2019 ASHS Annual Conference

Screening salinity tolerant plants is usually time intensive and only applicable to a limited number of salinity levels. The near-continuous gradient dosing system (NCGDS) developed by Hawk et al. (2009) allows researchers to evaluate a large number of plants for salinity tolerance with multiple treatments, more flexibility, and reduced efforts. Hibiscus syriacus (rose of sharon), Physocarpus opulifolius (common ninebark), and Spiraea japonica (japanese spirea) were irrigated daily using NCGDS with eight electrical conductivity (EC) levels ranging from 0.88 dS·m^-1 to 6.46 dS·m^-1. At 11 weeks after irrigation initiated, P. opulifolius and S. japonica had increased foliar damage along with increasing EC levels. The shoot dry weight of both species decreased linearly as EC levels increased. In addition, the stem diameter, growth index, number of inflorescences, relative chlorophyll content, and net photosynthesis rate of P. opulifolius and S. japonica decreased linearly or quadratically along with increasing EC levels. There was no significant difference among treatments in term of visual score, growth index, stem diameter, or dry weight of H. syriacus. However, the relative chlorophyll content and net photosynthesis rate of H. syriacus decreased linearly as EC levels increased. The salinity threshold of P. opulifolius and S. japonica was 5.42 dS·m^-1 and 4.6 dS·m^-1, respectively, but not determined for H. syriacus.