bambara groundnut does not have a reference genome
This is your biggest problem if you want to do any sequencing based analysis. Neither GWAS nor RNAseq data analysis are possible without a reference genome (or at least transcriptome).
Depending on the availability, quality & similarity of reference genomes from related species it may however be ...
According to recent studies, drought stress does not consistently lead
to increases in the pH of xylem sap. One article which discusses
interspecies differences is Vit Gloser, et al., "The dynamics of
xylem sap pH under drought: a universal response in herbs?," Plant and
Soil 409, nos. 1-2 (2016): 259-272.
As to what may have prompted the textbook authors ...
Looks like it is Phytolacca dioica. I found this by searching your first image in a phone app called Pl@ntNet (PlantNet). Looking at Wikipedia confirms the ID.
Interestingly, you said the fruit was sweet. The North American relative Phytolacca americana is extremely poisonous. A brief search suggests your species is possibly poisonous, with reports ...
Essentially, evapotranspiration is the sum of evaporation and plant transpiration from the Earth's land and ocean surface to the atmosphere.
Here are some links to articles about transpiration: https://biolympiads.com/plant-anatomy-and-physiology/
tl;dr We don't really know. A reasonable guess is that it's a weak sink, gradually turning into a source via increased drought frequency, but it's extremely hard to measure; carbon flux is highly variable both spatially and temporally (so it matters both when and where you measure), and it's difficult to make sure that you're accurately measuring all the ...