| Field experiments were conducted at Huajiachi Campus Experimental Farm of Zhejiang University in 2006 and 2007 to evaluate the effects of the low phytic acid (lpa) genotype on the agronomic performance and nitrogen levels on the phytic acid content and phosphorus compositions of maize using wild-type (WT)(X178 and Zheng 58) and lpa genotypes (X178M and Zheng58M). The plant height, the growth period, the photosynthetic rate, chlorophyll SPAD values, the content of phytic acid, total phosphorus and inorganic phosphorus in different organs were measured. The main results are shown as follows:(1) Compared with WT, lpa mutations had delayed growth rate, reduced the plant height and chlorophyll SPAD values, and increased the net photosynthetic rate. Chlorophyll SPAD values were decreased by 8.73%-9.77% in X178M and 6.44%-9.45% in Zheng58M. However, net photosynthetic rates were increased by 7.11%-12.6% in X178M and 8.95%-14.1% in Zheng58M.(2) The phytic acid content in seeds was significantly higher than that in other organs. The content of phytic acid in different vegetative organs were quite different, namely, leaf≈sheath> stem≈bract. The range of phytic acid content was 1.5333-1.6071mg/g and 3.0157-3.2169g/mg in lpa mutations and WT, whereas the phytic acid content of lpa mutations in sheath, leaf, stem, and bract contained 0.0423, 0.0419, 0.0365, and 0.0336 g/mg, respectively.(3) As for the same organ in different parts of corn, the phytic acid content in the lower part was significantly higher than other parts; there was almost no difference between the middle and upper part. For example, the 26.21% and 20.05% increase of sheath phytic acid content were observed in the lower part of plant over in the middle and upper parts; the one of leaves in lower part of plant rose by 11.88% compared with the middle and upper parts; the one of stems in lower part of plant were 6.65% and 7.27% higher than that of the middle and upper parts.(4) The phytic acid content is obviously sensitive to nitrogen levels. Except for the bract, phytic acid content of other organs showed a downward tendency with the increase of nitrogen. For instance, the phytic acid content of seeds was only 1.9047mg/g under the 270kgN/hm~2 nitrogen level, which was significantly lower than other nitrogen levels(5) The reduction of low phytic acid caused total phosphorus decrease and inorganic phosphorus increase, leading to the fall of phytic acid as the main component of the organic phosphorus. The content of total phosphorus and organic phosphorus in lpa mutations reduced by 7.8%-10.09% and 26.57%-28.23%, respectively. However, the content of inorganic phosphorus rose by 26.57%-28.23% compared with WT.(6) Nitrogen levels had an important effect on phosphorus compositions. When nitrogen levels ranged from 0 to 180 kgN/hm~2 , the total phosphorus in grains went up with N-application increased; the content of total phosphorus and organic phosphorus under 180 kgN/hm~2 nitrogen levels were 19.99% and 31.21% higher than that without nitrogen treatment. Otherwise, excessive nitrogen application could cause every type of phosphorus reduction. For example, When the nitrogen level was 270 kgN/hm~2, the content of total phosphorus, inorganic phosphorus, and organic phosphorus in seeds showed the lowest value during all nitrogen levels, being 5.58%, 12.37%, and 18.56%lower than under the 0 kgN/hm~2 nitrogen level. Meanwhile, with increasing of nitrogen application, there is a similar decreasing tendency for content of every type of phosphorus in leaf, sheath, stem or bract.
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