Table I.

Spatial and temporal effects of elevated [CO₂] (550 μmol mol⁻¹) on leaf growth of P. × euramericana at contrasting LPI

Leaf Age	Mean Leaf Area	Absolute Leaf Expansion Rate	Relative Leaf Expansion Rate	Leaf Thickness	Epidermal Cell Area	Epidermal Cell Number	Spongy Mesophyll Cell Area	Palisade Cell Area	Cell Production Rate
	103 mm2	mm2 d−1	d−1	μm	μm2	106 leaf−1	μm2	μm2	d−1
LPI 3 (after 5 d)
Ambient [CO2]	1	617	1.95	141	18	133	42	42	3.02
Elevated [CO2]	1.5 **	659	1.87	135	34***	88**	63	72	1.87
LPI 8 (after 13 d)
Ambient [CO2]	25	87	0.01	155	221	155	106	105	0.58
Elevated [CO2]	33 *	289**	0.21	160	206	200***	153	190***	19.7***
Summary of Analysis  of Variance
CO2	***	*	ns	ns	ns	ns	**	***	***
LPI	***	ns	ns	***	***	***	***	***	***
CO2 × LPI	**	*	ns	ns	*	***	ns	*	***

Results are the mean values of nine leaves at each stage from each concentration [CO₂]. ^*, ^**, and ^***, Significant at the <0.05, <0.01, and <0.001 levels of probability; ns, not significant. Significance of post-hoc comparisons for elevated [CO₂] is shown where a significant interaction with LPI was found