Calcium oxalate crystals in tomato and tobacco plants: Morphology and in vitro interactions of crystal-associated macromolecules

Plants form calcium oxalate crystals with unique morphologies under well-co ntrolled conditions. We studied the morphology of single calcium oxalate mo nohydrate (whewellite) crystals extracted from tomato and tobacco leaves. T hese crystals have a pseudotetrahedral shape. We identified the ((1) over b ar 01), (101) or (102), (1(0) over bar 2), and ((h) over bar(k) over bar0) faces as stable faces. The morphology is chiral with unique handedness. We also show that calcium oxalate monohydrate crystals isolated from tomato, t obacco, and bougainvillea leaves contain macromolecules rich in Gly, Glx, a nd Ser. Crystal-associated macromolecules extracted from tomato and tobacco influence the morphology of calcium oxalate monohydrate crystals grown in vitro, promoting preferential development of the {120} faces. Furthermore, crystal-associated macromolecules from tobacco promote nucleation of calciu m oxalate monohydrate crystals, whereas model polypeptides do not have any significant effect on nucleation. These results imply an active role of the crystal-associated macromolecules in the formation of pseudotetrahedral sh apes in vitro, and these properties may in part be responsible for the uniq ue chiral morphology of the natural pyramidal-shaped crystals.