Effects of calcium ion on growth, physiological responses and photosynthetic ability in salt-stressed Jerusalem artichoke (Helianthus tuberosus L.) seedlings

Jerusalem artichoke (Nanyu 2) was used to study the effect of calcium ion on superoxide dismutase(SOD) activity, malondialdehyde(MDA) content, net photosynthetic rate, fluorescent parameters and fresh weight under NaCl stress. The results indicated that the addition of Ca²⁺ did not significantly influence the growth of Jerusalem artichoke under half-strength Hoagland nutrient solution treatment but markedly protected Jerusalem artichoke leaves from oxidative damage caused by 150 mmol/L NaCl stress. Therefore, higher activity of SOD and lower content of MDA in Jerusalem artichoke leaves were maintained under salt stress. As a result, the increases in status of electron transport by PSⅡ(Fm/Fo), primary photochemical efficiency of PSⅡ(Fv/Fm), quantum efficiency of photosystem Ⅱ(φPSⅡ), photochemical quenching coefficient(qP), net photosynthetic rate(Pn) and the decrease in non-photochemical quenching coefficient(qNP) were observed under salt stress. All these were favorable to the dry matter accumulation so that the fresh weight was increased significantly. In conclusion, the addition of Ca²⁺ compensated the deficient Ca²⁺ induced by salt stress, made the normal metabolism and the intact cell membrane, balanced the ions absorbed and protected the photosynthetic system.