A better water status in wheat seedlings induced by Azospirillum under osmotic stress is related to morphological changes in xylem vessels of the coleoptile

Water stress can have major impacts on plant growth and development. Although it has been demonstrated that Azospirillum brasilense Sp245 improved growth and water status in wheat seedlings under salt and osmotic stresses, knowledge of the effects the bacteria could elicit in plant shoot morphology is still scarce. The aim of this work was to examine the average vessel area and the water potential of coleoptiles from seedlings inoculated with A. brasilense Sp245 and non-inoculated controls growing either in water or in osmotic stress conditions. Changes in vessel size have an important role in the adaptation to unfavourable environmental conditions. We found that coleoptiles of Azospirillum-inoculated seedlings showed wider xylem vessels and less negative water potential when grown in 20% PEG 8000. We concluded that Azospirillum inoculation induced wider xylem vessels that might imply an enhanced coleoptile hydraulic conductance which in turn could explain the better water status observed.

► Azospirillum improves water status in wheat seedlings under osmotic stress.
► Wider xylem vessels in coleoptiles of Azospirillum-inoculated osmotic stressed wheat seedlings.
► More efficient water transport in Azospirillum-inoculated osmotic stressed seedlings.