there is always a positive correlation between chlorophyll  content and nitrogen content in plant leaves. This is what i have found in most of my work .

Is there any published data?

Dear Darshan

there are a whole lot of data on this relationship. There is a variable but constraint correlation between leaf N and chlorophyll. This is due to the fact that the enzymes involved in photosynthesis plus the proteins that are integrated in the thylacoid membranes plus chlorophyll itself contain a substantial amount of nitrogen. Thus, in general: the more chlorophyll, the more thylacoid membranes, the more photosynthetic enzymes and in consequence the more nitrogen in all these components. The stoichiometry between the different components of the photosynthetic apparatus changes between sun and shade habitats and other environmental cues.Some exceptions as e.g. in the case of leaves that accumulate nitrate in vacuoles need to be scrutinised.

For a first introduction I suggest to read:

John R. Evans Photosynthesis and nitrogen relationships in leaves of C3 plants

Oecologia (1989) 78: 9-19

With this starting point you can find many papers treating the N-Chl relationship written in the context of remote sensing, precision agriculture, ecology.

Best wishes

Franz

Nitrogen content was close link with chlorophyll content. From all metabolic elements which plants use from soil, nitrogen needs in the largest amounts (TUCKER, 2004). Nitrogen exists in organic and inorganic form and the greatest nitrogen content is in seeds, leaves, shoots and roots. Deficiency of nitrogen leads to loss green color in the leaves, decrease leaf area and intensity of photosynthesis. Understanding the processes that govern N uptake and distribution in crops is of major importance with respect to both environmental concerns and the quality crop products. Nitrogen uptake and accumulation in crops represents two major components of the N cycle in the agro system (GASTAL and LEMAIRE, 2002). The relationship between N and biomass accumulation in crops, relies on the reciprocal regulation of multiple crop physiological process. Therefore, N uptake and distribution in plant and crops involves many aspects of growth and development.

Leaves exhibit a structural and functional acclimation of the photosynthetic apparatus to the light intensity experienced during their growth (PRIOUL et al., 1980). Nitrogen supply has large effect on leaf growth because it increases the leaf area of plants and, on that way, it influences on photosynthesis. Photosynthetic proteins represent a large proportion to total leaf N (EVANS, 1989; FIELD and MOONEY, 1986). Chlorophyll content is approximately proportional to leaf nitrogen content, too (EVANS, 1983).

Don't know exactly, we only studied the correlation between SPAD and N content in leaves or plants. See publications on tomato and lettuce by Tei et al o Benincasa et al

The correlation between chlorophyll contents and Nitrogen content in the plant is documented very well. However the Mg in the center chlorophyll molecule is surrounded by 4 N atoms and therefor what I am looking for is the relationship between N content from the chlorophyll and the total N content in the plant ( may be what that is found in lab tests ) How about 70-80%