Low seed manganese concentration and decreased emergence of Lupinus angustifolius

Seed of narrow-leafed lupin (Lupinus angustifolius L.) produced in Western Australia can have a low manganese concentration and exhibit poor seedling emergence, We determined effects of internal seed manganese concentration, exogenously applied manganese, and soil temperature on lupin emergence and seedling growth. Uniform-sized seed (cv, Gungurru) containing different manganese concentrations was collected from a manganese fertilizer experiment. Two greenhouse experiments were conducted with complete randomized block designs and two-way factorial treatments: (i) three internal seed manganese concentrations (7, 15, or 35 mg Mn kg(-1) DW) and four manganese treatments (no manganese fertilizer, MnSO4 banded below the seed or seed coatings of MnSO4 or MnO2; and (ii) four seed manganese concentrations (7, 11, 15 or 35 mg Mn kg(-1) DW) and four temperature regimes (12, 12/20, 20/12, and 20 degrees C), Emergence was 35 to 52% in all pots sown with 7 mg Mn kg(-1) seed compared with 88 to 100% in pots sown with other seed. Plants that emerged from 7 mg Mn kg(-1) seed generally had lower shoot dry weight than plants from other seeds. There were more abnormal seedlings in pots sown with 7 or 11 mg Mn kg(-1) seed than with other seeds. Although manganese fertilizer and higher soil temperature increased the manganese concentration of plants that emerged, they had no effect on final emergence or percentage of abnormal seedlings. Increased manganese availability did not overcome detrimental effects of sowing lupin seed with manganese concentrations of 11 mg kg(-1) or less.