| In this paper the effects of several different new plant growth regulators (PGR) on nitrogen metabolism, grain protein contents, grain protein yield and photosynthesis characters of maize were investigated in spring by field experiment to provide the theoretical basis for exploiting new plant growth regulators and popularizing new technology of increasing maize protein contents. And the best new PGR formula was selected. Furthermore, field trials were conducted in autumn in order to assess the effects of different concentrations of the best new PGR formula on nitrogen metabolism, grain protein contents, grain protein yield and photosynthesis characters of maize. The optimum concentration of the best new PGR formula was obtained. The results were shown as follows.I. Studies on available formulae of new plant growth regulatorsChlorophyll contents in the functional leaves of maize could be delayed decreasing by applying PGR to some extent. Chlorophyll contents of PGR treatments were higher than that of the treatment without PGR in grouting stage. Chlorophyll contents of PGR3 was the highest, and PGR4 followed. Compared to control, applying PGR could increase net photosynthetic rate except for PGR1. Net photosynthetic rate of PGR3 got the highest after grouting 21 day and PGR4 after grouting 29 day. CO2 concentration among cells of PGR4 attained the lowest after grouting 21 day and 29 day.The decreasing magnitudes of total N and protein N in the functional leaves and stems of PGR treatments were higher as compared with control. The highest decreasing magnitudes of PGR4 were in functional leaves, however PGR1 in stems.The activities of the nitrate reductase, glutamine synthetase, glutamine transferase and protease of functional leaves were remarkably increased with applying PGR, and the activities of glutamine synthetase and glutamine transferase of grain also significantly increased.The contents of total N, protein N and protein yield in grain were increased with applying PGR. In ripening stage, total N, protein N and protein yield in grain were in the order: PGR4 > PGR3 > PGR2 > PGR1 >control. Total N , protein N contents and protein yield of grain of PGR4 were the highest among these treatments. Protein N and protein content of grain of PGR4 wereincreased by 1.35 g kg-1, 8.25 g kg-1 as compared with control, and the protein yield increased by 19.66%.There were differences in nitrogen metabolism and photosynthesis characters of maize among vary PGR. From the experiment we could conclude that PGR4 was the best PGR formula.II.Study on available applying concentration of new plant growth regulatorsApplying different concentrations of PGR4 could increase chlorophyll contents and photosynthetic rate of functional leaves of maize, which was in favor of synthesis and accumulation of photosynthesis outcome, and development of grain yield and quality. Net photosynthetic rate of PGR4-3 was the highest after grouting 20 day and PGR4-2 followed. Net photosynthetic rate of treatment PGR4-2 was the highest after grouting 30 day.The transports of nitrogen from functional leaves and stems to grain were increased with applying different concentrations of PGR4. The experiment showed that the decreasing magnitudes of total N and protein N in the functional leaves and stems of treatments which applying different concentration of PGR4 were higher as compared with control.The activities of the nitrate reductase, glutamine synthetase, glutamine transferase and protease of functional leaves were obviously increased when applying different concentrations of PGR4, and the activities of glutamine synthetase and glutamine transferase of grain also remarkably increased.The contents of total N, protein N and protein yield of grain were increased with applying different concentrations of PGR4. In ripening stage, both total N and protein N in grain of autumn maize were in the order: PGR4-3 > PGR4-2 > PGR4-1 > control. Of all these treatments, total N and protein N contents in grain of treatment PGR4-3 were the...
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