Promotion by 5-aminolevulenic acid of pepper seed germination and seedling emergence under low-temperature stress

The effects of incorporating 5-aminolevulenic acid (ALA) into the priming solution on low-temperature germination and emergence percentage performance of red pepper (Capsicum annuum cv. Sena) seeds before and after seed storage were investigated. Seeds were primed in 3% KNO₃ solution for 6 days at 25 °C in darkness containing 0 ppm, 1 ppm, 10 ppm, 25 ppm, 50 ppm or 100 ppm ALA. Following priming, seeds were either immediately subjected to germination and emergence tests at 15 °C or stored at 4 °C or 25 °C for 1 month after which they were subjected to germination and emergence tests at 15 °C. Priming pepper seeds in the presence of ALA improved final germination percentage (FGP) and germination rate (MGT) at 15 °C compared to non-primed seeds. The highest FGP was obtained from seeds primed in the presence of 25 ppm and higher ALA concentrations while the highest MGT was obtained from seeds primed in KNO₃ supplemented with 10 ppm ALA. Emergence percentages were the highest for the seeds primed in the presence of 25 ppm ALA and 50 ppm ALA while non-primed seeds had the lowest emergence percentage. Highest emergence rates (MET) and heaviest seedlings were also obtained from seeds primed in KNO₃ supplemented with 50 ppm ALA. Although all priming treatments improved germination and emergence performance of pepper seeds at 15 °C following 1 month of storage under two different temperatures, inclusion of 25 ppm and 50 ppm ALA into the priming solution resulted in higher germination and emergence percentages and faster germination and emergence compared to seeds primed in KNO₃ only and non-primed seeds. These results indicate that priming seeds in 25 ppm and 50 ppm ALA incorporated into the KNO₃ solution can be used as an effective method to improve low-temperature performance of red pepper seeds and that these seeds can be stored for 1 month at 4 °C or 25 °C and still exhibit improved germination and emergence performance at 15 °C.