Effects Of Low Phosphorus Stress On Nutritional Characteristics Of Maize Seedlings With Different Phosphorus Or Aluminum Tolerance

Some typical low-P tolerant or low-P sensitive and Al tolerant or Al sensitive maize genotypes which were screened in our lab were selected to study their nutritional characters and physiological mechanism for low-P or acid-aluminum tolerance. The main results of this study were summarized as follows:1. A pot cultivation experiment was conducted to study the characteristics of growth and uptake of various nutrient elements at maize seedling stage under different acid and P treatments. The results demonstrated that P deficiency and acid stress severely hinder the growing of maize. No matter whether P deficiency was treated by pH4.6 or pH6.8 conditions, it had a negative influence on biological traits, especially on plant dry matter weight and number of living leaves. Acid and aluminum stress severely affects colour of lower leave and plant dry matter weight of maize. The low P severely affects the absorbing of P, K, Ca. The stress of acid and aluminum could significantly decrease the absorbing of P, K, Ca, Mg, Fe. The addition of P could alleviate the toxicities of acid and aluminum. There were genotypic differences in tolerance to low-P and acid stress among different lines. It was also found that there are some relation between low P tolerance and acid tolerance. M12 is sensitive line to both acid-aluminum stress and low P stress; the acid and aluminum tolerant lines M02 and M08 show the same tolerance to low P, whereas the low P tolerant line M01 has some tolerance to acid and aluminum stress, which are tolerant lines of both stress.2. A solution culture experiment showed that low phosphorus stress made plant height, longest root length, dry weight of root, dry weight of shoot and plant dry weight decrease obviously, R/S increase. The relative value of every trait of the low P tolerant lines M01, M02 and the acid tolerant lines M08 are higher than those of the low P sensitive line M05. Under low-P stress, M02, M08, Ml 1 and M01 show stronger abilities of P uptake and larger distribution coefficient, the absolute and relative accumulation of theirs are observably higher than that of the low P sensitive line M05.3. P deficiency has some influence on the uptake of K, Ca, Mg, Fe, Mn and Zn at seedling stage. P deficiency restrains the uptake of K for the maize. But the P tolerant lines show stronger abilities of K. uptake and accumulation than P sensitive lines. P deficiency results in the fewer uptakes of Ca and Mg for most of the lines. But P tolerant lines have more absolute and relative uptake amounts of Ca and Mg than that of P sensitive lines under low-P stress, this belongs to synergistic-effect. P deficiency increased Fe concentration but decreased Fe accumulation of shoot and root, and facilitate the uptake of Fe for M08 and M12. With P deficiency, P tolerant lines M01, M02 and acid tolerant line M08 uptake more Mn than P sensitive line M05. P deficiency increased Zn concentration of shoot but decreased Zn accumulation of shoot and root. However, M02, M08 and M11 have the larger amounts of Zn than M05.4. Phosphate uptake kinetics showed that Low P treatment significantly increased the I_max, but significantly decreased the K_m for all of five maize genotypes. the root uptakes of phosphate were obviously stronger in M02, M11, M08 than in P sensitive line M06 and acid sensitive line M12. The values of K_m, the Michaelis constant, which is the concentration where influx is half of I_max, of M02, M11, M08 were much smaller, but the index of I_max is higher than that of P sensitive line M06 and acid sensitive line M12, spectively. This indicated that they were much stronger than that of low P efficiency in the affinity of root system to phosphate and in tolerating P deficiency.