Table 4.

Wood anatomy in hybrid poplar stem (LS) after 46 days of treatment with different ozone concentrations

Treatment	Tension wood				Opposite wood
	Cambium cell layers (number)	Fibre frequency (number mm−2)	Vessel frequency (number mm−2)	Vessel lumen diameter (μm)	Cambium cell layers (number)	Fibre frequency (number mm−2)	Vessel frequency (number mm−2)	Vessel lumen diameter (μm)
Control	6.4±0.5	2890±200	173±33	40.7±2.8	6.2±0.3	2970±200	200±13	49.8±3.1
Ozone, 50 nl l−1	ND	3760±510*	142±25*	47.4±1.2*	ND	3120±480	179±12	49.7±3.6
Ozone, 100 nl l−1	ND	4560±730*	126±35*	45.1±4.5*	ND	3340±410	220±27	49.1±1.3
Ozone, 200 nl l−1	3.3±0.4*	3790±170*	124±15*	47.2±2.6*	3.0±0.5*	3500±180	188±22	49.4±0.8
Ozone, 300 nl l−1	ND	4050±240*	105±62*	47.9±2.1*	ND	3450±500	188±17	49.6±2.6

Data are mean values ±SD (n=3, individual replicates).

*Significant differences (P <0.05) between control and ozone treatments.

ND, not determined.