Table I.
Physiological and pigment characteristics of senescing leaves of red-osier dogwood with and without anthocyanins
| Variable | Yellow-Senescing Leaves | Red-Senescing Leaves |
|---|---|---|
| Fv/Fm (n = 15, relative units) | 0.80 ± 0.05 | 0.79 ± 0.03, NS |
| Anthocyanins (n = 10; μg cm−2) | 0.0 | 0.45 ± 0.0249*** |
| Chlorophylls (n = 10) | – | |
| a+b (μg cm−2) | 15.7 ± 1.7 | 13.2 ± 0.9, NS |
| b (μg cm−2) | 3.8 ± 1.6 | 2.1 ± 0.1, NS |
| Total carotenoids (n = 10, μg cm−2) | 3.1 ± 0.2 | 3.3 ± 0.2, NS |
| Total leaf thickness (n = 6, μm) | 74.6 ± 2.7 | 76.3 ± 5.6, NS |
| Palisade mesophyll (n = 6, μm) | 24.5 ± 1.8 | 27.3 ± 2.4, NS |
| Spongy mesophyll (n = 6, μm) | 44.3 ± 1.8 | 43.5 ± 5.5, NS |
| Lower epidermis (n = 6, μm) | 5.8 ± 0.8 | 5.5 ± 0.8, NS |
Chlorophyll fluorescence parameters and pigment contents (expressed on a fresh, leaf area basis) were determined as in Wellburn (1994). Fv/Fm, Maximal dark-adapted photosystem II photon yield (means ± sd, n = sample size; *, **, and *** denote the degree of statistical significance, <0.05, 0.01, and 0.001, respectively); NS, not significantly different (Student's t test). Red- and yellow-senescing leaves were the same age; low chlorophyll content reflects chlorophyll loss during senescence.