AOBPreview originally published online on February 23, 2006
Annals of Botany 2006 97(5):745-754; doi:10.1093/aob/mcl026
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Changes in Carbohydrate and Nutrient Contents Throughout a Reproductive Cycle Indicate that Phosphorus is a Limiting Nutrient in the Epiphytic Bromeliad, Werauhia sanguinolenta
1 Universität Basel, Botanisches Institut, Schönbeinstrasse 6, CH-4056 Basel, Switzerland, 2 Smithsonian Tropical Research Institute, Apartado Postal 0843-03092, Balboa, Ancon, Republica de Panama and 3 Universität Wien, Department of Chemical Ecology and Ecosystem Research, Althanstr. 14, A-1090 Vienna, Austria
* For correspondence. E-mail gerhard.zotz{at}unibas.ch
Received: 15 September 2005 Returned for revision: 2 December 2005 Accepted: 30 December 2005 Published electronically: 23 February 2006
• Background and Aims This study examined the physiological basis of the cost of reproduction in the epiphytic bromeliad Werauhia sanguinolenta, growing in situ in a tropical lowland forest in Panama.
• Methods Entire mature plants were sampled repeatedly over the course of 2 years, which represents the common interval between reproductive events. Due to the uncertainty concerning the appropriate currency of resource allocation to reproduction, the temporal changes of the contents of total non-structural carbohydrates (TNC) and of all major nutrient elements in different plant parts were studied (stems, green leaves, non-green leaf bases, roots and reproductive structures when present).
• Key Results Although TNC varied with time in all compartments, this variation was more related to seasonal fluctuations than to reproductive status. The contents of the nutrient elements, N, P, K, Mg and S, on the other hand, showed significant differences between reproductive and non-reproductive individuals, while Ca did not change with reproductive status. Differences in nutrient contents were most pronounced in stems. Seeds were particularly enriched in P, much less so in N and the other nutrient elements. Model calculations of nutrient fluxes indicate that a plant needs about 2 years to accumulate the amount of P invested in a fruit crop, while the estimated uptake rates for N were much faster.
• Conclusions Since most mature individuals of this species fruit every other year, it is hypothesized that P is the prime limiting factor for reproduction. These findings therefore add to an increasing body of evidence that P rather than N is limiting growth and reproduction in vascular epiphytes.
Key words: Barro Colorado Island, Bromeliaceae; cost of reproduction, nitrogen; non-structural carbohydrates; nutrient uptake; phosphorus; reproductive investment, seeds, Werauhia sanguinolenta