Improved germination of pansy seed at high temperatures by priming with salt solutions

Abstract

The priming of seed is a process in which the seeds are placed in an osmotic solution for a determined period of time, dried down to original moisture content, then germinated. The objectives of this study were twofold. The first was to compare various salt solutions at defined osmotic potentials as effective priming treatment for improving germination and emergence of pansy seed at high temperatures. the second objectives was to compare respiration rates during germination for primed and nonprimed seeds. Pansy seeds (Viola x wittrockiana 'Majestic Giant Blue Shade' and 'Crystal Bowl Sky Blue') were primed with several salts and PEG 15,000 at - 1.0 and - 2.0 MPa, for 3, 6, or 9 days at 23 C. Total percent germination (G) of nonprimed seeds decreased significantly for both cultivars as germination temperature increased from 25 C to 35 C. The particular priming solution and the duration of the treatment were significant factors in increasing percent germination and in reducing T50. Priming with salts (CaCl2 for Crystal Bowl' and K2HPO4 or MgCl2 for 'Majestic Giant') at either osmotic potential was significantly more effective than priming with PEG 15,000 at relatively high temperature. Seeds primed in aerated PEG 8000 at - 1.0 MPa for 7 days at 15 C compared to inorganic salt solutions (CaCl2, MgCl2, or K2HPO4) did not have higher emergence than nonprimed seeds when sown directly in plug trays and germinated in growth chambers. Pansy seed ('Crystal Bowl') primed with CaCl2 at - 1.0 MPa for 3 days at 23 C appeared to be effective for increasing seedling emergence and for reducing the time of emergence in summer greenhouse studies. For Majestic Giant', priming treatments had little effect in improving total emergence, but did reduce T50. Seed respiration was detected after priming. Priming treatments with CaCl2 for 'Crystal Bowl' resulted in an increase in respiration rate during germination over nonprimed seeds. Priming Majestic Giant with either MgCl2 or K2HPO4 did not result in an increase in respiration rate over nonprimed controls.