Effect of magnetite and paclobutrazol on growth and chemical composition of Schefflera arboricola Endl. cv. Gold Capella plant under salt stress conditions

A pot experiment was conducted under a plastic greenhouse at the nursery of Hort. Res. Inst., ARC, Giza, Egypt during 2019 and 2020 seasons to find out the benefits of both magnetic iron oxide (Fe3O4) as a broadcast incorporation at 2 and 4 g/plant rates, and paclobutrazol (PP333) as a foliar spray at 100 and 150 ppm concentrations, in reducing the harmful effect of saline irrigation water (NaCl + CaCl2 salts at equal parts) at concentrations of 0, 1000, 2000, 4000 and 6000 ppm on growth and quality of Schefflera arboricola cv. Gold Capella transplants gown in 20-cm-diameter plastic pots. The results of this experiment indicated that the mean values of vegetative and root growth parameters were progressively decreased with increasing saline water level to be minimum by the highest level (6000 ppm) compared to control means in the two seasons, except for root length, which was increased to be longer by various salinity levels than control length. Application of PP333 had the least effect on growth traits giving the minimal values comparing with control in most cases of both seasons, whereas application of Fe3O4 attained the best effect giving the highest means of plant height, stem diameter, No. leaves/plant, root length and the heaviest fresh and dry weights of leaves, stem and roots over control and PP333treatments in the two seasons, with the superiority of 2 g/plant rate which recorded the utmost high means in most growth traits measured in the two seasons. The interactions exhibited also a marked effect on the different growth characters, but the most effective treatment was combining between irrigation with either fresh water or 1000 ppm saline one and broadcast incorporating the soil mixture with either 2 or 4 g Fe3O4/plant, as these four interactions improved growth relative to the other ones with no major differences among themselves. A similar trend was also obtained regarding the chemical composition of the leaves, where concentrations of chlorophyll a, b, carotenoids, total carbohydrates, N and P were gradually declined with increasing salinity level, but markedly improved by applying Fe3O4, especially at 2 g/plant dose. The opposite was the right concerning K, Na, Cl and proline concentrations. In general, addition of Fe3O4, especially at 2 g/plant rate caused a marked reduction in the harmful salt ions (Na+ and Cl-), but greatly improved availability and uptaking the macronutrients (N, P and K) comparing with PP333 treatments, giving best growth and performance. Hence, it can be recommended to apply magnetic iron oxide at a rate of 2 g/plant to mitigate saline water hazards (up to 6000 ppm) on growth and quality of Schefflera arboricola cv. Gold Capella foliage pot plant.