The adaptations of root growth and rhizosphere processes for soil phosphorus (P) acquisition have been investigated intensively in wheat (Triticum aestivum). However, only a few studies paid attention to these responses to shoot P status. This study aimed at investigating the responses of root morphology and P-mobilizing exudation to increasing shoot P concentration. A broad range of wheat shoot P concentrations (1.0-7.1 mg per g dry weight) was set up with 11 rates of P supply: 0-1200 mg P per kg soil. Root morphology and exudation parameters were measured after 37 days of plant growth. Shoot dry biomass reached a maximum when shoot P concentration was 4.63 mg per g dry weight. The maximum shoot P concentration for total root length, specific root length and the proportion of fine root (diameter ≤ 0.2 mm) length to total root length was 3 mg per g dry weight. Rhizosphere acidification was positively correlated with shoot P concentration when this was < 5 mg per g dry weight. Shoot P concentration did not change acid phosphatase activity in the rhizosphere. Citrate concentration in the rhizosphere was suppressed by increasing shoot P concentration. In contrast, malate concentration in the rhizosphere showed a positive correlation with shoot P concentration. In conclusion, wheat root morphological and P-mobilizing exudation traits showed different behaviours with increasing P deficiency stress. Maintaining root biomass and length is the major strategy rather than root exudation for wheat to cope with extreme P deficiency.
Bibliographical noteFunding Information:
This study was financially supported by National Key R&D Program of China (2017YFD0200200 and 2017YFD0200202), the National Natural Science Foundation of China (NSFC)(31330070and 31210103906), the Innovative Group Grant of the National Natural Science Foundation of China (31421092), the National Basic Research Program (973-2015CB150405).
We thank the Associate Editor and two anonymous reviewers for their valuable comments. We also thank Prof. Hans Lambers from University of Western Australia for helpful comments on an earlier draft of this manuscript. This study was financially supported by National Key R&D Program of China (2017YFD0200200 and 2017YFD0200202), the National Natural Science Foundation of China (NSFC) (31330070 and 31210103906), the Innovative Group Grant of the National Natural Science Foundation of China (31421092), the National Basic Research Program (973-2015CB150405).
- Shoot phosphorus concentration