These structures release cells that perform neutrophil-like functions by expelling extracellular DNA, called border cells. The movement of specialized organelles within the columella cells of these structures helps direct their growth according to the starch-statolith hypothesis. These structures can recover from damage by triggering the proliferation of stem cells located in quiescent centers. The lengthening of cells in the zone of elongation (10[1])causes most of the growth (-5[1])of these structures, (-5[2])which often display positive gravitropism. These structures form symbiotic relationships with fungi (10[1])called (10[1])mycorrhizae. (10[1])Material in these structures is transported to the rest of the organism through the (10[1])xylem. (-5[1])For 10 points, (-5[1])name these structures (10[1])that plants use to take (10[1])up nutrients and water. ■END■ (10[3])