Young developing soybean seeds contain relatively large amounts of calcium oxalate (CaOx) monohydrate crystals. A test for Ca and CaOx indicated that Ca deposits and crystals initially occurred in the funiculus, where a single vascular bundle enters the seed. Crystals formed in the integuments until the embryo enlarged enough to crush the inner portion of the inner integument. Crystals then appeared in the developing cotyledon tissues and embryo axis. All crystals formed in cell vacuoles. Dense bodies and membrane complexes were evident in the funiculus. In the inner integument, cell vacuoles assumed the shape of the future crystals. This presumed predetermined crystal mould is reported here for the first time for soybean seeds. As crystals in each tissue near maturity, a wall forms around each crystal. This intracellular crystal wall becomes contiguous with the cell wall. Integument crystals remain visible until the enlarging embryo crushes the integuments; the crystals then disappear. A related study revealed that the highest percent of oxalate by dry mass was reached in the developing +16 d (post-fertilization) seeds, and then decreased during late seed maturation. At +60 d, CaOx formation and disappearance are an integral part of developing soybean seeds. Our results suggest that Ca deposits and crystals functionally serve as Ca storage for the rapidly enlarging embryos. The oxalate, derived from one or more possible metabolic pathways, could be involved in seed storage protein synthesis.

Developing soybean seeds accumulate very large amounts of both soluble oxalate and insoluble crystalline calcium (Ca) oxalate. Use of two methods of detection for the determination of total, soluble, and insoluble oxalate revealed that at +16 d postfertilization, the seeds were 24% dry mass of oxalate, and three-fourths of this oxalate (18%) was bound Ca oxalate. During later seed development, the dry mass of oxalate decreased. Crystals were isolated from the seeds, and X-ray diffraction and polarizing microscopy identified them as Ca oxalate monohydrate. These crystals were a mixture of kinked and straight prismatics. Even though certain plant tissues are known to contain significant amounts of oxalate and Ca oxalate during certain periods of growth, the accumulation of oxalate during soybean seed development was surprising and raises interesting questions regarding its function.

Consumption of soybeans and food products made from them is increasing because of their desirable nutritional value. However, the oxalate content of seeds from 11 cultivars of soybean showed relatively high levels of total oxalate from 0.67 to 3.5 g/100 g of dry weight. Oxalate primarily was found as calcium oxalate crystals. Thirteen tested commercial soyfoods contained between 16 and 638 mg of total oxalate per serving. These values compare to those of three other legume foods, peanut butter, refried beans, and lentils, which contained 197, 193, and 100 mg of total oxalate per serving, respectively. After oxalate has been absorbed from the diet, it cannot be metabolized and is excreted by the kidney into urine, where it binds to calcium forming an insoluble salt that may precipitate to form kidney stones. The amounts of total oxalate in soybean seeds, soy foods, and other common legume foods exceed current recommendations for oxalate consumption by individuals who have a history of calcium oxalate kidney/urinary stones. This study serves as the basis to find soybean cultivars lower in oxalate, which will have lower risk for kidney stone formation after human consumption.

Unidentified basidiomycete rhizomorphs growing on oak-leaf litter {Quercus alba) in Iowa and in Texas {Quercus gravesii) displayed arrays of crystals associated with their hyphae. X-ray diffraction and birefringence analyses identified the crystals as a mix- ture of calcium oxalate-monohydrate and -dihydrate. The Iowa oak-leaf-litter rhizomorph crystals occurred in two forms: young hyphae displayed either small styloid-like crystals oriented in all directions along the hyphae; or large clusters of elongated styloid-like crys? tals surrounding the hyphae, with individual crystals in each cluster displaying pyramidal ends. Crystals as? sociated with the Texas oak-leaf-litter rhizomorphs consistently covered all of the young hyphae and their tips with either small dagger-like crystals or thin, plate? like crystals whose margins were either smooth or fin- ger-like. Some larger crystal masses were also com- posed of crystals with pyramidal ends. The dagger-like and plate-like crystals were tentatively identified as the monohydrate form based on their higher birefrin? gence, whereas the crystals with pyramidal ends were identified as the dihydrate form based on their shape and lower birefringence. It is not known whether the two crystalline forms associated with the rhizomorphs are a function of the individual rhizomorphs, the litter source, the stage of crystal growth, or the ions present in the surrounding soil/ground water.

Liquid-cultured primary roots of Yucca torreyi L. (Agavaceae), which are similar to its intact roots, develop uninterrupted files of calcium oxalate crystal idioblasts with raphide bundles in their cortex, beginning just proximal to the terminal meristem. Each single file of idioblasts displays a basipetal ontogenetic sequence. [1-14C]glycolic acid, [1-14C]glyoxylic acid, and L-[1-14C]ascorbic acid, all of which are potential precursors of oxalate, were each added to different flasks that contained a sterile liquid medium and isolated roots and were allowed to interact with the roots for 45 min. After thorough washing, the roots grew for periods that extended from 1.6 h to 24 h postincorporation before being fixed for light microscope autoradiography. Autoradiography of root sections with the L-[1-14C]ascorbic acid at the 1.6–6.0-h incorporation times showed concentrations of silver grains over the idioblasts, primarily over the vacuole crystal bundles and cytoplasmic plastids. The [1-14C]glyoxalic acid– and [1-14C]glycolic acid–labeled root sections showed a smaller amount of silver grains distributed over the entire sections, but these grains were not concentrated over the crystal idioblasts. These results strongly indicate that the L-[1-14C]ascorbic acid is the immediate precursor of oxalate in the crystal idioblasts of Y. torreyi primary roots and support more recent biochemical data regarding oxalate synthesis in higher plants. The use of roots in liquid culture containing uninterrupted files of developing crystal idioblasts could serve as a model system for additional biochemical, physiological, and molecular studies that seek to understand the formation and functional significance of crystal idioblasts in higher plant organs.

Calcium oxalate dihydrate crystals form at or near the tips of sterile hairs on the apothecia of the oak leaf litter discomycete Dasyscypha capitata. Early in their development, the crystals appear to be covered by a wall or membrane, whereas later they appear external. The crystals on each hair form a mass of crystals called a druse. Quite often the smaller crystals near the apex of the tip form a rosette, whereas the more peripheral crystals are much larger and display shapes possibly related to environmental factors. The formation and development of Dasyscypha crystals are compared with recent studies of other litter and soil fungi and their presence in other biological systems is put into perspective.