Sorghum genotype differences in phosphorus uptake rate and distribution in plant parts

Abstract

Relatively low amounts of the phosphorus (P) added to soils is recovered by plants. Many plants show differences in their ability to take up and use P, but the mechanisms for these differences are not fully understood. The purpose of this study was to determine differences among sorghum [Sorghum bicolor (L.) Moench] genotypes for P uptake rates and distribution in plant parts.

Differences in P uptake rates were determined for six sorghum genotypes at 24, 38, and 52 days of age at three P levels. Larger differences were noted among genotypes in 24‐day‐old plants than for older plants. Uptake rates were 6‐ to 14‐times higher (dependent on genotype) in 24‐day‐old plants than in 52‐day‐old plants. NB9040 which had the highest dry matter yield at each age had the lowest rate of P uptake, and CK60‐Korgi which had the lowest dry matter yield at each age had the highest rate of P uptake.

Only small differences were noted among genotypes for distribution of P within plant parts for younger plants. Older plants showed differences in P distribution, and NB9040 translocated more P from lower to upper leaves, had higher efficiency ratios (dry matter produced/unit P), and had a larger root system than CK60‐Korgi.

The sorghum genotypes that produced more dry matter under low P conditions had lower uptake rates of P and had the ability to distribute P from older to younger developing tissues. When grown in soils, plants that have lower P uptake rates, greater ability to distribute P, and larger root systems may not deplete P from soil solutions as rapidly, could explore more soil, and possibly use P more efficiently than plants that do not possess these traits.

Key words:

• Mineral nutrition
• Nutrient solutions
• Phosphorus efficiency
• Phosphorus mobilization and utilization

Notes

Present address: Instituto Agronomico, C. P. 28, 13,000 Campinas, Sao Paulo, Brazil.