Parallel Coordinate Plots of Maize Traits Under Different Magnesium Application

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1 Parallel Coordinate Plots of Maize Traits Under Different Magnesium Application Jan Bocianowski 1, Piotr Szulc 2 and Kamila Nowosad 3 1 Department of Mathematical and Statistical Methods, Poznań University of Life Sciences, Wojska Polskiego 28, Poznań, Poland 2 Department of Agronomy, Poznań University of Life Sciences, Dojazd 11, Poznań, Poland 3 Department of Genetics, Plant Breeding and Seed Production, Wrocław University of Environmental and Life Sciences, pl. Grunwaldzki 24A, Wrocław, Poland Abstract The parallel coordinate plot is proposed as an efficient tool for visualization of 13 traits of stay-green maize (Zea mays L.) cultivar exposed to different methods of magnesium application. The field experiment was conducted in the Department of Agronomy, Poznań University of Life Sciences, on the fields of the Department of Teaching and Experimental Station in Swadzim in Experiment was conducted as a single-factor experiment with seven applications of magnesium in a randomized complete block design with four replicates. The highest mean values of grain yield and 1000 grain weight were obtained after application of variant T3 of magnesium (10 kg MgO ha -1 soil) in the all three years of study. Key words: magnesium, maize, parallel coordinate plots, visualization 1 INTRODUCTION Parallel coordinates are a two-dimensional technique for visualisation of multidimensional data sets and are an efficient tool for visualizing multivariate data (Inselberg 1985; Wegman 1990; Kozak 2010). PCPs were introduced by Inselberg (1985). Wegman (1990) was the first refereed paper suggesting the use of parallel coordinates as a method for exploratory data analysis. PCPs have been used in various research areas, although environmental and agricultural applications are rather scarce (Andrienko and Andrienko 2001; Bertero et al. 2004; Varela et al. 2006; Huh and Park 2008). Due to interpretation possibilities that this type of plot offers, it could be useful in multivariate analysis of agronomic experiments. In this paper it is shown that a parallel coordinate plot can be a very useful tool for visualization of differences in 13 traits of stay-green maize (Zea mays L.) cultivar under different methods of magnesium application. PCPs can be used at the analysis stage of the breeding research, which aims to compare and select optimal dose and method of magnesium application. RESULTS AND DISCUSSION The parallel coordinate technique is a powerful method for two-dimensional representation of multivariate data sets. Fig. 1 shows parallel coordinate plots for the six variants of magnesium application in 2006, 2007 and 2008, respectively. In the all three years of study we observed the largest mean values of grain yield Correspondence Jan Bocianowski, Tel/Fax: , jboc@up.poznan.pl 1

2 and 1000 grain weight after application of dose T3 of magnesium (10 kg MgO ha -1 soil) (Fig. 1). But, the smallest mean values for T5 dose (5 kg MgO ha -1 divided into 2.5 kg MgO ha -1 soil and foliar in the 4-5 leaf phase) in 2006 and 2007 (Fig. 1-A and B) and T2 dose (5 kg MgO ha -1 foliar in the 4-5 leaf phase) in 2008 (Fig. 1-C). For T3 dose in 2006 and 2007, we obtained small mean values of moisture of grain (Fig. 1-A and B), but in last year of observations the largest (Fig. 1-C). In the first year of study the smallest mean values of chlorophyll a, chlorophyll b and chlorophyll a+b for application of T3 dose of magnesium (Fig. 1-A) was observed. Fig. 1 Parallel coordinate plot for six variants of magnesium (T1, black ; T2, black ; T3, black ; T4, black ; T5, gray ; T6, gray ) application and 13 traits of interest in 2006 (A), 2007 (B) and 2008 (C). GY, grain yield; MoG, moisture of grain; TGW, 1000 grain weight; DMSP, dry matter of a single plant; DMY, dry matter yield; N, uptake of N; P, uptake of P; K, uptake of K; Mg, uptake of Mg; Ca, uptake of Ca; Chl A, chlorophyll a; Chl B, chlorophyll b; Chl AB, chlorophyll a+b; T1, 5 kg MgO ha -1 soil; T2, 5 kg MgO ha -1 foliar in the 4-5 leaf phase; T3, 10 kg MgO ha -1 soil; T4, 10 kg MgO ha -1 foliar, 5 kg MgO ha -1 in the 4-5 leaf phase and in the 5-6 leaf phase; T5, 5 kg MgO ha -1 divided into 2.5 kg MgO ha -1 soil and foliar in the 4-5 leaf phase; T6, 10 kg MgO ha -1 divided into 5 kg MgO ha -1 soil and foliar in the 4-5 leaf phase. In the Fig. 1-C, we observed lack of line for nine traits (DMY, N, P, K, Mg, Ca, chlorophyll a, chlorophyll b and chlorophyll a+b) for T4 magnesium treatment. This means that these traits had the highest of mean values in T4 magnesium treatment in compare to other treatments, and their lines overlaps with plot border. PCP s can be used to assess relationship between examined traits and to examine variability of each trait. In the Fig. 2 we may observed interaction between objects and years for GY, MoG and TGW. Parallel coordinate plots are good tool to observe of correlation between traits. In the presented results we observe positive 2

3 correlation between GY and DMSP, TGW and DMSP, chlorophyll a and chlorophyll a+b as well as negative correlation between GY and MoG (Fig. 2). Fig. 2 Parallel coordinate plot for six variants of magnesium application and 13 traits of interest in three years. From the above examples for three years of study follows that parallel coordinate plots can be an efficient visualisation tool for multivariate presentation of different variants of magnesium application. This efficiency has two main reasons: parallel coordinate plots offer quick access to information about performance of the variants of magnesium application and this information is easily interpretable for experimenters who do not possess advanced knowledge of statistical and visualization techniques (Kozak 2010). Presented results were based on the six variants of magnesium application only, but PCP can be applied to any number of variants of magnesium application. The main power of parallel coordinate plots is revealed at the analysis stage, by plotting the variants of magnesium application plots. This type of plotting offers clear information on how a particular variant of magnesium application performs in compare to, all other variants of magnesium application, and that is a very important piece of information for experimenters. Parallel coordinate plots are an efficient tool for visualizing multivariate data and they have been used in various research areas (Chang and Yang 1996; Edsall 2003; Ellis and Dix 2006; Novotny and Hauser 2006; Streit et al. 2006; Cheng et al. 2008; Viau et al. 2010; Joachimiak et al. 2011; Bocianowski et al. 2012, 2013). This method of visualization of experimental results is a good method for the presentation of relationships between the traits and the other variants of magnesium application which can be used as an alternative tool as compared to the traditional methods or it might be very useful as a supplement. This is more effective visualization technique as the other methods like: stripcharts, scatterplot matrix or multiplicative model-contour plot (Wnuk et al. 2013). PCPs are a way of visualizing high-dimensional geometry and analysing multivariate data. The advantage of this method is the easy of calculation and interpretation. CONCLUSION The parallel coordinate plots can be an efficient visualization tool multivariate presentation of different variants of magnesium application; the largest mean values of grain yield and 1000 grain weight we obtained after application of dose T3 of magnesium (10 kg MgO ha -1 soil) in the all three years of study; PCP s can be used to assess' relationship between examined traits and to examine variability of each trait. Materials and Methods 3

4 Plant materials LG 2244 stay-green cultivar was sown in the experiment. The field experiment was conducted in the Department of Agronomy, Poznań University of Life Sciences, on the fields of the Department of Teaching and Experimental Station in Swadzim in It was conducted as a single-factor experiment with seven applications of magnesium in a randomized complete block design with four replicates. The following variants of magnesium application were studied: T0) 0 kg MgO ha -1, control object, T1) 5 kg MgO ha -1 soil, T2) 5 kg MgO ha -1 foliar in the 4-5 leaf phase (BBCH 14-15), T3) 10 kg MgO ha -1 soil, T4) 10 kg MgO ha -1 foliar, 5 kg MgO ha - 1 in the 4-5 leaf phase (BBCH 14-15) and 5 kg in the 5-6 leaf phase (BBCH 15-16), T5) 5 kg MgO ha -1 divided into 2.5 kg MgO ha -1 soil and foliar in the 4-5 leaf phase (BBCH 14-15), T6) 10 kg MgO ha -1 divided into 5 kg MgO ha -1 soil and foliar in the 4-5 leaf phase (BBCH 14-15). Before the maize sowing, magnesium was used in soil application in the form of magnesium sulphate (kieserite), and in foliar application in the form of magnesium heptahydrate (bitter salt). The same nitrogen-phosphorus-potassium (NPK) fertilisation was used on the entire experimental field: 100 kg N ha -1 in the form of urea, 80 kg P 2 O 5 ha -1 in the form of Polifoska 6, 120 kg K 2 O ha -1 in the form of potassium salt 60%. The field experiment was conducted on the podzolic soil, light clay sand grade, shallowly deposited on the light clay belonging to a good rye complex. The abundance of soil in the basic macronutrients in each year of the study shaped at the average level, while its acidity ranged from 5.9 in 2008 to 6.2 in For present paper, six variants of magnesium application (T1, T2, T3, T4, T5, T6) were chosen. We left one variant (T0) because for this control object we obtained minimal values for all studied traits. The following traits were considered: grain yield (dt ha -1 ), grain moisture (%), 1000 grain weight (g), dry matter per plant (g), dry matter yield (kg ha -1 ), N uptake (kg ha -1 ), P uptake (kg ha -1 ), K uptake (kg ha -1 ), Mg uptake (kg ha -1 ), Ca uptake (kg ha -1 ), chlorophyll a ( g g -1 ), chlorophyll b ( g g -1 ), chlorophyll a+b ( g g -1 ). Random samples for moisture content in grain analyses were collected from the threshed mass in each plot. Measurements were taken using a Super Matic electronic hygrometer. Samples collected for moisture analyses were 250 gram in weight. Results are given in percent accurate to two decimal places kernel weight (g), this value was calculated by adding the results for two randomly collected samples, containing 500 kernels each. Maize was harvested using a maize combine harvested by Wintersteiger and grain yield was calculated in terms of a constant moisture content of 15%, according to the following formula: P=0.85 P o (100-Z w ) Where, P, yield of grain at a 15% moisture content; P o, fresh matter yield of threshed grain (kg); Z w, water content in threshed grain (%). The content of chlorophyll a, b and a+b was determined in the 7-8 leaf phase (BBCH 17-18). The content of chlorophyll a, chlorophyll b and total chlorophyll a+b was calculated using the formulas (Arnon 1949): Chlorophyll a=(12.7 OD OD 645 ) V (1000 W) -1 Chlorophyll b=(22.9 OD OD 663 ) V (1000 W) -1 Total a+b=( 20.2 OD OD 663 ) V (1000 W) -1 Where, OD w is the absorbance at a given wavelength w; V is the total volume of the extract (cm 3 ); W is the weight of a sample (g). 4

5 The analysis of mineral elements (nitrogen, phosphorus, potassium, magnesium and calcium) in the dry mass of maize in the 7-8 leaf phase (BBCH 17-18) was proved in the laboratory of the Department of Agronomy, Poznań University of Life Sciences, according to commonly used methods (Gawęcki 1994). In this paper the accumulation of individual macroelements with dry mass yield of plants in the 7-8 leaf phase (BBCH 17-18) was calculated according to the following formula: Uptake=Yield of dry mass content of nutrients/100 Where, uptake, in kg ha -1 ; yield of dry mass, in kg ha -1 ; content of nutrients, in %. The value of a particular variant of magnesium application is the mean value from four blocks (Szulc et al. 2011). Parallel coordinate plot The construction of a parallel coordinate plot is easy. Each trait is represented on the x-axis and it has its own y-axis. We may be used traditional mean values of traits or normalized or standardized date to construction of PCPs (we used original mean values data). PCPs constructed on the basis of original data are easy to interpretation for biologists and geneticists and agronomists. The y-axes are parallel, have the same length, and start with a minimum of the corresponding trait and end with its maximum. Note thus that when a particular variant of magnesium application is placed in the middle of a y-axis, it does not mean that its value is around the mean of the corresponding trait, it is the middle point within the trait s range. For a particular variant of magnesium application, the points on the adjacent y-axes are joined by a line, thereby picturing a multidimensional characterization of the variant of magnesium application. Since many variants of magnesium application are ploted on the same PCP, a particular variant s performance can be seen against a background of the whole pool of variants of magnesium application studied. All plots were drawn with statistical package GenStat 15. References Andrienko G, Andrienko N Exploring spatial data with dominant attribute map and parallel coordinates. Computers, Environment and Urban System, 25, Arnon D I Copper enzymem in isolated chloroplasts. Polyphenoloxidase in Beta vulgaris. Plant Physiology, 24, Bertero H D, De La Vega A J, Correa G, Jacobsen S E, Mujica A Genotype and genotype-by-environment interaction effects for grain yield and grain size of quinoa (Chenopodium quinoa Willd.) as revealed by pattern analysis of international multi-environment trials. Field Crops Research, 89, Bocianowski J, Joachimiak K, Wójciak A The influence of process variables on the strength properties of NSSC birch pulp. Towards the limits of optimization: part one the effect of liquor ratio. Drewno, 188, Bocianowski J, Joachimiak K, Wójciak A The influence of process variables on the strength properties of NSSC birch pulp. Towards the limits of optimization: part two the effect of temperature and cooking time. Drewno, 189, Chang D H, Yang S J Dynamic parallel coordinate plot and its usage. Journal of Korean Society Applied Statistics, 9,

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