Table 2.

Mass-based photosynthetic rates (A_N, nmol CO₂ g⁻¹ d. wt s⁻¹), leaf nitrogen concentration (N, %), photosynthetic nitrogen use efficiency (PNUE, µmol CO₂ mol N⁻¹ s⁻¹), chlorophyll content (Chl a + b, mg g⁻¹ d. wt) and stomata density (mm⁻²) in three carnivorous species

Species	AN	N	PNUE	Chl a + b	Stomata density
N. alata pitcher	−0·6 ± 0·9a	0·27 ± 0·05a	−2·9 ± 7·0a	1·60 ± 0·11a	12·3 ± 0·8a
N. alata lamina	36·8 ± 7·1b	0·73 ± 0·18b	74·5 ± 7·1b	3·20 ± 0·26b	110·8 ± 2·4b
D. capensis	31·2 ± 4·7b	1·39 ± 0·11c	31·0 ± 3·2c	2·19 ± 0·25ac	44·4 ± 1·9c †
S. psittacina	36·4 ± 6·1b	0·83 ± 0·16b	62·6 ± 4·0b	2·30 ± 0·21c	50·0 ± 3·4c
ANOVA	F3,23 = 11·49	F3,23 = 11·29	F3,23 = 38·70	F3,23 = 9·34	F4,07 = 189·8
	P = 0·0003	P = 0·0003	P < 0·0001	P = 0·0008	P < 0·0001

Values shown are mean ± s.e. Different letters in the columns indicate significant differences at P = 0·05 (ANOVA, LSD test, n = 5, for stomata density n = 3).

^† Stomata density in Drosera is the sum from both sides of leaves (amfistomatous type of leaf).