Both of these outcomes can improve reproductive success.

It would be a complicated arrangement to measure, mainly because plants do not live in isolation, but as part of a larger biological system.
posted by Blazecock Pileon at 2:57 PM on May 8, 2012

It would be a complicated arrangement to measure, mainly because plants do not live in isolation, but as part of a larger biological system

There's quite a lot of effort going on, though, including a a database of flowers as pollinators see them.
posted by cromagnon at 3:02 PM on May 8, 2012 [2 favorites]