Garrett T. Y., Huynh C. V., North G. B., Root contraction helps protect the “living rock” cactus Ariocarpus fissuratus from lethal high temperatures when growing in rocky soil, American Journal of Botany, 2010, 97(12):1951-1960, doi: 10.3732/ajb.1000286
Movement measurements, root anatomy and thermal experiments explain Ariocarpus fissuratus root contraction. Expansion of parenchymatous rays coexists with compression of xylem containing wide-band tracheids. In rooftop comparisons, the significance of low stem position depended on stony or sandy surroundings. Separate experiments concern water loss and acclimation of tissue temperature resistance.