Distribution patterns of peanut roots under different durations of early season drought stress

The distribution patterns of peanut roots in response to different durations of drought events might affect water acquiring capacity of peanut and this information has not been clearly investigated. In this study, the response to different durations of drought in root distribution was evaluated in peanut genotype ICGV 98305 for three seasons in rhizoboxes in a rainout shelter at Khon Kaen University. Two seasons of this study were in 2013 and one in 2014. The first and the second trials were conducted in the rainy season and the third trial was carried out in the dry season. A completely randomized design with three replications was used. Drought treatments were imposed at 14 days after emergence. The durations of drought imposition were 7, 14 and 21 days after the irrigation withholding. Root samples were divided into 11 soil layers at 10 cm intervals from the top to the bottom of the rhizobox. Drought imposed to peanut at early growth stages could change root distribution patterns of peanut, and the change in root distribution patterns was more pronounced with long duration of drought. In this study, imposing of drought for 21 days caused a clear difference of root distribution patterns between peanut grown under well-watered (WW) and under drought stress (DS) treatments. The peanut adaptation to severe drought appears to be through enhanced root length and the root system growing deeper. The knowledge obtained is useful to decide the duration of drought that causes discernible modification in root system and can help identification of genetic variation for such adaptation. As water stress can mean excess water stress too, generally the expression drought stress is adopted.