Irrelevant drought stress treatments and interpretations in plant physiology experiments – still in view

 

Despite calls from experts in publications, conferences and web sites, certain researchers still use very short stress treatments (by immersing roots in PEG or salt for 48h* or 72h** as published in the same issue of Plant Growth Regulation). After such treatments plants are analyzed for various metabolites (antioxidants, proline, polyamines etc’) which are then taken to explain drought resistance. It is reminded here again for the benefit of the beginner that plant responses to drought or salinity stress and the expression of stress responsive genes require time – which is the normal state in the real world, including seedlings.

 

These cited studies present an additional common problem already exemplified above on this web page. The drought resistance of the cultivars used in this study was derived from previous stated comparative studies of ‘drought resistant’ and ‘drought susceptible’ cultivars. The claimed drought resistance of the stated cultivars used in these seedling studies with PEG is not well proven or characterized in exact terms of their performance under drought stress in the real world. Drought resistance of the given cultivar might be due to, say, ‘escape’ (short growth duration) or constitutively deep roots, which most likely have nothing to do with, say, proline accumulation in seedlings immersed in PEG for 2 or 3 days. It is reminded here again for the benefit of the beginner that if cultivars used in a study are claimed to be drought resistant then this claim must be substantiated to the reader by hard facts. It should also be clarified if past proven stress ‘resistance’ was limited to performance a petri dish, the growth chamber, the greenhouse or was it expressed under field conditions.

 

There is no scientific issue with the study of brief stress treatments of crop seedlings in PEG or salt and the subsequent publication – as long as the results are not announced to be a “model for depicting water deficit tolerance” **, not even in seedlings.

 

(*) Maciej Grzesiak, Maria Filek, Anna Barbasz, Barbara Kreczmer, Herline Hartikainen, 2013. Relationships between polyamines, ethylene, osmoprotectants and antioxidant enzymes activities in wheat seedlings after short-term PEG and NaCl-induced stresses. Plant Growth Regul. 69:177–189.

(**) Samantha Pyngrope, Kumari Bhoomika, R. S. Dubey. 2013. Oxidative stress, protein carbonylation, proteolysis and antioxidative defense system as a model for depicting water deficit tolerance in Indica rice seedlings. Plant Growth Regul (2013) 69:149–165.