Productivity and Quality Responses of Salt-Stressed Roses to Supplemental Calcium

Abstract

Plants of Rosa × spp. L. ‘Happy Hour’ grafted on the rootstocks R. × ‘Manetti’ and R. × ‘Natal Briar’ were salinized with 12 mM NaCl and received supplemental calcium (Ca) applications (as CaSO4) of 0, 2.5, 5.0, 7.5 and 10 mM. Additional plants were salinized with 6 mM Na2SO4 and supplemented with 5 mM CaSO4 and compared to non-salinized, no supplemental Ca control plants. Cumulative flowers harvested, shoot length and leaf chlorophyll index were similar for both rootstocks across salt treatments, but Manetti plants had higher dry weights in flowers and most plant tissues except roots. Productivity and water relations in NaCl-salinized plants were not responsive to supplemental Ca. Conversely, calcium-supplemented plants salinized with Na2SO4 had better productivity and quality than those with NaCl, and were similar to non-stressed control plants. Salt injury symptoms were evident only on NaCl-treated plants, regardless of Ca supplements, and closely associated with chloride, but not sodium, accumulation, in leaf tissues. The extent of the ameliorative properties of supplemental calcium applications on salinized rose plants is influenced by the salinity level, the chemical composition of the salinizing solution (major ions and counter-ions) and the cultivar (scion) and rootstock selection.