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. 2017 Nov 27;12(11):e0188389. doi: 10.1371/journal.pone.0188389

Table 2. ANCOVA results for Ulva australis.

    Full Modela Partial Modelb
Variable Source of Degrees of F-value p-value* Model R2 Degrees of F-value p-value* Model R2
Variation Freedom (p-value)* Freedom (p-value)*
RGR pH 1 2.0011 0.1726 0.571 1 2.0900 0.1630 0.5687
  NH4+ 1 24.5112 0.0001  (<0.0001) 1 25.6000 0.0001 (<0.0001)
  pH x NH4+ 1 0.1070 0.7470      
  Residuals 20   21  
NH4+ pH 1 0.8715 0.3617 0.3195 1 0.9148 0.3497 0.3193
uptake NH4+ 1 8.5138 0.0085  (0.0485) 1 8.9374 0.0070 (0.01761)
rates pH x NH4+ 1 0.0048 0.9455      
  Residuals 20   21  
NH4+ pH 1 0.0007 0.9794 0.4094 1 0.0007 0.9789 0.4061
pools  NH4+ 1 13.0640 0.0018 (0.0165)  1 13.6771 0.0014  (0.0055)
  pH x NH4+ 1 0.1035 0.7511      
  Residuals 19   20  
Total pH 1 6.7120 0.0175 0.4865 1 7.0470 0.0148 0.4864
Chl NH4+ 1 12.2325 0.0023  (0.0034) 1 12.8430 0.0018  (0.0009)
pH x NH4+ 1 0.0018 0.9669      
  Residuals 20   21  
rETRmax pH 1 11.9689 0.0025 0.7062 1 12.4760 0.0020 0.704
  NH4+ 1 35.9519 <0.0001 (<0.0001)  1 37.4740 <0.0001 (<0.0001)
  pH x NH4+ 1 0.1473 0.7052      
  Residuals 20   21  
Ek pH 1 4.4425 0.0479 0.3164 — — — —
  NH4+ 1 0.8463 0.0385 (0.0506)  — — —
  pH x NH4+ 1 4.7757 0.0409  
  Residuals 20   —
α pH 1 0.0001 0.9936 0.3342 1 0.0001 0.9938 0.2565
  NH4+ 1 7.7059 0.0117  (0.0397) 1 7.2452 0.0137 (0.0445)
  pH x NH4+ 1 2.3354 0.1421      
  Residuals 20   21  
β pH 1 0.0215 0.8850 0.4442 1 0.0195 0.8902 0.3581
  NH4+ 1 12.8634 0.0018  (0.0073) 1 11.6938 0.0026 (0.0095)
  pH x NH4+ 1 3.1003 0.0936      
  Residuals 20   21  
Fv/Fm pH 1 10.4249 0.0042 0.6712 1 10.5410 0.0039 0.6586
  NH4+ 1 29.6389 <0.0001 (<0.0001)  1 29.9680 <0.0001 (<0.0001)
  pH x NH4+ 1 0.7693 0.3909      
  Residuals 20   21  
%N pH 1 5.7027 0.0269 0.7761 1 5.6892 0.0266 0.7643
  NH4+ 1 62.5572 <0.0001 (<0.0001)  1 62.4082 <0.0001 (<0.0001) 
  pH x NH4+ 1 1.0501 0.3177      
  Residuals 20   21  
%C pH 1 0.5404 0.4708 0.1021 1 0.5377 0.4715 0.05263
  NH4+ 1 0.6318 0.4360 (0.5307)  1 0.6288 0.4367 (0.5669)
  pH x NH4+ 1 1.1022 0.3063      
  Residuals 20   21  
C:N pH 1 6.8442 0.0165 0.793 1 6.9056 0.0157 0.7846
  NH4+ 1 68.9589 0.0000 (<0.0001)  1 69.5776 0.0000 (<0.0001)
  pH x NH4+ 1 0.8133 0.3779      
  Residuals 20       21      

RGR, relative growth rate; Chl, Chlorophyll; rETRmax, maximum relative electron transport rate; EK, light saturation point; α, the efficiency of light harvesting; β, slope of photoinhibition; Fv/Fm, maximum quantum yield of PSII photochemistry; %N, percent tissue nitrogen; % C, percent tissue carbon; C:N, carbon to nitrogen ratio.

*p-values in bold indicate significance (α = 0.05).

aThe full model ANCOVA included the interaction term (pH x NH4+) to test for differences in the slopes.

bIf the interaction was non-significant, the partial model ANCOVA including only NH4+ (the categorical variable) and the covariate pH (the continuous variable) as factors was used.