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The usefulness of the chlorophyll fluorescenceparameters in harvest prediction in 10 genotypes ofwinter triticale under optimal growth conditionsT. Hura a , K. Hura b & M. T. Grzesiak aa The Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Polandb Department of Plant Physiology, Faculty of Agriculture and Economics, AgriculturalUniversity, Poland

Version of record first published: 24 Nov 2009.

To cite this article: T. Hura, K. Hura & M. T. Grzesiak (2009): The usefulness of the chlorophyll fluorescence parameters inharvest prediction in 10 genotypes of winter triticale under optimal growth conditions, Plant Biosystems - An InternationalJournal Dealing with all Aspects of Plant Biology: Official Journal of the Societa Botanica Italiana, 143:3, 496-503

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Plant Biosystems

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Vol. 143, No. 3, November 2009, pp. 496–503

ISSN 1126-3504 print/ISSN 1724-5575 online © 2009 Società Botanica ItalianaDOI: 10.1080/11263500903178083

The usefulness of the chlorophyll fluorescence parameters in harvest prediction in 10 genotypes of winter triticale under optimal growth conditions

T. HURA

1

*,

K. HURA

2

, & M. T. GRZESIAK

1

1

The Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Poland and

2

Department of Plant Physiology, Faculty of Agriculture and Economics, Agricultural University, Poland

Taylor and Francis

Abstract

The aim of the experiment was to detect differences in the activity of the photosynthetic apparatus in 10 genotypes of wintertriticale. Measurements of gas exchange and chlorophyll fluorescence were performed. Among the tested genotypes, thephotosynthetic apparatus of Timbo and Piano was the most active, while the photosynthesis of both Babor and Boreas washighly reduced. Additionally, we have found significant correlations between the yield and some parameters of chlorophyllfluorescence and leaf gas exchange. Parameters of chlorophyll fluorescence are useful for estimation of the functional stateof the photosynthetic apparatus and could become selection criteria in plant breeding. Moreover, such parameters permitdefinition of the effectiveness of the utilization of chlorophyll

a

excitation energy and co-operation of the light phasereactions, with reactions occurring during the dark phase of photosynthesis.

Keywords:

Winter triticale, photosynthetic apparatus, chlorophyll fluorescence, leaf gas exchange, red fluorescence

Introduction

Nowadays, several methods enabling evaluation ofthe functioning of photosynthetic apparatus areavailable. Therefore, differences in photosyntheticactivity can be detected and become the basis, forthe selection of genotypes characterized by the mostactive/efficient photosynthetic apparatus (Baker &Rosenqvist 2004). The results obtained in this wayprovide vital information about the harvest potentialfor a genotype, and are important selection criteriaof material for cross-fertilization in plant cultivationaimed at increasing yields. It is possible to assumethat genotypes possessing an efficient photosyntheticapparatus will be better adapted to unfavorable envi-ronmental conditions (Fracheboud et al. 1999; Huraet al. 2007a; Yang et al. 2007).

At the leaf level, photosynthetic activity is estimatedon the basis of gas exchange and chlorophyll fluores-cence measurements (Maxwell & Johnson 2000;Medrano et al. 2002). These are non-destructivemethods, which allow measurements to be performed

for the same plant during the vegetative period.Measurements of gas exchange (net photosynthesis,transpiration rate, stomatal conductance) provideinformation about the intensity of photosynthesis andstomatal mechanisms of its control, whereas chloro-phyll fluorescence measurements characterize indi-vidual elements of the photosynthetic apparatus, onthe basis of parameters obtained during a singlemeasurement (Bolhar-Nordenkampf & Öquist1993). Chlorophyll fluorescence highlights the photo-chemical efficiency of photosystem II and the effec-tiveness of utilization of chlorophyll

a

excitationenergy in the photosynthesis process. It allows one toestimate the level of openness of reaction centers andthe amount of energy reaching the photosyntheticapparatus, which is released as heat (Maxwell &Johnson 2000; Lichtenthaler et al. 2004). Moreover,obtained results enable determination of the injuriesto the photosynthetic apparatus and the stage at whichphotosynthetic processes are affected (Hura et al.2007a). In addition to the above-mentioned methods,measurements of the red fluorescence emitted by

Correspondence: T. Hura, The Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Niezapominajek 21, 30-239 Kraków, Poland.Tel: +48 012 425 33 01. Fax: +48 012 425 32 20. Email: t.hura@ifr-pan.krakow.pl

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Chlorophyll fluorescence parameters in harvest prediction

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chlorophyll

a

, and registered as fluorescence spectra,were carried out. A high emission of red fluorescenceindicates disturbances in the functioning of the photo-synthetic apparatus (Schweiger et al. 1996; Huraet al. 2006, 2007a, 2007b).

The aim of the experiments was to detect differ-ences in the activity of the photosynthetic apparatusin 10 genotypes of winter triticale, grown underoptimal conditions on the basis of measurements ofgas exchange and chlorophyll fluorescence, and todetermine whether or not such measurementscould provide a correlation that explains the useful-ness of photosynthetic parameters in the estimationof harvest and growth of plants.

Materials and methods

Plant materials and plant growth conditions

The experiments were carried out on winter triticale(X

Triticosecale

, Wittmack) genotypes Babor,Boreas, Focus, Imperial, Kitaro, Lamberto, Piano,Ticino, Timbo, and Trimaran. The seeds of the 10genotypes were obtained from the State PlantBreeding Institute at the University of Hohenheimin Stuttgart, Germany. In order to eliminate theunfavorable influence of environmental factors, theactivity of the photosynthetic apparatus was studiedin an air-conditioned greenhouse chamber. Seed-lings were grown on vermiculite in a greenhouse toapproximately the first leaf stage before beingvernalized for eight weeks at 4

°

C, with a 10-h illu-mination, and with a photosynthetic photon fluxdensity (PPFD) of 200

µ

mol m

−

2

s

−

1

. After vernal-ization, seedlings were planted in pots (two seed-lings per pot to avoid shadows cast by neighboringplants) of 15 cm diameter and 18 cm height. Insteadof soil, vermiculite, being a more homogeneoussubstrate, was used. Plants were exposed in an air-conditioned greenhouse chamber to a 16-h light/8-hdark photoperiod, a 23/18

°

C (

±

2

°

C) day/nighttemperature, 50

±

5% relative air humidity (RH),and a PPFD of 350

µ

mol m

−

2

s

−

1

.There were 30 samples (2 plants

×

15 pots) for eachgenotype. Replication in an experiment was a singleplant (e.g., seven replicates means seven plants), andwithin each genotype plants were randomly assignedto measurements of physiological parameters.

For watering, 70% of FWC (field water capac-ity) was applied. The plants were fed with full-strength Hoagland’s nutrient solution once a week.The pots were weighed, and water was added inorder to maintain the original weight of the pots.All measurements were completed during flower-ing (110-day old plants), and performed on thefully developed and physiologically active flagleaves.

Leaf gas exchange

The leaf gas exchange was measured using an infra-red gas analyzer (Li-6400, Portable PhotosynthesisSystem, Lincoln, Nebraska, USA), operated withinan open system with a leaf chamber. Net photosyn-thesis, transpiration rate and stomatal conductancewere determined under a photosynthetic activeradiation (PAR) of 1000

µ

mol photons m

−

2

s

−

1

,and at a CO

2

concentration ranging from 380 up to400 ppm. The measurements for each genotypewere taken in seven replicates.

Chlorophyll fluorescence

Chlorophyll fluorescence was measured with apulse-modulated portable fluorometer FMS2(Hansatech Instruments, King’s Lynn, UK), atambient temperature in the dark (dark-adapted leaf)and then, after 10 min of irradiation at a PPFD of500

µ

mol of photons m

−

2

s

−

1

(light-adapted leaf).The photochemical quenching coefficient (qP), thenon-photochemical quenching coefficient (NPQ),and the quantum efficiency of PS II were calculatedaccording to van Kooten and Snel (1990).Additionally, chlorophyll fluorescence ratio (R

Fd

)was estimated according to Lichtenthaler et al.(1982), and electron transport rate (ETR) as definedby Stanhill (1981). The measurements for eachgenotype were taken in five replicates.

Spectrofluorescence

The fluorescence emission spectra of the red and far-red fluorescence were measured using a spectrofluo-rometer (Perkin-Elmer LS 50B, Norwalk, USA).Spectra were recorded between 650 and 800 nm,and the leaves were excited at 450 nm. The spectralslit widths were set at 10 nm (excitation and emis-sion). The measurements of the red and far-red fluo-rescence for each genotype were taken in fivereplicates.

Plants growth analysis

Growth analysis was performed during the flower-ing period and involved major shoot length, quan-tity of major shoot leaves, quantity of both lateralshoots and spikes. Ten plants were randomlytaken from among 30 of each genotype to growthmeasurements.

Data presentation

The results presented in the graphs are averages withstandard errors. Correlations between measuredparameters were tested at a probability of

p

< 0.05,

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and only statistically significant correlations arepresented in the figures.

Results

Leaf gas exchange

Two genotypes, Lamberto and Piano, revealed a highintensity of photosynthesis, whereas the genotypesBoreas and Ticino showed a photosynthetic rate thatwas more than halved (Figure 1a). Similarly, theintensity of transpiration was the highest for geno-types Lamberto and Piano (Figure 1b). A lowerintensity of transpiration (approx. four times) was

found for Imperial. It is possible to distinguish threegroups among the tested genotypes, on the basis ofstomatal conductance (Figure 1c). For the Ticino,Kitaro, Focus, and Trimaran genotypes, the stomatalconductance was the lowest in comparison to theother genotypes. Higher stomatal conductance wasobserved for the following genotypes: Lamberto,Timbo, Imperial, and Piano. The Babor and Boreasgenotypes, despite the fact that the intensity of theirphotosynthesis was low, showed the highest values ofstomatal conductance, thereby indicating the pres-ence of other factors that could affect the rate ofphotosynthesis.

Figure 1. Differences in photosynthesis rate (a), transpiration rate (b), stomatal conductance (c), intensity of red fluorescence – F

690

(d) far-red fluorescence – F

740

(e), and ratio of F

690

/F

740

(f) between genotypes of winter triticale under optimal plant growth conditions. Data are means

±

s.e. of five (fluorescence) or seven (leaf gas exchange) replicates.

Figure 1. Differences in photosynthesis rate (a), transpiration rate (b), stomatal conductance (c), intensity of red fluorescence – F690

(d) far-red fluorescence – F740 (e), and ratio of F690/F740 (f) between genotypes of winter triticale under optimal plant growth conditions.Data are means ± s.e. of five (fluorescence) or seven (leaf gas exchange) replicates.

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Chlorophyll fluorescence parameters in harvest prediction

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Spectrofluorescence

A significant increase in the emission of red fluores-cence (F

690

) was observed for Ticino (Figure 1d).Similarly, a high emission of far-red fluorescence(F

740

) was observed for the genotypes Ticino andTrimaran (Figure 1e). The lowest intensities of bothtypes of fluorescence, F

690

and F

740

, were detectedfor the genotype Babor. The ratio F

690

/F

740

is recog-nized as an indicator of the chlorophyll level inleaves, and, therefore, as an indicator of the health ofterrestrial vegetation (Stober & Lichtenthaler 1992;Gitelson et al. 1998). The higher the value of thisparameter, the lower is the level of chlorophyll. Lowvalues of F

690

/F

740

were detected for Babor andKitaro, while a high value was found for Ticino andTrimaran (Figure 1f).

Chlorophyll fluorescence

Among tested genotypes, the photosynthetic appara-tus of Timbo was the most efficient. High values of

Φ

PSII

were also found for Piano, Focus, Trimaran,and Ticino (Figure 2a). The lowest values of thisparameter were obtained for the genotypes Baborand Boreas. Values of qP for individual genotypesare presented in Figure 2b. Similarly, genotypesTimbo, Piano, Trimaran, Focus, and Ticino showedthe best utilization of light in the photosynthetic lightconversion, whereas Babor and Boreas revealed alow activity of the photosynthetic apparatus. Thephotosynthetic apparatus of Lamberto and Boreaslost most energy (NPQ) during photosynthesis,while in genotype Timbo, the photosynthetic appa-ratus utilized the excitation energy efficiently withminimal loss as heat (Figure 2c).

Figure 2. Differences in quantum efficiency of PSII –

Φ

PSII

(a), photochemical quenching coefficient – QP (b), non-photochemical quenching coefficient – NQP (c), maximal efficiency of PSII photochemistry – F

v

/F

m

(d), actual fluorescence – F

v

′

/F

m

′

(e), electron transport rate – ETR(f), and chlorophyll fluorescence ratio – R

Fd

(g) between genotypes of winter triticale under optimal plant growth conditions. Data are means

±

s.e. of five replicates.

In Figure 2d, values of F

v

/F

m

of PS II, measuredfor dark-adapted leaves, are shown. The majority ofgenotypes differed only slightly in terms of themaximum photochemical efficiency. The lowestvalues of F

v

/F

m

were obtained for Babor, Boreas,and Imperial. As shown in Figure 2e, the photosyn-thetic apparatus of Timbo exhibited the highestactivity of light quantum trapping, due to the levelof F

v

′

/F

m

′

.The highest values of ETR were found for geno-

type Timbo (Figure 2f), while the highest values ofR

Fd

were found for Piano, Lamberto, and Timbo(Figure 2g). The genotypes Babor and Boreasshowed the lowest values of both parameters.

Growth analysis

The genotype Piano exhibited the longest shoots,and Imperial the shortest ones among the studiedvarieties of winter triticale (Figure 3a). For the geno-type Focus, the highest quantities of leaves on major

shoots were observed (Figure 3b). Additionally,Piano was the genotype with the highest quantities oflateral shoots (Figure 3c), while Boreas was thegenotype with the highest amount of spikes persingle plant (Figure 3d).

Figure 3. Length of major shoot (a), quantity of leaves on major shoot (b), quantity of lateral shoots (c), and of spikes (d) in genotypes of winter triticale under optimal plant growth conditions. Data are means

±

s.e. of 10 replicates.

Relationships between parameters

A statistically significant correlation (

p

< 0.05) wasobtained between the rate of photosynthesis and R

Fd

,and the high intensity of photosynthesis in the flagleaves of genotypes Lamberto, Timbo, and Pianocorrelated with the high values of R

Fd

(Figure 4a).Among the parameters of plant growth analyzed,only the length of the major shoot significantly corre-lated with the rate of photosynthesis (Figure 4b).

Figure 4. Correlations between photosynthesis rate and chlorophyll fluorescence ratio – R

Fd

(a), and between shoot length and photosynthetic rate (b) for genotypes of winter triticale. Dashed lines represent the branches of a hyperbola and give the 95% confidence limit.

Figure 5 shows the significant correlationsbetween the yield potential of some winter triticalegenotypes, estimated according to a scale rangingfrom 1(lowest yield) to 9 (highest yield), andmeasured parameters of chlorophyll fluorescenceand photosynthesis. Information on the yield poten-tial was found in the Variety Lists (BeschreibendeSortenliste, Verlag: Landbuch Verlagsgesellschaft-mbH) and under www.bundessortenamt.de for theyears 2001–2006. Figures show values included inthe calculation of the correlations. However, somegenotypes were not included in the calculation of thecorrelations due to missing data in the Variety Lists(Imperial, Timbo and Babor). Moreover, valueswhich lie distinctly outside the confidence limitswere excluded from the calculation. A statisticallysignificant positive correlation between yield and theR

Fd

parameter was found (Figure 5a), as well as withphotosynthetic rate (Figure 5b). The highest yieldwas associated with the highest photosynthesis rateand high R

Fd

values in the genotypes Lamberto andKitaro. By contrast, a negative relationship wasfound between yield and parameters of red fluores-cence (F

690

, F

740

, F

690

/F

740

). Generally a high yieldcorrelated with reduced emissions of red (Figure 5c)and far-red fluorescence (Figure 5d) as well as witha low values of the fluorescence ratio F

690

/F

740

(Figure 5e).

Figure 5. Correlations between yield and chlorophyll fluorescence ratio – R

Fd

(a), photosynthetic rate (b), intensity of red fluorescence – F

690

(c), intensity of far-red fluorescence – F

740

(d), and the F

690

/F

740

ratio (e) for genotypes of winter triticale. Dashed lines represent the branchesof a hyperbola and give the 95% confidence limit.

Discussion

The activity of the photosynthetic apparatus is animportant physiological factor influencing the plantyield (Richards 2000). The availability of methods,enabling the estimation of the functioning of thephotosynthetic apparatus, can facilitate the selectionof genotypes with an efficient photosyntheticprocess. The application of chlorophyll fluorescencemeasurements enables one to quickly estimate thefunctional state of the photosynthetic apparatus(Fracheboud & Leipner 2003). Additionally, this is

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Figure 2. Differences in quantum efficiency of PSII – ΦPSII (a), photochemical quenching coefficient – qP (b), non-photochemical quench-ing coefficient – NPQ (c), maximal efficiency of PSII photochemistry – Fv/Fm (d), actual fluorescence – Fv′/Fm′ (e), electron transport rate– ETR (f), and chlorophyll fluorescence ratio – RFd (g) between genotypes of winter triticale under optimal plant growth conditions. Dataare means ± s.e. of five replicates.

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a quick and non-invasive method, which does notinflict any injuries to the leaf, and allows measure-ments to be taken on the same plant during thewhole vegetative period (Bolhar-Nordenkampf &Öquist 1993; Maxwell & Johnson 2000).

Only parameter R

Fd

correlated significantly withthe intensity of photosynthesis (Figure 5a). There-fore, it could be used in the selection of genotypesbased on the functioning of their photosyntheticapparatus, and replace the traditional method of gasexchange measurement, which has many limitationswhen applied (Bolhar-Nordenkampf & Öquist 1993;Fracheboud et al. 1999). Moreover, both R

Fd

andthe rate of photosynthesis correlated with yield(Figure 5a, 5b). Thus,R

Fd

seems to be a promisingtool in yield prediction. Apart from R

Fd

, statisticallysignificant correlations were obtained between yieldand red fluorescence parameters F

690

(Figure 5c),F

740

(Figure 5d) and F

690

/F

740

(Figure 5e). The lowemission of red and far-red fluorescence observedfor Lamberto and Kitaro is related to a well-func-tioning photosynthetic light conversion process.Moreover, low values of F

690

/F

740

correlated with ahigh yield in Lamberto, Kitaro, and Piano; a lowF

690

/F

740

ratio is recognized as an indicator of thegood health of plants (Stober & Lichtenthaler 1992).For other fluorescence parameters (F

v

/F

m

, ETR),which often correlate with the intensity of photosyn-thesis (Lichtenthaler et al. 2004), no such statisti-cally significant dependency was obtained (data notshown), suggesting that electrons may be used for

Figure 3. Length of major shoot (a), quantity of leaves on major shoot (b), quantity of lateral shoots (c), and of spikes (d) in genotypesof winter triticale under optimal plant growth conditions. Data are means ± s.e. of 10 replicates.

Figure 4. Correlations between photosynthesis rate and chloro-phyll fluorescence ratio – RFd (a), and between shoot length andphotosynthetic rate (b) for genotypes of winter triticale. Dashedlines represent the branches of a hyperbola and give the 95%confidence limit.

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photorespiration, which is an efficient electronacceptor in C

3

plants (Eichelmann & Laisk 1994).In the majority of the cases, the values of

measured parameters were the best for genotypesTimbo and Piano, while the photosynthetic appara-tus of Babor and Boreas displayed the lowest activ-ity. The parameters of chlorophyll fluorescence,enabling definition of the functional state of thephotosynthetic apparatus, and which could becomeselection criteria, are those which allow for estima-tion of the effectiveness of the utilization of chloro-phyll

a

excitation energy in the process of CO

2

assimilation (

ΦPSII), the level of utilization of lightenergy in the process of photosynthesis (qP) andthe co-operation of the light phase and dark phasereactions (RFd).

The above-mentioned parameters are applied toplant physiology in order to study the functioning ofthe photosynthetic apparatus, whose condition isa criterion in the selection of genotypes resistant to agiven stress factor (Smillie & Nott 1982; Havaux &Lannoye 1985; Pereira et al. 2000; O’Neill et al.2006). Genotypes possessing an efficient and well-functioning photosynthetic apparatus will yield a

Figure 5. Correlations between yield and chlorophyll fluorescence ratio – RFd (a), photosynthetic rate (b), intensity of red fluorescence –F690 (c), intensity of far-red fluorescence – F740 (d), and the F690/F740 ratio (e) for genotypes of winter triticale. Dashed lines represent thebranches of a hyperbola and give the 95% confidence limit.

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better harvest and, additionally, will be betteradapted to produce a harvest even under stressconditions, such as drought. Experiments carriedout by Hura et al. (2007a) showed that genotypesPiano, Timbo, and Lamberto, grown under waterdeficit in the leaf tissue, displayed the highest activityof the photosynthetic apparatus among the testedgenotypes, and were included in the group mostresistant to drought.

The fluorescence measurement method enablesthe detection of subtle differences in photosyntheticactivity under optimal plant growth conditions in theabsence of stress factors. Data obtained by thismethod can be applied in the culture of genotypesmost efficient in providing a good harvest, via selec-tion of genotypes with the most efficient photosyn-thetic process, for use in cross-breeding. However, itshould also be pointed out, that to maximize theusefulness of the fluorescence parameters in harvestestimation, the largest possible number of genotypesshould be tested.

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