For 10 points, name these plant structures typically located in the soil.
One type of this structure develops improperly in Alf mutants. These structures are formed from the lower layer of the heart-shaped embryo. Aquatic species possess a namesake "pocket" located at the ends of these structures, without which these structures would grow randomly. These structures are vulnerable to high metal concentrations and cannot uptake phosphate ions, disadvantages mitigated by their mutualistic association with fungi in mycorrizhae. The site of adenine-type cytokinin synthesis, they develop when the ratio of auxins to cytokinins is greater than one. "Stilts" are sometimes formed by the adventitious types of these structures, whose tuberous forms yield the potato and other foodstuffs. For 10 points, name these plant structures typically located in the soil.
One type of this structure develops improperly in Alf mutants.
roots [to prevent problems, accept specialized forms of roots as answers throughout the question]