Leaf protein contents and nitrogen-to-protein conversion factors for 90 plant species

Abstract

The leaf protein contents of 90 plants covering taxonomically diverse groups ranged from 0·2 to 7·5 g% fr. wt. The nitrogen-to-protein conversion factors (kA') based on nitrogen recovered from amino acid analyses ranged from 5·15 to 5·93, reaffirming that the traditional factor of 6·25 is not valid for plant proteins. A more practical conversion factor (kP) based on the ratio of protein from amino acid data to Kjeldahl nitrogen varied from 3·28 to 5·16. Variations in both leaf protein contents and the conversion factors to some extent correlated with the taxonomic groupings of the plants. For a good estimate of the leaf protein content from Kjeldahl nitrogen, factor kP, established using plants sampled from the same taxonomic group, should be used. However, for plants in general, a kP of 4·43 should provide a reasonably good estimate of the protein content. © 1994.