Agriculture Reference
In-Depth Information
Cumulative degree days (7.2°C base)
1402 1643 1835
351
584
851
1131
120
120
110
100
90
80
70
60
50
40
30
20
10
Alpine russet
110
To tal blomass
100
90
80
70
81 MT/ha
Tuber
60
50
40
30
20
10
0
A
B
Foliar
0
60
80
100 20
140 60
180
60
240
50
210
Sucrose
180
40
150
R 2 = 0.98***
30
120
90
20
Bud
60
g/tuber
10
Stem
30
Fig. 5.4. Foliar and tuber growth
responses of Alpine Russet at Othello,
Washington, USA, in 2012 (planted
9  April). Cumulative degree days at the
corresponding days after planting (DAP)
are shown (top row). Harvest index (HI)
equals tuber fresh weight as percent of
total plant (tubers + foliage) fresh weight
at maximum foliar growth. At maximum
foliar development ( 92 DAP, point A, top
graph), the HI was 44%. The DAP to 50%
HI (where foliar and tuber growth curves
cross, point B) is also indicated. Changes
in tuber sucrose concentrations, (bud
and stem halves of tubers) average tuber
weights (middle row), reducing sugars
(glucose and fructose), and specific
gravity (bottom row) are also shown as
components of physiological maturity
(PM). PM was estimated at 153 DAP.
0
0
60
80
100 20
140 60
180
10
9
8
7
6
5
4
3
2
1
0
1. 100
1. 095
1. 090
1. 085
Sp gravity
Bud
1. 080
1. 075
1. 070
1. 065
1. 060
1. 055
1. 050
1. 045
1. 040
1. 035
R 2 = 0.93***
Stem
PM
Red u cing sugar s
60
80
100 20
140 60
180
Days after planting
An  increase in stem number per plant is often
followed by an increase in tuber number per
plant, which ultimately leads to a decrease in
average tuber size, and vice versa (Knowles and
Knowles, 2006). Stem number per plant can be
changed by manipulating the physiological age
of seed potatoes (Knowles and Knowles, 2006),
and through the use of plant growth regulators
 
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