Tiller Length vs. Tiller Weight: Applications to Plant Growth Studies

Abstract

The growth and development of individual grass tillers is frequently monitored in intensive studies of plant response to treatments or environmental parameters. Since growth may be recognized as an increase in tiller weight or tiller length over time, knowledge of the relationship between them is important if researchers are to select the measure most appropriate for their needs. To make these comparisons, the mean weight and length of tillers from perennial ryegrass (Lolium perenne L.), colonial bentgrass (Agrostis tenuis Sibth.), softchess (Bromus mollis L.), and annual fescue (Vulpia Spp.) were measured on each of seven dates during the spring growing period, 1977. Sample sizes required to estimate mean tiller length were calculated on each date using Stein's two-stage procedure. The relationship between mean tiller weight and mean tiller length over time was evaluated by least squares analysis of a linear regression model. Results of these analyses indicated that mean tiller length can be estimated satisfactorily from a substantially smaller sample size than can mean tiller weight. In addition, a strong linear relationship was observed between mean tiller weight and mean tiller length over time. The strength and linear nature of this relationship suggests that both measures will yield similar relative growth curves when sequential observations are plotted over time. Actual growth curves plotted for perennial ryegrass and colonial bentgrass support this supposition. Therefore, since tiller lengths require a small sample size to estimate each mean, both time and money can be saved by basing growth analysis on observations of tiller length rather than on tiller weight.