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Novel mannose‐sequestration technique reveals variation in subcellular orthophosphate pools do not explain the effects of phosphorus nutrition on photosynthesis in Eucalyptus globulus seedlings
Author(s) -
Turnbull Tarryn L.,
Warren Charles R.,
Adams Mark A.
Publication year - 2007
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.2007.02229.x
Subject(s) - photosynthesis , phosphorus , biology , botany , phosphate , eucalyptus globulus , pi , horticulture , eucalyptus , chemistry , biochemistry , organic chemistry
Summary• Although only a small proportion of plant phosphorus (P) is used for photosynthesis, the relationships between P and photosynthesis can be strong. It was hypothesized, in this study, that variation in the allocation of orthophosphate (P i ) between active (cytoplasmic) and nonactive (vacuolar) pools would underpin differences in rates of photosynthesis in 4‐month‐old Eucalyptus globulus seedlings grown with a varying P supply. • Photosynthetic biochemistry was assessed by the response of net photosynthesis to increasing intercellular [CO 2 ]. Cytoplasmic P i was sequestered as mannose 6‐phosphate. • Total P and the proportion of P as P i were positively related to P supply. The ratios of active : stored P i (10–24%) varied little over the range of treatments. Active P i was positively related to P supply, as was photosynthesis (7 µmol CO 2 m −2 s −1 with 0 m m P vs. 16 µmol CO 2 m −2 s −1 with 0.32 m m P). Positive relationships between P supply and photosynthesis were explained best by leaf P content, not by active pools of P i . • The distribution of P i between the vacuole and the cytoplasm had little impact on the photosynthetic phosphorus‐use efficiency (PPUE), and reductions in cytoplasmic P i had little effect on photosynthesis. Hence, PPUE is an unsuitable guide for assessing plant responses to increasingly unavailable P in the environment.