Dear colleague,

Do you have access to a Ciras3? It is extremely easy and intuitive. Of course, you can control (via digital interface) air flow, air temperature and VPD, CO2 concentration and light (with the optional light source).

Usually, a measurement takes a few seconds for a combination of environmental setting.

Data analysis depends on the calculation you want to perform, as most physiological variables are calculated by the software.

Thank you Sir. My concern is regarding measurements in ambient conditions of CO2 and light where these are always fluctuating. I usually put on the system with the parameters and chemicals required for ambient conditions of CO2. After around 10-15 minutes when all the readings are visible and the CO2d is around +/- 0.5 I start taking the readings after putting the leaf in the cuvette.

Is there a

1. Check point where i can say the readings are right.

2. What would be the blank ( for example the cuvette without the leaf can be an air blank)

3. What values should we take into account for analysis. For example if I am looking at photosynthetic rate, should I take only values of CO2d that are negative (correspondingly A (photosynthetic rate) is positive.

Regards,

Balasubramanya Sharma

But in these new equipments you select the CO2 value and, usually, it keeps such value quite (or even very) stable...

Yes Sir, in case of controlled CO2 where you select the CO2 amount, it keeps stable but in case of ambient conditions where the outside air is the source of CO2 i see a lot of variation.

Dear Balasubramanya Sharma,

in my opinion, the best goal of this "new" generation of photsynthesis/conductance apparatus (such as those by PPsystems and others) is the ability for selecting a CO2 value by means of a CO2 source. When I started to use these equipments, they used a "buffering system" to reduce CO2 fluctuations. Basically, it was a container of a certain volume (may be 1 liter?) that established such buffering. Morever, you needed to capture free air at a distance from plants and so on. Once the incorporation of an "air supply unit" all these problems were resolved. So, I firmly recommend you to use this ability of your equipment. In case you were recording a continuous gas exchange (we are doing this in whole plant chambers by using a CIRAS3 DC), you cannot use this supplying method, but CO2 fluctations are matched with difCO2 values.

Dear Balasubramanya Sharma,

It is very easy to use CIRAS3. In order to avoid the variations of environmental parameters of occurrence of clouds we usually use the LED light source and take measurements at the saturated Photosynthetically Active Radiation (PAR) (depending on the research objectives). To avoid the CO2 changes either you can use a CO2 cartridge to provide the exact amount of CO2 concentration or use a CO2 buffer volume as suggested by the previous comments. It is not necessary to conduct a blank with no leaf inside the cuvette. You can observe that the photosynthesis values are getting stabilized when you clamp a leaf in the cuvette after few seconds and at this time you can record the data. You may contact the PPSystems or visit their website for further information.

Thank you for the response. Yes, we are using a CO2 cartridge and it helps. We do not have a LED light source and hence this was the main reason for the variation. We are in the process of procuring the light source.