Download Goldschmidt and Monselise

i. Erner, Y., R. Goren and S. P. ,\Jonselise. 1976. The rough fruit
condition of the 'Shamouti' orange-Connection with endogenous
hormonal balance. ]. Ho1·t. Sci. 51:367-374.
8. - - - - - , - - - - - - and ------. 1976. The reduction of peel
roughness of 'Shamouti' orange with growth regulators. ]. Amer.
Soc. Hart. Sci. 101:513-515.
9. - - - - - - , S. P. ;\lonselise and R. Goren. 1975. Rough fruit condition of the 'Shamouti' orange-Occurrence and patterns of development. Physiol. Veg. 13:435-4-13.
10. Feinstein, B., S. P. :\Ionselise and R. Goren. !975. Studies on the
reduction of seed number in mandarins. HortScience 10:385-386.
11. Fishier, ,\lichal and S. P. ;\fonselise. 1971. The use of ethephon (2chloroethyl phosphonic acid) to promote color development of
'Shamouti' orange fruits. Israel]. Agric. Res. 21:67-77.
12. Gibson, A. C. 1975. Developmental studies of pvriform fruits of
grapefruit.]. Amer. Soc. Hart. Sci. 100:674-678.
13. Goldschmidt, E. E. and S. P. Monselise. 19i7. Physiological assumptions toward the development of a citrus fruiting model. Proc.
Int. Soc. Citriculture 2:668-6/2.
14. Goren, R. and S. P. Monselise. 1965. Interrelations of hesperidin,
some other natural components and certain enzyme systems in deYcloping 'Shamouti' orange fruits.]. Hart. Sci. 40:83-99.
15. - - - - - - and - - - - - - . 19il. Effects of ringing on yield of low
bearing orange trees. 1- Hart. Sci. 46:435-441.
16. Gustafson, F. G. !939. The cause of natural parthenocarpy. Amer. ].
Bot. 26:135-!38.
li. Krezdorn, A. H. 1969. The use of growth regulators to improve fruit
set in citrus. Proc. lsi Int. Citrus SymjJ. 3:1113-lll9.
18. Lewin, I. J. and S. P. ,\fonselise. 1976. Further ·t .
tion of seeds in mandarins by !\'.-\.-\ spraYs. Scie', ~ldte, r,n th.
19. ;\lonselise, S. P. Growth regulators used to ex ten '1 "' ![,,._ ;'.-~-::'iii
of grapefruit. I Congreso Mundial de Citricu~t the t'i<kin;'"'li4.
393-398.
'"a, H;; \~
4
. '
' -~
20. ------, R. Goren and Israela 1\'allerstein. Jrt- 0
on orange fruit set and young fruit abscission ·;;· Cirr!;;,.,
515.
'
rL \ri,·nr:
21. - - - - - - and .-\. Sasson. 19i7. Effects of urch .
.
.
1
orange fruit quality and storage abilitY. Pwc. 111 ~ d trearn 1rn•·
·.Soc ° r.
· "Ill! ,
1 ·939
•- -M 23-'
''lTf(•t&lJ
22. ------, ,\L Weiser, ~- Shafir, R. Goren and F :
"'~ ~I
1976. Creasing of orange l)eel-l'hniolog.- and cr 1,~- L. Go],!•• ~,..._ _ ·,
;
•
...
~
•
'
ttroJ. }
.... ,~ . .lt
,, ::>1.341-3~1.
.
.
J
-/f~rt.\:t''l
'
23. Peled, ~oa, B. Fe1ns~eu~ and S. I . ~I_ons~lisc. 1();G
.
· . ,, rt'
seed number and frmt srze regulatron rn ·I cmpl!'' b; Rcduulf11111 \"
homwnal means. (Heb1ew). A ion Hmwtea 3! II" II~ hcllll<~] &tit
::<l
24. Soost, R. K. and R. H. Burnett. 1961. Effect o[.o 11 ;,· h.
',
.
· ·
· • mand,u " I'>t·n·lltn '''' ·~ · :• •
· c h aracte11strcs
an d f rmt
o f 'Cl ementme
111
11
Ho1t. Sci. /7:194-201.
·
"- -~''"'.!.,.
!].1
25. vVallerstein, _Israela,_ R._ Goren and S. P. MonscJisc. l'l-·
.
changes m grbberellm-hke substances of 'Shatnorni' .: d. Sn"lllll
sinensis (L.) Osbeck) trees in relation to rinoing ,O'j~ 1 ~"' lf,tr111
75-82.
" · · · '"'· \'ci. !l:.
j)[l
26. \Vutscher, H. K. 1976. Influence of night tcntpnatur ..
on fruit shape of grapefruit. I- A1ner. Soc. Ho,t. Sii. ~O~~~~ •1~!11~ . :.•· I
,,
I)
0
..)j3·~)jl
·;t't'
j
I' _:,:
'\[l
Il ' !.til
:l~ I)
PHYSIOLOGICAL ASSUMPTIONS TOWARD THE
DEVELOPMENT OF A CITRUS FRUITING MODELl
E. E.
S. P. MONSELISE
Department of Horticulture,
Hebrew University of jerusalem,
Rehovot, Israel
GOLDSCHMIDT AND
Additional index words. biomass, flowering, abscission, fruit
set, fruit size, plant hormones, photosynthesis.
Abstract. The difficulties in assessing the fruiting potential
of a perennial plant like citrus are outlined. A biomass
balance sheet for citrus trees is compiled using the 'Shamouti'
orange as a standard variety. The sequence of biological
processes from flowering through abscission and fruit set to
the acquisition of full size are analyzed from a biometric
point of view and assembled into a relational flow-diagram.
Three major "decisions" seem to determine the yield: The
no. of flowers, the final percentage of fruit set and the potential for fruit enlargement. The existence of control
mechanisms to secure a reasonable crop is indicated. The
role of plant hormones and availability of photosynthate as
principal regulatory mechanisms of fruiting in citrus is evaluated.
The ever increasing basic knowledge of Citrus allows
today, more than in the past, to provide a rather detailed
description of the host of environmental and endogenous
factors which modulate the biological systems of production.
The translation of such knowledge into a series of coefficients can be further transformed into equation-models
which may eventually be utilized for economical forecast as
well as for gaining a broader overall understanding of the
biological processes themselves. By doing so, the integrated
lThe authors are indebted to Prof. Y. Yaadiah for stimulating discussions during the early phases of this study. This work was supported
by the Israeli l\finistry of .-\griculture.
668
-
~
t
Pr-oc. Int. Soc. Citriculture. 2:668-672. 1977.
tH
'\(
!
)\l<l
1
behavior and the manifold interactions of dilfcrent iwli~/i:1
vi duals in a large plant community or witlti 11 a populatitln , ''. ~ ' '
f ocus. rl'l 1ese are tl1e .,,to 1'
. on t I1e same tree comes Into
.
o f f nuts
biometric aspects which cannot be fully ev~tluated bv mean! 1
:l
of physiological investigations at the individual org:;n lml
1 1
Methods of simulation-modeling· have lreen mer! until , ·nplr,
now mostly in the study of annual plants such as forage or i ·ttha
pasture crops which are consumed in full, or industria! uor~ t
a_s ~otton (16) and alfalf~ (6). With trees work ltas hl'rll 1
hmlted to wood productiOn by forest trees (1·1) wherrb1
only part of the peculiar characteristics of perennial pl.ull ! Fi~
productivity are taken into account. Quite recently some · ,.,, o
work with peaches has been published (1). Tints, when lJ> ·ut~t
proaching the problem of citrus productivity it sccmsa~,.\:>a1
propriate to outline several major differences bctween [rUJt ,, n
trees and annual crops.
.
l1l
The complexity of a large tree unit bearing at one wne . 'Ill!
a variety of organs differing in age and activity is i1;unctlr· j .t.
ately evident. Even more important is the fact that tile rre-:
which builds up its skeleton during its early years, a~cumu
lates reserves which are not necessarily utili1etl dunng tht.
same season. The long time storage of pan of the rcscflli
in the tree makes it difficult to prepare a detailed balan(t
1
sheet of annual and cumulative production aml pre1·c~Jt;
1111
direct and reliable estimation of potential lltT producll , ..,., ,
0
After years of investigation into the biological aspect\ ;
1
citrus tree productivity it seems now time to pool dcLll ~
physiological knowledge into an integrated lramew_ork ~I .',~;
lowing an overall description of the beh:l\ ior ot t!llfete:: j ''"
spe_cies of citrus unde1: v_ariou~ condi Lions wit il the prac:~ . -,~·;.'
ultimate go~ I- of attami~g higher product!\ IL ~, t~not\It ·:::!,
better_ defimt~on of optimum growth conclJtiOm- I~-e"<C
·''"
followmg sectwns we will analyze the sequence oi P10 . -~
l"tt
involved in fruiting of citrus trees, pointing out eu-n.. 1' '.,[
knowledge as well as missing links.
l
't
I
! .,
II!,) I
I
I
fruiting Potential and Biomass Balance Sheet
collected in past years concerning 'Shamouti' or(Citrus sznenszs (L.) Osbeck) have been used for
n of the yearly biomass balance sheet which
the first step to·wards modeling of a biological
our sheet (Table 1) includes some rough approxibut can neYertheless form the basis for the expresbioma'' in a medium, 20-year old 'Shamouti' tree
to 5,1·eet lime (Citrus limettioicles Tan.), with a top
of 26 m: (11 ). ·we suggest that the balance of antiritY can be calculatedv,;ith a perennial plant havJ(
'
. l l
l
l '
.
1
.
n!ans ,dliC
1 c eve opec In prevwus seasons, )y bnng~tno account the rate of renewal of perennial and other
111
• percentage d ry wt. A mature tree d oes not
and their
·tr<re
annual
addition to its main skeleton; however
a l' b
branches and roots are produced, ~he volume of existing
jun·cascs and starch res~rves bmld up. On the other
the turnover of leaves IS almost complete every year
[ flowers. frui tlets and fruits are by definition a new
1
product. Dry wt. productio? is. in the rang~ of 40
per yc~n_-, about h~lf of which 1s mature frmt. The
is invested Ill productiOn of leaves (10 kg/tree), which
build up the yearly dry matter necessary for growth
,ield. Shedding of Bowers and fruitlets is a waste in
'of eflicicnt dry matter utilization. The sheet presented
Table l is only the expression of factual evidence but
uot tell us if and how the balance can be improved to
yield.
seems important to ascertain whether the photosyndficiency of leaves is the limiting factor and if the
·nthetic performance of a given variety can be imThe fact that 'Marsh' seedless grapefruit (Citrus
i\facL) trees are able to produce up to twice as much
1ti' orange trees of comparable size and more than
'Valencia' orange trees (Table 2) illustrates
Grapefruit and oranges do not seem to vary
in their net assimilation rates (7) and the reasons for
different fruiting potential must therefore be more
related perhaps to sink-source control of phototranslocation or to photorespiration (10).
Fruiting Processes in Citrus
Fig: I depicts .in a very. schematic way the chronological
ot processes mvolved m crop production of 'Shamouti'
over a period of I c1months. Processes along the time
spelled out in rectangles above the two main curves
. the no. of reproductive units present at any time
thCJr average wt. Using this scheme we will discuss the
critical stages of the fruiting system.
I. .\ yearly biomass sheet for an average 20 year old 'Shamouti'
otange on sweet lime with a top volume of 26 m3.
Total
Fresh
fresh
wt.(organ No. of wt.(tree
unit (g) units(tree
(kg)
%
dry
wt.
40,000
25,000
5,000
100
26
16
5
50
40
15
20
10
100
100
100
5.0
10.5
2.5
1
200.00
500
100
20
100
20
Int. Soc. Citriculture, 1977, Vol. 2.
..
Species
Yarien
Citrus
sinensis
Source
Fruit
Yield
kg( tree
Fresh
wt of
Jeayes
kg(tree
Kg fruit
per kg
leaves
Valencia
late
(li)
60
30
2.0
Citrus
sinensis
Shamouti
(11)
100
26
3.8
Citrus
paradisi
:\farsh
seedless
(17)
700
50
14.0
The flower formation stage. This is certainly a critical
stage as a hypothetical lack of Bowers would mean no yield
at all. Flower no., however, is very rarely a limiting factor
as the large ~ajority of Bowers drops anyway and very few
of th~m persist on the tree to become mature fruits. Only in
margn:al cases (young trees entering the bearing age, offye~r~ m alternately bearing varieties) the no. of Bowers
o~·Igmally produced is insufficient to produce satisfactory
yields. On the other hancl, many relatively unfruitful types
('Clementine' mandarins, certain 'Navel' strains) produce
only a marginal crop despite extremely profuse amounts of
flowers (in the range of 2 x 10" and more). In this case it is
co~ceivable that excessive Hower production may hamper
satisfactory set.
. In most varie~ies, when flower population varies over a
wide range, we. fa1l to detect a clearcut relationship between
Hower ancl fr~It no. At most, we find a moderate optimum
curve connectmg the extremes. Additional data are needed
to learn more about the significance of this curve.
Type of inflorescence and flower position. Not all flowers
have identical chances of set. There is a considerable no. of
abortive Bowers (mostly staminate) or defective because of
pest and diseases. About 35% 'Shamouti' Bowers (15) are
mcapable of setting. In certain varieties, staminate flowers
can attain very high percentages for internal or climatic
causes which need elucidation. The type of inflorescence and
the position of individual Bowers are also factors in set. It
has been shown by different workers (8, 9, 12) that mixed
-·
~r~[----~
~ tg>- FRUIT DEVELOPMENT 1! i MATURATION
~~~_N__j ~N~j ~J
-~----~---------.. __j•IL_ ____
I
INOUC- 1 [FLUSH&ll
TION & i :FLOWER,
D.IFFEREN-j DEVELORj
j
1
~-DROPG
I
I II Ill
L
.L
__j__ _
PRE-I
HARVEST I
DROP i
Annual
Annual
dry
incrematter
ment
producrate
tion/tree
(Kg)
(%)
0.65
0.65
1.00
247
Table 2. Fresh wt of leaYes and of mature fruits, as well as the efficiency
of one kg leaYes as to Yield production in different \·arieties and
species. Approximate data from different sources, as indicated.
39.0
Fig. 1. Schematic description of the chancres in the no. of reproduc·
tive units (flowers, fruitlets, fruits) and th~ weight of the individual
reproductiYe unit during the course of 'Shamouti' orange fruit development. Rect.angles. above the 2 main curves spell out rna jor processes
along the t1me ax1s.
669
inflorescences comprising flowers and leaves are most successful in producing fruits. In one specific case (8) initial set was
high in 'Shamouti' on leafless inflorescences (which blossom
first) but during the progress of subsequent drop tJ1e proportion of fruitlets on these leafless inflorescences decreased
in favor of leafy inflorescences. :1\ ew leaves have an apparently important nutritional (9, 10, 12) or hormonal (2,
8) task in ensuring the persistence of frui tlets. ·when several
flowers are borne on the same axis, complex interactions will
probably occur expressing competition as to rate of flower
development and chances of set.
Drop of flowers, fruitlets and fntit. The different stages
of abscission is the main factor responsible for the fact that
the no. of persisting fruit is extremely small if compared
with the no. of flowers initially produced. The amount of
fruit units is so small that we rna y actually say that the
whole flower population abscises at different stages except
for a negligible portion eventually developing into the crop
we are interested in.
It is customary to define the process whereby ovaries
adhere and become fruits as "fruit set." The final set is
determined, however, only at the end of the abscission process. At earlier stages it is possible to speak of an initial set,
though obviously its value changes daily with the progress
of abscission. The percentage final set expresses the relationship between flower and fruit no., and relatively small deviations in the set percentage make all the difference between
a small, an average or a large yield.
Fig. 2 shows the relation between flower no. and percentage set. Flower no., plotted on a logarithmic scale, is
based on data collected from 90 9-year old individual
'Shamouti' orange trees (8) budded on sour orange (Citrus
aurantiurn L.) growing in heavy soil and having a large
variability in flower no., perhaps because they were in the
early stages of fruiting.
The figure shows quite clearly that when flower no. is
small, the tree attains large percentages of final set (up to
11%) and thereby compensates for the initial lack of flowers.
On the other hand, when flower no. is excessive, final set
percentage progressively decreases clown to 0.1 %. There
must therefore be a control system, whose mechanism is not
clear, but which cannot be questioned as to its importance
in adjusting the level of yield to the tree's potential.
Abscission may be split into several stages showing some
degree of overlapping (Fig. 1). It is evident that a very large
no. of units abscise during the first weeks; at this stage their
individual weight is still small so that the tree has not invested so much in the building of each unit. The no. of
units lost progressively decreases toward the end of the
abscission period, but each unit is by now much heavier
(2-5 g). \Ve also know that the abscission zone .
switches from the pedicel to the calyx zone (5).P~o~(·s,h~
during the abscission period changes may a], 0 0 relu;n,,;:!
sensitivity of fruits to endogenous and exogenotccur
in t~
1
and growth regulators (4) reflecting the chancring ' l:th;:.<
of the fruit to abscise. vVe therefore assum~ tha.~tn~en,::
abscission stages exist although a better character·d 1 ffe:~~:
these stages and their control is still wanting.
llattQn ~
. Final c?mPor:ents of yield: no. and size of fruit.j
;
y1eld obtamed Is actually the product of the no he fil'.,~;
vested fruit by their weight. The ability of a tre ·of f1.:;1
~ruit fluctuates w~thin a giver~ ra?ge, th~ n?. of fr~rito ~ l:
mversely proportiOnal to then srze. This IS true .~ ~~ l
given variety, but also holds when we compare ci';ulnn i j
tivars and species producing widely different frui.t r~H tll ( .
man~larins_, oranges and ~rapefruits. ~s an_ exampl~ 1 ;,M, <1
relatiOnship between frmt no. and siZe, F1g. 3 sho 1 .• f lh~·l
from sizing experiments with 'vVilking' mandarin (~(ht,
nobilis Lour. x Citrus deliciosa Tenore), 'Shamouti' 0 :ltr.,, t
and 'Marsh' seedless grapefruit. That data from 3 (!i[t_ng,
species should fit naturally onto a line expressing· 111 trrn: 1;
·
1·
l'b
f'
d
·1
ere4
tiv~ re_ atw.nsllbiP etweben nut no. an we_I~ 1t is not rtt·c~; .,
san y 1mp11e( y t11e a ove genera 1 proposJtwns 'Shar · ·.
,
,
l
. ' II<)Uil
and Marsh usually possess a remarkab e amount of . ,
1
contr~l maintaining the fi.nal_ y~el~ within ~~ narrow ras; ;:. 1
I'"
of frmt no. per tree. The vVllkmg mandann on the <l}
.1
1
.
ule ,.,
hand, presents ~ st:ong tenuency to a ternat10n as do manv
of th~ mandann-hke ~rees, and the dat~ reported reflect . ,~
cher~ucal or agr~techmcal treatments wh1ch reduced fruit
no. m a very radical way (2). We do not know about sitU:!· I· ·
tions in grapefruit or oranges where a reduction in fruir no ·' 1
can cause a two- or three-fold increase in fruit weight. In .,: ,
the ''Wilking' variety (as in other mandarin-like fruits) ron. '.:
trol of fruit no. is rather loose and as a compensation, tht j ~ ..
tree is able to vary fruit size within a remarkable ranw·.
, '\
A more detailed perusal of 'Wilking's data (Fig. ·1) sh0111 .m
that it is possible to subdivide the curve into two portions:
a decrease in fruit no. from 3000 to 1300 does not camn .'.~i
significant increase in average wt., while additional thinning .. 11 •
markedly affects size. The danger of reserve cxhall\tum.
i·
I
1
l':
!. ;(
!
103
r--___, ----,-t
f
~
l
0
Pc_ ~ MARSH SEEDLESS
~
GRAPEFRUIT
n
0
f-
I
6
<C)
w
5
flft
6
m f#;4::o.
'!1',
SHAMOUTI
ORANGE
l '•)1\1
i "1!
l II\(
0
f--
0
~102~
lL
.
....J
I
<l:
::J
0
0
o
00
0
0 O 0
0 0
0 Q)
0
WILKING
MANDARIN
~0
0
>
0
I,
I
I
:1'11
'H.\'~
::1)d
·::.\11
'idt
z
'1\'.
f-
~ 4-
101
L___ _--L___
)J2
10 4
NO. OF FLOWERS I TREE
Fig. 2. The relationship bemeen no. of ftowersjtree (logarithmic
scale) and final percentage of fruit set in 90 'Shamouti' orange x Sour
orange trees. (From (8)).
670
_L__L__.L_L_L_LLL
103
NO. OF FRUITS/TREE
L
, _ __l_
.. r
L-"-~
n
,, ;
, •.. 11
off.n~:r~: I
Fig. 3. Weight of indiYidual fruit plotted against the no.
''•!!
1
(logarithmic 'cale on Loth axes). Data from experiment; pcrfoi':1; 1fl'lll'l) -'"·"
each \·ariet\' separatelY. Each point represents an average froiii '
·1r
:
of a single tree. (From (2) and unpublished data).
•
hoc. 1n t. Soc. C;, t icu lMe, !97 ;, rol. ,~, .,,
,--I
0
0
0
0
Oo
0
0
0
oo
0
0
00
ao00
0
r:P /}J
0
00
0
0
0
l.--~~~~--~~~~~~
1000
2000
3000
the developing fruit. The decision about the partitioning of
flow, the actual control of its channeling towards different
aims, is crucial with regard to levels of yield. Distributing
assimilates between different processes seems even more
intricate in a perennial, where distances between organs are
large and there is a need to provide for life continuation in
following years. The dashed line linking control of partitioning and energy converter represents the reversed control
(feed back) on energy conversion. An increased demand for
assimilates may accelerate their production by leaves and
cause a better expression of potential production by a tree.
On the other hand a lack of suitable utilization may congest
production centers of leaves. The same clashed line also
hints as to possibilities of biochemical and hormonal controls of a more refined type.
PRODUCT
ENVIRONMENT
NO. OF FRUITS/TREE
. r'll· 4. \\'ciglu ol individual 'Wilkin&' mandarin fruit plotted.against
•, ~t of fruit/ tree. Data fran~ a thmn.mg expenment. Each pomt rep-
\
an average !rom all frmts of a smgle tree (2).
_____ /
FEED BACK
alternate bearing in these varieties, probably lies in
of excessive fruit no. The tree is apparently unrecluce fruit size, perhaps because of genetic
above data deal with the average size of fruit; inclisizcs, however, vary within relatively large limits.
behind this variability probably lie in comsource-sink relationships, governed by efficiency of
and rei a tive positions of leaves and fruit.
Fruit no. vs. size is undoubtedly one of the important
ts which will need to be considered when developmodel. It will also be necessary to pay special attention
economic importance of size, one of the main paramdctcrmining fruit acceptance by consumers.
Diagramming Citrus Fruiting
A host of factors has a direct or indirect bearing on yield
ritrus trees. A full enumeration should include environ. macro- and micro-climatical elements, water avail' nutrients and physiological data specific for cultivar
JTI
0
WILKING
MANDARIN
~0
of non-irrigated crops (as natural pasture, winter
etc.) place a considerable emphasis on physical com. ls o[ environment and especially on water availability,
influence is extremely important under the growing
of these plants.
agriculture, as found in orchards of our area,
a suitable supply of water and nutrients permitting
fair expression of their potential productivity. A
a citrus orchard is obviously dealing with a well
irrigated crop, though there are still ample possi,
.
tv improve orchard care. At this preliminary stage,
r~ 1h~l! presuppose in our discussion normal care as sup~~Ill an average commercial orchard.
fhe simplest way to describe in universal terms the
of yield production by means of a diagram as used
engineering, is depicted in Fig. 5. Environfactors including carbon dioxide, water and solar
participate in the photosynthetic process occurring
the gTeen leaf. The solar energy is converted into
the building blocks of production. Assimilates
their different goals: i.e. to build a framework of
roots, leaves, new growth, spare buds, flowers and
Int. Sor. Citriculture, 1977, Vol. 2.
Fig. 5. A simple flow diagram demonstrating major processes (circles)
involved in crop production in an agricultural plant.
The application of the above principles to the production system of a citrus tree is detailed in Fig. 6. Here each
rectangle stands for a different type of organ, the arrows
denote organ development, wide-stemmed arrows express
direction of assimilate How, the dashed lines stand for possibilities of control and the springs depict interactions between organs. The horizontal axis describes the time dimension and the continuity of processes within such dimension.
The scheme starts with the initiation of flower bud one year
and ends with the bud due to initiate flowers next year, and
includes all the set of processes pertaining to the formation
of yield. Three different types of shoot develop from the
flushing bud in close competition: leaves only grow from the
vegetative flush, while fruits will develop from the other
two. The task of leaves is to provide assimilates (building
blocks, energy and regulators) to the developing fruit as well
as to other tissues. The importance of leaves becomes evident during set when competition is most severe. The
chances of setting are better for a fruitlet borne on a mixed
ORGAN DEVELOPMENT - - - 7
FLCJW OF ASSIMILATESZ'LZ$
CONTROL
~
COMPETITION
:;
_ _ .1
INDUCTION----"> FLUSH
1975
----'>-~~Jp---~G~~~~H------">- INDUCTION
1977
Fig. 6..-\ flow diagram representing the overall processes involYed in
fruiting of citrus trees and the relations between different tree organs
during the period between flower bud induction in one year and flower
bud induction in the following year.
671
shoot as the proximity of leaves has an important nutritive
and/or regulative influence in this connection (8, 9, 10, 12).
On the other hand proximity of many fruitlets may have a
negative value because of competition.
At the stages of fruit development, the scheme is simpler.
I\' ow assimilates are partitioned mainly between developing
fruits and reserve pools at different tree places, if we disregard the time when summer flush is growing (by far a
smaller no. of new vegetative shoots than in spring).
The nature of the regulatory systems involved is still
greatly unknown. On one hand, there may be some sinksource control from developing fruits to photosynthesizing
leaves, as noted above. On the other hand, all organs may
exercise nutritional and/ or hormonal control on the fate of
buds due to flower in the following season.
Points of Decision and Control Mechanisms
In conclusion we may assume the existence of 3 points of
decision where the fate of yield would be settled.
The first is at the level of flower formation. An absolutely negative decision at this point, completely precludes
yield production in the present year. On the other hand
profuse production of flowers is not sufficient to ensure a
high level of productivity in certain cultivars.
The alternative between abscission or set, which is a
continuous one during a number of weeks, is the second
crucial decision period. At the end of complex and elaborate
abscission processes the final size of fruit population will be
settled. By means of abscission control the tree may correct
up to a certain level the first decision: if the no. of flowers
is too small abscission can be inhibited, so that yield will
still be fair.
The third piece of decision-making concerns the final
size of the average individual fruit also emphasizing the
importance of quantitative differences in the partition of
reserves between individuals within the fruit population.
If fruits are relatively few they may grow more, if they are
numerous they grow less, while the product of no. x wt of
fruits tends to be constant within reasonable limits.
In the present paper we endeavor to set the basis for a
quantitative analysis of_ yield comp<_>nents ~n _a commercial
citrus grove. In so clomg we utilized ex1stmg data and
knowledge. There are still several links requiring additional
logical and experimental elaboration. One of these is the
relative importance of photosynthetic production and of
hormonal regulation in controlling yield levels. The question of regulative systems in a perennial plant, extends beyond the limits of one particular year and includes accumulative effects of reserve pools and age effects which are
unknown to the annual plant.
In future, attempts will be made to deve]o
fruiting model into a quantitative tool which P__ the
ized in the ~liagnosis and cure of specific low '~ ll! bt 110~
problems. \\ e feel confident that an overall ul~tOduqi~~
of ways to control and increase citrus tree proclu t~t~lltii~-even tuall y ensue.
CtJ\·n; ._,;
I
Literature Cited
I. Chalmers, D. J. and B. \"an der Ende. 1975. Proc!uct' .
:
trees: factor affecting dry weight distribution durin~' It:· ''f ;.,.,~Ann Bot. 39:423-432.
tree~'-""<
2. Galliani, S., S. P. Monselise and R. Goren. 19/j_ hn
,,.
size and breaking alternate bearing in '\Vilking' 1 ~' 01 '1li: ~"-!
ethephon _and ~t~er agents. H or/Science 10:_68.
n.rn<fatilll ;,
3. Goldschmrdt, E. E. and S. P. l\Ionselrse. !9,2. Honnon·I .
flowering in citrus trees and in other woody perennial;' 10 ~;:')( ,,
In Plant Growth Substances 1970. D. J. Carr, ed., Spri;, P: ••_-1-~ ; ,.;: 1
Berlin.
gn '<lilt i .~i
4. Greenberg, J., R. Goren and J. Riov. 1975. The role f
-~ .and polygalacturonase in abscission of young and matnre\ ctllu)o
1lanu"'-.
orange fruits. Pilysiol. Plant. 34:1-7.
_Iii
!
j .
. 110 n o:
5. Bar-Even, E. and S. P. Monselise. 1959 .. \ study on th
1
'Shamouti' oranges from set to harvest. Pror. l·ift/, lilt/ '"'Pff.l
terp
Mediterr. Citriculture, Catania, p. 181-187.
·"'· C""f ~
0
G. Holt, D. A., R. J. Brrla, G. E. Miles, M. M. Schreiber a I)\ -~i ;)!!n
Peart. 1975. Environmental physiology, modeling anti ,;~Ill ·It OC'ur,
of alfalfa gr_owth. I. Concep}ual development of SIME!l. p~~ lll varl
Unm., A gr. Sta. Res. Bull. 90,, 26 p.
• ., ofrUS
7. K hairi, 1\f. M. Ah. and A. E. _Haii. I'l76. T~tn[JeLtture and hrnnidito lorex
11
e eels on net p otosynt 11esrs an< 1 transptratwn of citrus. Pf,.,,.;
P_lant. 36:29-34,- _
.
<an 1 .
8. Kolodner, Y. E., I-.. E. Goldschnudl and S. P. Monsdise. 1971 i ttpar.
1
fluence of number of flowers and inflorescence type on yiehl ,1
~n-ex
'Shamouti' orange. (Hebrew) Alan Hmwtea 2R:!i·10-G·l~.
i HPLC
9. Lcnz, F. 1966. Flower and fr~it developmenL in 'Valencia' hll! d
5
orange as affected by type of rnflorescence and nutritional , ~~~, 1 10 I
Hurt. Res. 6:65-78.
hon r
10. ~~~~~~, P. E._ Kriedemann and H. J. Daunicht. l!ln_ Elf<ttl(l! 111ily
roots and emergmg axrllary shoots on photosynthesis hdwi.,r Ill. ~e<tor
citrus cuttings. Angew. Bot. 46:2~7-231.
. I ibsorl
11. Monselise, S. P. and Lotte Heymann Herschberg. l'l'i:l. lnllurncel!(l It
exposure and age on dry matter content, area and mineral rum.
ms
position of 'Shamouti' orange leaves. Proc. Awer. Soc. 1/ml. S<i. lure, •
62:67-74.
A'
12. Moss, G. I., B. T. Steer and P. E. Kriedemann. 1'172. The rcgnl•r.tq quJie
1
role of inllorescence leaves in fruit setting by sweet orange (Ci:;.; i HPLC
sinensis). Physiol. Plant. 27:432-438.
l·
13. Omer, A. 1969. Internal and external factors alkctin~ ahsri"i<>nolf iriph
'Shamouti' orange leaves. (Hebrew). M.Sc. Thesis, l!ehrew t:ni•. !liner
of Jerusalem, Rehovot, 57 p.
I !elect
1-l. l'romnitz, L. C. 1975. A photosynthate allocation model for tr~' lows
r;row_th. Phot_usynthetica 9_(1):1-15:
.
, I tissue
15. Shavtt, A. 19~6. An mvesttgatron mto the process of flower ami fllllll
abscission in the 'Shamouti' orange. Bull. Res. Couucil hmrl lrt txam
189-199.
, 1nd g
16. Stapleton, H. N., D. R. Buxton, F. L. Watson, D . .J. Nolting •1111 1111ay
D. :-1. Baker. 1975. Cotton: a computer simulation ol rotton h'Tn•tb..
U. of Ariz., Agr. Exp. Sta. Tech. Bull. 206, 124 p.
.
17. Turrell, F. l\I. 1973. Appendix III, Frost Protection. !11 Reutht·r, II
\I
ed. The Citrus Industry, Vol. 3, p. 506-520.
<1d1
,_,I
i:!
111
I
j
1
:.:nil
{ ::!lot
I
Ull)
·:l.h
:an
!',1n
.. ,,;
·:·.:o
;:.tpl
: th
·!'io
:lrll)
672
. .
-- roL!
Proc.lnt. Soc. C1trzculturc, 1911,