Improvement of High-temperature Germination of Spinach Seed with Acid Scarification and Priming with Polyethylene Glycol 6000.

Abstract

Seed germination of spinach (Spinacia oleracea L. cv. Jiroumaru) was inhibited markedly at temperatures above 25°C. Exposure of the seeds to 36N sulfuric acid for 30 min or 18N for 60 and 120 min increased the final germination percentage at 25°C to 80-95%, compared to about 30% for the water-soaked control. In the de-coated seeds, the germina-tion percentage was increased to 90%; likewise, germination was also promoted by physi-cally cracking the pericarp. But at 30°C, the final germination percentage was 50% in the both acid-scarified and de-coated seed treatments.The acid scarification followed by priming with polyethylene glycol 6000 solution (-1.3 MPa, 1 week at 10°C) increased the germination percentage even at 30°C to more than 80% within 8 days after sowing for 6 cultivars including 'Jiroumaru'. Treatment with PEG alone was less effective in promoting germination.Scanning electron micrographs showed that the acid removed the pericarp cuticula, that the epidermal layer was pitted, and that some of pits had pores of 1-2μm in dia-meter on their bases.After acid scarification, the use of priming using PEG had beneficial effect on the ger-mination of spinach at 30°C, but very little is known about the physiological process of priming.