Absorption and redistribution of copper in orange plants grafted on different rootstocks

Abstract

Deficiency of copper (Cu) has been observed in citrus plants, particularly in new and vigorous orchards planted in soils with low levels of Cu, which receive reduced foliar applications with copper fungicides. However, in mature orchards, the opposite can happen, with situations of Cu toxicity caused by an excessive number of fungicide applications to control foliar and fruit diseases such as citrus canker. As a result, the Cu concentration in the soil can increase and cause damage to the roots, the severity of Cu toxicity depends on the variety of rootstock. The purpose of this study is to evaluate the absorption of Cu by orange plants grafted on different rootstocks and the redistribution of the Cu in the old parts of the plant to the new organs. The experiment will be carry out in a greenhouse with seedlings of sweet orange grafted on three different rootstocks (Rangpur lime, Sunki mandarin, and Swingle citrumelo double-grafting on Hamlin). The orange plants are transplanted to pots containing nutrient solutions with different concentrations of Cu (2, 20.0, and 200.0 µg L-1 Cu), the plants will be grown in these solutions until the development of the second vegetative flush. This flush will be cut to the determination of the dry matter and sampled for nutrient analysis and enzyme activity. From this point forward, on all treatments, the nutrient solutions will be replaced by another one, without Cu. After the growth of the new flush, which was developed in a free Cu solution, the plants will be destructive harvested. Will analyze the nutritional status, plant growth, and changes in the activity of enzymes related to Cu metabolism. The results will contribute to understanding the Cu absorption by different citrus rootstocks and the redistribution of Cu accumulated in the plant reserves to new flush. (AU)