Mineral Nutrition, Growth, and Germination of Antirrhinum majus L. (Snapdragon) when Produced Under Increasingly Saline Conditions

The conservation of quality water is of special concern, especially in California, as the need for quality water increases with a growing population. Reusing saline wastewaters to irrigate salt-tolerant floral crops provides a viable option to produce quality marketable cut flowers while conserving the highest quality water for other purposes. A completely randomized design with three replications was used to investigate the effects of five salinity treatments [2.5 (control), 5, 8, 11, 14 dS·m-1] and two water ionic compositions: concentrations of Colorado River water (CCRW) and dilutions of sea water (SWD), on the mineral uptake, germination, growth, and quality of two cultivars of Antirrhinum majus ('Monaco Rose' and 'Apollo Cinnamon'). Seeds of both cultivars were sown in 30 greenhouse sand tanks. Leaves were collected 2 months after planting and analyzed for concentrations of Ca2+, Mg2+, Na+, Cl-, K+, total P, and total S. As salinity increased, Ca2+, Mg2+, Na+, Cl-, and total S increased in plant tissues, whereas K+ and total P decreased in plant tissues for both cultivars in both irrigation solutions. Leaf nutrient composition was related to the interactions of ions within the substrate solutions and their ability to compete for uptake at the site of root membranes. Phenotypic measurements, made when plants were harvested, showed only slight decreases as salinity increased. A 2 x 5 factorial design was used to determine the effects of water ionic composition and salinity on the germination of seeds. Four replicate Petri dishes each with 25 seeds were exposed to constant temperature (20 °C) and an 8-h dark : 16-h light photoperiod to promote germination. Germination was checked daily for 16 d. Snapdragons can be produced from seed when exposed to salinities up to 14 dS·m-1 using both SWD and CCRW ionic solutions for irrigation because germination remained at 92% or greater. Quality of the flowering stems was rated according to standards developed by the Society of American Florists. Marketable stems of both cultivars were produced in all treatments. Overall, quality of stems produced with saline waters ranging from 2.5 to 11 dS·m-1 was very high ("special"). Irrigation with more saline water (14 dS·m-1) resulted in a slight reduction in quality and stems were rated as "fancy" depending on the cultivar. Both cut flower cultivars can be produced for commercial use under saline conditions up to at least 14 dS·m-1.