Crassulacae Acid Metabolism

[Sallubrious]

I've been reading a bit lately about the metabolism of cactus & succulents and it seems they respire at night

Wiki has it listed as Crassulacean_acid_metabolism

Where the Cactus and Succulent Society of NZ has it listed as Crassulacae Acid Metabolism

Anyway it's got me thinking about the possibility of exploiting this phenomena to hopefully increase the growth rate of Lophs

If the plants are placed in a high C02 environment at night would they be able to store extra C02 to fuel extra photosynthesis during the next active photoperiod. Obviously there would be limits but it would nice to find those limits.

I've had Lophs in my bedroom that seem to grow faster than others not in the bedroom possibly the extra C02 is boosting their growth rates.

Has anyone done any experiments along these lines or can they point me to any relevant papers associated with CAM and high C02 levels ?

[Illustro]

I believe, though I do not know for sure, that the amount of CO2 which can be stored as malate is limited to some degree, so if this true, adding CO2 will only decrease the time needed to sequester CO2. Just don't take my word on this. Though, if this is true, you could conceivably shorten the dark period and extend the light perioid, which would increase the amount of stored carbon they could potentially convert to sugars. Though the flipside of this is that the plants may run out of stored carbon during the light period, halting photosynthesis. CAM plants also need to expel excess O2 from photosynthesis at night, so prolonged light periods with closed stoma may potentially cause oxidative damage. Perhaps you could try multiple day/night cycles per 24hrs with increased CO2 during dark? And try playing around with the dark/light ratio of each cycle?

Also, a curiousity I came across a couple years ago is that some leafy cacti actually employ CAM in their stems and C3 in their leaves, when transpiration becomes too excessive they drop their leaves and rely on CAM, when the conditions become more moderate they grow leaves and exploit the advantages of C3. Pretty cool!

[2Deep2Handle]

Also, a curiousity I came across a couple years ago is that some leafy cacti actually employ CAM in their stems and C3 in their leaves, when transpiration becomes too excessive they drop their leaves and rely on CAM, when the conditions become more moderate they grow leaves and exploit the advantages of C3. Pretty cool!

 

Pereskopsis is one of these? Maybe the c3 is one of the reasons pere has exceptional growth rates for scions. I have noticed some direct corellation between stem thickness and No. of Leaves as to the rate of growth of scions, although im pretty sure some reputable members here also dispute this.

This CAM is the reason they can not adapt a 24/0 light cycle?

I do a 18/6 with my pere/loph grafts, and they seem to absolutely love it.....the humidy chamber gets closed up each night, where i beleive the CAM produces lots of warm CO2, as even though they are enarly dry, there is so much condensation on the chambers each morning, makes me think the CAM is speeding up the heating of the chambers as well.

[Illustro]

Not sure, I can't remember the species that were looked at but I remember Austrocylindropuntia spp. and Opuntia spp. being part of the study. I would say it is highly likely that Pereskiopsis has evolved some form of C3, as the natural growing conditions would probably cause CAM types to have less fitness and competivness.

Even if Pereskiopsis did not have C3, more leaves could conceivably cause increased growth rates due purely to the increased surface area to capture light energy, transfer gasses, and store products.

Yep, CAM is the reason why most cacti can't adapt to a full light cycle as unlike other plants, they close their stomata during the day whereas most plants (C3 & C4) will keep their stomata open - if a CAM plant were exposed to constant light it would quickly run out of 'food'.

Scientifically speaking, it is believed the reason they close their stomata is to avoid evaporative waterloss (evapotranspiration) and to reduce RuBisCO fixing O2 into useless metabolic products (photorespiration) which is an increasing problem at increasing temperatures. Plants in cooler conditions have a much lower rate of evapotranspiration and photorespiration so C3 is usually most effective for them, but C3 plants will be seriously affected in hot conditions as they largely have no way to circumvent photorespiration and are prone to evapotranspiration. Whereas C4 plants will convert CO2 into membrane-diffusible products which essentially deliver CO2 straight to chloroplasts which are in cells 'insulated' from atmospheric O2, causing much lower rates of photorespiration, but this also means their stomata are left open during the day, making them to vulnerable to evapotranspiration. Though they have evolved several mechanisms to minimise this like rolled leaves and trichomes growing over stomata which minimise airflow and subsequently evapotranspiration rates. CAM on the other hand converts CO2 into solid products (malate) during the night which are stored in vaculoes, during the day they close their stomata and get their CO2 from the malate by converting it back into CO2 in the cell, this means there is a much lower abundance of O2 (reducing photorespiration) and evapotranspiration is dramatically reduced as water is less able to diffuse from plant, which is further reduced by employing trichomes, thick cuticles, and epicuticular wax; hence hairy, thick-skinned, and waxy desert plants.

Edited May 1, 2012 by Illustro

[Sallubrious]

Thanks for the feedback.

I was thinking of a setup where a symbiotic relationship could benefit the CAM plant through elevated C02 & extra moisture from the symbiotic partner could also help to water the CAM partner.

If the CAM plants were in an almost closed environment with a C3 or possibly a mix of C3 & C4 plants the C02 and moisture produced by the non CAM plants through the dark period could benefit the CAM partner.