Calla Lily Growth and Development In Response to Saline Irrigation

Salinity is an important factor impacting plant growth world-wide.  Salinity is increasing not only in agricultural areas, but also in urban areas, where ornamental plants are often grown; however, very little research has been done on salt stress and ornamentals.  The purpose of this research is to quantify the effect of moderate salt stress on Calla Lily growth and developmental timing. Salt stress was measured in four different Calla Lily varieties(Flame, Pink Rehmanii, Pillow Talk, and White Alba) with three different concentrations of NaCl (0, 25, and 50mM). In both the spring and the fall a group of rhizomes were irrigated with saline irrigation solutions immediately after planting.  The time to emergence and time to first flower were recorded for 150 days.  When the salt stress was applied pre-emergence there was no variation in emergence or flowering time in the fall.  However, in the spring the plants exposed to 50 mM NaCl had a lower percentage of plants that flowered.  Salt stress was also applied to a group of rhizomes after emergence for 63 days.  Although there were differences among varieties for height, biomass, and flower number there was no salinity by variety interaction for any of the parameters measured.  None of the salinity treatments had a significant effect on plant height, chlorophyll, or fresh weight.  While flower number was not affected by salinity in the fall, it was significantly decreased in the spring.  The dry weight of the shoot was significantly decreased in the 50mM treatment, which was correlated with decreased midday photosynthetic rates.  Despite the decrease in plant dry weight, the effect of salinity was so minimal to overall appearance of the plants when the salt stress was applied post-emergence that it was impossible to determine which plants were being stressed just by visual inspection.  It appears that there is tolerance to moderate salinities in these varieties of calla lily; therefore, irrigation with lower quality water may be possible in both landscapes and greenhouse conditions without loss of ornamental quality.