| The studies consisted of four experiments. They were "effect of uniconazole applied to seeds on germination and material conversion", "effect of uniconazole applied to seeds on strong seedlings and the related physiological indicators", "effect of spraying uniconazole on photosynthetic characteristics, dry matter accumulation and distribution of soybean" and "effect of uniconazole on growth and development and dry matter production of relay cropping soybean after blooming under different nitrogen level". The effects of uniconazole on morphological and physiological characteristics, yield and grain quality of relay cropping soybean were studied from 2006 to 2009. The results were as follows.1 Effect of uniconazole on morphological of soybean1.1 The strong seedlings established by uniconazole waterless-dressed seedThe seedling height, first internode length, cotyledonary node height, root length and leaf area per plant were decreased significantly accompanied with the increase in uniconazole concentration. While the stem diameter, root volume, root dry weight, shoot dry weight and root to shoot ratio were increased by uniconazole treatment, and the concentration which showed the best effect was 4 mg/kg, the second was 2 mg/kg.1.2 The flourishing growth of soybean was controlled by spraying uniconazole at branching stage (V5)The soybean grows flourishing easily below corn in relay cropping system. Spraying uniconazole at V5 stage significantly decreased plant height, the main stem height, the first internode length, leaf area per plant and LAI of R1 to R5 stage accompanied with the increase in uniconazole concentration; the stem diameter was increased significantly at R5 stage by spraying lower concentration uniconazole (30,60 mg/kg). Spraying higher concentration uniconazole (120,150 mg/kg) at R1 stage significantly decreased plant height, the main stem height, the first internode length, leaf area per plant and LAI of Ri to R5 stage, while significantly increased stem diameter. Thus, the results suggested that spraying the lower concentration uniconazole at V5 stage showed the best effect of controlling flourishing growth, until higher concentration uniconazole can reach the effect of controlling flourishing growth if spraying uniconazole at R1 stage.2 Effect of uniconazole on physiological characteristics of soybean2.1 Uniconazole changed the endogenous hormone content and their balance Uniconazole waterless-dressed decreased GA content, increased IAA content, and delayed peak time of ZT content, and increase ZT content levels at late time after seed germination. This showed that uniconazole inhibited germination in the earlier stage, while promoted germination in the later stage. The content of KT, GA and IAA was decreased significantly, while ABA content, ABA/GA and ABA/KT ratio were increased significantly from R2 to R5 stage with uniconazole spraying treatment. Uniconazole spraying treatment increased KT, GA, IAA content, while decreased ABA content, ABA/KT and ABA/GA ratio significantly in R7 stage. This showed that uniconazole could inhibit the vegetative growth after blooming which is beneficial to pods formation, and uniconazole also could delay leaf senescence.2.2 Uniconazole waterless-dressed treatment changed the physiological characteristics of soybean seedlingUniconazole waterless-dressed treatment increased SOD, POD and CAT activity, while decreased MDA content of soybean seedling leaves and roots. The Chlorophyll content, root vigor, root active absorption area, root to shoot ratio and dry matter accumulation, and the concentration which showed the best effect was 4 mg/kg. Thus, uniconazole enhanced the plant's anti-shading capacity and dry matter accumulation, improved the distribution of dry matter. 2.3 Uniconazole changed the physiological characteristics of soybean after bloomingLAI of soybean plant population was decreased, while the C/N ratio of leaf was increased after blooming (R1-R5) with uniconazole treatment (waterless-dressed and spraying), which was conductive to transmitting air and light and increased photosynthetic leaf area, and controlled the flourishing growth effectively. Uniconazole treatment (waterless-dressed and spraying) prolonged green leaves time, increased chlorophyll content and LAI of R7 stage. These suggested that uniconazole treatment could delay leaf senescence.Pn, Gs, Tr, Chl a content and dry matter accumulation were increased with uniconazole treatment (waterless-dressed and spraying), while the performance of which was different under different N level. They were increased accompanied with the increase in uniconazole concentration with uniconazole waterless-dressed treatment under the low N (0 kg/hm2) level, which of spraying 60 mg/kg uniconazole at V5 stage were the best, the second was spraying 30 mg/kg uniconazole. Uniconazole waterless-dressed treatment enlarged Pn, Gs, Tr, Chla content and dry matter accumulation, the most remarkable promotion of which occurred at the concentration of 4 mg/kg, followed by 2 mg/kg under the middle N (31.2 kg/hm2) level, which of spraying uniconazole treatment were increased at V5 stage and the most remarkable promotion occurred at the concentration of 30 mg/kg, followed by 60 mg/kg. Pn, Gs, Tr, Chl a content and dry matter accumulation were increased only by 2 mg/kg uniconazole waterless-dressed treatment under the high N (62.4 kg/hm2) level, which of spraying uniconazole treatment were increased at V5 stage and the most remarkable promotion occurred at the concentration of 90 mg/kg.Soluble sugar and the total N content of soybean leaves and stems after flowering were increased with uniconazole treatment (waterless-dressed and spraying) (except high N), while the performance of which was different under different N level. The most remarkable promotion occurred at the concentration of 8 mg/kg in uniconazole waterless-dressed treatment, and 60 mg/kg in spraying uniconazole treatment under the low N level. The most remarkable promotion occurred at the concentration of 4 mg/kg in uniconazole waterless-dressed treatment, and 30 mg/kg in spraying uniconazole treatment under the middle N level. Soluble sugar and the total N content of soybean leaves and stems after flowering were increased only with 2 mg/kg concentration in uniconazole waterless-dressed treatment, and which was increased accompanied with the increase in uniconazole concentration with uniconazole spraying treatment under the high N level. Uniconazole could increase the carbon and nitrogen metabolism of plants and the Pn, Gs, Tr, Chl a content and dry matter accumulation after flowering under the low and middle N level; the promotion effect is not remarkable with uniconazole waterless-dressed treatment under the high N level.3 Uniconazole changed the soybean yieldUniconazole treatment (waterless-dressed and spraying) increased the soybean yield, which was because of the increase of pod number and 100-seed weight, while the performance of which was different under different N level. The yield was increased accompanied with the increase in concentration with uniconazole waterless-dressed treatment (2-8 mg/kg), and the most remarkable promotion of yield occurred at the concentration of 60 mg/kg with uniconazole spraying treatment at V5 stage under the low N level. The most remarkable promotion of yield occurred at the concentration of 4 mg/kg, followed by 2 mg/kg with uniconazole waterless-dressed treatment, and which occurred at the concentration of 30 mg/kg with uniconazole spraying treatment at V5 stage under middle N level. The yield was increased only with 2 mg/kg concentration in uniconazole waterless-dressed treatment, and which was increased accompanied with the increase in uniconazole concentration with uniconazole spraying treatment (30-90 mg/kg) at V5 stage under the high N level.4 Uniconazole changed the soybean qualityThe total AA content and the human essential AA content (except Met) of seed were increased with uniconazole treatment (waterless-dressed and spraying), while the fat content with uniconazole treatment (waterless-dressed and spraying) was not significant difference with control (except the high N level) under every N level. The grain protein and soluble sugar content of seed by uniconazole treatment (waterless-dressed and spraying) were higher than those of the control under the low and middle N level. The content of grain protein and soluble sugar of seed with uniconazole spraying treatment was higher than that of the control, which was increased only with 2 mg/kg concentration in uniconazole waterless-dressed treatment under the high N level. |
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