54
J. Kuo and C. den Hartog
A
B
C
D
E
G
I
H
F
J
K
L
M
N
Fig. 2. Morphology and anatomy of roots. A. Zostera caespitosa. Root hairs normally are produced some distance from the root tip.
Scale = 500 µm. B. Zostera marina. A root cap protects the root tip. Scale = 160 µm. C. Thalassodendron pachyrhizum. Relatively
thick hairs are produced near the root tip. Scale = 1 mm. D. Cymodocea rotundata. The root has a small stele (S) and a large cortex (C),
which has three distinct regions. The outer and inner cortexes have smaller cells, some of which contain tannin substance (T), while
the middle cortex has large air lacunae (A). Scale = 300 µm. E. Thalassodendron pachyrhizum. Sparse but rather thick root hairs (R)
are produced. Scale = 140 µm. F. Posidonia sinuosa. The division of cortical tissues (C) is not distinct. Some tannin substances occur
near the stele (S). Scale = 500 µm. G, H. Zostera japonica. A simple cortical tissue (C) is surrounding the central stele (S) near root tip
(G), while large air lacunae (A) form in the mature root region (H). Scales = 200 µm. I, J. Zostera marina. Root epidermal cells (E) are
small and have thick cell walls, some of these cells produce root hairs (Rt). Scales I = 40 µm, J = 300 µm. K. Phyllospadix scouleri.
Differentiating root tissues near root tip. Note a rather complex peripheral region. Scale = 300 µm. L, M. Phyllospadix japonica. Each
epidermal cell produces a root hair (Rt). Scale L = 100 µm, M = 2 mm. N. Phyllospadix iwatensis. Dense short root hairs. Scale =
50 µm.