Table 2.

Stomatal characteristics of hybrid poplar saplings grown under control (‘Light control’), shade, and high humidity (‘High RH’) conditions All parameters were measured on abaxial leaf surfaces.

Experimental treatment	Stomatal length (μm)	Stomatal density (no. per mm2)	Pore aperture (μm) before/after application of ABA
Light control	35.18 (0.58) a	132.6 (4.5) a	6.83 (0.36) a/4.20 (0.36) a
Shade	32.84 (0.53) a	118.1 (8.7) a	6.81 (0.30) a/4.18 (0.20) a
High RH	39.36 (0.77) b	161.7 (6.1) b	8.55 (0.10) b/7.07 (0.22) b

The standard error of the mean is given in parentheses. Values are grand means of five plants. Different letters indicate significant differences between treatments (P ≤ 0.05).

In the case of pore apertures, two separate statistical analyses were conducted; one on apertures measured before application of ABA and one after ABA application. i.e. apertures were not compared before and after ABA application.