Abstract:

The aim is to study the effect of exogenous Spd on the tolerance of snap bean under low temperature. The seedlings of the low-temperature sensitive cultivar ‘P16093’ and the low-temperature tolerant cultivar ‘P16165’ were used as test materials, and three treatments were set up, including normal temperature control (CK), 4℃ low temperature treatment (LT) and 4℃ low temperature with spraying exogenous Spd (LT+Spd). The plant growth morphology, antioxidant system, osmotic adjustment substance, biofilm and endogenous polyamine content were measured in the three treatments. The results showed that the spraying of exogenous Spd at low temperature promoted plant growth and alleviated the effects of low temperature on plant height, stem thickness, fresh weight and dry weight of snap bean seedlings; the spraying of exogenous Spd reduced the electrolyte permeability in the seedlings’ leaves of both varieties at low temperature compared with the LT group with a maximum decrease of 16.94%. The malondialdehyde content of the two varieties increased, rising by 42.81% and 70.59% on the 8^th day, respectively. The soluble protein content decreased while the proline content increased; the antioxidant enzyme activity increased, as well as the endogenous Put and Spd content. The results indicate that the exogenous Spd could alleviate the damage of snap bean seedlings under low temperature stress by regulating polyamine metabolism and enhancing ROS scavenging system in plants.

Key words: Phaseolus vulgaris, seedlings, low temperature stress, spermidine, polyamines metabolism, antioxidant systems