ARS | Publication request: Effects of global climate change on the allocation of defense metabolites

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 13, 2011
Publication Date: N/A

Technical Abstract: Global climate change is expected to alter various abiotic factors, of which precipitation patterns is of most concern. When plants experience stress, the optimal defense theory suggests that plants will use their energy on defending the more vital plant tissues. For example, to a plant experiencing drought stress, the roots may be the more vital tissue. Phytoalexins are produced in response to the infection of fungal pathogens. Surprisingly, we found that phytoalexins were induced in uninfected roots of Zea mays var. 'Golden Queen' plants in response to drought stress. We hypothesized that defense resources were being allocated to the roots in anticipation of a possible pathogen infection. We designed a study to test if we could divert the drought induced reallocation of resources to the roots by increasing the value and risk of attack on the aboveground parts of the plant. In order to do this we introduced two additional stress factors: limited light and pathogen infection. This was done by placing drought stressed maize in a partially shaded environment and infecting the stock with the fungal pathogen Fusarium verticillioides. The roots were then analyzed for the production of phytoalexins. Drought stressed roots of pathogen infected plants still had significantly more phytoalexins than watered plants; however, the pathogen infection reduced the phytoalexin accumulation. Shading had minimal effect on the drought stress induction of phytoalexins in the roots. Our results suggest that the induction of phytoalexins in drought stressed roots is an allocation of resources to roots, signifying that during drought stress alone the roots are the most valuable tissue. Severe aboveground pathogen infection can reduce but not eliminate the allocation of resources to the roots. Furthermore, conditions of limited light did not increase the value of the leaves enough to reduce the importance of roots during drought stress.