Measuring the RGR of Individual Grass Plants

Abstract

Vegetative growth of grasses was analysed by dry mass increase of growing leaves.Holcus lanatuswas grown in a controlled environment and leaf extension rates of leaf numbers 5–10 of the main tiller were monitored daily. Leaf appearance and leaf extension rates (LER) of leaves 5–7 enabled the prediction of the final length and dry mass of leaf 8 during its growth. A linear increase of leaf mass per unit leaf length (LML) of leaf 8 was observed during growth. After harvest the daily increase in dry mass of growing leaves was calculated from the LER and corresponding increase in LML. The relative growth rate (RGR) of the main tiller showed day-to-day fluctuations and was gradually reduced by 50% over a 16-d period. The RGR of the shoot was maintained by tillering. The RGR of a single (grass) plant can be calculated from four parameters only: LER, LML, leaf appearance and tillering. Variation of RGR over a period can be reconstructed after harvest and the impact of these four parameters on RGR can be established.