Abstract:

To clarify the impacts of flooding stress on the morphological structure and activities in different types of roots for maize at seedling,two typical maize cultivars Zhengdan 958(ZD958,a tolerant genotype)and Liyu 16(LY16,a susceptible one)were selected,and five flooding durations at three leaf stage were established:0(CK),2,4,6,8 d,to explore the response law involving morphology and root activities of embryonic and adventitious root to excessive moisture.The results showed that after 2 days of flooding,the root length,root surface area,root volume,root tip number and root fork number of primary root,seminal root and adventitious root in maize were significantly higher than those of CK.With the extension of flooding duration,these indexes decreased obviously,but the average root diameter displayed an outstanding enhancement.Compared with CK,the morphological indexes of emerging adventitious root under flooding performed better,and among them,the root length and root tip number suffered the most from flooding.The total number,the layer number and the angle of adventitious root increased after flooding.With the elongation of flooding duration,except dry weight at the first layer of adventitious root,the primary root,seminal root and secondary layer of adventitious root of ZD958 increased first and then decreased,but those of LY16 decreased from the start.The root-shoot ratio rose from 2 days to 6 days,and then declined after that.The root activities of primary root and seminal root were significantly reduced under flooding,however,the function of adventitious root could be maintained for 4—6 days.It is concluded that the negative effects of flooding on different root types indicated primary root>seminal root>adventitious root,and response features were different from both varieties.In addition,the adventitious root activity and root-shoot ratio of flooding resistant variety begin to decrease after 8 days of flooding.

Key words: Maize, Flooding stress, Root morphology, Dry weight, Root activity