A dry mass and zinc accumulation model of young apple tree in sand culture under zinc stress

A sand culture experiment was conducted to build a model of the dynamic accumulation and distribution of dry matter in organs of apple trees under three zinc application levels (Zn1 0.013, Zn2 0.254 and Zn3 5.07 mg L -1 ). The dry mass and zinc accumulation of young apple tree showed a logistic model response to the date, so three rate curve equations of dry mass accumulation under different zinc application levels were built. There are little effects on the accumulation and distribution of dry matter under different zinc levels at the early growth stage, and the nutrients in roots and stems are utilized by branches and leaves for quickly growth. In the later stage of growth, the young apple tree showed a significant decrease trend in all the treatments, but the dry mass accumulation rate with the moderate zinc application was significantly higher than in other treatments. The zinc accumulation rate at different zinc levels to the date can also be simulated by logistics function with R = 0.99. The mean and max rate of zinc accumulation and the day of max rate of zinc accumulation occurrence showed the significant difference among the treatments, which was Zn1>Zn2>Zn3. The dry matter accumulation is constrained by the deficiency and excess zinc supplies at the later growth stage, and zinc toxicity is happened under the excess zinc supply. The correlation of dry mass and zinc accumulation could be fitted by y = Alnx + B (x = nutrient accumulation amount). The results could support some of the hypothesis about the zinc distribution and accumulation in apple trees. Also, they provide some foundation for decision support system of apple tree management.