Changes in physiological and morphological traits of roots and shoots of wheat in response to different depths of waterlogging

The growth reduction of wheat (Triticum aestivum L.) during and after water logging stress depends on the depth of water from the soil surface. In a po t experiment with 3-week-old plants, soil was waterlogged for 14 d at the s urface, or at 100 or 200 mm below the surface, and pots were then drained t o assess recovery. A fully drained treatment kept at field capacity served as control. During waterlogging, the relative growth rate of roots decrease d more than that of shoots (by 6-27% for shoots, by 15-74% for roots), and plant growth was reduced proportionally as the water level was increased. L ight-saturated net photosynthesis was reduced by 70-80% for the two most se vere waterlogging treatments, but was little affected for plants in soil wa terlogged at 200 mm below the surface. The number of adventitious roots for med per stem in plants grown in waterlogged soil increased up to 1.5 times, but the number of tillers per plant was reduced by 24-62%. The adventitiou s roots only penetrated 85-116 mm below the water level in all waterlogging treatments. Adventitious root porosity was enhanced up to 10-fold for plan ts grown in waterlogged soil, depending on water level and position along t he roots. Porosity also increased in basal zones of roots above the water l evel when the younger tissues had penetrated the waterlogged zone. Fourteen days after draining the pots, growth rates of plants where the soil had be en waterlogged at 200 mm below the surface had recovered, while those of pl ants in the more severely waterlogged treatments had only partially recover ed. These findings show that the depth of waterlogging has a large impact o n the response of wheat both during and after a waterlogging event so that assessment of recovery is essential in evaluating waterlogging tolerance in crops.