13
F
r
esearch Br ief ing
F
(measured using an
f
D
r
sensor) ranged from0.8dS/m
to
1.4dS/m
for both systems. A fertilizer cost saving of
approximately 41%was achieved in
f
D
r
. The automated
technique for coir substrate hydroponics can be used in
large-scale hydroponic farms, resulting in the efficient and
environmentally sustainable use of water and fertilizer.
T
he
frui
TG
rower
•
JAN
u
A
r
Y 2017
i
mpact of long-termwater stress on tree
architecture andproduction inGranny Smith
Studies on fruit-thinning andbitter
pit at the
eufri
Nmeeting
w
ater stress creates physiological andmorphological
responses in plants that depend on the intensity and
duration of stress aswell as the plant species and
development stage.
i
n perennial plants, water stressmay
affect plant development through cumulative effects that
modify plant functions, architecture andproduction over
time. Plant architecture depends on the fate of the terminal
and axillary buds that can give rise, in the case of apple, to
reproductive or vegetative growth units of different lengths.
i
n
a
f
rench study, the impact of long-termwater stress (over
seven years) on the fate of terminal and axillary budswas
investigated in relation to flowering andproduction pattern
(biennial versus regular) inGranny Smith (
TreePhysiology
).
i
t was observed that water stress decreased the total
number of growth units per branch, regardless of their type,
but did notmodify the timing of the two successive
developmental phases characterizedby the production of
long andmedium growth units and an alternation of floral
growth units over time, respectively.
w
ater stress reduced
the transition towards long andmedium growth units and
increased the transition toward floral, short anddeadgrowth
units.
w
ater stress slightly increased the proportion of axillary
floral growth units. The higher relative frequency of floral
growth units comparedwith vegetative ones reduced the
tendency tobiennial bearing under water stress. The
acceleratedontogenetic trend observed under water stress
suggests lower vegetative growth that could, in turn, be
beneficial to floral induction and fruit-set.
A summary of the outcome of the 2016 annual meeting of
the
eufri
N
w
G thinninggroup inPorto can be found in
Erwerbs-Obstbau
.
eufri
N is an
eu
-sponsored scientific
and technical co-operation programme.
Among the new thinningproducts discussed, the
emphasiswas onBrevisTM - the new fruitlet thinning agent
for pome fruit in
e
urope, that is basedon the inhibition of
leaf photosynthesis at the 8 to10mm fruitlet stage for apple
andpear.
ACC (1-aminocyclopropane-1-carboxylic-acid), the
ethylene precursor, was trialledon both pome and stone
fruit inSouthAfrica, Geneva (
u
S) and
e
urope. ACC
stimulated fruitlet abscission
at the late 18 to20mm stage in
apple, with occasional leaf-fall, depending upon the
concentrationmimickingphotosynthesis inhibition, with
a direct positive effect on preventing alternate bearing.
The first experiments at Cornell
u
niversity, Geneva,
u
SA,
investigating the potential of S-ABA
(abscisic acid)
for bitter
pit control were reported. The use of five
applications after
full bloom at 10-day intervals on
h
oneycrisp apples resulted
in an increase in fruit calcium from 3mg to5mg
calcium/100g, but 10 to15% smaller fruit size and slight
leaf yellowing under NewYorkState climate conditions.
f
uture researchwill showwhich of these compounds
showpersistently positive results, making them suitable for
u
K varieties, growing region and climate, and legal approval.
