| Using four maize genotype F1(HD4), ♂(478), ♀(TS) and F2 as materials, some important aspects in the root traits and whole water relations were studied under solution culture and plotted, including:(1) relationship between root hydraulic conductivity(Lpr)of maize and its water status.(2) Effect of maize root morphological traits on it's drought resistance and water use efficiency(WUE).(3) Relationship between signal root hydraulic conductivity(Lpsr) and whole roots system hydraulic conductivity(Lpwr) of maize, as well as relationship between whole root surface area(WRS) and active root surface area (ARS).(4) Mechanism of N, P nutrition regulate to water relation through affecting roots traits. The major conclusions are as the follows:1 Solution culture method was used to study the relationship between Lpr and drought resistance. The results indicated that there is a significant positive co-relation between Lpwr and drought resistance, but no significant co-relation between Lpsr and drought resistance. Under both normal water supply and water stress by -0.2MPa PEG, Fl has a higher Lpwr while has a higher Lpsr, which means that Fl can maintain capacity of continually absorbing water from dry soil under water deficiency condition. At the same time, Fl has a lower Cs compared with other two genotypes, which means that Fl can effectively resist water transpiration under water deficiency. This capacity of exploring new source and blocking transpiration flow in water use maybe account for the Fl's higher drought resistance. However, under water deficiency, as a lower Vs, which means that it has higher osmotic adjustment attribute to its drought resistance. There is a significant positive co-relation between Lpw and leaf V s, Pn, Tr and Cs.2 The relationship between Lpsr and Lpwr, relationship between WRS and ARS as well were studied under solution culture conditions. The results indicated that there is a positive but not linear relation between Lpsr and Lpwr. Whole root surface area (WRS) and active root surface area (ARS)are two different defmations , the former contribute to root bio-mass, and the later to roots' metabolism activity. There is a difference among genotype in ratio of ARS to WRS. The drought resistance genotype (such as Fl) has a significant higher ARS/WRS than that of drought tolerant genotype(such as $), the former has ahigher water use and WUE.3 The relationship between root characteristics and WUE on maize was studied under plotted conditions. The result indicated that there is a remarkable difference in varieties and different treatments. Regressive analysis of WUE and total roots length, roots system surface area and its bio-mass present three times curve relation. Their trends were basically similar. Namely when roots bio-mass, total root length and root surface area were relative lower, with the increase of bio-mass, total roots length and area, the WUE increased too. However, when those parameters increased to certain value, the WUE began to drop.4 Using artificial growth chamber, the relationship between water, fertilizer, also the reciprocations of them and maize root system hydraulic conductivity were studied from single root and whole root systems level under PEG-6000 simulating drought stress conditions. The results demonstrated that single root hydraulic conductivity and whole root system hydraulic conductivity were decreased under N, P deficit either water supply or water deficit. But the Lpwr was higher and Lpsr was lower under P deficit than N deficit. Moreover, root system properties took place plastic changes under water and fertilizer stress, including dry weight of whole root systems, lateral root numbers, root hair density, total roots length and absorbing area. And this kind of plasticity has difference of dealing with one of nutrition. Compared with water and nitrogen deficit, more lateral root and deeper root hair density under P stress can increase total root system absorbing area and Lpwr. Hg inhibition experiment indicated that i...
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