The effects of NaCl on calcium-deficiency disorder vary with symptom development stage and cultivar in hydroponic Portulaca oleracea L.

Abstract

Kong, Y., Rozema, E. and Zheng, Y. 2014. The effects of NaCl on calcium-deficiency disorder vary with symptom development stage and cultivar in hydroponic Portulaca oleracea L. Can. J. Plant Sci. 94: 1195–1201. Purslane (Portulaca oleracea L.) is a traditional food crop in some Mediterranean, Central American and Asian countries. Our recent study showed that this crop can be produced hydroponically in NaCl-rich nutrient solutions. Increased NaCl salinity has been found to increase the occurrence of Ca-deficiency related disorders in many horticultural crops. To explore the effects of NaCl on calcium-deficiency disorder and the associated impacts on plant growth in purslane, two commercial cultivars ‘Green’ and ‘Golden’ were hydroponically grown in nutrient solutions without Ca for the first 3 wk (Ca-deficiency period) and then in nutrient solutions with added 2.4 mM Ca(NO3)2 for 2 wk (Ca-supplement period). Two levels of NaCl (0 and 10 mM) were used in the above nutrient solutions as the two NaCl treatments (control and NaCl). Plants began to express visual symptoms first on the apical leaves and then on the apical stems 12 d after the start of Ca deficiency treatment, but recovered from the disorder during the following Ca-supplement period, suggesting that the symptoms were caused by Ca-deficiency. During the Ca-deficiency period (early stage of symptoms development), NaCl alleviated the Ca-deficiency disorder and reduced leaf unfolding rate in the ‘Green’ cultivar, but not in the ‘Golden’ cultivar. However, during the Ca-supplement period (late stage of symptoms development) exposure to NaCl increased the severity of the disorder and inhibited stem extension and leaf unfolding for both purslane cultivars. The results suggest that purslane Ca-deficiency disorder responses to NaCl vary with symptom development and cultivars, and that the responses are associated with changes in plant growth.