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FOLIAR UREA APPLICATION AFFECTS NITRIC OXIDE BURST AND GLYCINEBETAINE METABOLISM IN TWO MAIZE CULTIVARS UNDER DROUGHT

LIXIN ZHANG^1,2*, XIFENG ZHANG¹, KAI WANG¹, YONGGUI ZHAO¹,YOUYA ZHAI¹, MEI GAO¹, ZHENFENG AN¹, JIANCHAO LIU¹AND JINJIANG HU¹

Abstract: Foliar urea has been proved to act a better role in alleviation of the negative effects of drought stress (DS). However, the modulation mechanism of foliar urea are not conclusive in view of nitric oxide (NO) burst and glycinebetaine metabolism and their relationship. Two maize (Zea mays L.) cultivars (Zhengdan 958, JD958, Jundan 20, ZD20) were grown in hydroponic medium, which were treated with spraying of urea concentration of 15 g L^-1 and two water regimes (non-stress and DS simulated by the addition of polyethylene glycol (PEG, 15% w/v, MW 6000). The ten-day DS treatment increased betaine aldehyde dehydrogenase (BADH) activity, choline content and nitric oxide (NO) content acted as the key enzyme, initial substrate and a nitrogenous signal substance respectively in GB synthesis metabolism, thus, induced to great GB accumulation. The accumulation of NO reached the summit earlier than that of GB. The more positive/less negative responses were recorded in JD958 as compared with ZD20 to DS. Addition of foliar urea could increase accumulation of choline and BADH activity as well as NO content, thereby, increase GB accumulation under DS. These positive effects of urea applying foliarly on all parameters measured were more pronounced in cultivar JD20 than those in ZD958 under drought. It is, therefore, concluded that increases of both BADH activity and choline content possibly resulted in enhancement of GB accumulation. Foliar urea application could provoke better GB accumulation by modulation of GB metabolism, possibly mediating by NO burst as a signal molecule during drought, especially in the drought sensitive maize cultivar.

¹College of Life Sciences, Northwest A & F University, 712100, Yangling, Shaanxi, P.R. China,

²State Key Laboratory of Soil Erosion and Dryland Farming, Institute of Soil and Water Conservation,

Chinese Academy of Sciences and Northwest A & F University, 712100, Yangling, Shaanxi, P.R. China