Tiller Production and Development in Perennial Ryegrass in Relation to Nitrogen Use

Abstract

The amount of soil nitrogen (N) available to perennial ryegrass (Lolium perenne L.) will influence the distribution of N within the plant. At low amounts of plant available N the relative proportion of N in the roots will be high. As under conditions of high N availability, the proportion of N in vegetative and reproductive tillers as well as the number of vegetative and reproductive tillers will increase. However, the correlation between plant N content and tiller production is not known. Therefore, a growth chamber experiment was performed to investigate this relationship in perennial ryegrass. The relation is important to better predict the effect of N application on tiller production. Plants were grown in nutrient solutions containing diminishing amounts of N over 36 days. At the end of the growth period, N and carbon (C) concentrations of the plant tissues, as well as the tiller production, were analyzed. Higher N concentrations were found in leaves than in roots. Depending on the N concentration in leaves, two groups of plants could be identified. One group (I) had an average leaf N concentration of 1–2%, which was distinct from the other group (II) with an average leaf N concentration of above 2%. At the end of the experimental period, the accumulated N content was equally distributed between roots, stems, and leaves in group I, whereas N was preferably stored in the leaves and stems in group II. The lowest production of tillers was achieved with 0.01 g N plant⁻¹, and the greatest number of tillers was reached with 0.19 g N plant⁻¹. The greatest number of tillers produced per plant in group II was reached before the end of the experimental period, indicating that maximum tiller production was reached under the given conditions. In group I, a linear model described the correlation between the number of tillers produced per plant and N content per plant. In group II, a model with an exponential rise to maximum described the relationship between these parameters. The results indicate, that the production of tillers in perennial ryegrass is closely related with N content in the plant. The results are further discussed in relation to N dynamics during vegetative and reproductive growth in perennial ryegrass.

Keywords:

• Nitrogen distribution
• Nitrogen concentration
• C:N ratio
• Tiller production

Acknowledgments

We thank D. J. Streeter for skilful technical assistance and Søgaard Foundation and Ellen, Christian and Anders Petersens Foundation for partly funding this experiment. B. Wollenweber, B. Boelt, and E. S. Jensen are acknowledged for critical review of the manuscript.