Depletion of the heaviest stable N isotope is associated with NH4+/NH3 toxicity in NH4+-fed plants

BMC Plant Biology

Table 2 Analysis of variance of the N concentrations, species and organ effects.

Factor	δ ¹⁵N (‰)		Total Biomass (g DW)		Total Biomass Ratio (NH₄⁺/NO₃^- )
Effect on NO ₃ ^- -fed plants	F	P > F	F	P > F	F	P > F
N Conc.	0.78	0.4743	38.53	< 0.0001	10.92	< 0.0001
sp.	13.20	< 0.0001	80.73	< 0.0001	64.81	< 0.0001
N Conc. × sp.	1.18	0.3655	4.26	< 0.0001	1.43	0.1912
Organ	1.80	0.1966	-	-	-	-
Whole model R²	0.884		0.942		0.927
*Effect on NH* ₄ ⁺ *-fed plants*	F	P > F	F	P > F	F	P > F
N Conc.	34.69	< 0.0001	1.57	0.2183	8.93	0.0005
sp.	17.73	< 0.0001	80.56	< 0.0001	59.10	< 0.0001
N Conc. × sp.	0.93	0.5418	6.84	< 0.0001	1.40	0.1999
Organ	4.76	0.0392	-	-	-	-
Whole model R²	0.916		0.936		0.908

The effects of N concentration and species (sp.) and the corresponding interactions are shown separately by the N source on the isotopic composition (‰), total biomass (g DW) and total biomass ratio (NH₄⁺/NO₃^--fed plants). The organs did not influence the N concentration interaction (N Conc. × Organ; P > 0.8) or the species interaction (sp. × Organ; P > 0.05) or N Conc. × sp. interaction (N Conc. × Sp. × Organ; P > 0.8) with either N source. The interaction terms, including the organ effects, are therefore not shown above. Significant effects (P ≤ 0.05) are shown in bold text.

ISSN: 1471-2229