Nitrate effects on mobilisation of seed reserves in temperate cereals

Effects of additional nitrate (20 mol m·3 NO;) on growth of barley (Hordeum vulgare L. cv. Triumph), oat (Avena sativa L. cv. Amuri), rye (Secale cereale L. cv. Rapaki), triticale (x Triticosecale Wittm. cv. Aranui) and wheat (Triticum aestivum L. cv. Otane) prior to emergence from a sowing depth of 70 mm were examined under controlled environment. conditions. For all five cereals, additional N03caused an increase in shoot dry weight (DW) of 17-40% and a decrease in residual seed DW but it did not affect shoot length. In a second experiment in which wheat was supplied with either 0 or 10 mol m·3 N03·, growth and N03• content of root and shoot were measured at 3 to 4 d intervals prior to emergence. Nitrate did not affect shoot length or root DW. Root and shoot fresh weight (FW) and shoot DW were greater with additional N0310 d after sowing (DAS) when shoot length was approximately 15 mm. Twenty one DAS (shoot length= 55 mm approximately), shoot FW and DW were respectively 30% and 17% greater with additional N03•• For plants grown without N03-, N03levels were low in both root and shoot throughout the experiment. With N03·, root and shoot N03content increased with increased harvest date to concentrations substantially greater than that applied. It is concluded that N03• stimulated mobilisation of seed reserves is likely to be of common occurrence with temperate cereals. Advantages and disadvantages of increased rate of mobilisation of seed reserves are discussed and areas for further research are considered. Additional key words: germination, seedling growth.