Effects of Ca2+- and Mg2+-enriched germination media on germination and sugar leakage of Ca-deficient soybean seed

Inadequate seed Ca concentrations are associated with reduced seed quality of soybean [Glycine max (L.) Merr.]. Standard germination and sugar leakage tests were conducted to determine the effect of seed Ca content and exogenous Ca2+ or Mg2+ on seed quality and seed leakage. Soybean seeds containing different Ca levels were germinated in rolled towels that had been soaked in distilled water, 0.01 M Ca(NO3)2, or 0.01 M Mg(NO3)2. Sugar leakage was measured by soaking seed containing 1.10, 1.72 or 2.36 mg g−1 Ca in distilled water, 0.01 M Ca (NO3)2, 0.01 M Mg(NO3)2 or polyethylene glycol (PEG). An aliquot of the bathing solution was analyzed for sugar content after 6, 12 and 24 h of soaking, by using high-performance liquid chromatography. As seed Ca content decreased from 2.36 to 1.10 mg g−1, germination in distilled water decreased from 87 to 56%. Addition of either Ca(NO3)2 or Mg(NO3)2 to the medium resulted in increased germination of low-Ca seed, but Ca(NO3)2 was more effective in improving germination of low-Ca seed than Mg(NO3)2. Total sugar leakage was significantly greater in low-Ca seed than in high-Ca seed. Bathing solutions of Ca(NO3)2 or Mg(NO3)2 significantly decreased sugar leakage, compared with distilled water or PEG. These results suggest that the role of Ca in seed germination may involve membrane stabilization. They also indicate that the addition of Ca(NO3)2 or Mg(NO3)2 to the germination medium may improve germination of Ca-deficient seed. Key words: Soybean, germination, calcium, magnesium, sugar leakage, membrane integrity