Genotypic variation of rape in phosphorus uptake from sparingly soluble phosphate and its active mechanism
Phosphorus deficiency is one of the most growth-limiting factors in soils in various parts of the world. Two rape cultivars, which differed in Phosphorus (P) uptake from Fe-P (FePO4·4H2O) and Al-P (AlPO4), were investigated to elucidate the contributions of root morphology and organic acids exudation to P uptake by rape from iron phosphate and aluminum phosphate. By solution culture and sand culture experiments, the activation capacity of insoluble Fe-P and Al-P of organic acids secreted by different rape genotypes roots was studied. The results show that two rape cultivars has significant genotypic variations in both plant dry weight and P uptake per plant when supplied with Fe-P and Al-P as the P source. When supplied with sparingly soluble phosphate (Fe-P and Al-P), the root length, surface area and number of roots tips of genotype HG (phosphorus efficient rape) were significantly higher than genotype LG (phosphorus inefficient rape). The rape grew better in Al-P treatment than Fe-P treatment. Root exudates of rape has certain ability to activate insoluble P and it had better activation capacity of insoluble Fe-P under the condition of P stress than normal supply of P. Hence, the large differences show traits for more phosphorus efficient plants between in the tested rape genotypes. The genotype HG showed increased P acquisition from the Al-P and Fe-P than the genotype LG. This opens the possibility to breed for more P uptake-efficient varieties as a way to bring more sparingly soluble soil P into cycling in crop production.
Key words: Sparingly soluble phosphate, phosphorus efficiency, genotypic differences, rape.