EFFECTS OF SEED MANGANESE CONCENTRATION ON LUPIN EMERGENCE

Seed of narrow-leafed lupin (Lupinus angustifolius L.) produced in Wes tern Australia often has low manganese (Mn) concentration because of l ow Mn availability in the soil during grain filling. A major problem o f lupin production is poor seedling establishment. We tested the hypot hesis that low Mn concentration in lupin seeds decreases emergence. Th e experiment was a factorial design comparing emergence of lupins (cv. 'Gungurru') grown under glasshouse conditions from seed with 2 differe nt internal Mn concentrations (7 or 35 mg Mn kg(-1) DW) and with 2 ext ernal Mn fertiliser treatments (O or 10 mg MnSO4.H2O kg(-1) soil). The re were no visible differences between the seeds. Emergence was monito red and plants were harvested 17 days after sowing. Emergence was appr oximately 60% in all pots sown with low Mn compared to 100% in pots so wn with high Mn seed. Application of Mn did not increase the final eme rgence of low Mn seed. Seed viability was assessed by staining with te trazolium chloride, a common test used in seed testing laboratories. A ll high Mn seed were viable while 34% of low Mn seed were completely o r partly unstained and therefore were non-viable. We have shown that l ow Mn supply during seed filling may lead to production of non-viable seed that cannot be visually distinguished from viable seed.