A tool for simplified evaluation of salt and heavy metal stress – Example of salt stressed basil plants (Ocimum basilicum) amended with castor cake

A tool is proposed for integrating the results from studies on alleviation of heavy metal or salt stress in plants. The results of such studies are usually presented as separate variables for each treatment, but their interpretation is not intuitive, and sometimes what is assumed as stress alleviation is simply the balance between the detrimental effect of the stress and the beneficial effect of the alleviating treatment. The synergy index integrates the results from the stressing, alleviating, and combined treatments in just one value that objectively indicates if the plant stress was alleviated. The tool is demonstrated in a study on basil ( Ocimum basilicum ) exposed to salinity and amended with castor cake for stress alleviation. The concept is also illustrated on the results extracted from several research papers on plant stress alleviation. • Interpretation of stress alleviation is not intuitive, and it is frequently mistaken • A new tool is proposed for interpreting studies on plant stress alleviation • Synergy index integrates the isolated effects of stressing and alleviating treatments • Synergy index is demonstrated in salt-stressed basil amended with castor cake • The method is illustrated with examples from the scientific literature