Studies On The Change Of Phytic Acid Accumulation And Its Response To Environmental Factors In Barley Grains

Phytic acid (InsP₆) is a naturally occurring compound formed during maturation of plant seeds and grains. It is regarded as the primary storage form of both phosphate and inositol in plant seeds. In mature grains, InsP₆ is deposited as salts of mineral cations and organized into globoids that are in turn found within protein bodies. The major concern about the presence of InsP₆ in plant is its negative effect on mineral uptake, It forms very stable complexes with mineral cations such as Ca²⁺, Fe^2+/3+ and Zn²⁺, rendering them unavailable by humans and other non-ruminant animals. Furthermore, the excretion of "phytate-phosphorus" which is less nutritionally available by non-ruminant animals can contribute to water pollution. Thus, it is important and meaningful to keep InsP₆ content at a proper level via breeding or improving agronomic practices. This investigation was carried out to study: (1) dynamics of InsP₆ during grain filling and its correlation with protein and total phosphorus; (2) effects of nitrogen and phosphorus supply levels on InsP₆ accumulation in kernel and (3) variation characters of InsP₆ content of barleys differing in tolerance under stress conditions, based on the research of genotypic variation of kernel InsP₆ content and its environmental effect.1,Dynamics of InsP₆ in relation to protein and total phosphorus accumulation during kernel developmentThree barley genotypes were field-grown, and the changes of InsP₆, protein and total phosphorus during grain filling and their relationships were investigated. MMF equation was used to describe the dynamics of InsP₆ accumulation during grain filling. The results showed that InsP₆ accumulation was similar in all cultivars, and considered to conform to a "S-curve". The rate of InsP₆ accumulation could be fitted to a "single-peak curve" and peaked at about 13-14 days after anthesis. CAW453 showed higher peak value and much longer accumulation time as compared to 03-34 and 06-08 whose rates of InsP₆ accumulation seemed reversely stable. Variation in the InsP₆ content of three barley genotypes matched changes in grain weight during grain filling. However, protein and total phosphorus accumulation appeared to be no effects on InsP₆ formation in kernel, and there was no certain association between the rates of InsP₆, protein and total phosphorus accumulation. These results suggest the independence of N and P accumulation during grain filling and it is possible that exists a p metabolic pathway which more active than InsP₆ synthesis.2,Effects of nitrogen and phosphorus fertilizer application rates on InsP₆ accumulation in kernelResplit-plot design was carried out to study the effect of three N levels and three P levels on InsP₆, protein and total phosphorus content of two barley cultivars. The results showed that InsP₆ content declined highly significantly with increasing external N levels, and hull-less barley was much more affected than hull barley though it got much lower InsP₆. Highly significant phosphorus fertilizer effects were identified, but these were less than the nitrogen fertilizer effects. Hull barley kernel InsP₆ content increased highly significantly in P₂ treatment compared with P₁ treatment, but decreased highly significantly in P3 treatment compared with P₂ treatment. However, this did not appear to be the case in hull-less barley, suggesting that the effect of phosphorus fertilizer on InsP₆ content was genotype and amount-dependent. The significant interaction between N level and P level suggests that the effect of nitrogen fertilizer on InsP₆ content seemed to be at least partly dependent on phosphorus fertilizer. For all cases, no significant correlation was detected between InsP₆ and protein content, suggesting the independence of N and P accumulation during grain filling. Significant and positive relationship between kernel InsP₆ and total phosphorus content only found in hulled barley indicated that this relationship can be affected by genotype and environmental conditions.3,Variation characters of InsP₆ content of barleys differing in tolerance in response to different stressUsing three DH populations to study the changes of InsP₆ content in genotypes with different salt, acid, and waterlogging tolerance under the condition of salt, acid stress and waterlogging, respectively. A significant reduction of InsP₆ content in kernel was observed under 200mM NaCl treatment. The decrease in InsP₆ content in response to salt stress is possibly one of the "truly adaptive responses" to release more Pi, inositol which involve in plant stress response. By contrast, little correlation was found between InsP₆ content and yield under salt stress, suggesting the detrimental effect of salt stress on these two parameters varied with genotypes. Little regulation of variation in the InsP₆ content can be found in both acid stress and waterlogging. The difference between two kinds of genotypes in InsP₆ content was not significant under both normal and stress condition in three different stress testing, respectively. There was no certain association between InsP₆ content and yield under salt, acid stress and waterlogging, respectively. It could be concluded that InsP₆ content has no direct relationship with tolerant ability of barley.