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Nitrogen to phosphorus ratio of plant biomass versus soil solution in a tropical pioneer tree, Ficus insipida.

Garrish V, Cernusak LA, Winter K, Turner BL - J. Exp. Bot. (2010)

Bottom Line: Plant P concentration varied as a function of transpiration rate at constant nutrient solution P concentration, possibly due to transpiration-induced variation in the mass flow of P to root surfaces.The transpiration rate varied in response to nutrient solution N concentration, but not to nutrient solution P concentration, demonstrating nutritional control over transpiration by N but not P.Water-use efficiency varied as a function of N availability, but not as a function of P availability.

View Article: PubMed Central - PubMed

Affiliation: Department of Geography, McGill University, Montréal, Québec H3A-1B1, Canada.

ABSTRACT
It is commonly assumed that the nitrogen to phosphorus (N:P) ratio of a terrestrial plant reflects the relative availability of N and P in the soil in which the plant grows. Here, this was assessed for a tropical pioneer tree, Ficus insipida. Seedlings were grown in sand and irrigated with nutrient solutions containing N:P ratios ranging from <1 to >100. The experimental design further allowed investigation of physiological responses to N and P availability. Homeostatic control over N:P ratios was stronger in leaves than in stems or roots, suggesting that N:P ratios of stems and roots are more sensitive indicators of the relative availability of N and P at a site than N:P ratios of leaves. The leaf N:P ratio at which the largest plant dry mass and highest photosynthetic rates were achieved was approximately 11, whereas the corresponding whole-plant N:P ratio was approximately 6. Plant P concentration varied as a function of transpiration rate at constant nutrient solution P concentration, possibly due to transpiration-induced variation in the mass flow of P to root surfaces. The transpiration rate varied in response to nutrient solution N concentration, but not to nutrient solution P concentration, demonstrating nutritional control over transpiration by N but not P. Water-use efficiency varied as a function of N availability, but not as a function of P availability.

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Photosynthesis (A and B), stomatal conductance (C and D), and the ratio of intercellular to ambient CO2 mole fractions, ci/ca (E and F), plotted as functions of nutrient solution nitrogen and phosphorus concentration for seedlings of Ficus insipida. The left-hand panels (A, C, and E) show variation as a function of nutrient solution nitrogen concentration with nutrient solution phosphorus concentration held constant at 1.33 mM. The right-hand panels (B, D, and F) show variation as a function of nutrient solution phosphorus concentration with nutrient solution nitrogen concentration held constant at 12 mM. Different lower case letters within a panel indicate significantly different means at P <0.05.
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fig9: Photosynthesis (A and B), stomatal conductance (C and D), and the ratio of intercellular to ambient CO2 mole fractions, ci/ca (E and F), plotted as functions of nutrient solution nitrogen and phosphorus concentration for seedlings of Ficus insipida. The left-hand panels (A, C, and E) show variation as a function of nutrient solution nitrogen concentration with nutrient solution phosphorus concentration held constant at 1.33 mM. The right-hand panels (B, D, and F) show variation as a function of nutrient solution phosphorus concentration with nutrient solution nitrogen concentration held constant at 12 mM. Different lower case letters within a panel indicate significantly different means at P <0.05.

Mentions: Photosynthesis, expressed on an area basis, was lower at the lowest nutrient solution [N] than at other nutrient solution [N] (Fig. 9A). Area-based photosynthesis did not vary in response to variation in nutrient solution [P] (Fig. 9B). Stomatal conductance increased as nutrient solution [N] increased from 0.6 mM to 4 mM, then decreased as nutrient solution [N] increased further (Fig. 9C). Stomatal conductance did not vary in response to nutrient solution [P] (Fig. 9D). The ratio of internal to ambient CO2 mole fractions, ci/ca, decreased in response to increasing nutrient solution [N] with nutrient solution [P] held constant (Fig. 9E). However, ci/ca showed no response to variation in nutrient solution [P] with nutrient solution [N] held constant (Fig. 9F).


Nitrogen to phosphorus ratio of plant biomass versus soil solution in a tropical pioneer tree, Ficus insipida.

Garrish V, Cernusak LA, Winter K, Turner BL - J. Exp. Bot. (2010)

Photosynthesis (A and B), stomatal conductance (C and D), and the ratio of intercellular to ambient CO2 mole fractions, ci/ca (E and F), plotted as functions of nutrient solution nitrogen and phosphorus concentration for seedlings of Ficus insipida. The left-hand panels (A, C, and E) show variation as a function of nutrient solution nitrogen concentration with nutrient solution phosphorus concentration held constant at 1.33 mM. The right-hand panels (B, D, and F) show variation as a function of nutrient solution phosphorus concentration with nutrient solution nitrogen concentration held constant at 12 mM. Different lower case letters within a panel indicate significantly different means at P <0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2921206&req=5

fig9: Photosynthesis (A and B), stomatal conductance (C and D), and the ratio of intercellular to ambient CO2 mole fractions, ci/ca (E and F), plotted as functions of nutrient solution nitrogen and phosphorus concentration for seedlings of Ficus insipida. The left-hand panels (A, C, and E) show variation as a function of nutrient solution nitrogen concentration with nutrient solution phosphorus concentration held constant at 1.33 mM. The right-hand panels (B, D, and F) show variation as a function of nutrient solution phosphorus concentration with nutrient solution nitrogen concentration held constant at 12 mM. Different lower case letters within a panel indicate significantly different means at P <0.05.
Mentions: Photosynthesis, expressed on an area basis, was lower at the lowest nutrient solution [N] than at other nutrient solution [N] (Fig. 9A). Area-based photosynthesis did not vary in response to variation in nutrient solution [P] (Fig. 9B). Stomatal conductance increased as nutrient solution [N] increased from 0.6 mM to 4 mM, then decreased as nutrient solution [N] increased further (Fig. 9C). Stomatal conductance did not vary in response to nutrient solution [P] (Fig. 9D). The ratio of internal to ambient CO2 mole fractions, ci/ca, decreased in response to increasing nutrient solution [N] with nutrient solution [P] held constant (Fig. 9E). However, ci/ca showed no response to variation in nutrient solution [P] with nutrient solution [N] held constant (Fig. 9F).

Bottom Line: Plant P concentration varied as a function of transpiration rate at constant nutrient solution P concentration, possibly due to transpiration-induced variation in the mass flow of P to root surfaces.The transpiration rate varied in response to nutrient solution N concentration, but not to nutrient solution P concentration, demonstrating nutritional control over transpiration by N but not P.Water-use efficiency varied as a function of N availability, but not as a function of P availability.

View Article: PubMed Central - PubMed

Affiliation: Department of Geography, McGill University, Montréal, Québec H3A-1B1, Canada.

ABSTRACT
It is commonly assumed that the nitrogen to phosphorus (N:P) ratio of a terrestrial plant reflects the relative availability of N and P in the soil in which the plant grows. Here, this was assessed for a tropical pioneer tree, Ficus insipida. Seedlings were grown in sand and irrigated with nutrient solutions containing N:P ratios ranging from <1 to >100. The experimental design further allowed investigation of physiological responses to N and P availability. Homeostatic control over N:P ratios was stronger in leaves than in stems or roots, suggesting that N:P ratios of stems and roots are more sensitive indicators of the relative availability of N and P at a site than N:P ratios of leaves. The leaf N:P ratio at which the largest plant dry mass and highest photosynthetic rates were achieved was approximately 11, whereas the corresponding whole-plant N:P ratio was approximately 6. Plant P concentration varied as a function of transpiration rate at constant nutrient solution P concentration, possibly due to transpiration-induced variation in the mass flow of P to root surfaces. The transpiration rate varied in response to nutrient solution N concentration, but not to nutrient solution P concentration, demonstrating nutritional control over transpiration by N but not P. Water-use efficiency varied as a function of N availability, but not as a function of P availability.

Show MeSH
Related in: MedlinePlus