Changes in Phosphorus Fractions in Response to Uniconazole Application in Cotton Functional Leaves

The growth regulator uniconazole is used in cotton production globally to control plant growth and maximize yield and quality of cotton. Phosphorus (P) is one of the essential nutrients and contributes substantially to cotton production. However, uniconazole application effects on P fractions in cotton plants remain unclear. Here, we conducted a field experiment with cotton cultivar CCRI 60 under two uniconazole application rates (0 and 2250 ml ha(-1)) at full bloom stage and peak boll setting stage. P fractions in cotton functional leaves (i.e., the fourth leaf from the apex) were measured using P-31- nuclear magnetic resonance (NMR) technology. The results showed that the uppermost phosphorous compounds were orthophosphate, pyrophosphate, phosphate monoesters, and phosphate diesters. Uniconazole application had significant effect on phosphorous compounds, increased orthophosphate content by 10-22%, alpha-glycerophosphate by 30-43%, and pyrophosphate by 20-149%, respectively. Spraying uniconazole had greater effect on orthophosphate, phosphate monoesters, choline phosphate, and phosphatidylethanolamine exclusively at full bloom stage, but had significant effect on pyrophosphate at two period. In conclusion, the positive interaction between uniconazole and phosphorous may provide a direction for studying more deeply on the physiological mechanism of the effects of uniconazole on photosynthesis and adverse resistance.