Quote:
Originally Posted by mameroo2000
In bade the hyphotesis you used, you also can have a look at the following paragraphs on the same book, I just will writte a part!
Appl Microbiol Biotechnol (2011) page 1279; Kimmareddy and Anderson 2004:- In view of the relatives magnitude of aforementioned time scales, the turnover time of the photo-synthetic unit (PSU) or photosyntetic reaction center, is given by the dark reaction time for practical purposes. The light-dark cycle period, which is determined by the travel time of cells between the dark and lit portions along PBR, should accordingly be made AS SHORT AS POSSIBLE, this usually means an optical path of 0.5 to 1.0 cm (to make it clear if the dark time was not necessary then they would mentioned)
Appl Microbiol Biotechnol (2011) page 1279 "Effects of excessively low and high light supply"
"Althought light is required for photosynthesis, too low or high levels thereof will entertain serious disaventantages!! ..."
To who is interesting this pages could be read at http://www.hcmv.vn.refer.org/moodle/...ic-aspects.pdf
You can have more information on Plakton Culture Manual by Frank H. Hoff & Terry W. Snell.
http://en.m.wikipedia.org/wiki/Phytoplankton
Also you can read it all, but if you just want to be more secure about the light process, look on the last paragraph of Aquaculture.
Just to make it clear, it is always good to try or do different things, for some reason what you suggest didn't work for me on one of the Golden Brown Species of phyto which one required a strong illumination. I am just try to pass on all the information I learned and help any one who is interesting, I have six species of phyto and other live foods and I learn to don't expouse your culture to something that may don't work or you are not 100% sure, but I still respect all the opinion of other people. 16 hours on and 8 hours off it works for me since I start the cultired. |
You are misinterpreting what that first reference is saying. It is saying that the light-dark cycle should be repeated all day by circulating the culture vigorously, not that a long dark period is helpful. I never did say the dark time is not necessary. I said it should be on very, very short and that they get ample dark periods in a dense culture by moving in and out of the "photic zone" of the culture.
I do not doubt you have been culturing phytoplankton for a long time with good results. So have I. You obviously have a solid practical knowledge about how to do it, but based on your explanations you do not understand the physiology. If I'm wrong, just answer this simple question:
As you said, from a physiological standpoint, why do you think microalgae need a prolonged dark period to "breath oxygen"?
That just doesn't make sense. Plant cells produce oxygen during photosynthesis by splitting water. Outside of the chloroplast, cellular respiration is occurring and uses up some of that oxygen (although there is a net production of O2 if light intensity is high enough). This is a major advantage of having a chloroplast - it provides oxygen to the rest of the cell. So why would they need a dark period to "breath oxygen" if they actually are able to obtain plenty of oxygen internally when illuminated?
We are not talking about multi-cellular plants here, which have many reasons to need a dark periods. Microalgae can be seen as the most basic photosynthetic unit and there is no physiological reason microalgae need a dark period. It is not "unhealthy" - I'm actually not sure what you mean by that, as it is a pretty vague statement. What process is being disrupted by illuminating with 24/7 light?
Again, I'm not saying you should switch methods as your method works for you. But I do feel if incorrect information is being spread, which is a problem in our hobby, that it should be corrected.
I do not think global warming has anything to do with our conversation.