Accumulation of phytate in vegetable-type soybean genotypes harvested at four developmental stages

Effect of harvest at different times of day on the physical and chemical characteristics of vegetable-type soybean

The objective of this study was to evaluate the effect of harvest at different times of day on the chemical and physical characteristics of vegetable-type soybean BRS 267 cultivar, harvested at the R6 stage (seed development) and to compare it with that on the grains harvested at the R8 stage (maturation). The pods of the BRS 267 cultivar were harvested at the R6 stage (at 8:00 AM, 12:00 AM, and 6:00 PM), the color parameters were evaluated, and the grains were analyzed for chemical composition, activity inhibitor trypsin, phytic acid content, starch, sugars, fatty acids, and isoflavones. No differences were observed among the different harvest times in terms of the chemical constituents of vegetable-type soybean BRS 267 cultivar harvested at the R6 stage. Isoflavones content did not change with different harvest times, and the aglycone forms (daidzein, glycitein, and genistein) were found in smaller quantities at the R6 stage compared to the R8 stage. The color of the pods of soybean BRS 267 cultivar, harvested at the R6 stage did not change with different harvest times. The grains harvested at the R6 stage had lower protein content, phytic acid, and sucrose and higher levels of lipids, carbohydrates, starch, glucose, fructose, stachyose, and linolenic acids than those collected at the R8 stage. The different times of harvest did not affect the quality of the vegetable-type soybean BRS 267 cultivar harvested at stage R6. Nevertheless, it is recommended to harvest in the morning, when the temperature is milder, like other vegetables, to facilitate and optimize its marketing and in natura consumption.

Seed phytate content and phosphorus uptake and distribution in dry bean genotypes

Phytic acid is the major storage form of phosphorus in seeds of legumes and cereals. Since phytate can form complexes with proteins and minerals, reducing the digestive availability of these nutrients, it is usually regarded as an antinutrient, although recent work indicates that it has important beneficial roles as an antioxidant and anticarcinogen. Therefore, there is an interest in the assessment and manipulation of phytate contents in important food grains such as beans. The objective of this work was to compare eleven dry bean genotypes with regard to grain contents of P, phytate, inorganic P and protein and to examine if differences between genotypes could be explained by differences in grain protein content or in uptake and partitioning of P. Plants were grown in a greenhouse in pots containing soil and commercial substrate amended with 7.4 and 37 mg P.dm-3. The experimental setup was a random, complete block design with five replications. Genetic variability in grain phytate contents was observed. At the higher dose of P fertilization, genotype Una presented the highest phytate content (1.48 %) and the highest fraction of P as phytate (72 %), whereas these features were lowest in Paraiso (0.70 % and 47 %, respectively). Inorganic P made up 8 % of total P in Paraiso. A correlation between phytate and protein contents among genotypes was significant (r = 0.73) only under the higher dose of P fertilization. With the exception of genotype 4AP, differences in phytate content could not be explained by differences in uptake and partitioning of P in the plant. In the case of Paraiso, it is inferred that the lower phytate contents were due to differences in the metabolism of P and dry matter accumulation in the grain.

Effects of phytic acid and xanthotoxin on growth and detoxification in caterpillars

Phytic acid is abundant in the fruits and seeds of many plants and is found in foliage to a lesser extent. Among its several properties, phytic acid is a potent chelator of essential minerals and proteins; thus, the possibility exists that heme-based enzymes such as cytochrome P450 monooxygenases in herbivores are detrimentally affected by phytic acid via chelation of dietary iron. Mortality, growth performance, and P450-mediated metabolism of xanthotoxin, a plant allelochemical, were examined in the presence of phytic acid in three lepidopteran species: a polyphagous seed-feeding species (Heliothis virescens), a polyphagous foliage-feeding species (Trichoplusia ni), and a species oligophagous on immature reproductive structures of two genera of Apiaceae (Depressaria pastinacella). While first instar H. virescens experienced no increase in mortality after 120 hours on a diet containing 1% phytic acid compared to a control diet, both T. ni and D. pastinacella experienced virtually complete mortality over the same time period. Ultimate instars of all three species experienced reductions in relative growth rates (RGR) and relative consumption rates (RCR) in the presence of phytic acid, although the only species to experience reduced digestive efficiency (ECI) was H. virescens. Cytochrome P450-mediated metabolism of xanthotoxin was reduced 60% in the presence of phytic acid in D. pastinacella, although metabolism remained unaffected in the two noctuids. These studies suggest a defensive function of phytic acid in addition to its primary functions of phosphorus storage, energy storage, and cell wall precursor source.