PARENT SESSION
Posters P3B Photosynthetic acclimation: Ecophysiology, diverse environments. Abstracts (479-522)

Phosphorus affects photosynthesis, chlorophyll fluorescence and nitrogen partitioning in eucalyptus obliqua (l'herit). Tarryn Turnbull^*,1, Mark Adams¹, Charles Warren¹, ¹ Forest Science Centre, Creswick, Victoria, Australia

ABSTRACT- We tested the hypothesis that photosynthetic responses to phosphorus (P) are initially attributable to the effect of luxuriant P on photochemistry, and later to differences in the allocation of nitrogen (N) between different compounds, mainly ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). This hypothesis was tested via a field study during which P was added to 18 month old Eucalyptus obliqua (L'Herit) seedlings at five rates (up to 80kg ha ^-1). Light-saturated rates of photosynthetic gas exchange and chlorophyll fluorescence measurements were measured at 1, 2, 4, 8 and 32 weeks after P application. Leaves were sampled for nutrient analysis at 4 week intervals. The integration of P into leaves was rapid, with significant treatment differences in concentration of leaf total P appearing within one week of P application. The effect of P on photosynthesis and fluorescence, and leaf nitrogen allocation was evident within one and four weeks of P application respectively.

KEY WORDS: eucalypt, phosphorus, nitrogen allocation