Table 2.

Effects of gravity on anatomical traits of P. patens

	Top of the stem			Base of the stem
Traits	1×g	10×g	P value	1×g	10×g	P value
Stem
Diameter (mm)	0.19 ± 0.02	0.23 ± 0.03	*	0.21 ± 0.03n.s.	0.23 ± 0.04n.s.	n.s.
Cell density (0.1 mm−2)	206 ± 9	225 ± 32	n.s.	226 ± 16#	257 ± 29n.s.	n.s.
Epidermal cells
Length (μm)	163 ± 52	121 ± 23	**	157 ± 39n.s.	123 ± 22n.s.	**
Diameter (μm)	21.2 ± 4.9	20.4 ± 4.9	n.s.	21.1 ± 5.4n.s.	21.4 ± 4.1n.s.	n.s.
Cell wall thickness (μm)	1.08 ± 0.19	1.08 ± 0.19	n.s.	1.07 ± 0.23n.s.	1.13 ± 0.2n.s.	n.s.
Leaf
Length (mm)	2.29 ± 0.17	1.98 ± 0.25	***	2.44 ± 0.32n.s.	2.03 ± 0.29n.s.	***
Lamina cell diameter (μm)	32.0 ± 3.0	23.2 ± 4.9	***	21.2 ± 2.6##	20.6 ± 3.1n.s.	n.s.
Lamina thickness (μm)	26.1 ± 6.4	23.9 ± 7.9	n.s.	23.6 ± 4.7n.s.	22.1 ± 0.7n.s.	n.s.
Lamina cell number	10.0 ± 3.3	11.6 ± 3.6	n.s.	14.4 ± 1.3#	14.7 ± 0.6n.s.	n.s.
Cell wall thickness (μm)	0.26 ± 0.05	0.21 ± 0.04	***	0.25 ± 0.03n.s.	0.22 ± 0.04n.s.	***

Stem and leaf traits were measured at the top (3 mm from the top) and base (3 mm from the base) of stems, respectively. Average ± SD values are shown for all traits. Fresh gametophores with averaged sizes were used to measure stem diameters (n = 10–15) and leaf lengths (n = 20). The cell density of stems was measured from transverse sections of stems (n = 4–6). The averaged length and diameter (n = 20–22) and cell wall thickness (n = 45) of the epidermal cells of stems were measured from longitudinal and transverse sections of gametophores, respectively. The lamina thickness (n = 3–11), lamina cell number from the costa to lamina margin (n = 3–6), and cell wall thickness of leaf cells from the 1st to 5th cell from the margin of the lamina (n = 60) were measured in a cross section of the leaf lamina. Differences were analyzed using Welch’s t-test, with significant levels of * P < 0.05, ** P < 0.01, and *** P < 0.001 for the effects of gravity, and # P < 0.05 and ## P < 0.001 for the effects of stem position (top or base). n.s. means no significant difference