Effects of Zinc and Nitrogen fertilizations on grain yield and some parameters effecting Zinc bioavailability in lentil seeds
I. Erdal, M. Kaya, Z. Küçükyumuk
Legume Research An International Journal
This study aimed to investigate the effect of Zinc (Zn) and Nitrogen (N) fertilizations on grain zinc (Zn) phosphorus (P) and phytic acid (PA) concentrations, PA/Zn molar ratio, yield, phytase activity and protein content of lentil varieties. Zinc fertilization led to decrease in grain P concentrations and related parameters. Phytic acid/Zn molar ratios decreased with the increment of Zn and protein concentrations in grains, but increased with the increase of grain P levels. While there were
... itive relations amongst the grain P concentrations and P-related parameters, there was a close negative relation with Zn generally. Although, protein concentrations negatively affected by grain P and PA concentrations, there was a significant positive relation with N fertilization. Increase of both Zn and P concentrations in grains negatively affected phytase activity, but a positive correlation was seen between the protein and phytase. Grain yield increased with both Zn and N fertilization. Phytic acid is found in most cereal grains, legumes, nuts, oilseeds, tubers, pollen, spores, and organic soils. Phytic acid is the storage form of P and usually accounts for 60-80% in wheat, 66-70% in barley, 71-88% in corn 50-70% in soybeans, 27-87% in lentils and 40-95% in chickpeas of total P (Lolas et al., 1976; Chitra et al., 1995; Erdal et al., 2002; Mate and Radomir, 2002). In the studies conducted by different authors on different seeds, PA content varied from 0.39-1.35% in wheat, 0.83-2.2% in corn, 0.50-1.89% in triticale, 0.54-1.46% in rye, 0.74-2.10% in beans and 0.28-1.26% in chickpeas (Reddy et al.,1982; Singh and Reddy, 1977; Lolas et al., 1976). A clear major role for phytate is as a store of inositol, phosphate, K, Mg, Ca, Mn, Fe and Zn for use by the seedling (Lott and Buttrose, 1978 ; Chen and Lott, 1992). These are released to developing seedlings by the action of phytase enzymes (Chen and Pan, 1977). Phytic acid, by binding nutritionally important minerals such as Zn, impairs their biological utilization. Phytic acid is also able to form complexes with proteins, and thus impairs digestibility and bioavailability of proteins in seeds (Reddy et al., 1982). In most cases, PA to Zn molar ratios in foods are considered a predictor of Zn bioavailability rather than P, PA and Zn concentrations. Ratios above 20 to 30 have been reported to reduce Zn absorption and growth of animals (Oberleas and Harland, 1981). In the literature, it was documented that genetic variation effected plant P and PA concentrations (Raboy et al., 1991; Erdal et al., 2002; Kaya et al., 2009). As root uptake and shoot accumulation of P are greatly affected by Zn deficiency (Loneragan et al., 1982; Rengel and Graham, 1995), it can be suggested that varied Zn supply can influence PA concentration of seeds of plants grown under Zn-deficient conditions. Containing about 25% protein, 56% carbohydrate, and 1.0% fat in seeds, lentil is one of the best and cheapest sources of vegetable protein. Phytate content in legumes has been involved in reducing the bioavailability of minerals and inhibiting the activity of several enzymes (Knuckles et al., 1989) .