PIIOTOSY]TTHETIC EFFICIENCY AS BASISFOR YIETD FORMATIOI{ I]\{ SU]\FLOWER HYBRtrT)

1\S.H.43 AI{D ITS PAREI\TAL LII\ES

MATERIAL AND METHODS

The object of this study was the sunflowerhybrid NS-H-43 and its parental components,OCMS-22 (female component) and RHA-SNRF(male component). Experiments were condu.c-ted under field conditions. The parental linesand the hybrid were sown in separate plots,in three rows, 12 plants in each row, in thearrangement 70 X 30 cm.

The efficiency of solar energy conversion atplant level (photosynthetic efficiency) was esti-mated from the ratio :

chemical energy of dry matter(calorimetric readings) x 100Energy of photosynthetically active

radiation (PAR)

Total photosynthetically active radiationreaching the plot during the period of studywas estimated from the meteorological data onthe duration of insolation in the period May-October 19Bb in the locality of Rimski Sanëevi(Mihaj lovié and Acs, 19Bb ; Katié andD j a k o v i é, 1978). NAR and LAI were as-sessed (eupina and Jocié, 1972) at thestages of budding, flowering and \Max matu-rity. Photosynthetic efficiency (%) for thewhole plant was assessed at the same stages.A1so, we assessed photosynthetic efficiency (%)in individual nlant Darts.

RESULTS AND DISCUSSION

1. LAI and NAR in the parental linesOCMS-zz and RHA-SNRF and the hybridNS-H-43

Table 1 shows the values of LAI inOCMS-22, RHA-SNRF and NS-H.4'3. In thelines, the LAI kept increasing frorn the stageof budding till flowering and then it wentdown to the stage of wax maturity. The valuesof NAR displayed a similar trend. In the hy-brid, the LAI decreased from the stage of bud-ding to wax maturity while the NAR increa-

T. CUPINA, M. PLESNICAR and D. SKORICInstitute of Field and Vegetable CropsNovi Sad, Yugoslavia

INTRODUCTION

The sunfiower is characteristic for its highphotosynthetic potential (EI - S h a rka wy etal., 1965), high growth rate (Warren Wil-s o n, 1967), capacity to take up water fromdeep soil layers and to transport it throughthe vascular tissue (B 1 a c k, 1979), and theheliotropic movement of leaves and head(Shell et âL, 1974; Lang and Begg,1e7e).

Differences among sunflower genotypes inphotosynthetic efficiency may result in consi-derable differences in the yields of biomassand seed per plant and per unit area (L 1 o y dand Canvin, 1977).

Photosynthetic efficiency in the course ofplant development, translocation, use, and ac-cumulation of assimilates and energy accumu-lated in chemical bonds of certain organiccompounds (photosynthates), especially at thetime of seed setting and filling, are essentialfor correct understanding of the formation ofthe yields of biomass and seed per plant andper unit area. Therefore, the physioiogical fac-tors may limit the formation of sunfloweryietds (McWilliam et al., J974). Biornassand seed yields per sunflower. plant are theresult of a cornplex interaction involving anumber of physiological processes (actions ofsolar energy, mineral nutrition, respiration,growth, etc.). It ensues that the productivityof sunflower plants cannot be increased bychanging individual factors affecting it (A n -dreeva et aI., 1P80).

Our objective was to study the importanceof the efficiency of solar energy conversion atthe level of the plant (photosynthetic effici-ency) and dry matter redistribution and ac-cumulation in the course of plant growth anddevelopment as well as the importance'of theseparameters for the formation of seed and bio-mass yields in the sirnflower hybrid NS-H-43and 'ifs parental lines OCMS-2| and RHA-SNRF.

33

iable iLeaf area index (LAl) (m2rm2) and net assimilationrate (NAR) (slm2/dl in the course of developmentanrt yieltl (kg/m2) of sunflower hybriil NS-H-43 antl

: its parental lines OCMS-zz antl RHA-SNRF

Distribution of ilry matter among plantdifferent stages of plant development forhybriil NS-H-43 and its parental lines

antl RHA-SNRF (g per plant)

Table 2

organs atsunflowerocMs-22

Genotype L"q.I/NARu'ro- | *g*

werinel m?lu-- | rlry

Bud-ding YiEId

ocMS-22 1.83

3.99

2.30 I

8.02 |

-l3.20

|

7.72 |

-l5.43

|9.35 |

1.51

L.97

1.49

3.60

6.85

8.30

RHA-SNRF4.23

2.25

4.28

LeafStemHead

24.4

IJ.I

0.?

38.2

22.9

14.5

0.6

38.0

29.5

19.9

0.4

50.2

39.3

55.6

20.6

115.5

32.0

50.0

16.0

143.0

ocMS-22

Total :

22

36

42

100

tl1

43

40

100

25

29

46

100

JO

46

t7

t00NS-H-43 4.720

sed from budding to flowering and decreasedfrom flowering to wax maturity. It might beconcluded that the hybrid's LAI is larger thannecessary at the early stages of development.It is also evident that the hybrid surpasses thelines in the NAR at flowering and wax matu-,rity, which is most probably related with thevalues of LAD from flowering to wax ma-turity.

Rawson and Constable (1980) founda correlation between the LAI at floweringand seed mass per plant (r: 0.86) in sunflo-wer hybrids Suncross 51, Suncross 52, Hysun30, Sunfola 68/2 and the variety VNIIMK.R a w s o n et al. (1980), found similar rela-tionships. Some authors, e.9., Terbea et al.(1976) did not find correlations between theNAR and seed yield in parental lines and hy-brid progenies. Merrien et a1., 1984 (unpu-blished results) found significant correlations

"between the LAD and biomass yield per plantand the LAD and seed yield per plant, r: 0.93

.and r : 0.94, respectively. M a ri j an a c (198b)obtained r: 0.22 and r: 0.8rb for the seedyieid vs. LAD, respectively. According to J o -c i é (1974), there exists the highly significantcorrelation of r: 0.93 between the level ofseed yield and LAI at flowering and the re-gression equation is Y: 1,641 + 0J114 LA (leafarea), indicating that each ml of leaf area

: brings the average increase in seed yield of0.14 kg/ha. The partial coefficients of cor-relation also indicate a large dependence ofseed yield on the LAI at flowering. Thereexists a significant correlation between theLAI at milk maturity and seed yield per hec-taqe, the regression equation being linear,Y: 1,575 + 0.21 LA (leaf area).

Ràwson et al. (1984) found a correlationbetween the nurrr.-ber of fiùled seeds on the.head and the LAI at flowering (R2: 0.175).

2. Distribution and accumulationof dry matter in different parts

of sunflower plant

Table 2 shows the dynamics of dry matterdistribution in plant parts of the male lineRHA-SNRF, the female line OCMS-22 and the

34

RHA-SNRF

Total :

44

42

rt00

31.5

79.3

75.8

186.6

NS-H.43

Total :

60

39

I

100

92.8

,t23.r

45]9

26r.8

I

145.0

170.0

265.6

581.0

hybrid NS-H-43. The results are given for dif-ferent stages of development, expressed ingrarns per plant.

The hybrid NS-H-43 had a significantlyhigher accumulation of dry matter per plantthan the parental lines OCMS-22 and RHA-SNRF, at all stages of development. AlsoRHA-SNRF had a higher dry matter accumu-lation per plant than OCMS-2,2. The parentalIines and the hybrid differed in the distributionof dry matter per plant parts at differed sta-ges of development. The accumulation of drymatter in the leaves and stem of OCMS-22lasted for 70 days; after that period, the ac-cumulation in the stem dropped rapidly. WithRHA-SNRF and NS-H-43, the accu,mulation ofdry matter in the leaves and stem lasted lon-ger and a slowness at the end was quite low.The accumulation of dry matter in the head,i.e. seeds, increased gradually. The parentallines differed from the hybrid in the'dynamicsof dry matter accumulation in the head, i.e.the accumulation was considerably more in-tensive to the hybrid. It led us to assume thatthe redistribution of dry matter in favour ofthe head is one of the factors which bringabout increased yields of seed and biomass perplant in hybrids as compared with their par-rents. Cupina and Plesniéar (1986) ob-tained similar results for the hybrid NS-H-27-RM and its parental lines.

There are numerous literature data dealingwith the distribution of dry matter, i.e. assmi-lates, per sunflower plant parts at differentstages of growth and development.

T e r b e a et a'1. (1976) found that hybridsare superior to their parental iines regardingthe accumulation of dry matter per plant andper unit area. They also found that the accu-

LeafStemHead

Leaf.Stem

Head

Genotype

mulation is most intensive in the leaves at thebeginning of the season. After the stage ofbudding, the major portion of dry rn-atter ac-cumulates in the stem and later on in theseeds. The same authors point out that thegrowth of the vegetative plant parts is moreintensi.ve at early stages which is related withsunflower hybrids.

Blanchet et al. (1'982) applied the met-hod of carbon balance which makes use ofcoefficients of glucose equivalents. They foundthese equivai.ents to be 1.2' 2.5 and 3 for car-bohydrales, nitrogen cornpounds, and lipids,respectively, and drew the following conclu-sions on the redistribution of assimilates insunflower plant :

- The stem and leaves reach maximumcontent of assimilates at the stage of flowering.After that, the 'content starts decreasingslowly, probably on account of assirnilatetransler into the seed. The rate of redistribu-tion, especially from the leaves, dependson genotype and environmental factors, waterregime in first Place.

- At the stage of flowerin$, the head hasa small growth compare with the total plantgrowth.

- Seed filling results from photosynthesisas well as frorn transformation or redistribu-tion of assimilates.

Chemical energy of dry matter production(in %) in individual plant parts of the parentaliinesIHA-SNRF (male) and OCMS-22 (female)and their hybrid NS-H-43 at different stagesof growth and developments is presented inFigùre 1. The percent of accumulated chemicalenérgy in the leaf dropped sharply from thestage of budding to wax maturity. The percent

in the stem grew to the stage of flowering andthen went down to the end of the vegetativeseason. The percent of chemical energy in thehead, i.e. seÀds, increased gradually frorn thestage of budding to the end of physiologicalmaturity.

3. Efficiency of solar energy conversionat plant level (efficiency of photosynthesis)

The indicator of the efficiency of solarenergy conversion at plant level (efficiency ofphotoiynthesis) used represents the ratio bet-ween the chemical energy of dry matter inwhole plant or plant part (estimated ex,peri-mentally by means of a calorimeter) and theenergy

-of photosyntheticallv active radiation(PAÈi. Its value is expressed in percent (K a -m e l, 1959).

It should be pointed out that the parentaliines were inferior to the hybrid in relation tothe photosynthetic efficiency per plant (Figu-res 1 and 3), at all stages of plant develop-ment. AIso, RHA-SNRF had a higher photo-synthetic efficiency per plant than OCMS-22'fn tne parental linôs as weII as the hybrid, thephotosynthetic activity per ,plant kept increas-ing frôm the stage of budding to wax matu-riiv. tt is in agreèment with our previous fin-dings (C u p i n a et a1., 19S4). The hybrid hada significantly higher photosynthetic efficiencythan the parental lines. Its values at the stages

of flowering and wax maturity were 1.22 and2.230f s, respectiveiy. It appears that the photo-syntnêtic ètticiu.tèy in the hybrid is relatedwith the expression of heterosis, bringing, in-creases in diy matter and seed yield per plant'

*-* LEAFo< STEMv-v HEAD+

z.IF tôn

Iu=ÉnEÂO

uzJ

!2

=LU-

TIME ( DAVS ) AFTER EMEROENCE

Fig. 1 - Distribution of accumulated chemical energy among leaf, stem and head for sunflowert vuiiO NS-H-4I ilà itr parental lines in different stages of plant development

35

1,n

2.23

a

1.0 nIa

BUDDING

FLOWERINO

WAX MATUR]ÏY

oà-;c)zLlJ

C)I'LLLLLI

çJt-

= r.,

z.V,ot-o-o-

SNRFFig. 2 - Photosynthetic

its parental lines at

NS- H -43 ocMS -22efficiency per plant for sunflower hybrid NS-H-43 andthe stage of budding, flowering and wax maturity

1.

I(J2'u(J&urg

s2]-^uu.Fzanoo

BUDDINO nFLOWERINC I

w{x MAruRfiY a

SNRF N5-H-/.3 0CMS-22 SNRF NS-H-43 0Cl'1S-22 SNRF

Fig' 3 - Photosynthetic efficiency per plant organ for sunflower hybridand its parental lines at different stages of plant development

NS-H-13 0CMS-22

NS-H-43

Similar conclusions were drawn by Terbeaet aL (1976).

Figure 3 shows the efficiency of P-AR con-,r"rrio.r in plant parts of the parental lines andthe hybrid- at dilferent stages of growth anddevelôpment. The photosynthetic efficiency. ofthe leâf increased from the stage of buddingto flowering and then decreased tiltr wax ma-turity. In the hybrid, however; the photosyn-thetiô efficiency of the leaf kept increasing tothe stage of wax maturity. The photosyntheticefficiency of the stem followed a similar pat-tern. Regarding the photosynthetic efficiencyof the hèad, it kept increasing from the stageof budding to wax maturity in the parentallines and In" nytrtia alike. The hybrid scoreda significant inèrease in the effi'ciency at thestagé of wax maturity on account of an in-creàsed portion of seeds in the head whichutilized the energy of che'mical 'bonds to formcarbohydrates and oil, dominant componets in

.seed at that time.The sunflorver requires a certain amount of

solar energy for its development' A reductionof light iniènsity by 400/s lowered the yield-ofseed by 640,,6. A reduction of light intensity for27 days at the stage of seed filling lowered'the yiô1d of seed by 3601 (R o b i n s o n, 1978).The sunflower reaches photosynthetic satu-ration at relatively high light intensities (R o -binson, 1978).

Many authors demonstrated a high positivecorrelaiion between the rates of absorption oflight energy and synthesis of phytomass persunflower plant and ,per unit area (Stern,1962 ; Shibles and Weber, 1,96i6 ; Fas-heun and Dennett, 1982). According toRawson et aI. (1984), there exists a 'cor-relation between the total solar radiation ab-sorbed and the synthesis of biomass per plant.Phytomass (g/pl) is linearly dependent on thetotal light energy absorbed from sowing toflowering (in MJ). The determination coeffi-cient is R2: 0.86, indicating the absorbedenergy as the main determinant in the phyto-mass production per sunflower plant. It is quitereasonable since the uptake of CO2 dependsdirectly on the absorption of light energY. Ho-wever, seed yield per plant and solar radiationabsorption are not invariably correlated be-cause other factors too may affect the ratioof carbon distribution to seeds and the otherplant parts. Solar radiation creates conditionsfor yield forming, but the development of seedbuds and their subsequent performances aregoverned also by other ecological factors (e.g.temperature). According to Rawson et al.(1984) there are factors which are as irnportantfor seed forming in sunflower as CO2 assimi-lation. They also found a partial correlationbetween the radiation absorbed from floweringto maturity and the number of filled seeds,estimating the determination coefficient bet-ween the two parameters at R2: 0.90.

CONCLUSIONS

The hybrid NS-H-43 had a significantly hi-gher accumulation of dry matter per plant atà11 rtugut of growth and developmen-t than itsparentËl line*s, OCMS-22 (female }ine) andnHa-SNnn'(ma1e line)

The content of leaf dry matter in OCMS-22increased. to the stage of flowering, remainingat that level almost up to the stage of vv'ax

maturitv. The drv matter content in the stemalso increased tili llowering but after that itdropped sharply. RHA-SNRF had a. slightlymoi" itttuttsivè

-increase of dry matter in theleaf and stem. NS-H-43 had the highest con-tent of drv matter in the head.

The perËent of ,chemical energ54 in the leafwent dàwn rapidly frorn the stage of Uqa{r.tgto wax maturify, especially in RHA-SNRF' Thepercent of chemical energy in the stem increa-ied to the stage of flowering, decreasing to-wards wax mâîurity. The percent of chemicalenergy in the head, i.e. seedS,.kept increasingup to the stage of wax maturitY.

The photosynthetic efficiency per plant was

significàntlv iower in the parental lines thanin" the rrybiia at all stages of development' Itappears ittut tttu photoJynthetic efficiency oftÀô nynria is related with the expression ofheterosis per plant, ultimately bringing in-

. creases in its biomass and seed vield'The photosyntheti'c efficiency per individual

plant pàrts varied in dependenôe on the stageôf growth'and deve-lopmen-t as well as amongthe*parental lines and the hybrid.

. REFERENCES

Andreeva T. F., Strogonova L' E', Prota-sova N. N.' Murasov I. N', StaPenkoS. J., Maevskaja S. N., NiqiPorovièA. A.; 1980, Fotosintez i rost rastenij kukuruzi ipod'sotneëniko, Fiziologija rastenij, tom 27, vip'r, r05-112.

B 1 a c k C. R., 19?9, The relationship between trans-piration 'rate, water potential and resi'stance to

. uater mooement in sunflouer (Helianthus an'annuus L.), J. ExP. Bot., 30, 235-247-

Blanchet R., Merrien A., Gelf i N.,- RoI-'l i e r M., 1982, Euolution d,es biosynthèses aucours ilu' cgcle de iléueloppement du tournesolet répartition d'es assimilates selon les organeset leurs cÔnstituants, Proc. 10th Intern. Sun-flower Conference, Surfers Paradise (Austra-lia), 29-33.

Cupina T., Jocié 8., 1972, Relationship bettaeen- photosynthetic actiuitg and mineral nutritionin sunflouser (in Serbo-Croat), Savr. Poljopr',20, 5-12.

e upina T., Plesièar M., TomaÉevié M., 1984,Energg accumulation and utilisation i'n sun-tlouser lines, }Je],a, Nr. 7, 55-59.

Cupina T., Plesniéar M., 1986, PhAsi'ologicalproperti,es of sources and si'nk Jor some NShgbrids of sunflouser (in Serbo-Croat), ProcXX Seminar of agronomists, Kupari, pp' 445-4itl-

E1-Sharkawy M, 4., Hesketh J. D., Mura--m o t o H., 1965, Leaf photosynthetic rates anil

37

other grolDth chatacteristics among 26 speciesof GNsApium. Crop. Sci., 5, 173-1?5.

Fasheun A. and Dennett M. D., 1982, Inter-ception of rad,iati,on arld grouth efficiencg inlield beans (Vicia laba). Agric. Meteorol., 26.

J o c i é B., 1974, Relations between lea! area, N. P. Kand, Ca contents in plant material s,nd Uielil,depeniling on rnineral nutrition in corn, sun-llotoer and, sugarbeet (in Serbo-Croat), Ph. D.Thesi;s, Faculty of Agricu'lture, Novi Sad.

K a m e I M. S., 1959, A physiologàcal stuilg of shading'and density effects on the grousth anil the effi-ciency oî solar energq conuersion in somefield, crops, Medelingen van de landbouwhoge-school te Wageningen, Nederland, 59, (5), 1-104.

Katié P., D jakovié P., 1978, Erperimentalmeteo-rologg and climatologg (in Serbo-Croat), Facultyof Agriculture, Novi Sad, 1-204.

Lang A. R. G., B.egg J. 8., 1979, Mooements ofHelianthus annulrs Leaaes and, heods, J. Appl.EcoI.. 16. 299-305.

Lloyd N. H., Canvin D. 1., 1977, Photosgnthesisand, photorespiration in sunflotaer selections,Can. J. Bot., 55, 3006-3012.

Marijana.c D., 1985, StudA of the efJects of plan-ting methoil and stand densitg on biological,phgsi,ological ancl agronomical properties of ge-neti.cally d,iuergent sunflouer hgbrid,s (in Ser-bo-Croat), Ph. D. Thesis, Faculty of Agri-culture, Novi-Sad.

McWilliam J. R., English S. D., McDou-g â I l, 19?4, The effect of leaf age and position onphotosynthesis and, the supplA of assimilatesd,uring deuelopment in sunflotner, Proc. 6thrlntern. Sunflower Conference, Bucharest, 123-t79.

Mihai'l ovié D., Acs F., 1985, Calculation oT daitqanlounts ol global railiati,on in Noui Sad (inHungarian), Idojaras, 89, 257-26L.

Rawson H. M., Constable G. A., 1980, Carbonprod,uction of sunflower cultiuars in fielitr andcontrolled enuironments. I, photosynthesis andtranspiration of leaves, stem and heads, Aust.J. Plant. Physiol., ?, 555-573.

Rawson H. M., Constable G.4., Howe G. N.,l9B0,Carbon production of sunfloroer cultioarsin field and controlled, enoironments. II. Leafgrowth, Aust. J. Plant Physiol., ?, b?S-586.

Rawson H. M., Dunstone R. L., Long M. J.,B e g g J. E., 1984, Canopg cleuelopment, Iightinterception and seeil proiluction i,n sunflotoeras influenced by temperature anil radiation,Ar-rst. J. P[ant Physiol ., tt, 255-265.

R o b i n s o rn R. G., 1978. Prod.uction anëI culture, In :

Sunfùower science and technology (Ed. by Car-ter J. F.), pp. B9-143, American Soc. Agronomy,Crop Sci. Soc. America, Soil Sci Soc. of Ame-t'ica, Inc. Publishers, Madison, Wisconsin.

Shell G. S., Lang A. R. G., Sale p. J. M.. 19?4.Quantitatitse tneasuîes of IedI orientation anilheliotropic response in sunflouser, bean, pepperand cucumber. Agric. Meteorrol., 14.

Shihles R. M., Weber C. R., t966, lntercepti,onof solar radiation anal drA m,atteî producti.onbg uari,ous bean planting paterns, Crop Sci.,6, 55-59.

S t e r n \,V. R., 1962, Light rnedsure'tnents in pastures.Herb. Abstr. 32.

Terbe,a Maria, Vrânceanu A. V., Voines-cu Alexandrina, Hurduc N.. 19?6. pho-tosqnthetic prod"uctiuitg in relation to heterosiseffects in sunflouer, proc. ?th Intern SunflowerConference, Krasnodar, U.S.S.R., 360-369.

\{arren Wilson J., 1.967, High net assi,milationrafus of sunflouer plants in an arid climate,Ann, Bot. (London), 80, ?4b-?b1.

3B

EFFICIENCE DE LA PHOTOSYNTHÈSËCOMME RASE DE LA PRODUCTION

DE L'HYBRIDE DE TOURNESOL NS.H-43ET DE SES LIGNÉES PARENTALES

Résumé

L'efficience de la conversion de l'énergie 'solaireau niveau de la plante a été étudiée, ainsi que l'ac-cumulation de la matière sèche le long de la crois-sance et du développement et l'importance de cesdeux paramètres pour la formation du rendementen graines et de la biomasse.

L'hybride a montré une âccumulation de matièresèche par plante significativement plus élevée pen-dant tous les stades de végétation, par rapport àses lignées parentales : OCMS-22 (mère) et RHA-SNRF(père). La teneur en matière sèche des feuilles s'estaccrue jusqulà Ia floraison, restant presque au mêmeniveau jusqulà la maturité physiologique ; en re-vanche, celle de la tige a augmenté jusqu'à la florai-son, mais elle a diminué rapidement après cettephase. L'hybride a eu une teneur bien plus éIevéeen matière sèche dans le capitule, par rapport auxlignées.

Le taux d'énergie chimique des feuilles s'est ré-duit r.apidement à partir de la période de formationdu bouton floral jusqu'à la maturité physiologique,tandis que celui de la tige a commencé sa diminu.tion lors de la ifloraison. Le taux d'énergie chimiquedu capitule et des graines ont eu une croissancecontinuelle, jusqu'à la maturité physiologique.

L'efficience de la photosynthèse par plante a étéde même significativement plus importante chezl'hybride qu'aux lignées parentales, pendant tous lesstades de développement, suggérant I'influence duhétérosis même à cet égard. L'efficience de la pho-tosynthèse par parties individuelles de la plante aenregistré une variation importante en dépendant dustade de croissance et de développement, ainsi quedu génotype.

EFICACIA DE LA FOTOSINTESISCOMO BASE DE LA PRODUCCIÔN

DEL HIBRIDO DE GIRASOL NS-H-43Y DE SUS LINEAS PAREN?ALES

Res{tmen

Se estudiô la eficacia de la conversiôn de la ener-gia solar al nivel de las plantas y la redistribuci6n yacumulaci6n de la sustancia seca durante el creci-mento y el desarrollo, asi como la importancia deestos parametros para formar la producciôn de se-millas y biomasa.

EI hfbrido tuvo una acumulaciôn de sustancia secapor planta significativamente mâs elevada en todoslos estadios de vegetaci6n comparando con sus lineasparentales : OCMS-22 (madre), RHA-SNRF (pa'dre).El contenido de sustancia seca de las hojas creci6hasta la fase de florecimiento, queldando casi al mis-mo nivel hasta la madurez fisiolôgica, en cambio é1del tallo creciô hasta el florecimiento, pero bajô râ-pidamente tras esta fase. El hibrido, frente a laslineas, tuvo un contenido mucho mâs elevado desustancia seca en el capitulo.

El procentaje de la energia quimica de las hojasbaj6 rapidamente empezando del periodo de la for-maciôn del botôn floral hasta la madurez fisiolôgicamientras que é1 del tallo empezô su decrecimiento enla fase del florecimiento. El porcentaje de la ener-giâ quimica del capitulo y semillas tuvo un creci-miento continuo hasta la madurez fisiol6gica..

La eficacia de la fotosintesis por planta fue tam-bién significantemente mejor en el hibrido frente alas lineas parentales, en todos los estadios de desar-rollo, s'ufiriendo la influencia del heterosis tambiéndesde este punto de vista. La eficacia de la fotosin-tesis por partes individuaies de planta tuvo una va-riaciôn notable en funciôn del estadio .de crecimientoy desarrollo y del genotipo.