Table 1.

Basal (nonstressed) alterations to plant physiology of English oak (Quercus robur L.) at week 2 after paclobutrazol (PBZ) application.zy

ParameterControl2 mL (0.06 fl oz) PBZ foliar spray4 mL (0.12 fl oz) PBZ foliar spray5 mL (0.15 fl oz) PBZ root drench10 mL (0.3 fl oz) PBZ root drenchPercent change by PBZ
Membrane integrity2.231.79*1.89*1.70*1.67*−17.9--33.5
Carotenoids (lutein: β-carotene:neoxanthin:α-carotene)4.13 (58:17:21:4)5.28* (59:16:22:3)4.40* (61:15:22:2)5.63* (56:19:20:5)4.48* (60:17:20:3)+14.9–21.8
Xanthophylls (zeaxanthin:antheraxanthin:violaxanthin)3.18 (45:17:38)3.47ns (43:18:39)3.45ns (46:15:39)4.50* (42:18:40)4.07* (44:18:38)+15.5–23.3
Total carotenoids (x + c)7.319.11*7.85*10.13*8.55*+17.2–22.3
Leaf necrosis0.10.4*0.0ns0.0ns0.0ns0-+75
Chlorophyll a/b2.973.01ns3.00ns2.89ns3.05ns−2.7-+2.6
Total chlorophylls82.1101.3*93.5*112.5*98.3*+12.1–27.0
  • zTrees were placed under glasshouse conditions (22°C ± 2°C [71.6°F ± 35.6°F], 16 hr light/8 hr dark photoperiod and minimum 250 μmol/m−2/s−1 photosynthetically active radiation at the tree crown).

  • yMembrane integrity, PI, chlorophylls, carotenoids, xanthophylls, leaf proline, SOD, catalase, and leaf necrosis values mean of ten trees. Membrane integrity (percent electrolyte leakage), leaf chlorophylls, carotenoids, and xanthophylls content μg/g fresh leaf weight), leaf proline μg/g dry leaf weight), SOD (units g fresh leaf weight), catalase μmol/min−1 g fresh leaf weight).

  • *Significantly different from controls according to least significant difference at P < 0.05; ns = not significantly different from control value.

  • PI = photosynthetic efficiency; Pn = light-induced CO2 fixation; SOD = superoxide dismutase.