Table 1.

Allometric relationships between morphological stomatal traits

Species selection	X variable	Y variable	Sample size	Offset	Median offset	Lower 95% CI offset	Upper 95% CI offset	Exponent	Median exponent	Lower 95% CI exponent	Upper 95% CI exponent	r 2	P
All species	D s	a gc	1032	b s	0.10	0.04	0.25	S	−1.03	−1.07	−0.98	0.43	***
Angiosperms	D s	a gc	927	b s	0.17	0.06	0.47	S	−1.05	−1.11	−1.00	0.37	***
Gymnosperms	D s	a gc	38	b s	12	0.02	8.4 × 103	S	−1.25	−1.60	−0.90	0.31	***
Pteridophytes	D s	a gc	67	b s	3.0 × 10−5	3.9 × 10−6	2.3 × 10−4	S	−0.58	−0.70	−0.46	0.36	***
Amphistomatous dicot	D s	a gc	72	b s	2.1 × 10−4	2.4 × 10−5	1.7 × 10−3	S	−0.70	−0.81	−0.58	0.53	***
Amphistomatous monocot	D s	a gc	40	b s	67.00	0.21	2.1 × 104	S	−1.43	−1.75	−1.13	0.56	***
All species	a gc	a max	251	b p	0.05	0.01	0.29	P	0.92	0.84	1.01	0.50	***
Angiosperms	a gc	a max	214	b p	0.05	0.01	0.31	P	0.92	0.84	1.00	0.58	***
Gymnosperms	a gc	a max	23	b p	–	–	–	P	–	–	–	–	ns
Pteridophytes	a gc	a max	14	b p	–	–	–	P	–	–	–	–	ns
Amphistomatous dicot	a gc	a max	19	b p	5.0 × 105	3.8 × 103	6.5 × 107	P	1.68	1.45	1.91	0.93	***
Amphistomatous monocot	a gc	a max	10	b p	1.17	9.7 × 10−6	1.5 × 105	P	1.07	0.51	1.63	0.59	**

Offsets and exponents reflect standardized major axis regressions calculated on the species average trait data expressed in the following units: stomatal density (D _s, no. stomata∙m⁻²), average size of the guard cell pair (a _gc, m²), anatomical maximum aperture (a _max, m²). The r ² denotes the Pearson product–moment correlation coefficient between log₁₀‐transformed traits values. Significance levels of correlation are indicated: ***, P < 0.001; **, P < 0.01; ns, P ≥ 0.05.