The Beneficial Effects of Aluminum on the Plant Growth in Camellia japonica

The aim of this research was to investigate the effect of aluminum (Al) on the plant growth, nutrient uptake, and Al accumulation in Camellia japonica. A hydroponic experiment was performed in a completely randomized design with four concentration of Al (0, 0.5, 1, and 2 mM). After growing 8 weeks in the hydroponic nutrient solution, the fine roots and mature leaves of plants were sampled to analyze the biomass, photosynthetic parameters, nutrients uptake, and Al accumulation. The 0.5, 1, and 2 mM Al supplement presented an increase of 71, 118, and 42% on the root biomass, respectively, comparing to the control. The Al-induced growth stimulation in 0.5 and 1 mM Al treatment of Camellia japonica was associated with increased levels of chlorophyll a and b, promotion of net photosynthesis rate, raised contents of soluble sugar and total soluble protein, and decreased levels of malondialdehyde (MDA) and free proline in both leaves and fine roots. The concentrations of nitrogen (N), phosphorus (P), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) in fine roots of 1 mM Al-treated plants were significantly higher than those in the control plants, whereas the levels of calcium (Ca) and magnesium (Mg) were much lower. The mean Al levels in the 1 mM Al-treated plants were 1587, 7189, and 11,192 mg kg (dry mass, DW) for the 1st/2nd, 3rd/4th mature leaves, and fine roots, respectively. This study indicated that 0.5 and 1 mM Al were beneficial to the growth of Camellia japonica. This Al-induced growth enhancement was presumably associated with the increased uptake of nutrient elements. This study also confirmed Camellia japonica as an Al-accumulator.