Agriculture Reference
In-Depth Information
(a)
Stages of tuberization
10 mm
V
I
VI
II
III
IV
I Hooked stolon with no apparent swelling.
II Slight swelling below the apex results in apical hook beginning to straighten.
III Stolon terminal continues to swell until the hook is completely open;
developing tuber is less than twice the diameter of the stolon.
IV Tuber continues to swell; developing tuber is approximately twice the
diameter of the stolon.
V 0.6-1.5 g tuber.
VI 1. 5-2.5 g tuber.
(b)
8
7
1 cm
6
5
4
3
4-8
3
4-8
2
2
4-8
3
3
2
2
1
1
1
1
A
B
C
D
0.2 cm
0.3 cm
0.8 cm
2.0 cm
Fig. 5.3.
Stages of tuberization (a and b) showing stolon and tuber morphology and thickening of the perimedullary zone
(dark-shaded area) (b). The numbers
1-8
indicate the nodes. Dimensions below the letters A-D indicate stolon
(A only) and tuber diameter. (Figures reproduced with permission from
Postharvest Biology and Technology
,
Blauer
et al
., 2013 (a), and
Journal of Experimental Botany
, Xu
et al
., 1998 (b).)
ABA. A higher ratio of GA to ABA in the plant
inhibits tuber production and growth in favor of
foliage growth. The reverse ratio leads to tuber
initiation. Excessive nitrogen fertilizer, long
day length, and warm night temperatures can
delay tuber initiation by increasing GA rela-
tive to ABA (Krauss, 1985).
Excluding disease, once a tuber is initiated,
it either continues to expand and develop or is
resorbed by the plant (Walworth and Carling,
2002). Those that remain are “set” to grow and
expand. This stage is typically referred to as
“tuber set”; however, tuber set may also be used
to describe tuber number per plant. Despite the
