Root morphology and anatomy respond similarly to drought and flooding in two wheat cultivars.

BACKGROUND AND

aimsWheat (Triticum aestivum L.) is widely grown in regions prone to both drought and flooding conditions. Although root responses to drought and flooding have been extensively studied separately, studies comparing key anatomical root traits in wheat in both conditions side-by-side are rare. We tested the hypothesis that wheat roots respond in a similar manner to both drought and flooding, despite these being contrasting water regimes.

methodsTwo wheat cultivars ('Jackson' and 'Frument') were grown hydroponically in control conditions, drought and flooding, and the responses in plant growth, root morphology, root anatomy, development of apoplastic barriers and their capacity to reduce radial water loss were measured. KEY

resultsXylem-to-stele ratio decreased by 33% under water stress compared with control conditions, whereas aerenchyma-to-cortex ratio increased 2.1-fold during both drought and flooding compared with control conditions. Compared with control conditions, lateral root growth was more reduced than adventitious root growth, 86% and 67%, respectively, under both types of water stress. There was comparably stunted root and shoot growth under water stress, and adventitious roots grew slower likewise and to one-third of length compared with control conditions. Our findings did not indicate differences in soil flooding tolerances between the two cultivars.

conclusionsWe conclude that different underlying physical processes during contrasting water regimes, e.g., water limitation during drought and oxygen deficiency during flooding, result in similar root responses, e.g., increased relative aerenchyma area, lignin and suberin deposition in the endodermis, and decreased lateral-to-adventitious root length. Future research should provide a more comprehensive understanding of cross-stress effects on root morphology, anatomy and physiology.