Combined effects of phosphorus and analog of brassinoesteroids in the initial phase of sugarcane: growth and photosynthesis

Abstract

In view of the imminent shortage of phosphorus (P), there is a need for research to understand strategies that will contribute to the supply of this nutrient for agriculture. Publications show that hormonal activity beneficially influences processes in which P is vital for occurrence, highlighting the analogs of brassinoesteroides (BR) for their influence on meristemmatic growth, suggesting synergism. Studies with BR in large cultures and its interaction with P, such as sugarcane, are scarce. Thus, the aim of the present study was to evaluate and the effect of applying doses of the BR 24-epibrassinolide analogue (0; 0.5; 1.0; 2.0 mg.L^-1), associated with the presence or absence of fertilization phosphated on the growth, phosphatase, mycorrhization and photosynthesis parameters of young sugarcane plants. The experiment was carried out in a greenhouse, in DBC with factorial 4x2 with six replications. The application of BR provided an increase in root dry mass values ​​up to the maximum point of the curve of 1.27 mg.L^-1. The P interaction with BR benefited air dry mass values ​​in doses of 0.5 and 1.0 mg.L^-1 of the hormone in 30% and 48%, respectively; and showed a positive Pearson correlation of BR doses with the addition of P on this variable. The presence of P stimulated all sugar cane growth variables. BR triggered a significant peak in acid phosphatase enzyme activity at a dose of 1.0 mg. L^-1 and did not affect root mycorrhizal colonization. The internal leaf temperature and stomatal conductance responded positively to the addition of P. Liquid CO₂ assimilation increased in the presence of P and doubled in its interaction with BR. A positive influence of phosphorus and brassinoesteroids was observed, as well as their interaction on the initial development of sugarcane. The results add to the studies about BR and are pioneering about the interaction with P.