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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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The nitrogen concentration of leaves (A and B), stems (C and D), and roots (E and F) of Ficus insipida seedlings as a function of variation in the nitrogen and phosphorus concentration of nutrient solutions fed to the plants. 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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fig3: The nitrogen concentration of leaves (A and B), stems (C and D), and roots (E and F) of Ficus insipida seedlings as a function of variation in the nitrogen and phosphorus concentration of nutrient solutions fed to the plants. 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: Variation in the [N] of plant biomass as a function of the nutrient solution [N] and [P] is shown in Fig. 3. The [N] of leaves, stems, and roots increased with increasing [N] of the nutrient solution when [P] was held constant, as seen in Fig. 3A, C, and D, respectively. The [N] of plant biomass showed little response to variation in nutrient solution [P] when nutrient solution [N] was held constant (Fig. 3B, D, and F). However, the stem [N] did increase significantly at the lowest nutrient solution [P], as seen in Fig. 3D.


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)

The nitrogen concentration of leaves (A and B), stems (C and D), and roots (E and F) of Ficus insipida seedlings as a function of variation in the nitrogen and phosphorus concentration of nutrient solutions fed to the plants. 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

fig3: The nitrogen concentration of leaves (A and B), stems (C and D), and roots (E and F) of Ficus insipida seedlings as a function of variation in the nitrogen and phosphorus concentration of nutrient solutions fed to the plants. 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: Variation in the [N] of plant biomass as a function of the nutrient solution [N] and [P] is shown in Fig. 3. The [N] of leaves, stems, and roots increased with increasing [N] of the nutrient solution when [P] was held constant, as seen in Fig. 3A, C, and D, respectively. The [N] of plant biomass showed little response to variation in nutrient solution [P] when nutrient solution [N] was held constant (Fig. 3B, D, and F). However, the stem [N] did increase significantly at the lowest nutrient solution [P], as seen in Fig. 3D.

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