In order to enhance tolerance of Copper acalypha transplants (Acalypha wilkesiana Müll. Arg.) to soil salinity, this investigation was carried out under the full sun at the nursery of Hort. Res. Inst., ARC, Giza Egypt during 2013 and 2014 seasons, as 5-months-old transplants of this ornamental shrub were cultured in 30-cm-diameter plastic pots filled with about 6 kg/pot of sand + loam + cattle manure compost mixture (1: 1: 1, v/v/v), salinized with an equal parts mixture of NaCl and CaCl2 pure salts (1:1, w/w) at the rats of 0, 2000, 4000 and 6000 ppm. Magnetic iron (Fe3O4) was applied as soil drench at the rates of 0, 3 and 6 g/pot, 4 times with 2 months interval. The effect of interaction between salinity and Fe3O4 treatments was also studied.
The obtained results have shown that means of vegetative and root growth traits were descendingly decreased, with few exceptions as the rate of salinity was increased to reach the minimal values compared to control in the two seasons by the highest salinity level, while they were progressively increased with increasing Fe3O4 rate to reach the maximal values over control in the two seasons by the rate of 6 g/pot. Indeed, 3 g/pot Fe3O4 treatment significantly raised the means of most vegetative and root growth measurements, but the upper hand was for the rate of 6 g/pot in both seasons. The effect of interaction treatments was fluctuated, but the best gains were attained in the two seasons by combining between planting in either unsalinized soil mixture or salinized one at 2000 ppm concentration and drenching with Fe3O4 at any level. The connecting between cultivating in 4000 ppm-salinized soil mixture and treating with 6 g Fe3O4/pot significantly improved some growth characters. In general, increasing the rate of Fe3O4 caused an additional improvement in most growth parameters (plant height, stem diameter, No. of leaves/plant, root length and aerial parts and roots fresh and dry weights) regardless of salinity level. The leaf content of chlorophyll a, b, carotenoids, N, P and K was gradually decreased with increasing salinity level, but was progressively increased as the rate of Fe3O4 was increased. The content of Na, Cl and free proline was linearly increased with elevating salinity concentration. On the other side, Na content was descendingly diminished, but that of Cl and proline was gradually increased with increasing Fe3O4 dose. The effect of interaction treatments on chlorophyll a and b, N, P and K content was greatly similar to their effect on growth parameters, but the opposite was the right regarding the content of Na, Cl and proline.
Hence, it can be recommended to apply magnetic iron at the rate of 6 g/pot, 4 times with 2 months interval to the salinized soil mixture in which Copper-leaf transplants is grown to improve their tolerance to salinity stress up to 6000 ppm concentration.