| Popis: |
High and low stress temperatures during seed germination and seedling development limit total germination and the rate of germination and growth. Changes in polyamine (PA) concentrations in seeds of different species have been associated with germination, growih and enviroiunental stresses such as temperature, drought, oxygen, chilling injury and osmotic conditions. Two studies were conducted to determine the effect of stress temperatures during germination and seedling development on polyamine titers in soybean seeds. Three germination temperatures, 25, 30, and 36 °C were used in the first study to evaluate their influence on changes in polyamine concentrations in soybean seeds germinated at 76 and 90 hours. The polyamines (PAs), cadaverine (Cad), putrescine (Put), spermidine (Spd). agmatine (Agm), and spermine (Spm) were quantified by HPLC using a cation exchange column and an electrochemical detector. Cad, Put, Agm, and Spd declined as the germination temperatures increased from 25 to 36 °C. Conversely, Spm increased considerably with an increase in temperature. Total germination was reduced from 97.2 to 92.5% as germination temperatures increased from 25 to 36 °C. Germination time did not affect Cad, Agm and Spm, and total germination, however, the interaction between temperattire and germination time for Put and Spd concentrations was significant. In the second study, changes in PA concentrations, seedling growth, germination time (tso), fresh and dry weight, and moisture content were measured in the embryonic axis and cotyledons of soybean seeds germinated at 10 and 25 °C through six stages of germination dry seed (DS), testa split (TS), radicle at 10 mm (Ra-10), root hairs visible (RHV), secondary root primordia (SRP), and complete seedling (CS). The concentrations of Cad and Put in the embryonic axis, were significantly higher in seeds |
