can try using sterile petriplates used for histological studies and measure the length & breadth of grid in the histological plate. This may help you to measure size of callus without spoiling / distrubing the profilerated callus under in vitro condition. 

Hi,

In addition to the answer above, I can suggest:

- grow the callus on sterile filter paper on the plate. This way you can take it with minimal disturbance and weigh it in sterile conditions.

- you could take a photo from above and do image analysis (e.g. with ImageJ) to obtain area. It would give you bi-dimensional information (which you could represent as square root vs. time to get the slope and see your growth rate), but it really depends on what you want to obtain.

Cheers,

Ruben

It sonds nice, but filter paper will interfere with the growth of the calli.....and absorb "things"

Well, that's how they did all the growth analysis with pinus somatic embryos in my old lab, on Whatman filter paper weighed in a laminar flow hood... you need to choose a high-quality filter membrane, something ideally non-reactive, of course. In terms of interfering with the callus, yes, it would, but so would any growth condition that you work with (agar concentration, salts, plate replica period, sealing tape, etc), so you would need to set up the appropriate controls to compare.

Image analysis would be non-invasive though.

All in all, it really depends on what Saba wants to obtain with these growth measurements.

Cheers,

Ruben

Hi Saba,

Sometimes I measure the sizes of callus or tiny plants in the plates.  I do this in a sterilized hood. Similar to Gj's suggestion, I placed a ruler instead under the plate and then place them above a sheet of 'clean white paper' to measure them. With the white paper we can see the numbers on the ruler much better due to the stronger 'contrast' between the white paper and the numbers on the ruler (which printed in black). See my attachment for an example, although this picture the ruler has not yet placed under the plate. And, as Ruben's suggestion, I will take some pictures of it from different angles for documentation, and chose the best one for publication.  Use a camera with lens which can get you close-up photos from a distance (without contaminating the samples; usually I open the lid, so the pictures will be clearer). This method is depending on how clear you can see through the medium to get to the numbers on the ruler. Some people add 'active charcoal' into their medium, which blacken the medium, and there is no way you can see through and use this method. In our paper, we usually describe the 'size' of our calli measurement as 'the diameter of the callus'.

Check this out...

http://www.sciencedirect.com/science/article/pii/S1369703X99000030

this paper or book in below links maybe useful

http://link.springer.com/article/10.1007%2FBF00042336

http://books.google.com/books?id=sZ_2HlWsHQIC&lpg=PA162&ots=iMvjjT_5ZE&dq=Compton%20ME%20%281994%29%20Statistical%20methods%20suitable%20for%20the%20analysis%20of%20plant%20tissue%20culture%20data%2C%20Plant%20Cell%20Tiss.%20Org.%20Cult.%2037%3A%20217-242.&pg=PP1#v=onepage&q=Compton%20ME%20%281994%29%20Statistical%20methods%20suitable%20for%20the%20analysis%20of%20plant%20tissue%20culture%20data%2C%20Plant%20Cell%20Tiss.%20Org.%20Cult.%2037%3A%20217-242.&f=false

http://www.sciencedirect.com/science/article/pii/S0044328X77800263

Dear all, thank you for your nice suggestions, I suppose the method of Yuan-Yeu Yau  is more applicable.

Hi Saba, I wanted to tell you all along how I did measure the growth of fungus mycelium. But I dont know how these transparent plastic sheets are called we used them all the time to copy the diameters which were then counted with Image J as someone mentioned too. And they could be clean with EtOH. very practical.They came in the size of A4. These pages were used then to draw or copy some results for a lecture.now we use powerpoint... And these drawings would give the diameter of callus or mycel, but of course not the amount in height.

Dear S. Wenkart, Thanks for your explanation. Can I kindly ask you to send a picture of that transparent plastic sheet and let me know where you put it under the plant or not?

Hi Saba, already some years ago I had to measure the  growth of hairy roots on medium in dishes. You turn the dish , lay the plastic on the bottom of the dish, and start drawing.

It was also very helpful for the growth of fungi, as they grow in circles.

I attach the source of the transparent films as they call them. It should be possible to buy it of an English or US source, I hope.

You can try use Newbauer chamber.

Of course you can, but you want to go on growing the callus. I don't know if the callus would like to be in water. Some calli are very light and maybe swim....

If you dont want to compromise with the callus..then you ma take help of a image analysis system...

The following paper may be of some help:

Article Indirect assessment of callus fresh weight by non-destructive methods