Are orchids C3, C4, or CAM plants?

[Angurek]

Which of these carbon fixation mechanisms do orchids use? I wouldn't be surprised if the orchid family had representatives of all three, given the sheer diversity of its members.

I ask the question because I'm reviewing for a final exam, and the subject came up. My plants are sitting in the balcony, and I just thought about them.

[fieldsofgold]

BUMP! I'm interested as well

[camille1585]

Good question. I remember wondering the same thing during my plant physio classes! I think about orchids way too much. I think orchids are mainly C3 and maybe CAM. I looked it up right now, and it pretty much confirmed what I thought, though I was surprised that there may be some C4 orchids as well.

If you can, try to get a hold of "The physiology of tropical orchids in relation to the industry" (2004). It has some good stuff about carbon fixation in orchids. Or go to Google books, most (if not all) of the book is viewable. Really interesting book, I think I'll go see tomorrow if the university library has it. It's very informative reading!

From what I read of it now, generally (but like always, there are exceptions!) it seems that thin leaved orchids fall into C3 and thick leaved orchids have all the characteristic of CAM fixation.
There is some evidence that some Cyms and a handful of other genera may be C4, but there is little concrete evidence for now.

What are you studying that involves learning carbon fixation? I love meeting other will be plant scientists here!

[fieldsofgold]

thanks Camille for the info and the book recommendation. Sadly my Uni doesn't have it but I took your suggestion and went on google!

here's the link:
The physiology of tropical orchids ... - Google Book Search

off to study for finals. Gosh will have to read this in my downtime but man does the book look juicy!

[Angurek]

Originally Posted by camille1585

Good question. I remember wondering the same thing during my plant physio classes! I think about orchids way too much. I think orchids are mainly C4 and maybe CAM. I looked it up right now, and it pretty much confirmed what I thought, though I was surprised that there may be some C4 orchids as well.

If you can, try to get a hold of "The physiology of tropical orchids in relation to the industry" (2004). It has some good stuff about carbon fixation in orchids. Or go to Google books, most (if not all) of the book is viewable. Really interesting book, I think I'll go see tomorrow if the university library has it. It's very informative reading!

From what I read of it now, generally (but like always, there are exceptions!) it seems that thin leaved orchids fall into C3 and thick leaved orchids have all the characteristic of CAM fixation.
There is some evidence that some Cyms and a handful of other genera may be C4, but there is little concrete evidence for now.

What are you studying that involves learning carbon fixation? I love meeting other will be plant scientists here!

I'm actually a marine biology major, but I was taking a general biology course, and one of the topics covered was this. I'm gonna take botany sometime in the future, as one of my electives. It should be an interesting class.

Originally Posted by fieldsofgold

thanks Camille for the info and the book recommendation. Sadly my Uni doesn't have it but I took your suggestion and went on google!

here's the link:
The physiology of tropical orchids ... - Google Book Search

off to study for finals. Gosh will have to read this in my downtime but man does the book look juicy!

Wow, thanks so much for the link! That fixation chapter was pretty interesting. I guess I should have known we'd see a mix of mechanisms from this family.

[epiphyte78]

Not sure how I missed this thread! It's a fun subject...even though I've read over a few articles and still have difficulty with the details of the process.

Here's a list of articles on the subject...not sure if you're only interested in reading up on orchids....

• Comparative Rates of Dark CO2 Uptake and Acidification in the Bromeliaceae, Orchidaceae and Euphorbiaceae
• Crassulacean Acid Metabolism and Its Possible Occurrence in the Plant Family Orchidacea
• Crassulacean Acid Metabolism in Australian Vascular Epiphytes and Some Related species
• Crassulacean Acid Metabolism in Orchids under Water Stress
• Crassulacean acid metabolism in the shade. Studies on an epiphytic fern, Pyrrosia longifolia, and other rainforest species from Australia.
• The Occurrence of Crassulacean Acid Metabolism Among Vascular Epiphytes From Central Panama
• Utilization and Dissipation of Absorbed Light Energy in the Epiphytic Crassulacean Acid Metabolism Bromeliad Tillandsia ionantha

My favorite article was easily "Crassulacean Acid Metabolism in Australian Vascular Epiphytes and Some Related species". It's been a while since I've read it but I think the authors noted a correlation between leaf thickness and CAM...with a few exceptions of course. What's interesting is while I was looking through a book on Australian Succulents I was surprised to find several orchids listed in the book.

PM me your e-mail address if you have difficulty finding any of the articles.

[Becky15349]

Orchids are monocots, that's all I know...HA! I'm real useful aren't I?

[Ray]

I would speculate all 3, as well, but would put the majority on C4 and CAM - I know that phals are CAM plants.

[markr]

Terrestrial orchids are C3 photosynthesizers. Epiphytic orchids are divided in how they carry out carbon assimilation: thin leaved epiphytes perform C3, though there is some evidence for C4 too; thick leaved succulent-type epiphytes (almost every monopodial epiphyte) are CAM photosynthesizers. This makes sense, as CAM is an adaptation for conserving water.
However, I've often read that the metabolic pathways used by many orchid families are not well understood.

[silverelf]

This is indeed a very interesting topic. It led me to wonder whether its possible to hybridize a C3 orchid with a C4 orchid? Would it be possible for an orchid hybrid to have a hybrid of carbon fixation methods? This is interesting haha.. I also believe that most orchids should be mainly either C4 or CAM plants as cited above. Hope that more experts can share their knoweldge.