Mineral composition and accumulation of silicon in tissues of blueberry (Vaccinum corymbosus cv. Bluecrop) cuttings

Research was carried out with the objective of investigating the mineral composition and Si accumulation in tissues of young cuttings of blueberry (Vaccinum corymbosus L. cv. Bluecrop). Blueberry cuttings were irrigated every day for 1 hour (140 ml per pot) with river water containing 0.66 to 1.0 mol m(-3) SiO2, and after 7 months of growth their mineral composition and silicon distribution were investigated by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The mean contents of N, K, Mg, Cu and Zn in young leaves were the same as those in old ones. On the other hand, the mean contents of P, Ca, Si, Fe and Mn in old leaves were higher than those in young leaves. Although Si is not known to be an essential element for growth of blueberries, it was the element that accumulated the most in leaves, with a mean content of 32.0 and 60.0 mg g(-1) dry weight in young and old leaves, respectively. The mean Si content in young leaves was 3.1, 56.7, 4.8, 4.9 and 85 times higher than the mean contents of N, P, K, Ca and Mg, respectively, and was 5.4, 60.0, 8.8, 6.8 and 100 times higher than in old leaves. Scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis of dry ash samples showed that Si accumulated in many parts of the leaves, forming phytoliths in the upper epidermis, including some parts of the palisade mesophyll, in the lower epidermis around the stomata, including guard cells, and in some parts of the spongy mesophyll, and in the veins. There were also silica bodies of unknown origin on the upper epidermis.