Many researchers use the term "nutrient concentration" in plant tissue or grain. While others are using the term "nutrient content" in plant tissue or grain? I think all researches should follow uniform unit for scientific articles.
When we measure the amount of element/nutrient per unit dry weight (percent,ppm), then we should use the term concentration. On the other hand, we should use the term 'content' when we measure total amount of nutrient/element in plant tissues. Nutrients content depends on both concentration and total biomass.
Excellent answer given by M N Islam. The attached pdf file clearly described the content and concentration of an element in plant tissue. Content of an element in plant tissue may increase with the increase of plant's volume but the concentration may decrease due to dilution effect (due to increase of biomass).