Effects of the Ca 2+ /Mg 2+ ratio on the growth and Mg absorption and distribution in cuttings of two grapevine cultivars ( Vitis vinifera )

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To clarify the effects of the Ca2+/Mg2+ ratio on the growth and mineral nutrient absorption and distribution of grapevine cuttings, a sand culture experiment was conducted using cv. Xinyu, a major table grape cultivar in Xinjiang, and cv. Ugni Blanc, a wine grape cultivar. Four Ca2+/Mg2+ ratios (16:1, 12:1, 8:1 and 4:1) were set with a constant Mg2+ concentration of 1.25 mmol·L−1 to investigate the influence of suboptimal Ca–Mg ratio in calcareous soils. However, Ugni Blanc wilted and became necrotic at a 16:1 ratio; therefore, only the data from the other three treatments were analyzed. The results revealed that the biomass of both cultivars first increased then decreased with increasing Ca2+/Mg2+ ratio, and the 8:1 ratio resulted in the optimal plant height, stem diameter, shoot dry weight, SPAD value and photosynthetic parameters. Ca and Mg ratio significantly affected the Ca and Mg concentrations in various plant parts (P < 0.05). With Ugni Blanc, the accumulations of Ca and Mg both increased to a peak and then declined. With Xinyu, Ca accumulation increased continuously, while Mg accumulation showed the same trend as that in Ugni Blanc. The 16:1 ratio caused obvious Ca–Mg antagonism and reduced the Mg concentration in all the tissues, whereas the 8:1 ratio significantly increased the distribution rates of Ca and Mg. In conclusion, a Ca2+/Mg2+ ratio of 8:1 was most favorable for the growth and Mg absorption and translocation of grapevine cuttings, and a suboptimal ratio inhibited plant growth through Ca–Mg antagonism.