Original Articles
Myrene R. DâÂâ‚Â
Abstract
The effects of short-term salinity stress and spermidine pre-treatment on polyamine metabolism, mineral composition and growth of Hyacinth bean were investigated. The levels of diaminoputrescine (DAP), putrescine (Put), spermidine (Spd) and spermine (Spm) were evaluated as possible biomarkers for salinity stress. Ten-day old seedlings were subjected to stress at five different concentrations of NaCl (100-500 mM) and pre-treatment with 0.5 mM Spd in the presence of 300 mM NaCl under strictly controlled growth conditions. Salinity stress resulted in significant reduction in growth index, fresh and dry weight and total chlorophyll content of Hyacinth bean, but pretreatment with Spd significantly enhanced these growth parameters. The results also showed that exogenous application of Spd maintained higher values of [K+]/[ Na+] as compared with NaCl-stressed plants. Salt injuries in plants are mostly due to excess Na+ entry. Therefore, a possible survival strategy under saline environments is the effective compartmentalization of excess Na+ by sequestering it in roots and preventing its uptake into shoots. This study showed that exogenous Spd can be applied as short-term pre-treatment prior to introduction of salt stress to help elevate salt tolerance in Hyacinth bean seedlings.