Growth analysis of solution culture-grown winter rye, wheat and triticale at different relative rates of nitrogen supply

At low nitrogen (N) supply, it is well known that rye has a higher biomass production than wheal. This study investigates whether these species differences can be explained by differences in dry matter and nitrogen partitioning, specific leaf area, specific root length and net assimilation rate, which determine both N acquisition and carbon assimilation during vegetative growth. Winter rye (Secale cereale L.), wheat (Triticum aestivum L.) and triticale (X Triticosecale) were grown in solution culture at relative addition rates (R-N) of nitrate-N supply ranging from 0.03-0.18 d(-1) and at non-limiting N supply under controlled conditions. The relative growth rate (R-W) was closely equal to R-N in the range 0.03-0.15 d(-1). The maximal R-W at non-limiting nitrate nutrition was approx. 0.18 d(-1). The biomass allocation to the roots showed a considerable plasticity but did not differ between species. There were no interspecific differences in either net assimilation rate or specific leaf area. Higher accumulation of N in the plant, despite the same relative growth rate at non-limiting N supplies, suggests that rye has a greater ability to accumulate reserves of nitrogen. Rye had a higher specific root length over a wide range of sub-optimal N rates than wheat, especially at extreme N deficiency (R-N = 0.03-0.06 d(-1)). Triticale had a similar specific root length as that of wheal but had the ability to accumulate N to the same amount as rye under conditions of free N access. It is concluded that the better adaptation of rye to low N availability compared to wheat is related to higher specific root length in rye Additionally, the greater ability to accumulate nitrogen under conditions of free N access for rye and triticale compared to wheat may be useful for subsequent N utilization during plant growth. In general, species differences are explained by growth components responsible for nitrogen acquisition rather than carbon assimilation. (C) 1999 Annals of Botany Company.