The influence of Ca(NO3)2, Ca(NO3)2H3BO3, and N:P:K (24:7:7) fertilization on the salinity tolerance of evergreen oak and holly. Leaves were detached at months 1, 2, 4, and 8 post-fertilization from trees growing under field conditions and subjected to 8% salt (NaCl) exposure under laboratory conditions. Improvements in tolerance as measured by chlorophyll fluorescence (Fo, Fv/Fm) and leaf chlorophyll content (SPAD) values were quantified by repeated measures analysis (regression analysis; the slope value represented by β3).
| Species/fertilizer | Fo | Fv/Fm | SPAD | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Intercept | Slope (β1) | r2 | Intercept | Slope (β1) | r2 | Intercept | Slope (β1) | r2 | |
| Evergreen oak | |||||||||
| Control | 351.89 | −23.96 | 69.2 | 0.610 | −0.043 | 70.2 | 44.09 | −3.19 | 68.6 |
| Ca(NO3)2 (20 g/m2) | 331.91 | −22.51ns | 67.5 | 0.709 | −0.050ns | 64.0 | 48.27 | −3.51ns | 67.2 |
| Ca(NO3)2 (40 g/m2) | 279.53 | −17.35* | 68.4 | 0.791 | −0.058* | 68.6 | 54.23 | −3.80* | 70.3 |
| Ca(NO3)2 (80 g/m2) | 314.39 | −20.52ns | 67.0 | 0.631 | −0.048ns | 57.8 | 45.46 | −2.99ns | 63.6 |
| Ca(NO3)2H3BO3 (20 g/m2) | 300.78 | −19.33* | 70.5 | 0.689 | −0.048ns | 69.0 | 53.55 | −3.60* | 64.7 |
| Ca(NO3)2H3BO3 (40 g/m2) | 281.43 | −17.22* | 66.3 | 0.729 | −0.051* | 68.5 | 51.48 | −3.66* | 70.5 |
| Ca(NO3)2H3BO3 (80 g/m2) | 310.68 | −21.70ns | 70.2 | 0.685 | −0.049ns | 70.2 | 47.75 | −3.13ns | 67.4 |
| N:P:K (24:7:7) (20 g/m2) | 329.48 | −21.44ns | 43.5 | 0.619 | −0.042ns | 69.7 | 55.63 | −3.69* | 65.2 |
| N:P:K (24:7:7) (40 g/m2) | 315.35 | −20.89ns | 68.9 | 0.634 | −0.043ns | 69.0 | 57.74 | −3.72* | 66.4 |
| LSD | 4.11 | 0.0072 | 0.409 | ||||||
| Holly | |||||||||
| Control | 439.62 | −30.88 | 74.6 | 0.493 | −0.034 | 69.9 | 34.58 | −2.30 | 67.9 |
| Ca(NO3)2 (20 g/m2) | 397.21 | −26.91ns | 61.0 | 0.539 | −0.038ns | 68.9 | 37.12 | −2.70ns | 69.7 |
| Ca(NO3)2 (40 g/m2) | 361.26 | −23.20* | 67.5 | 0.619 | −0.045* | 68.6 | 42.86 | −2.92* | 65.3 |
| Ca(NO3)2 (80 g/m2) | 404.43 | −27.66ns | 67.0 | 0.520 | −0.040ns | 51.8 | 34.66 | −2.21ns | 63.4 |
| Ca(NO3)2H3BO3 (20 g/m2) | 382.81 | −25.96* | 68.7 | 0.544 | −0.037ns | 69.0 | 41.17 | −2.81* | 64.4 |
| Ca(NO3)2H3BO3 (40 g/m2) | 369.14 | −24.67* | 70.0 | 0.567 | −0.041* | 68.4 | 41.56 | −2.83* | 67.1 |
| Ca(NO3)2H3BO3 (80 g/m2) | 392.58 | −26.97ns | 70.3 | 0.531 | −0.038ns | 69.9 | 36.94 | −2.46ns | 67.8 |
| N:P:K (24:7:7) (20 g/m2) | 422.90 | −28.89ns | 74.9 | 0.497 | −0.031ns | 69.5 | 44.17 | −2.95* | 65.1 |
| N:P:K (24:7:7) (40 g/m2) | 414.73 | −27.80ns | 69.1 | 0.491 | −0.033ns | 67.0 | 43.41 | −2.88* | 65.3 |
| LSD | 4.70 | 0.0068 | 0.447 | ||||||
Intercept = value through y axis (calculated); slope = rate of Fo, Fv/Fm, SPAD, electrolyte leakage with time.
All values mean of 15 trees, 2 leaves per tree.
↵* = significantly different at P < 0.05, ns = not significantly different from control value.