Effects of Plant Growth Regulators on Sugarcane Productivity and Quality of the Art Through the Increase in Photosynthetic and Antioxidant Activity

The foliar application of plant growth regulators to sugarcane can increase crop growth and yield per cultivated area, improve crop productivity and quality, and mitigate possible abiotic stresses by optimizing photosynthesis. The productive potential of sugarcane has not been fully tapped, and plant growth regulator technology via foliar application could greatly benefit the production of food and renewable energy from the sugarcane production chain. In this study, we conducted 15 sugarcane field trials to evaluate the effects of plant growth regulators (17 ppm GA(3) activity, 817 ppm IAA activity and 43 ppm zeatin) via foliar application at the vegetative stage (V) or vegetative and maturation stages (VM) on the photosynthetic and antioxidant enzyme activities, carbohydrate production and yield production of three harvest periods (early, mid-late and late harvest sugarcane). In general, foliar application increased the enzymatic, agronomic, quality and energy parameters of sugarcane. The application of plant growth regulators in V and VM increased the activities of the photosynthetic enzymes phosphoenolpyruvate carboxylase and ribulose-1,5-bisphosphate carboxylase-oxygenase, decreased the contents of malondialdehyde and hydrogen peroxide, and increased superoxide dismutase, catalase, ascorbate peroxidase, and proline content. The average stalk yield over the three harvest times increased by 5.4 and 8.0% in V and VM, respectively, compared to the control (101 Mg ha(-1)). In addition, V and VM increased the sucrose concentration, theoretical recoverable sugars (TRS), and sugar productivity by averages of 2.9%, 2.6% and 9.3%, respectively compared to the control (13.9% of sucrose, 139 kg sugar stalk(-1) of TRS, and 13.9 Mg ha(-1) of stalk yield), across all harvest seasons. The best results for straw, bagasse and energy production were observed in VM, with average increases of 8.0%, 7.7% and 8.0% compared with the control (14.1 Mg ha(-1), 6.1 Mg ha(-1) and 69.8 kWh, respectively). Thus, plant growth regulator application can increase sugarcane metabolism, growth and development. Although single plant growth regulator application in the vegetative stage improved all sugarcane parameters, the double application of plant growth regulators in the vegetative and maturation stages ensured improvements in yield and product quality.