| A method of producing high oil maize (HOM), the TEU system (three effect utilization system) has been developed in China recently, which involves a blend of a cytoplasmic male-sterile version of an elite single cross normal oil maize (NOM) hybrid (account for above 90 %) and a male fertile version of HOM pollinator ( 8 %). The oil concentration of NOM will increase because of xenia, and the grain yield maybe increased because of heterosis, which can minimize the yield disadvantage associated with HOM hybrids. This HOM production system has been licensed by DuPont Specialty Grains, which has been regarded as the preferred method of producing HOM in the United States. The ecophysiological mechanisms of the yield enhancement of NOM in the TEU system were explored through versifying the hypothesis that the increase of grain yields in cross-pollination might be a result of improved photosynthetic rate and related traits.Three NOM hybrids, ND108, LY20, SCF03-62, and three HOM hybrids, HOM202, HOM115, HOM4515 have been selected for planting in the true field. The NOM hybrids were pollinated by HOM hybrids respectively at anthesis, and NOM hybrids were self- pollinated to be control. Yield, oil concentration, photosynthetic traits and nitrogen efficacy associated with yield forming process were determined. The main results were as follows:1 The changes of grain yield of normal oil maize after pollinated by high oil maizeFor the grain yield of NOM in F0 generation, four of the nine combines were higher than that of NOM self pollination treatments, and two combines (ND108×HOM202, ND108×HOM115) had significant difference to NOM self pollination treatments. The grain yield of others was lower than that of ND108 self pollination treatments, and ND108×HOM4515, SCF03-62×HOM202, SCF03-62×HOM115 had significant difference to NOM self pollination treatments. There was significant difference in grain yield between ND108 after pollinated by HOM hybrids and ND108 self pollination treatments.The same trend as grain yield was noted in biomass when NOM was pollinated by high oil HOM hybrids. As for harvest index (HI), no significant difference was observed in harvest index among all the pollination treatments. As there was a positive and significant correlation was found between grain yield and biomass (r2 = 0.998, P = 0.0014), however, such correlation was not found between grain yield and HI (r2 = 0.904, P > 0.05). Our results confirm that the increase of biomass production was more responsible for the enhancement of grain yield in cross-pollinated treatments than the increase of HI.2 The changes of oil and starch content of normal oil maize after pollinated by high oil maizeCompared to NOM self pollination treatments, oil concentration of kernels significantly increased when NOM were pollinated by HOM hybrids, which reached to 51.8 g kg-1～61.2 g kg-1, and the mean oil concentration in the crossed-pollination treatments was 57.4 g kg-1. The dry weight and volume of embryo in the crossed-pollination treatments was bigger than that of NOM self pollination treatments. This might be the main reason for the oil concentration enhancement in the crossed-pollination treatments.The amylase content of kernels decreased by 5.1 %～20.9 %, while the amylopectin content of kernels in creased by 0.5 %～9.5 % when NOM were pollinated by HOM hybrids. But the starch content of kernels had little change.3 The changes of photosynthetic traits of normal oil maize after pollinated by high oil maizeThe net photosynthetic rate and stomatal conductance of yield-increased cross pollination combines (ND108×HOM202, ND108×HOM115) increased, as for the diurnal trends of net photosynthesis rate, the net photosynthetic rate of yield-increased cross pollination combines was higher than that of ND108 self-pollination treatments about midday. In yield- increased cross pollination combines, the leaf area index, the Chlorophyll content, the soluble protein content and the PEPCase activity in the ear leaves were greater in the cross-pollination than that of self-pollination treatments during late leaf senescence. While the yield-decreased cross pollination combines had lower photosynthetic characteristics4 The changes of root traits of normal oil maize after pollinated by high oil maizeUnder N deficiency condition, the decrease percent of the dry matter and the volume of root in cross pollination combines were bigger than that of self-pollination combines, and that of the yield-increased cross pollination combines was less sensitive to N deficiency than yield-decreased cross pollination combines.The root activity of yield-increased cross pollination combines decreased (9.2 %～17.7 %) lower than that of yield-decreased cross pollination combines (11.5 %～26.3 %). That indicated that the yield-increased cross pollination combines was less sensitive to N deficiency than yield-decreased cross pollination combines.5 The changes of nitrogen efficacy of normal oil maize after pollinated by high oil maizeAlthough the nitrogen use efficacy (NUE) of ND108 was decreased when pollinated by HOM, but the agronomy nitrogen use efficacy (ANUE), physiological nitrogen use efficacy (PNUE), nitrogen harvest index (NHI) and soil nitrogen dependent rate (SNDR) of yield-increased cross pollination combines was higher than those of self-pollination combines, and those of yield-decreased cross pollination combines was lower relative to self-pollination combines.The yield enhancement of yield-increased cross pollination combines was related to the increase of leaf photosynthetic activity and nitrogen use efficacy mechanism. The cross pollination combines with high yield had higher leaf photosynthetic activity and nitrogen use efficacy, and so the biomass.
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