Agriculture Reference
In-Depth Information
Table
.
The effect of different degrees of severity of pruning of apple rootstock
hedges on the percentage rooting of cuttings taken from them
Rootstock
Pruning
'M.
'
'MM.
'
'MM.
'
Ultrasevere ( cm framework)
Severe (
cm framework)
Normal (
cm framework)
Light (
cm framework and one-third
of annual shoot length retained)
From Howard, (
). Reprinted by permission of John Wiley & Sons Inc.
are relatively free from sclerotic cells in the primary phloem compared with
lateral shoots from fruiting branches close to the apex.
Seedling apple and pear trees exhibit juvenile characteristics throughout
when very young. As the tree matures the plant tissues in the lower part of the
tree remain juvenile, Beakbane (
,
) finding typical juvenile shoots at
the base of
-year-old seedling trees which were fruiting at the top. Juvenile
characteristics are also found in shoots developing from adventitious buds
in roots (root suckers), watersprouts from latent buds in the basal parts of
trees (epicormic shoots) or sphaeroblasts, which are masses of shoots from
adventitious buds in the trunks of trees and can be induced to develop by
heavily cutting back stock plants (Stoutemyer,
; Wellensiek,
; Baldini
and Mosse,
).
Cuttings from severely pruned apple rootstock hedges, stools and layer beds,
whichallshowjuvenilecharacteristics,haveenhancedrootingability(Howard,
; Beakbane,
; Rom and Brown,
), as do cuttings of shoots developing from adventitious buds
on the roots of mature apple trees (Robinson and Schwabe,
; Table
.
) and shoots
developed from sphaeroblasts on apple (Stoutemyer,
).
In vitro
culture can be used as a technique for rejuvenation. Although propa-
gation of apple trees
in vitro
is achieved most readily with explants from young
nursery trees (Jones,
), it can be fully successful with shoot tips in either
the juvenile or the adult phase (Welander and Huntrieser,
). Rejuvenation
takes place during
in vitro
subculture and the capacity of the
in vitro
shoots to
initiate roots increases with the number of subcultures (Figure
.
). Shoots of
'M.
%
of them could be rooted, while the corresponding figure for the apple scion cv.
'Greensleeves' was
' apple rootstock required
months of subculture before more than
months (Jones
et al.
,
), and the cvs. 'Jonathan' and
'Red Delicious' required
months of subculture, respectively, be-
fore rooting was achieved (Sriskandarajah
et al.
,
and
). Apple trees pro-
duced by grafting scions and rootstocks produced by micropropagation show
