Evaluation of the tolerance of Kalanchoe delagoensis viviparous seedlings to NaCl stress

In order to investigate the mechanisms reflecting the growth and physiological characteristics of Kalanchoe delagoensis viviparous seedlings under NaCl stress, we aimed to provide a scientific and theoretical basis for the stress-resistant cultivation of K. delagoensis plants. Adventitious buds at the top of K. delagoensis leaves were used as materials, using nutrient bags filled substrate cultivation and saline water irrigation for roots method to control soil salinity, and five concentration gradients were set for NaCl, which were 0, 0.1, 0.2, 0.3 and 0.5 mol/L, the changes of growth and physiological indexes of the rooted viviparous seedlings of Stick leaf drop-root were investigated under the stress conditions of different NaCl concentrations, and evaluated by the principal component analysis. The results showed that the growth and physiological performances of the rooted viviparous seedlings under NaCl stress showed different degrees of responses, especially with the increase of NaCl stress concentration, the plant height and leaf water content decreased, the number of rod leaves increased and then decreased, while the root system elongated, but the difference of the leaf width was not significant compared with that of the control (P > 0.05). With the time extension of NaCl stress, the chlorophyll, soluble sugar, malondialdehyde contents, SOD and POD activities were increasing, and soluble protein, starch and proline contents, as well as CAT, PAL and PPO activities were firstly increasing and then decreasing, which showed that the fetal seedling enhanced its NaCl stress tolerance by regulating the contents of osmoregulatory substances and antioxidant enzyme activities in vivo. Based on the growth indicator with a salt tolerance threshold of 50%, seedlings could survive at a NaCl concentration of 0.5 mol/L, but most growth and physiological indicators are inhibited, indicating that the K. delagoensis could adapt to NaCl stress below 0.5 mol/L. Principal component analysis showed that plant height, leaf water content, soluble protein, and antioxidant enzyme activity could be used as indicators for evaluating the strength of salt tolerance in K. tubiflora.