Blueberry (Vaccinium spp.) is well known for its rich anthocyanins and other bioactive compounds, which contributes to prevent from cardiovascular disease and other chronic illnesses. Thereby, many countries including China have attached great importance to the economic value and development prospect of blueberry. However, the main root of blueberry tree is not obvious but exceedingly slender, intertwined and lack of root hair. Meanwhile, blueberry prefers acidic even strongly acidic soil, and its most suitable pH value of culture is from 3.8 to 5.0. As the soil pH value of cultivating blueberry is generally higher than 5.0, large amounts of sulfur powder are applied to reduce the soil pH value. Wufanshu (Vaccinium bracteatum Thunb.), belonging to the same family and genus with blueberry, is a stock with developed root system, strong barren tolerance and extensively ecological adaptability, which has been cultivated as a kind of economic or landscaping plant species. There are many examples of grafting and improving native blueberry with Wufanshu scion in folk. Grafting blueberry with Wufanshu is well worth popularizing in blueberry cultivation at least in the Yangtze River area of China. However, few studies have been reported on the effects of soil pH values on the growth of different Vaccinium plants.
To evaluate the effects of different soil pH values on the growth and relative physiological indices of Wufanshu (V. bracteatum) and rabbiteye blueberry (Vaccinium ashei Reade) cv. Brightwell plants, three different soil pH values (4.2, 5.2 and 6.2) were applied to the 9-month-old plants of Wufanshu and rabbiteye blueberry under greenhouse conditions. Plants were grown in the medium of V(sand):V(perlite)=1:1 and irrigated every 2 days with half-strength Hoagland’s No. 2 nutrient solutions with different pH values (4.2, 5.2, and 6.2). Leaves, stems and roots were separately sampled after 187 days to determine their relative physiological indices.
The results showed that the biomass, chlorophyll content and root activity of Wufanshu and blueberry were the lowest at pH 6.2 level, but the maxima of the biomass and root activity in Wufanshu and blueberry were found at pH 5.2 and 4.2 levels, respectively. The soluble sugar and protein contents of Wufanshu and blueberry were the highest at pH 6.2, and the lowest ones were detected at pH 5.2 and 4.2, respectively. The contents of phosphorus (P), ferrum (Fe) and zinc (Zn) in the roots, stems and leaves of Wufanshu were the highest at pH 5.2 level; however, the contents of P and Fe in the roots, Fe in the stems, and Fe and Zn in the leaves of blueberry were the highest at pH 4.2 level. The activities of peroxidase (POD) and catalase (CAT), and malondialdehyde (MDA) content of Wufanshu and blueberry were the highest at pH 6.2 level, while the minima of them were presented at pH 5.2 and 4.2, respectively.
These results indicate that pH 5.2 and pH 4.2 are the optimal soil pH values for the growth of Wufanshu and blueberry plants, respectively; however, soil pH 6.2 will inhibit their growth, especially the blueberry.