There is good literature which shows there is a linear correlation between chlorophyll content and nitrogen content  in many plant species  but first you must use a concentration of chlorophyll in mg,  or,ug,per gram fresh weight.

You can see a discussion about your question in the link below

https://www.researchgate.net/post/What_is_the_relationship_between_leaf_nitrogen_and_total_chlorophyll/1

Dear Puriya

there is a good MSc thesis about sugar beet in library of IAU- karaj Branch.(Shadi Javaheri)

good luck

Dear Puriya

I suggest you the below reference as well.

Javaheri, Sh., M. Abdollahian-Noghabi, A. Kashani, H. Noshad and D. Habibi. 2011. Effect of leaf position and age on the nitrogen content and chlorophyll meter value in sugar beet. Iranian Journal of Crop Sciences. 13 (1) 87-98. (In Persian).

There is a good linear relationship at lower nitrogen content.

Numerous studies correlating N with Chl have been done showing a fairly strong relationship. Check out the reference below for a detailed look at this correlation:

Bonneville M-C, Fyles JW. 2006. Assessing Variations in SPAD-502 Chlorophyll Meter Measurements and Their Relationships with Nutrient Content of Trembling Aspen Foliage. Communications in Soil Science and Plant Analysis.37:525–539.

The relative chlorophyll content in leaves estimated by the SPAD-502

chlorophyll meter can be an efficient way to evaluate plant nitrogen (N) status in

many crops and some tree species. In this study, the SPAD meter was used to look

for relationships between relative leaf chlorophyll content and leaf nutrient concentration

in trembling aspen. The variations in leaf chlorophyll measurements were

also evaluated by using three sampling times and three measurement techniques.

Hypothetical experimental designs were created to achieve better design efficiency.

The best representation of overall leaf chlorophyll was found when six SPAD

readings were taken at different locations on each leaf. There was a positive correlation

between overall leaf N and estimated chlorophyll content, especially in the top part of

the trees. Overall, this study suggested that the SPAD meter can give an estimation of

trembling aspen nutritional status, especially if the differential partitioning of N within

trees is considered.

Dear Dr. Thomas Noland,

Thank you very much for your attention.

It was very useful for me.

Best regards,

Gharavi

Chlorophyll contents Nitrogen, so, there is linear correlation between content of chlorophyll and nitrogen.

Hello Gharavi

There is generally a strong correlation between N content and chlorophyll /unit area (or concentration i.e. per unit fresh or dry mass) in late developing and early mature leaves. But it is affected by senescence. Also  I think (can't recall reference) that it can be affected by factors such as Mg supply which may decrease chlorophyll synthesis more than protein synthesis. The amount of N in chlorophyll is generally small compared to the N in proteins, so the link is not necessarily strong. For careful work SPAD readings should be converted to chlorophyll amount/area or /fresh or dry mass  using a good calibration.  And to use SPAD as a measure of N, ideally calibrate against N measurements.

Hope this helps Best wishes David

Hello David

Your answer was excellent.

Thank you very much for your attention.

Please help me in other cases.

Sincerely,

Gharavi