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

Abstract

Seed germination of spinach cv. Jiroumaru was inhibited markedly at temperatures above 25 deg C. Exposure of the seeds to 36 N sulphuric acid for 30 min or 18 N sulphuric acid for 60 or 120 min increased the final germination percentage at 25 deg to 80-95%, compared with about 30% for water-soaked controls. In de-coated seeds, germination percentage was increased to 90%; likewise, germination was also promoted by physically cracking the pericarp. At 30 deg C, the final germination percentage was 50% in the both acid-scarified and de-coated seed treatments. Acid scarification followed by priming with polyethylene glycol (PEG) 6000 solution (-1.3 MPa for 1 week at 10 deg ) increased germination percentage even at 30 deg 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 1-2 micro m in diameter on their bases.