Response of Roots of Maize Varieties Released in Different Years to Low Ni-trogen and Drought Stresses
The changes in root characteristics were studied under low nitrogen stress (LN) and combined stress of low nitrogen and drought (LD) using six maize varieties released from 1973 to 2009, including Zhongdan 2, Danyu 13, Yedan 13, Nongda 108, Zhengdan 958, and a new variety Yudan 606. The result showed that root dry weight, root length and root surface area of the va-rieties increased at first and then decreased, finally increased again in the process of time. The increase of the three parameters in earlier released varieties could get more water and nutrition from soil, the decrease of these in later released varieties was avail-able to reduce the redundant organ’s dry matter consumption, and the increase again of these in the new variety would meet water and nutrition requirements for yield increase continuously. Compared with the old varieties, root dry weight of the modern varie-ties changed smaller, root length and surface areas increased more, root average diameter became thinner, root bleeding sap de-creased non-significantly under the LN and LD conditions. These results suggested that root characteristics of the varieties have been optimized gradually, the adjustment ability of root morphology, and the LN and LD stress tolerance in modern varieties have been increased.
Different erasMaizeRootLow nitrogenCombined stress of low nitrogen and drought