Integrating gas exchange and GC-MS data throughout the diel course
Angiosperms have higher absolute values of A andg s (Franks & Britton-Harper 2016; Tosenset al. 2016; Gago et al. 2019; Lima et al. 2019). Thus, to investigate the dynamic of gas exchange and the accumulation of primary metabolites throughout the diel course, both gas exchange and GC-MS data were subjected to a maximum-minimum transformation (0-to-1 range) according to the equation below:
\(f\left(x\right)=\ \frac{xi-\min\left(x\right)}{\max{\left(x\right)-min(x)}}\), where xi is an observation of a variable (metabolites or gas exchange parameters).
This equation was applied to each variable, transforming them to a 0-1 scale throughout the diel course (05:00 h, 08:00 h, 14:00 h and 17:00 h). The lowest average value of each variable was set to zero (0) and the highest to one (1). The values in between were then proportionally normalized between the maximum and the minimum observed throughout the diel course (Deans et al. 2019). Variables with similar trends throughout the diel course were clustered by Dynamic Time Warping (DTW) analysis, using the dtwclust package in R (Sardá-Espinosa 2019).