Mechanism Of Phosphorus High Uptake And Utilization Efficiency In Different Maize Cultivars

The low phosphorus availability in soil was becoming one of the limitting factor for plant growth. Screening high-endurance P-deficiency and high-P uptake and utilization plant cultivars is very important for solving the P-deficiency problem and keeping agricultural sustainable development. In the present study, different P efficient maize cultivars were collected to cultivate in hydroponic culture, then in high and low P soil. High and low P efficient maize cultivars were gained by the final yields and different P efficient indexes. After this, the mechanism of phosphorus high uptake and utilization efficiency in different maize cultivars were studied under the conditions of nutrient solution and quartz sand. The main results were as followed:1. Results in hydroponic culture and yield experiments were both proved that liyu16 cultivar had a higher yield and jidan28 cultivar had a lower yield under both high and low P conditions, kuancheng10 had a lower yield in the low-P condition.2. For the P uptake mechanism, under P-deficient condition, the height, dry weight and P content increment in maize shoot and whole seedling all decreased while the dry weight of roots and ratio of root to shoot increased. Moreover, root length enhanced by 61%, 62% and 17%, root radius depressed by 19%, 29% and 4%, and root surface area increased by 31%, 18% and 13%, respectively. Total uptake area and specific surface area of roots were both lower, and pH in the nutrient medium respectively reduced by 1.3, 0.8, and 0.7 units, but the three cultivars all had higher uptake kinetics of H2PO4? and stronger abilities to endure P deficiency. The acid phosphatase (APase) activities in root tissue were improved. Compared with jidan 28 and kuancheng 10, liyu 16 had higher dry weight increment, root length and root surface area, root activity and proton exudation, stronger tolerance ability to P deficiency, larger uptake kinetics of H2PO4– and APase activity in root tissue.3. For the P utilization mechanism, during the study periods, compared with high-P treatment, plant dry weight, P content in each organ and P amount transported in the xylem under the low-P condition were significantly depressed, while P amount retranslocated from leaves to the root by phloem increased. P activated in each organ were recycled to roots through phloem, and then transported to the upper new leaves via xylem. Dry matter and P within plant allocated into the upper leaves were not synchronous. Liyu16 had a higher ratio of root to shoot in any P levels. Compared with kuancheng10 and jidan 28 under the low-P condition, dry weight of liyu 16 increased 32.8 and 26.9%, P content increased 8.8% and 12.0%, P uptake efficiency enhanced 8.8% and 12.1%, P utilization efficiency enhanced 22.1% and 13.3%, P proportion of from xylem transported into upper leaves improved 4.7% and 27.5%, respectively. In conclusion, the biomass of P-high-efficiency maize cultivar with the low-P treatment was larger because it had higher ratio of root to shoot, more P transported to upper leaves in the xylem, higher P uptake and utilization efficiency.