Coefficient of Variation Can Identify the Most Important Effects of Experimental Treatments

Abstract

Most agricultural experiments involve evaluation of multiple variables and at times it can be difficult to identify the biologically relevant effects of the experimental treatments after performing the traditional ANOVA, Tukey and t-tests.  The coefficient of variation formula could be an important tool to focus ‘Result and Discussion’ sections only on the most important changes produced by the experimental treatments. This short report is intended to exemplify the use of the coefficient of variation in three plant physiology experiments. The first one dealt with the effects of common bean plantlet exposure to high temperature under controlled conditions (levels: 28 and 40 °C).  The second experiment was related to common bean seed exposure to liquid nitrogen during five different periods of time (levels: 0, 7, 14, 21 and 28 days). The third experiment was bi-factorial: factor 1 was the ‘type of plant material’ (levels: pineapple plants genetically transformed and the untransformed control); and factor 2 was the ‘time of in vitro-plantlet hardening’ (levels: 0, 15 and 30 days).  Contents of phenolics, aldehydes, chlorophylls and proteins were determined. Percentage of seed germination, electrolyte leakage, peroxidase activity, plant height and weight were also measured. Experiments were monofactorial with two levels, monofactorial with five levels and bifactorial, respectively, with randomized design. The coefficient of variation showed that the most remarkable effects of high temperature were recorded in free phenolics and chlorophylls (a, b, total). Electrolyte leakage and chlorophyll b concentration were the most modified indicators as a result of seed exposure to liquid nitrogen.  In the third experiment, modification in the levels of malondialdehyde and other aldehydes were the most relevant changes resulting from factors interactions. A similar procedure has not been published, except for our previous publications, not focused on the use of the coefficient of variation, just on the biological results.