GENOTYPIC DIFFERENCES IN ROOT MORPHOLOGY AND PHOSPHORUS UPTAKE KINETICS IN BRASSICA NAPUS UNDER LOW PHOSPHORUS SUPPLY

Abstract

Application of phosphorus (P) fertilizer is important in crop production because of the low bioavailability of phosphorus to plants in both acidic and calcareous soils. Although rapeseed (Brassica napus) is generally sensitive to P deficiency, different cultivars differ widely in this respect. Differences in P uptake and utilization between two rapeseed cultivars, one P-efficient (‘97081’) and one P-inefficient (‘97009’), were evaluated in solution culture by studying the changes in root morphology and parameters of P uptake kinetics in response to low-P stress. The P-efficient cultivar had lower Km and Cmin values and higher Vmax and developed longer and denser lateral root hair with greater number of root tips and branches under low-P stress, which resulted in a better developed root system and more efficient uptake of P. That, in turn, led to higher concentration and accumulation of P in the plants, culminating in higher biomass production. However, P utilization efficiency (biomass production per unit P accumulated in plant) of the P-efficient ‘97081’ was lower than that of ‘97009’ when P was deficient. These results suggest that P efficiency in rapeseed is due to a better developed root system as well as efficient uptake of P.

Keywords:

• Brassica napus
• phosphorus acquisition
• kinetics parameters
• root morphology
• P utilization efficiency

ACKNOWLEDGMENTS

This work was supported by the National Basic Research and Development Program (2005CB120905), National 863 High Technology Program (2006AA10A112), and Specialized Research Fund for the Doctoral Program of Higher Education (20050504009), China. The authors sincerely thank Professor Xiaolong Yan for providing the blue paper without P and for his help in analyzing root architecture. The authors are also grateful to Professor Shuxin Tu for his suggestions related to P uptake kinetics and for carefully reading the manuscript.