Submitted to: PLoS One
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/1/2013
Publication Date: 10/15/2013
Citation: Barnaby, J.Y., Kim, M.S., Bauchan, G.R., Bunce, J.A., Reddy, V., Sicher Jr, R.C. 2013. Drought responses of foliar metabolites in three maize hybrids differing in water stress tolerance. PLoS One. 8(10):1-10. Interpretive Summary: Drought and high temperatures can decrease maize yields in rain-fed growing regions. Increased frequency of severe drought is likely because of forces driving global climate change. Seed companies are currently marketing maize lines that produce high yields when the soil water content is inadequate. We compared seedling growth of drought resistant and drought susceptible maize lines from Pioneer Hi-Bred International that were grown in controlled environments with either ambient or elevated carbon dioxide. We observed that the most drought tolerant maize line investigated in this study produced less above ground foliage than the other two lines under well watered treatment conditions. Reduced foliage in the drought tolerant hybrid line decreased the demand for soil moisture and had broad implications for whole plant stress avoidance. Elevated carbon dioxide delayed the impact of drought on all three maize hybrid lines by about two days. These experiments showed that minimizing top growth is part of an important strategy for improving the resistance of maize to drought stress. Our findings should benefit environmental scientists, agronomists and crop breeders interested in producing stress resistant crops.
Technical Abstract: Three maize genotypes, differing in drought tolerance, were grown in controlled environment chambers using either ambient (38 Pa) or elevated (70 Pa) carbon dioxide. Water stress treatments were imposed on one half the plants beginning 17 days after sowing. Shoot DW of the drought tolerant hybrid in both CO2 treatments was 44 to 73% less than that of the intermediate and sensitive to drought maize hybrids when seedlings were well watered. Decreases of shoot DW of the tolerant maize hybrid line in response to drought also were about one-half that of the other two maize hybrids when the results of both CO2 treatments were combined. Root growth of the tolerant maize hybrid was also less affected by drought than the other two hybrid lines. Genotypic differences were observed in decreases of soil water content, leaf water potential, net photosynthesis and stomatal conductance in response to drought. Essentially, these parameters were less affected by water stress in a drought tolerant compared to more drought sensitive maize hybrids. Eleven of 19 amino acids measured in this study increased, methionine was unchanged and alanine and aspartate decreased in reponse to drought in the ambient CO2 treatment. The other amines measured in this study exhibited mixed responses to water stress. Drought response of all three genotypes was ameliorated by carbon dioxide enrichment. Our results demonstrated that shoot and root growth as well as the amino acid metabolism of a highly drought tolerant maize genotype selected for improved yields in water stressed environments differed from those of more sensitive hybrids when measured during vegetative growth.