# 1) If it's a plant, it \*must\* have green stuff? 2) chlorophyll system with biggest bang for buck? **URL:** \ **Category:** Factual Questions\ **Created:** [May 11, 2015, 1:20am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735 "2015-05-11T01:20:54Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [May 11, 2015, 1:20am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/1 "2015-05-11T01:20:54Z")
1. Spring has sprung, and my brain came up with: is a plant a plant because it has green (chlorophyll), sort of by definition? Thinking more about green, I wondered about “a just ok green” vs some other frequency “super-duper green” which for a given area produces more energy. Then I thought that of course the whole system can work together to increase the energy generated, even given a relatively “inefficient” energy absorber. So, “bang-for-the-buck” means as a frequency/area unit of where the sun hits the green stuff, or as a plant as a whole, can “efficiency” be discussed in any coherent units? Am I completely off-base here? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 11, 2015, 1:25am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/2 "2015-05-11T01:25:34Z")
There are certainly non-plant organisms that photosynthesize (cyanobacteria, for starters), and I’m pretty sure that there are some plants that don’t photosynthesize, or at least photosynthesize very little (they’re parasites that fill a similar niche as fungi). ---
**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\ **Post date:** [May 11, 2015, 1:26am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/3 "2015-05-11T01:26:12Z")
Remember we see green because the plant isn’t using that range of radiation very well. There are many [photosynthetic pigments](http://en.m.wikipedia.org/wiki/Photosynthetic_pigment) that have different optimum wavelengths. ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [May 11, 2015, 1:35am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/4 "2015-05-11T01:35:51Z")
Plants don’t necessarily have chlorophyll, seeing as they can be parasitic, living off other plants’ chlorophyll (i.e. dodders and [Indian pipe](http://www.fcps.edu/islandcreekes/ecology/indian_pipe.htm)). I haven’t heard of any quantitative ways to measure this, but in general variegated plants with green and white foliage are not as vigorous as their all-green counterparts. ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [May 11, 2015, 1:42am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/5 "2015-05-11T01:42:18Z")
I’m pretty sure they’re not considered a species, but there are [albino redwoods](http://en.wikipedia.org/wiki/Albino_redwood), that [can’t photosynthesize](http://blogs.discovermagazine.com/discoblog/2010/12/08/a-creepy-monster-of-the-forest-the-albino-vampiric-redwood-tree/). [NPR’s take](http://www.npr.org/2010/12/05/131826715/Ghostly-Redwoods-Are-Forest-s-Rare-Haunting)on it. Google “plants without chlorophyll” and this is one of the things you’ll find [Monotropa uniflora - Wikipedia](http://en.wikipedia.org/wiki/Monotropa_uniflora) ---
**Author:** ![Twoflower](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/twoflower/32/22_2.png) [@Twoflower](https://boards.straightdope.com/u/Twoflower)\ **Post date:** [May 11, 2015, 1:50am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/6 "2015-05-11T01:50:50Z")
There are also chlorophyll-free plants (saprophytes) that “eat” decomposing matter in the soil. [Pine drops](http://en.wikipedia.org/wiki/Pterospora), [snow plant](http://en.wikipedia.org/wiki/Sarcodes), and several types of [orchids](http://en.wikipedia.org/wiki/Corallorhiza), to name a few. ---
**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\ **Post date:** [May 11, 2015, 1:53am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/7 "2015-05-11T01:53:04Z")
The OP is not asking about plants that do not photosynthesize. ---
**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\ **Post date:** [May 11, 2015, 1:59am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/8 "2015-05-11T01:59:22Z")
What is the op asking? Part 1 seems to be about whether all plants are green… (no) ---
**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\ **Post date:** [May 11, 2015, 2:09am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/9 "2015-05-11T02:09:40Z")
Ah yes. I skipped that part. ---
**Author:** ![Projammer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/projammer/32/559_2.png) [@Projammer](https://boards.straightdope.com/u/Projammer)\ **Post date:** [May 11, 2015, 2:23am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/10 "2015-05-11T02:23:03Z")
I read it as asking whether there is an ideal shade of green to maximize the energy return on photosynthesis. Not that I can answer that particular question. ---
**Author:** ![Twoflower](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/twoflower/32/22_2.png) [@Twoflower](https://boards.straightdope.com/u/Twoflower)\ **Post date:** [May 11, 2015, 2:48am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/11 "2015-05-11T02:48:43Z")
I don’t have an answer for the efficiency question, but I’ll note that plants are green because that’s the color of light that they _don’t_ use. They reflect the “waste” light, and absorb the other colors as they photosynthesize. ---
**Author:** ![Ranger\_Jeff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranger_jeff/32/2065_2.png) [@Ranger\_Jeff](https://boards.straightdope.com/u/Ranger_Jeff)\ **Post date:** [May 11, 2015, 5:02am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/12 "2015-05-11T05:02:40Z")
I believe the OP is wanting the most efficient conversion of CO2 to O2. ---
**Author:** ![Obtenebrate](https://avatars.discourse-cdn.com/v4/letter/o/9f8e36/32.png) [@Obtenebrate](https://boards.straightdope.com/u/Obtenebrate)\ **Post date:** [May 11, 2015, 8:27am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/13 "2015-05-11T08:27:49Z")
> [@Ranger\_Jeff](#): > > I believe the OP is wanting the most efficient conversion of CO2 to O2. Yeah, but the problem with questions of efficiency is that you have to define what you mean by efficient. Total energy efficiency, overall cost efficiency, use of space, mass, some combination, and do you just need pure sugar and oxygen, or do you need vitamins and lipids and cellulose and so forth? In a closed system, red and blue light in combination are the most effective at stimulating metabolic activity. But most places on earth, it can’t compete on a dollar basis with sunlight, which is very nearly free. Similarly, algae has the lowest overhead in terms of non photosynthetic mass. But if you try growing it in the ocean, you’ll quickly find much of your crop eaten by the critters living there. Despite that it could still be the most efficient option if all you want is oxygen production. We can answer any number of plausible interpretations of the question, but there’s no ‘right’ answer until the question is pinned down a bit more. ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [May 12, 2015, 4:54am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/14 "2015-05-12T04:54:30Z")
This [reddit science thread](https://www.reddit.com/r/askscience/related/352wvo/as_photosynthesis_requires_light_why_arent_plants/) might be of help to the OP ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [May 12, 2015, 5:25am UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/15 "2015-05-12T05:25:51Z")
> [@Twoflower](#): > > I don’t have an answer for the efficiency question, but I’ll note that plants are green because that’s the color of light that they _don’t_ use. They reflect the “waste” light, and absorb the other colors as they photosynthesize. Indeed; a fully efficient photosynthetic organism would appear black. (There are plants that appear black, or nearly so, but not for that reason) ---
**Author:** ![purplehorseshoe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/purplehorseshoe/32/2996_2.png) [@purplehorseshoe](https://boards.straightdope.com/u/purplehorseshoe)\ **Post date:** [May 12, 2015, 7:47pm UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/16 "2015-05-12T19:47:42Z")
Do mind elaborating a bit on that point, Mangetout? I’m curious. 🙂 _props chin on hands_ ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [May 12, 2015, 7:59pm UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/17 "2015-05-12T19:59:14Z")
Ornamental plum trees have purple leaves, and use anthocyanin to get energy from sunlight. They also use chlorophyll but the high levels of anthocyanin keeps the leaves from being green. > **[Photosynthesis in Leaves That Aren't Green -](https://baynature.org/article/photosynthesis-in-leaves-that-arent-green/)** > > Q: How does photosynthesis occur in plants that are not obviously green, such as ornamental plum trees with deep purple-colored leaves? \[Paul, Santa Cruz\] A: Photosynthesis (which literally means “light put together”) is that very elegant chemical... ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [May 12, 2015, 8:13pm UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/18 "2015-05-12T20:13:06Z")
Thanks to all. The first part of OP I’ll have to take up with Linnaeus, or whoever it was, besides God, who decided what makes a plant. **Obtenebrate** nails the bang-for-the buck part of OP. I knew so many different conditions/costs/benefits must exist in such a complicated system, but didn’t know where to start. About green being the color that isn’t: thanks, of course, and it was silly of me to put it that way. Don’t humans have particularly acute retina receptors in the green areas? [Warning: Finnegans Wake cite perhaps in a subsequent post] > [@Obtenebrate](#): > > Yeah, but the problem with questions of efficiency is that you have to define what you mean by efficient. Total energy efficiency, overall cost efficiency, use of space, mass, some combination, and do you just need pure sugar and oxygen, or do you need vitamins and lipids and cellulose and so forth? > > In a closed system, red and blue light in combination are the most effective at stimulating metabolic activity. But most places on earth, it can’t compete on a dollar basis with sunlight, which is very nearly free. Similarly, algae has the lowest overhead in terms of non photosynthetic mass. But if you try growing it in the ocean, you’ll quickly find much of your crop eaten by the critters living there. Despite that it could still be the most efficient option if all you want is oxygen production. > > We can answer any number of plausible interpretations of the question, but there’s no ‘right’ answer until the question is pinned down a bit more. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [May 12, 2015, 8:17pm UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/19 "2015-05-12T20:17:35Z")
I thought someone else might have been along to educate us; perhaps they will, but in the meantime I might as well put down what I can remember. Chlorophyll is not the only photosthesising pigment, although it is the most common one; there are bacteria that use a form of rhodopsin, the sort of pigment we use in our retinas to convert light into nerve impulses. > **[Microbial rhodopsin](https://en.wikipedia.org/wiki/Bacterial_rhodopsins)** > > Microbial rhodopsins, also known as bacterial rhodopsins, are retinal-binding proteins that provide light-dependent ion transport and sensory functions in halophilic and other bacteria. They are integral membrane proteins with seven transmembrane helices, the last of which contains the attachment point (a conserved lysine) for retinal. > This protein family includes light-driven proton pumps, ion pumps and ion channels, as well as light sensors. For example, the proteins from halobacteria include ... it may be the case that life on some other planet out there has never evolved chlorophylls, so would rely on the rhodopsins for their metabolism. But this would be much less efficient. Many forms of Algae use additional pigments to gather more energy, although they use chlorophyll fr the main event; these pigments, called accessory pigments, allow algae to live deeper beneath the waves. Fucoxanthin gives brown algae their colour, > **[Fucoxanthin](https://en.wikipedia.org/wiki/Fucoxanthin)** > > Fucoxanthin is a xanthophyll, with formula C42H58O6. It is found as an accessory pigment in the chloroplasts of brown algae and most other heterokonts, giving them a brown or olive-green color. Fucoxanthin absorbs light primarily in the blue-green to yellow-green part of the visible spectrum, peaking at around 510-525 nm by various estimates and absorbing significantly in the range of 450 to 540 nm. > Carotenoids are pigments produced by plants and algae and play a role in light harvesting as par... while phycobiliproteins give red algae their colour. > **[Phycobiliprotein](https://en.wikipedia.org/wiki/Phycobiliprotein)** > > Phycobiliproteins are water-soluble proteins present in cyanobacteria and certain algae (rhodophytes, cryptomonads, glaucocystophytes). They capture light energy, which is then passed on to chlorophylls during photosynthesis. Phycobiliproteins are formed of a complex between proteins and covalently bound phycobilins that act as chromophores (the light-capturing part). They are most important constituents of the phycobilisomes. > Many applications and instruments were developed specifically for R... Maybe plants on another planet around a different star would use some, or several, of these accessory pigments to gather more light energy. I suspect, but can’t prove, that chlorophylls aren’t the only option for photosynthesis, and maybe these other light-collecting compounds will have their own accessory pigments, creating a very wide possible range of plant colours. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [May 12, 2015, 9:05pm UTC](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735/20 "2015-05-12T21:05:57Z")
> [@purplehorseshoe](#): > > Do mind elaborating a bit on that point, Mangetout? I’m curious. 🙂 > _props chin on hands_ Ophiopogon is a good example: [https://www.rhs.org.uk/plants/details?plantid=3636](https://www.rhs.org.uk/plants/details?plantid=3636) It’s black, but I dont think it’s any more photosynthetic as a result. It’s absorbing more visible light than some other green plants, but not necessarily making food with it. [Next page](https://boards.straightdope.com/t/1-if-its-a-plant-it-must-have-green-stuff-2-chlorophyll-system-with-biggest-bang-for-buck/719735.md?page=2)