Assessing Tolerance to Sodium Chloride Salinity In Fourteen Floriculture Species

The use of saline irrigation water may eventually be required for floriculture production or in landscapes as the supply of potable/freshwater is decreasing.  In some regions of the United States producers of both ornamental and agronomic crops are already facing a limited supply of high quality water.  Given these facts, it is necessary to determine the salt tolerance of commonly used greenhouse bedding plants to minimize potential salt damage before use of nonpotable water sources is mandated.  In this work, we screened fourteen floriculture species and classified them based on their relative tolerance to sodium chloride salinity.  Seedlings of fourteen common annual bedding plants were transplanted into 10 cm pots containing a peat-based substrate and were irrigated daily using drip irrigation.  Five salt treatments 0 (control), 20, 40, 60 and 80 mM of NaCl were prepared in 525 L tanks along with a commercial fertilizer (21N-2.2P-16.6 K) at 150 ppm N.  Treatments were randomly divided so that each bench contained a reservoir with one salinity treatment.  Within each treatment, five plants were randomly sampled each week for electrical conductivity (EC) using the pour-thru method. Six weeks after transplanting destructive harvest was used to obtain total shoot fresh weight (FW), plant height and plant width. Total dry weight (DW) was recorded after plants were oven-dried at 80 °C for 4 d.  Pansy (Viola tricolor) and Zinnia angustofolia, the most sensitive species examined, exhibited 100% mortality when exposed to 80 mM NaCl.  The least affected species based on dry weight was Snapdragon (Antirrhinum majus) with a 54% reduction as NaCl increased from 0 to 80 mM.  Only Fuchsia hybrida and Snapdragon were unaffected by 20 mM NaCl and in comparing the control to 40 mM NaCl all of the species had a significantly reduced dry weight.  Verbena x hybrida, Petunia, Coleus (Solenostemon scutellarioides) and Begonia hiemalis were the only species that did not undergo a significant height reduction in comparing the control to 40 mM of NaCl.  A four category classification system was developed to describe species response to salt based on percent plant dry weight reduction; the classification provides guidance as to which species could be irrigated with more saline water while not compromising plant growth and quality.  The classification may be used by operations deciding which plants to grow based on their water quality.