Leaf water status, osmotic adjustment and carbon assimilation in colored calla lilies in response to saline irrigation

Colored calla lilies (Zantedeschia K. Koch) are popular cut flowers and potted plants, which have a recommended irrigation water electrical conductivity (EC) of less than 1.5 dS m−1. Calla lilies exposed to an NaCl imposed EC up to four times the recommended EC showed no reductions in visual quality, with maintenance of growth, albeit at a reduced rate. The leaves of the plants in all treatments were able to maintain turgor even though there were decreases in carbon assimilation rate of 50-80% compared to the control in the 50 mM NaCl treatment starting 35 days after treatment. This reduction in photosynthesis is most likely responsible for the reductions we observed in growth. Within this same time period we observed osmotic adjustment of 0.16-0.20 MPa and reductions in stomatal conductance of 53-97% compared to the control. We propose that osmotic adjustment and reductions in stomatal conductance were integral in maintaining leaf turgor throughout the stress period. By 63 days of treatment the cation content (Na+, Ca2+ and Mg2+) in the leaves of the 25 and 50 mM NaCl treatments were two and three times the concentration observed in the control respectively. We hypothesize that osmotic adjustment is the result of ion accumulation. Osmotic adjustment in addition to reductions in stomatal conductance may be adaptations to ensure that colored calla lilies survive stressful conditions until their dormant period and reemerge successfully under more favorable conditions.

► Colored calla lilies maintain turgor under NaCl induced reductions in growth. ► Salinity reduces carbon assimilation rate, with greatest reductions at midday. ► Reduced photosynthesis is associated with lower stomatal conductance. ► Osmotic adjustment and low stomatal conductance maintain turgor. ► Osmotic adjustment accomplished through accumulation of Na, Ca, and Mg ions.