Ayuda en la fotosintesis y en la transformación de carbohidratos. 

Hi Chandan, your question is not very clear to me, btw I suggest you to have a look at this paper which can guide you through the right path.

Griffiths, B., A. Spilles, and M. Bonkowski. 2012. C:N:P stoichiometry and nutrient limitation of the soil microbial biomass in a grazed grassland site under experimental P limitation or excess. Ecological Processes 1:1-11.

Elisabetta

Here are some papers on soil-nutrient studies, although they are not all specifically on C4 grasses and phosphorous, they should be helpful in developing your study:

http://www.tandfonline.com/doi/abs/10.1080/10549811.2010.550256#.VSBR19w-NfR

http://www.sciencedirect.com/science/article/pii/S0168192312001992

http://link.springer.com/article/10.1007/s11104-013-1771-4

Most of these papers use some kind of photosynthesis system to determine the effect of the nutrient. Taking readings from each treatment group with a gas exchange system can give you a lot of data including photosynthesis, transpiration, stomatal conductance as well as environmental readings. Here’s a link to a great handheld photosynthesis system that you might find helpful as you move forward with your research:

http://www.cid-inc.com/products/photosynthesis/handheld-photosynthesis-system

Hope that helps.