Table I.
Effects of 1 h of daily exposure to direct sunlight of shade-grown seedlings of A. exelsum on Fv/Fm and photosynthetic pigments
| Control | Exposure | d 1 | d 2 | d 3 | d 4 | d 7 | d 8 | |
|---|---|---|---|---|---|---|---|---|
| PAR dose (mol m−2) | 3.6 | 3.2 | 2.1 | 3.0 | 3.2 | – | ||
| Fv/Fm | (a) +UV | 0.79 ± 0.001 | 0.70 ± 0.02 | 0.45 ± 0.13 | 0.62 ± 0.05 | 0.30 ± 0.13 | 0.42 ± 0.12 | |
| −UV | 0.79 ± 0.005 | 0.73 ± 0.01 | 0.52 ± 0.08 | 0.66 ± 0.07 | 0.54 ± 0.10 | 0.58 ± 0.10 | ||
| (b) +UV | 0.44 ± 0.01 | 0.23 ± 0.08 | 0.45 ± 0.05 | 0.15 ± 0.08 | 0.22 ± 0.10 | |||
| −UV | 0.51 ± 0.02 | 0.26 ± 0.07 | 0.53 ± 0.06 | 0.37 ± 0.05 | 0.38 ± 0.08 | |||
| (V+A+Z)/Chl a+b | 22.3 ± 2.1 | +UV | 20.7 ± 1.4 | 22.3 ± 0.8 | 24.5 ± 2.1 | 23.8 ± 1.6 | 30.3 ± 2.3 | 32.2 ± 3.1 |
| (mmol mol−1) | −UV | 20.0 ± 1.4 | 22.9 ± 1.4 | 23.9 ± 1.9 | 28.0 ± 1.8 | 28.2 | 33.0 | |
| Z/(V+A+Z) | ND | +UV | 34.5 ± 3.7 | 51.5 ± 2.7 | 42.5 ± 1.1 | 41.4 ± 5.3 | 54.4 ± 7.1 | 15.3 ± 1.0 |
| (mol %) | −UV | 34.6 ± 1.5 | 50.5 ± 4.7 | 39.1 ± 1.0 | 32.6 ± 5.6 | 57.3 | 10.9 | |
| A/(V+A+Z) | ND | +UV | 8.9 ± 1.5 | 3.1 ± 1.6 | 12.3 ± 2.7 | 14.7 ± 4.5 | 10.5 ± 2.3 | 7.0 ± 1.6 |
| (mol %) | −UV | 9.2 ± 2.9 | 4.0 ± 0.9 | 13.3 ± 2.0 | 22.7 ± 2.2 | 8.4 | 2.7 | |
| L/Chl a+b | 179 ± 8 | +UV | 202 ± 6 | 220 ± 7 | 213 ± 6 | 216 ± 4 | 284 ± 8 | 284 ± 6 |
| (mmol mol−1) | −UV | 208 ± 12 | 208 ± 3 | 225 ± 11 | 217 ± 11 | 254 | 256 | |
| α-Car/β-Car | 1.19 ± 0.20 | +UV | 1.26 ± 0.24 | 1.41 ± 0.16 | 1.03 ± 0.07 | 0.97 ± 0.04 | 0.72 ± 0.06 | 0.69 ± 0.01 |
| (mol mol−1) | −UV | 1.05 ± 0.15 | 1.03 ± 0.06 | 1.18 ± 0.18 | 1.06 ± 0.16 | 0.84 | 0.81 | |
| Chl a/Chl b | 2.64 ± 0.05 | +UV | 2.68 ± 0.10 | 2.86 ± 0.06 | 2.72 ± 0.04 | 2.89 ± 0.05 | 2.78 ± 0.06 | 2.79 ± 0.07 |
| (mol/mol−1) | −UV | 2.60 ± 0.03 | 2.70 ± 0.01 | 2.77 ± 0.05 | 2.74 ± 0.03 | 2.65 | 2.65 |
Plants were kept under shade conditions and exposed daily for 1 h to sunlight in the presence and absence of UV-B radiation on 7 consecutive d (d 1–7). PAR doses during 1-h sun exposures varied with cloudiness. Fv/Fm was determined before (a) and after (b) sun exposure. Pigments were analyzed in unexposed plants (control), immediately after exposure (d 1–4, d 7) and after 1 d under shade conditions (d 8). Fluorescence and pigment data are means ± se of samples from three different plants (pigment controls, n = 6; other pigment data, n = 3, except for d 7 and 8, −UV, means of two samples; ND, not detectable). V, Violaxanthin; A, antheraxanthin; Z, zeaxanthin; L, lutein; Car, carotene.