ISHS Acta Horticulturae 694: International Symposium on Harnessing the Potential of Horticulture in the Asian-Pacific Region
ADAPTATIONS OF CAUSTIS BLAKEI TO LOW PHOSPHORUS CONDITIONS AND ITS SUSCEPTIBILITY TO PHOSPHORUS TOXICITY |
| Authors: | C.W.S. Playsted, M.E. Johnston, C.M. Ramage, D.G. Edwards, S. Hamilton |
| Keywords: | Cyperaceae, dauciform roots, phosphorus sensitive plants |
| Abstract:
Attempts to domesticate Australian native plants into conventional nursery production systems have been hampered by the sensitivity of a number of species to the essential mineral element phosphorus (P). However, this toxic response to P is highly variable, with sensitive and non-sensitive species present in the same genus. This paper presents details of a solution culture experiment examining the P absorption and internal requirement of the P-sensitive Australian native plant Caustis blakei. This study shows that with increasing solution P concentration above 10 µM, Caustis growth steadily declines. At these concentrations P toxicity symptoms were also evident and associated with accumulation of up to 1.2% P in the shoot at solution P of 250 µM. In contrast, under P limiting conditions, Caustis appears to be highly efficient in its acquisition and internal use of P. This is demonstrated by the fact that the highest total dry weight of 12.8g was achieved at solution P of 1.0 µM. Adaptations for low-P conditions by Caustis include an increased root to shoot ratio and the formation of dauciform roots at very low solution P concentrations  1 µM. Current research explores the role of dauciform roots in the production of organic acid and acid phosphatase exudates in response to P deficiency.
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