PJB-2012-216
EFFECTS OF NITROGEN FORMS AND DROUGHT STRESS ON GROWTH, PHOTOSYNTHESIS, AND SOME PHYSICO-CHEMICAL PROPERTIES OF STEM JUICE OF TWO MAIZE (ZEA MAYS L.) CULTIVARS AT ELONGATION STAGE
LIXIN ZHANG1,2*, YOUYA ZHAI1 , YUNFEI LI3, YONGGUI ZHAO1, LIXIA LV3, MEI GAO1, JIANCHAO LIU1 AND JINJIANG HU1
Abstract
Drought stress (DS) usually causes a serious yield reduction in maize production. Nitrogen (N) has been reported to be able to alleviate DS damage in previous studies; however, which N form is beneficial for plant growth in drought-stress maize and its mechanism is still poorly understood. The objective of this study is to examine the effects of different nitrogen forms on growth, photosynthesis and stem juice characteristics of maize (Zea mays L.) under drought, and find out better and convenient measurers for drought resistance ability of the C4 crop. Pot experiments were carried out using two maize cultivars (Zhengdan 958 and Jundan 20) under integrated root-zone drought stress (IR-DS) by irrigating 10% PEG-6000 solution and non-DS conditions grown for 33 days, and their tested indexes were determined at elongation stage. Dry matter (DM), net photosynthetic rate (Pn), stomatal conductance (gs) and oxidation-reduction potential (ORP) in stem juice were decreased while pH, electric conductivity (EC), soluble protein concentration (SPC) and ABA concentration (ABAC) in stem juice increased of both cultivars in all N forms treatments under IR-DS above non-DS. However, the responses of two examined cultivars to DS were different: significantly higher DM production, Pn and drought index (DI) were observed for ZD958 than JD20, therefore the former could be treated as a drought tolerance cultivar comparatively. Better correlations were obtained amongst the above parameters, especially for DM, Pn and pH, EC, ORP, ABAC in stem juice under IR-DS than non-DS. By comparison with sole ammonium (NH4+), sole nitrate (NO3-) and the mixed supply of NH4+ and NO3- both obviously improved DM and Pn as well as pH, EC, SPC and ABAC whereas decreased Gs and ORP in both drought-stressed cultivars. The effects of NO3--supplied were more evident than NH4++NO3--supplied in the above responses. These impacts were superior in ZD958 than JD20. Further analysis of variation indicated that the impact of N form treatment on almost all parameters measured were, in general, less than those of water regime. It is, therefore, concluded that pH, EC and ORP in stem juice could be regarded better and convenient indicators for evaluating drought resistance ability of the C4 crop. The NO3- supplied could be more beneficial for enhancing photosynthesis and plant growth by improving stem juice characteristics than NH4+ supplied, especially for a drought tolerant cultivar.
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