Growth rate is a very important term to describe plant development over time, in most cases growth development. As long as plants primarily invest their energy in the development of new leaves, the growth curves of leaf areas mainly follow an exponential pattern. Exponential growth is merely an ideal growth pattern, where all energy produced by existing leaves is transferred to new leaves, which again produce energy for additional leaves, and so on. As this is not the case in later stages of plant development, during flowering and fruiting, growth rates will subsequently decrease, so that other growth models may be more appropriate to describe later plant growth stages.
In any case, it is important to acknowledge that almost the worst approach to growth quantification is to simply use the measured values like leaf area, fresh/dry weight or plant height directly. To compare plant growth directly on the basis of this one parameter without taking appropriate transformation steps is problematic, especially if rates (differences between a set of points in time) are to be compared. High and systematic standard deviations or, rather, systematic faults will occur, because a bigger plant at a certain point in time will always have a higher absolute difference in the measured parameter than smaller plants. By using the exponential or other growth models as a first data transformational step, the different start values will be considered appropriately, which in turn results in similar growth rates, even for plants of different sizes.
Growth rate modelling is an essential parameter in developing a functional physiological and genetic understanding of the hidden processes behind the phenotype
Growth rate measurement using LemnaTec scanalyzer technologies
The LemnaTec scanalyzer systems PL, HTS and 3D allow the repeated quantification of e.g. projected leaf areas in a non-destructive way. The LemnaMiner software can easily calculate for example image-based bio volumes, even if the basic leaf areas must be taken from different images of a LemnaTec scanalyzer snapshot. In a subsequent step, easy to perform with the LemnaMiner software, growth rates are calculated between different measurement points in time (snapshots), considering the fluctuating time spans and even different numbers of snapshots available for one specific plant. The resulting growth rates of replicates can then be averaged in a mathematically correct way and compared to other treatment groups.