Citrus plants generaly depend on arbuscular mycorrhizal fungi (AMF). There are several reports indicating interaction between hormones and AMF. It has also been proven that plant and AMF symbiosis benefits from auxin aplication to roots. The present study had the objective to determine if plant-hormone interaction occurred with hormone groups other than auxins. Mycorrhizal and nonmycorrhizal Carrizo citrange (Citrus sinensis (L.) Osb. X Poncirus trifoliata (L.) Raf.) root systems were submerged for 10 seconds in a 10ppm gibberelic acid (GA3) solution. AMF increased the vegetative growth of Carrizo citrange seedlings as well as P, Zn and Cu leaf contents. Mycorrhizal seedlings had lower Ca, Mg, Fe and Mn concentrations in leaves than nonmycorhizal seedlings, while N and K concentrations were not affected by AMF. GA3 treated seedlings had a bigger trunk diameter but the treatment did not increase seedling height, dry weight, leaf number and leaf area per plant. GA3 treatment also resulted in increased levels of P and Fe in the leaves, reduced K leaf contents but had no effect on other nutrients and did not affect root colonization by AMF. Moreover, the interaction between AMF and GA3 had a significative effect on Carrizo citrange vegetative growth, indicating that GA3 favored plant-AMF symbiosis.
endomycorrhizal fungi; citrus; growth regulators
