Agriculture Reference
In-Depth Information
Effect of rootstock on the transport of auxin ([
H]-IAA) and
carbohydrate ([
C]-sorbitol) from mature leaves to roots
Table
.
Total activity in roots
Specific activity in roots
after h (dpm mg
−
dry wt)
after h (dpm)
H
C
H
C
'M.'
.
.
'M.'
.
.
'MM. '
.
.
'MM.'
.
.
LSD .
.
.
From Kamboj (
). Reproduced with permission.
', similarly induce pre-
cocious flowering and heavy cropping, the effects being proportional to the
length of interstock (Roberts and Blaney,
Interstocks of dwarfing apple rootstocks, e.g. 'M.
).
'Quince C', the dwarfing rootstock for pear, appears to exert its dwarfing
effect primarily through its effect on cropping. It roots readily from cuttings
and gives strong maiden growth in the nursery. Trees on it grow vigorously
for the first few years in the orchard before their growth is checked by heavy,
precocious cropping (Parry,
; Parry and Rogers,
).
The size of apple trees on some relatively vigorous rootstocks may also be
reduced to below their potential because they induce precocious cropping.
This is particularly so for 'MM.
'.
Although in general the root/shoot ratio is relatively constant for any
given set of environmental conditions, irrespective of rootstock (Rogers and
Beakbane,
' and 'M.
' appears to be a particularly weak
sink for assimilates in competition with shoot growth. Young and Werner
(
), the root system of 'M.
' at plant-
ing led to much poorer root growth, in the face of competing shoot growth,
than was the case with 'Golden Delicious'/'MM.
) found that shoot pruning of trees of 'Golden Delicious'/'M.
'. The root/shoot ratio of
trees on 'M.
' is usually lower than that on more vigorous rootstocks (Avery,
; Young and Werner,
) and is also reduced by an 'M.
' interstock
(Swarbrick
et al.
,
), which may lead to root-supplied growth factors being
limiting.
.
Dwarfing rootstocks show limited ability to transport auxin from shoots to roots and
have high ABA levels.
Basipetal transport of auxin from the region of the shoot
tips towards the root system (Table
.
) is slower in dwarfing than in more
vigorous rootstocks (Soumelidou
et al.
,
b; Kamboj
et al.
,
b). Gur and
Samish (
) found that the amount of IAA destroyed by root and shoot
bark of various apple rootstocks was negatively correlated with their effects
