HELU,I3, Nr. 13, p.p. 63-71(1990)

EFECT OF ARTIFICAL DBFOLIATION ON SUNFLOWER(Helianthus annuur l,.) 1

Paola Belloni, Diletta Piccotino, Gian Paolo Yannozzi z

SUMMAI{Y

The authors present results of a study concering the artificial defoliation of twoself-pollinated sunflower lines. Defolation treatments of increasing intensities on leaves indifferent positions were carried out at two different times of plant growth (before and duringflowering). The results stress the importance of upper and intermediate leaves for yield whichdecreased with the increase in artificial defoliation percentale.

INTRODUCTION

This work was carried out in ordcr to gain furthcr knowlcdge on the relation shipbetween leaf apparatus, plant development and yield in sunflowcr. Artificial defoliationwas chosen as an experimental means since plant bchaviour following a reduction in leafarea - which may occur in the field as a consequence of pathogcns or atmosphericconditions - can be properly assessed. It also makes it possiblc to evaluate the effect ofsuch a recluction at different phenological stages ancl the portions of lcaf apparatus thatcontributc greatly to the yield.

Defoliation has already bccn expcrimentecl with on a widc numbcr of species. Insoybean (Glycine max (L.) Mcrrrl), for example, it was short'n to reduce the yieldparticulary if it occurs during thc final stages of developmcnt (Malonc ancl Caviness,1985; Goli and Weave, 1986) andwhcn thc pod bcgins ro tlcvelop (R5) (Fehr etall.,I97l,1977, t98I).

After defoliation, a decrease in grain yicld of maize (Zu ntais L.), was observed(Hanway, 1969; Hicks et al.,197'71, Conti and Lancli, 1981; Vasilas and Seif, 1985) as wellas a drop in dry weight (Conti and Landi, 1981).

Tbtal defoliation before flowing in sunflower causes aboutg3Vo reduction in yield(Johnson, 1972); defoliation during {lowering may eithcr block achcne productionaltogether (Gonzalez de Schelotto, 1978) or cnormously reduce achens size ancl oilcontent. A progressive increase in the percentage ofdefoliation corrcsponds to a progres-sive decrease in yield (Gonzalez de schelotto,1978 Tuberosa antl conti, 1978; Danusoet al., 1983).

The dimension of the effect of artificial defoliation in sunflower depencls on thephenological stage at which it is carried out and the part of leaf apparatus eliminated.With regard Lo the phenological stage, defoliation has its most marked effects on yielcljust before flowering (Tuberosaa and conri, 1978) and during flowering (sackston,1959;

The research was supported in part by the Italian Ministry of AgricultureGraduate assistents and associated professor, respectively, Institute of Agronomy, Pisa University,Italia.

1

2

HELU,l3, Nr. 13, p.p. 63-71(1990)

Gonzalez de Schelotto,I9TS), but effccts are far lcss notable when carried out duringlater stages of development (Rodrigeus Pereira, 1978). As far as the portion of plantdefoliated is concerned, it can be said thal the more apical it is, the greater is its effecton yield, although the yield incrcascs if among the remaining leaves there is a highpercentage of young ones (Rodrigues Pereira, 1978; TLrberosa and Conti, 1978). This maybe due to their greater capacity to transport assimilates to the flowers (Mc William et al.,L974\.

MATERIALS AND METHODS

Thials were carrie<l out during 1987 at the "Duccio Ducci" Experimental Station ofPisa University, Institute of Agronomy, Torretta, Pisa.

A split-plot arrangement was made with three treatments of three replicationseach. Each plot was planted with four rows, 6.5 m in lenght and 0.8 m apart. The seeding

was done on 12 May L987.

The main treatment was made up of two selfed sunflower lines (S10), chosen by

this Institute ancl countersigned by the letters IAP 72 and IAP 48. They were chosen forsuitability of leaf characteristics (numbcr and total arca; see Thbles 1 and 2).

Table l.Defoliated lines' charâcteristics

Table 2.Defoliared lines' characteristics at the time of first defoliation (10 July 1987)

The leaf apparatus was divided into trce sectors (A,B and C)raccorcling to the totalnumber of leaves present (Fig. 1) and the defoliation was as follows:

N1. - untreated control;N2 - removal of leaves in sector A (33,3% of total leaves present);N3 - removal of leaves in sector B (33,37i of total leaves prësent);

N4 - removal of leaves from sector B and C (66,6Vo of total leaves present);N5 - remeval of leaves from sector A and C (66,6% of total leaves present);N6 - removal of one leaf in fle (20% of total leaves present);

Plant height (cm)Head diameter (cm)Number of leavcsMedium leaf area (cm2)Total leaf area(cm')

11311

11

35tt.2391 rJ.53

r2915

202f9.1

578r.4

Plânt hight (cm)Head diameter (cm)Number of leaves

94.25.9

1)

207.7

95.75.7

2L

r79.53768.9

Medium leaf area (cm')

HELU,13, Nr. 13, p.p. 63-71(7990) 65

N7 - removal of every other, leaf (5OVo of totalleaves present);

N8 - total removal of leaves(IOO% of total leavespresent).

Leaf removal was carriedout at lwo different stages, i. c., on1C July 1987 (12 days previous roflowering for line IAP 72 and 16days previous to flowering for IAP48), on 22 July 1987 and 26 July1987, rhe dares on which IAp 72and IAP 48, respectively,flowered.

Leat area was measured byan automatic area meter (AAM -7) and the following chàracierswere investigated: achene yield(g at 0 moisture) and dryweighr ofplants, including root apparatusbut exclu<ling,seeds, at {inaturity

(g) and that ofthe ûntire plant (g).Stomatal conductance

(cm/s) was determinated on 27July, logether with transpiral.ion F;.. , e ..1 ,:,

1m! ffô p"r "m21

,"" 'e _Oi! ^lqii .1 Subdivision of leaf apparatus in the defoliation trial

p.hotosynthestl (me CO2per dm'lhour); light (PAR = phorosynrhcricalyacriveradia-tion) and VPD (vapor pressure deficit) (KILOPASCAL) wcre also mcasurecl severaltimes during the day on plants from line IAP 48 deprivccl of leaves in scctors A ancl Cduring flowering (treatment N5,66.6Vo leaves removecl), using an infrarccl gas analyzer,to determine whether the removal of leaves cause<l changes in photosynthe;is.

RESULTS AND DISGJJSS ION

" làble 3 reports mean values in variance analysis of the considered characters.

No statistically significant differences wcre found in yicld between leaf rcmoval at33.3, 66.6 and Sovo of allle_aves prescnt (trearmenrs from N2 to N5 wirh N7), whereaswith leaf removal in toto (N8) the differcnce was evident - as was to be expected. It snouldbe noted that the plants in both 66.6 (N4 and N5) an<|33.3vo (N2 anôN3) defoliationtreatments showed a4OVo loweryield than the control. This suggcsts that to lheyield therem.oval of apical (N2) or medium (N3) sectors is more damaging than their complemen-ral (N4 or N5).

66 HELIA,13, Nr. 13, p.p.63-71 (1990)

The removal oî 50% leavcs tlistributcd over thc whole plant gave the same results

as 66.6Vo removal as spccified above. With the cxception ofN6 (20%reduction of leaves),

all treatments gave achene yielcls differcnt from that of the control. Values for N6 wcre

not statistically clifferent, showing that thc loss of one leaf in five does not seem tojeopardize yield to any extent.

Statistical dil'Lerences in plant dry weight cxclucling achenes among treatment N2

to N5 with N7 followed a pattern similar to that lor yicltl, while N4 (which left leaves in

sector Awifh66.6% rcmoval) and N6 (rcmoval of one lcaf out of five,207o removal), N1

(control) and N6 wcre not significantly different.

Table 3.Meanvalues for different defoliation treatments in the considcrcd characters

-- I vreldeltect | -rpr\ dry weight excluding seeds(er)

total dryweight(sr)

I 2 J 4

64.41

138.54

b 90.4220r.57

linesIAP 72IAP 48

26.9562.96

ba

BA

BA

b

a

BA

defoliation treatmentsN1N2N3N4N5N6N7N8

a

cb

d

213.00131.56142.52144.82140.05t84.5',1

144.3866.47

a

c

ccb

d

73.3543.45

44.444t.6941.1563.4843.065.01

r39.9987.8698.07

103.1298.89

121.08101.31

6t.46

aAdc

cdCcBC

cdCbAB

cdCeD

AccccBCD

ABBBBABC

defoliation timesprefloweringflowerins

t4-1 .20L50.73

9('.88l{16.06

b

â{{.JI

14.60 a

bBaA

BA

AA

149.36 d cD8r.74 f EF78.14 f EF97.11 ef E80.16 f EF

113.98 e DE75.04 fg EF47.84 g F

277.34 a A181.39 c BC206.90 bc B192.52 bc B199.94 bc B255.L6 a A2r3.7r b B85.10 ef EF

eEFfh GHgh GIIef FGfh GHeg FGgh GHhHaAdDEcCD

cd CDcCDbABcBCef FG

59.77

20.6522.9920.4418.9240.9827.tr

2.7486.9466.2665.8962.95

63.4085.9965.01

7.29

bBdDEdDdDEdDEcCdDEeFaAbBbBbBbBaAbBeEF

89.5860.5955.7476.6667.2473.0053.9345.10

190.40115.13141.01

729.57136.55169.76118.7077.81

lines - defolialion lreatmcntsIAP 72-N1IAP 72-N2IAP 72-N3IAP 72-N4IAP 72-N5IAP 72-N6IAP 72-N7IAP 72-N8IAP 48-N1IAP 48_N2IAP 48-N3IAP 48-N4I-AP 48-N5IAP,A-N6IAP 48-N7IAP 48-N8

88.34 c C92.50 c C

194.05 b B

208.97 a A

cb

a

26.50?5.3962.L2

63.81

bba

a

lines - defoliation timesIAP 72-prefl.IAP 72-flow.IAP zt8-pretl.

IAP 48-flow.

CcBA

BBAA

6t.8466.98

r3r.93145.15

HELU,l3, Nr. 13, p.p. 63-71(1990) 67

(P : O.oS and 0.01)Anglogous patterns were followed by whole plant dry weight, with the exception of

Me ments

effectyield(er)

dry weight excluding seedst/or\

total drywelghtfsr)

1 2 4defoliation treatments-defoliation times

N8-flow. 7.24

N1-prefl.N1-flow.N2-prefl.N2-flow.Nlprefl.N3-flow.N4-prefl.Nzl-flow.N5-prefl.N5-flow.N6-prefl.N6-flow.N7-prefl.N7-flow.N8-prefl.

73.5373.1,844.2242.6843.8645.O243.7439.6638.7943.5248.6952.2838.8847.U

2.79

aAaA

cdCcdCcdCcdCcdCdcdC

cdCaAbBdccCeDeD

t44.43135.5584.5891.13

toz.t494.0795.50

710.7489.06

108.72127.05115.1190.79

111.8441.5081.41

2r7.95208.74128.81134.32146.00139.03739.24150.40727.86152.24r95.75173.39129.67159.08

44.2988.65

aAabAghFfh EFdg DFeh DFeh DFdf cFhF

de CEbABcBC

gh EFcd CDIHiG

aAabACGHfg EHdf cGeg DFIeg CHdBEfg FHde BFbc ABcd BCfg EHdBDhISH

IAP 72-Nl-prefl.IAP 72-Nl-flow.IAP 72-N2-prefl.IAP 72-N2-flow.IAP 72-Nlprefl.IAP 72-N!flow.IAP 72-N,$-prefl.IAP 72-N4-flow.IAP 72-N5-prefl.IAP 72-N5-flow.IAP 72-N6-prefl.IAP 72-N6-flow.IAP 72-N7-prefl.IAP 72-N7-flow.IAP 72-N8-prefl.IAP 72-N8-flow.IAP 48-Nl-prefl.IAP 48-Nl-flow.IAP 48-N2-prefl.IAP 4&-N2-flow.IAP 48-Nlprefl.IAP 48-Nlflow.IAP 48-NzS-prefl.IAP 4&-Nzt-flow.IAP 48-N5-prefl.{AP 48-N5-flow.IAP 48-N6-prefl.IAP 48-N6-flow.IAP 4&N7-prefl.IAP 48-N7-flow.IAP 48-N&prefl.

iGitGit G

il GiG

96.4182.7655.1266.0760.9049.3874.3978.9558.3264.1668.1876.8251.2656.6130.r260.09

192.44188.35114.06tt6.2l1,43.37138"64116.6rt42.53119.81153.29r85.92152.41130.32167.07

52.89102.73

157.03141.6877.2586.2383.7272.5694.6999.5378.4981.82

tt2.lI1 r 5.00

7 L:2378.8132.1963.50

278.88275.80180.38182.41208.28205.51183.78201.26177.22222.67279.39230.93188.07239.35

56.4011? RO

lines-defoliation treatments-defoliation times60.62 eg DE58.93 fg E22.L3 iG19.16 il c22.82 i c

hi EFiFG

mp LNmo HNmo HNnp LNln HMlm HLmp LNmo IN

IGIIGH

np LNmp LNpO

op MOaAaA

gh DEfg DEce BDdf cDeg DEdg CDgh DEbd BcaA

bc BCIeg DEIbBl

pq NolI r-:II

imcln FILqr LOnr LNor LNrs NOnq HNmo HMor LOnr LNnr IN

mp HNrs Mopr LOsO

or LNaA

abAgi ECgi DGde BDdf BEgi DGde BEgh DGcd BCabAcd BCeg CFdc ABrMO

hl

23.r720.3020.58

20.0122.20

20.17 it c77.67 il G43.93 h F38.03 h ff

2.07 m Il3.41 m H

86.44 ab AB87.44 ab AB66.32 dg CE66.20 dg CE64.91 dg DE66.87 dg CE67.18 df cE58.73 rg E57.42 g E69.38 ce CE93.46 a A78.53 bc Bs7.75 fg E72.28 cd CD3.51 m H

IAP 48-N8-flow. 71.07 lm GHln a row sâme lelter are not significantly different accordintlo a pairwlse t test

N4 and N6, the latter of which, in fact, proved to rliverge from all the others.

N1 controlN2N3N4N5N6N7.N8

*.ou67.5465.8168.3537.4464.69

zi.tzu.2227.6027.O8

1.1025.33

HELU,13, Nr. 13, p.p.63-71 (1990)

Different removal times, whether before or cluring flowering, did not seem to affect

yield results. Removal during flowering did, however, give rise to greater dry weight.

Analysis of the interaction between these two lines antl the treatments reveals that

there were no statistically significant yield differences among treatments N2 to N5 with

N7 for IAP 48 and Nl for IAP 72 (untreated control), or among N2, N4, N5 with N7 forl4p T1and N8 for IAP 48. This means that even at high leaf loss rates IAP 48 gives a

yield comparable to lhat of IAP 72 even at maximum intensities of damage. When 3rd

ôrder intéraction is analysed, however, this is seen to occur only in the case of total

removal during flowering, probably because the plants had at this stage already stored

enough reseruès in the flower head. IAP 48 which proved to give better yields than IAP

n ana percentagewise, suffered the consequences of defoliation less than the latter

(Tàble 4); this may be due to IAP 48 having a greater number of leaves (about 7) than

iap ZZ, ûttich enabled it to maintain sufficient leaf area to guarantee a certain yield level.

Plant dry weight excluding achenes clicl not reveal results significantly divergent

from the fully leaved IAP 72 control or N2 and N8 for IAP 48, or among treatments

N2-N7 for IAP 72anrJ N8 for IAP 48 (total removel of leaves).

Tbtal dry weight of the plant followed a different pattern from the above in

trearmenrs Ni for lp.p lZanO NZ for IAP 48; these were statistically diffent from N8 forIAP 48.

The two lines dicl not show differences in yield according to the time of leaf removal,

whether before or cluring flowering, although plant dry weight was in all cases greater inIAP 48 defoliated at flowering.

Inspection of interaction between the lines and leaf removal time did not reveal a

significant difference in values of dry weight excluding achcncs, apart from N7 and N8'

*Éi"h gau" greater values for removal tturing flowering. Ttrtal dry weight was greater for

leaf loss during flowering for N5 trxl.

Table 4.Yield reducrions (%) in IAP 72 and LAP 48 for the different defoliation treatments

Concerning line/ defolation treatment/removal time interaction, significant values

for yield could be observecl only for N6 anil N7 treatments carried out on IAP 48 before

or during flowering, while dry wcight for this line was different in all cases, including N5

and N8.Measurements made with the IRGA the day following leaf removal did not reveal

(Figures 2,3 and 4) significant differences in net photosynthesis, stomatal conductance

or transpiration in plants with 66.6Vo defoliation (treatment N5) as compared with th€

control. Differencei in yield and dry weight between defoliated plants and controls

HELU,13, Nr. 13, p.p. 63-7t (1990) 69

cannot, therefore, be attributed to an increase in photosynthesis rates in the remainingl-""u:t. It could be supposed, however, that the defoliated plants at a later stage in plan'idevelopment are in a more favourable situation than the control, regarding waier supply,and with their smaller leaf area are better able than the conrrol to âoapt io water sireiidev-eloping in the soil. It seems to be confirmed from this: with no highér phorosynrhesisrate and lower leaf area (-66.6%) the defoliared plants (line IAp 48, treaimenr i{5) hadonly 27.[Vo lower yield than the control.

(t

ul

oo

oooN

o

a

t

F

''rt 1. s-.1

1:- O-1

ro. si10. o-J

"'=-l

Hours

f'& 2 T:!to.f riel_ptotosynthesis in detbliated plar)ts and untreated control on rhe day tottowing leaf removal(27 Juty 1987)

Control

ooq

co

oEo

4t

Hours

f:rg11l.J

Eg JThend ofstomatalconductanceindefoliatcd plantsand untreated control on thedayfottowing leafremoval(n Juty 1987)

70 HELIA,l3, Nr. 13, p.p. 63-71(1990)

ct

IBI(to6({

o

6l

o'

É!eg

L

r"Irr.sJ

"'-lres-.i

,0. oJ

3.

ÉHout 5

Fig. 4'ttend of transpiration in defoliated plants and untreated control on the day following leaf removal

(n JutYresT)

CONCLUSIONS

Results of these trials may be summarized as follows:- total leaf loss (100%) reduced yield by about93Vo;

- an even distriburion of leaf removal ovcr the whole plant (SOVo) reduces yield to

the same extent as a grcater (66.6Vo), but localizcd, dcstruction;- the remgva I o12O% leaves tlo not givc risc to a significant decrease in yield with

respect to the control;- apical and central lcaves are clefinitcly the most important for yield, making a

fundamental contribution in product of photosynthesis;

- leaf removal times (before or during flowering) does not seem to affect yield;

-the plants with more, although smaller, leaves (line IAP 48), were always less

affected Uy Oefofiation than those with fewer but larger leaves. This may be due to the

former's better phyllotaiic distribution, enabling more efficient capture and utilizationof radiation;

- no differences were measured in net photosynthesis, stomatic conductance ortranspiration between defoliated plants and the control.

REFERENCES

Conti" S. and P Landi.1981. Effetti della defogliazione in realizione al portamento fogliare e alla densità dipiante in ibridi di mais. Riv. Agr.3-4: 151-L55.

Danuso, F., E Miceti and G. Venrui.1983. Asportazione delle foglie, componenti della produzione e sviluppo

delle piante. Inf. Agr. 2O:.25931-33.Fehr W R, è. E. Cavinesi, D. T Burmo{ and J. S. Pannington.1971. Stage of development descriptions for

soybeans, Gfrlne max (L.) Merril. Crop Sci. 11: 929-931-andJ. J. Vorest.1977. Response ofindeterminante and determinante soybean

iultivan to defoliation and half- plant cut off. Crop Sci. 17: 913-917.

HELU,l3, Nr. 13, p.p. 63-71(1990)

B. K Lawrmce, and T. A. Thontpson. 1981. Critical stages of development for defoliation ofsoybean. Crop Sci. 2l:259-262.

Goli,A., and D. B. Weaver.Defoliation responses of detcrminateand indeterminate Iate-planted soybeans. CropSci.26: 156-159.

Gonmlez de Schelotto, A. L. 1978. Efectos de la defolacion no natural sobre el rendimento de girasol. Sun. New.2,nl: 19-22.

Hanway, L J. 1969. Defoliation effects on different corn hybrids as influenced by plant population and stage ofdevelopment. Agron. J. 6l: 534-539.

lohtnon, B. J. 1972. Effect of artificial defoliation on sunflower yields and other characteristics. Agron. J. 64:688-689.

Malone, S. R., and C. E. Calviness.1985. Cut-otf, break over, and defoliation effect on a determinate soybeancultivar. Agron. J.77: 585-588.

Mc William, J. R., S. D. English, andC. N. Mc Dougall.1974.'theeftect of leaf age and position on photosinthesisand the supply of assimilates during dwclopment in sunflower p. 773-179.In 6th Int. Sun. Conference(Bucharest).

Rodrigtes Pereira,,4. S. 1978. Effect of artificial defoliation on yield components in sunflower. Sun. Neu,. 2, n 3:7-73.

Sackston, W E. Ellect ofartificial defoliation on sunflowers. Can. J. Plant Sci.39: 108-118.Tùberosa, R., and S. Conti. 1978. Effetti della defogliazione ârtificale su giresole. Convegno sugli aspetti genetici

ed agronomici del giresole. Pisa.Vasilas, B. L., and R D. Seif, 1985. Pre-athesis defoliation effects on six corn inbreds. Agron. J. 77:831-835.

EFFETS DE I"ADEFOLIATION ARTIFICIELLE SUR LE TOURNESOL(Helianthus Annuus L'1

Beloni, P, Piccotino, D. Vannozzi, G. P

Les auteurs présentcnt les résultats d'une étude concernant I'effet d'une défoliationartificielle sur deux lignées autofecondées. Des défoliations d'intensité croissante à differentsétages folliaires ont été pratiquées à deux stades de dweloppment de la plante (avant etpendant floraison). Les résultats r)nt souligné l'importânce du rôlr: des feuilles intermediaireset superieures dans le rendement qui décroit d'âutant plus cluc le pourcentage de défolliationartificielle augmente.

EFECTOS DE DESFOLIACION ARTII-ICI^L EN GIRASOL (flelianthusÀtututu L.)

Paola Belloni" Rialete Picitino, Gian Paolo VanozzL

Los autores se refieren a resultados de un estudio referente a la desfoliacidn artificialen dos lineas autofecundadas de girasol. El tratamiento de desfoliaciôn de intensidadescrecientes en diferentes posiciones de hojas fueron llevadas a cabo en dos diferentes estadosde crecimiento (antes y durante floraci6n). Los resultados han puesto de manifiesto laimportancia de las hojas superiores e intermedias en el rendimiento que decreciô con elincremento del procentage de desfoliaci6n.

7l