International Journal of Agriculture and Crop Sciences. Available online at www.ijagcs.com IJACS/2013/5-1/69-79 ISSN 2227-670X ©2013 IJACS Journal

A study on source-sink relationship, photosynthetic ratio of different organs on Yield and Yield Components in bread wheat (Triticum aestivum L.) Omid alizadeh1*, karim farsinejad2, siavash korani1, Arash Azarpanah2 1. Department of Agriculture. Firooz abad branch, Islamic Azad University, Firooz Abad, Iran 2. Department of Agriculture Arsanjan branch, Islamic Azad University, Arsanjan, Iran Corresponding author email : [email protected] ABSTRACT: Wheat is an important crop whose research in this aspect is highly noticeable related to food quality. In order to determine, effect of yield components position on wheat and the effect of each part of these components on increasing seed yield, A farm experiment was conducted at Agriculture Research station of Firoz Abad ,Fars, in Iran during autumn 2008-2009 (located at 52°, 15´N & 52°, 40S) and 1876 m altitude to evaluate source-sink relationship, photosynthetic ratio of different organs on Yield and Yield Components in bread wheat (Triticum aestivum L). the Experiment was done to split plot and randomized complete blocks (RCB) in three replications and consisted of 20 treatments. In addition, main plots were consisted of four wheat cultivars (V1: PISHTAZ, V2: SHIRZ, V3:DARAB2 and V4: NIKNEJAD) and sub plots included five phonotypical manipulation treatment (P1: Control, P2: Awns cutting, P3: flag cutting, P4: Cutting of the leaves which is below the flag leaf and P5: Spike covering), respectively. The results demonstrate the maximum number of spike and number grain per spike and 1000- kernel weight were regarding to DARAB2 and NIKNEJAD cultivars, respectively. At finally this fact cause dry matter and seed yield were increased. There was significant difference between mainpluting treatment and control. Conclusively, Darab 2 and Niknejad cultivars are the best cultivars for achieve to high yield. Results of analysis of variance (ANOVA) showed that was excelsior than others in all traits. In this study result indicate awn cutting, flag leaf and spike covering cause1000-kernel weight, grain yield, biological yield and harvest index were decreased. The ratio of different organs on Yield and Yield Components in bread wheat cultivars was illustrated that maximum 1000- kernel weight and seed yield relating to spike photosynthetic which covering spike minimum 1000-kernel was obtained Minimum ratio in this trait was relating to cutting of the leaves which is below the flag leaf treatment. In present study, evaluation cultivars sink limitation was emphasized that none of cultivars sink limitation, but all of them were source limitation. Key words: Wheat (Triticum aestivum L.), Source-Sink Relationship, grain yield, Yield Components INTRODUCTION Bread wheat (Triticum aestivum L.) is an important crop worldwide and is grown on about 200 Million ha in a range of environments, with an annual production of more than 600 million metric tons. Global wheat production must continue to increase 2% annually until 2020 to meet future demands of imposed population and prosperity growth (Singh et al., 2007). About 35% of the human population consumes wheat as food, covering 29% of caloric intake. Wheat shares largest cereal market due to its global production at more than 651.4 million metric Tones per annum (FAO, 2012). Fars Province is the largest wheat producer in Iran (Emam et al., 2007). It plays a vital role in the national economy to decrease the gap between food production and food import in developing countries (Alam et al., 2008). The wheat grain yield mainly depends on the formation, translocation, partitioning and accumulation of assimilates during grain filling period. Also, photosynthetic activity of source (leaves) and storage ability of the sink (grains) after anthesis are the main factors limiting wheat grain yield (Emam and Seghatoleslami, 2005). One of the most important subjects in plant physiology is source and sinks. The fact that source or sink can limit the

Intl J Agri Crop Sci. Vol., 5 (1), 69-79, 201 yield is a challenging subject to plant physiologists (Taiz and Zeiger, 2002). Dry matter production in wheat is highly related to sink-source relationships under different environments (Alam et al., 2008; Shekoofa and Emam, 2008). Manipulation of the source-sink ratio in wheat by artificial reduction in grain number per spike (Borras et al., 2004). Zhenlin et al. (1998) reported that removing of all leaves declined partially the grain number of wheat 3 to 6%. In a study with 20 cultivars and lines of wheat Alam et al. (2008) asserted that number of grain per spike decreased significantly by removal of all leaves after anthesis. Singh and Singh (2002) showed that source restriction reduced 30 to 40% yield of wheat cultivars. Cruz-Aguado et al. (1999) concluded that final grain weight limited by the ability of the source to provide assimilation during grain filling period. In contrast, Borras et al. (2004) reported that under most conditions grain growth in wheat was more sink-limited. Ahmadi et al. (2009) suggested that the relative limitation of yield by source or sink is influenced by several factors and varies in different environments. The importance of source-sink relationship in the formation of yield and its components has been studied by Herzog (1982), Lafitte and Travis (1984) and Ashraf et al. (1994). In rice, the upper leaves are the main source of assimilates for grain filling (Yoshida,. 1981). Large sink size is a prerequisite for high yield and high harvest index (Ashraf et al. 1994). Efficient transport of assimilates from leaves and stems to developing spikelets is required for better grain filling and high yield. The capacity to transport assimilates from source to sink could limit grain filling (Ashraf et al. 1994). Relations between the number of large vascular bundles and yield traits such as grain yield, number of filled grain and grain weight have been reported in wheat, oat and rice (Peterson et al. 1982; Ashraf et al. 1994; Li et al. 1999).Potential yield in cereals is limited by the capacities of both the sink (Slafer and Savin, 1994) and the assimilatory source (Duggan et al., 2000). Limited resource availability will mainly result in resource restrictions by reducing current photosynthesis, and less by sink limitations. Therefore, the amount of mobile reserves in the vegetative parts will determine the yield gap (Karam et al.,2009).The carbohydrates that are needed for grain growth are provided from two sources (1) during GF via leaves and spike (Tambussi et al., 2007; Maydup et al., 2010) and (2) excess carbohydrates that are produced after and before anthesis, stored in the stem and remobilized to the grains during GF stage (Ehdaie et al., 2008). The contribution of leaves and spike photosynthesis and carbohydrate remobilization from stem affect the final grain weight. Traditionally, the flag leaf has been considered as the main photosynthetic organ in grain yield formation (Evans et al., 1972) but Ahmadi et al. (2009) and Aggarwal et al. (1990) reported that defoliation at anthesis had only small effects on grain yield of wheat, and they stated that the yield of cultivars used under those conditions was more controlled by sink than source strength.There is evidence that when a photosynthesis organ of plant is detached, the compensations in the remaining photosynthesis tissues or remobilization may occur and diminish the photo assimilate reduction (Chanishvili et al., 2005). Thus, the source limitation of grain yield in previous works (Ahmadi et al., 2009) may be because of the fact that the photosynthetic role of spike was neglected.The contribution role of ear photosynthesis in grain yield formation in wheat and barley has been reported from 10% to 76%, respectively (Bisco et al., 1985). A recent study by Maydup et al. (2010) showed that the ear photosynthesis makes a significant contribution to grain yield of wheat from 13% to 33% in control and 22% to 45% under drought stress condition. Sink strength is defined as the potential capacity of sink tissues to accumulate assimilates(Marcelis and Heuvelink, 2007). Experimentally, the sink strength can be derived from the Growth curve under conditions ensuring abundant source supply, either by removing competing sinks or by enhancing photosynthesis. Based on several growth chamber experiments using the same wheat cultivar as in the present study, sink strength values for various organ types (blades, sheaths, internodes, spikes, root system) have been calculated by a non-linear least squares root fitting procedure (Kang et al., in press).To simulate the distribution of assimilates from the sources to the sinks, the semi-mechanistic concept of carbon allocation being determined by the relative sink strengths of competing sinks can be implemented (Heuvelink, 1996; Marcelis, 2007). However, bud break and the appearance of tillers is not straightforward: whether or not particular tillers will appear will not ‘automatically’ emerge as a result of the simulation. Here extra rules might be needed, e.g. specifying that the local assimilate production of the parent leaf has to be taken into account (Bos, 1999).To elucidate the regulatory mechanism for leaf photosynthesis under excessive photosynthetic source capacity, experimental construction of the excessive photosynthetic source capacity is important. Excising sink organs such as pods, fruits or flowers from plant materials is a way to construct excessive photosynthetic source capacity, and it has often been conducted to study the regulatory mechanism of photosynthetic source-sink balance in plants (Marcelis, 2007).Board (2004) in a study about leaf elimination on soybean observed that the decrease of LAI in 1/3 leaf removal in middle stage of grain filling was 41% and in 2/3 leaf removal was 56%. The results of 41% decrease in LAI were 92.1% decrease in light absorption and 7.6% decrease in yield loss.There is also evidence for the excessive photosynthetic source capacity causing down regulation of photosynthesis in plants under field

Intl J Agri Crop Sci. Vol., 5 (1), 69-79, 201 conditions (Smidansky et al., 2002, 2007). The objectives of this research were source-sink relationship, photosynthetic ratio of different organs on Yield and Yield Components in bread wheat (Triticum aestivum L.) in order to recognize optimum bread wheat cultivar during vegetative and generative stage of development. MATERIALS AND METHODS A farm experiment was conducted at Agriculture Research Station of Firoz Abad, Fars, in Iran during 2008-2009 growing season (located at 53°, 20´N & 28°, 38S) and 1100 m altitude to 52°, 15´N & 52°, 40S) and 1876 m altitude to evaluate source-sink relationship, photosynthetic ratio of different organs on Yield and Yield Components in bread wheat (Triticum aestivum L). The minimum and maximum cultivation temperature were 21.1 and 38.1 , respectively. The annual raining was 550 mm by average and it had a relative humidity of 36%. The studies were carried out in a split – plot, using Randomized Complete Block design with three replications. In recent study, main plots were consisted of four wheat cultivars (V1: PISHTAZ, V2: SHIRZ, V3:DARAB2 and V4: NIKNEJAD) and sub plots included five phonotypical manipulation treatment (P1: Control, P2: Awns cutting, P3: flag cutting, P4: Cutting of the leaves which is below the flag leaf and P5: Spike covering), respectively. Plots were established initially according to experimental design study. Thus each experimental plot area had a surface area of 20 , with 4 5 dimensions. Each plot was consisted of 7 plant lines and six meter length. In addition, the distance between main plots was estimated three meters, whereas the plant distance on each row was 20 cm and the rows were 25 cm far from each other. Plough, two vertical disks, leveling, furrow, mound were used regarding plot making. The soil texture was loamy silt clay as well (Tab.1). Frequent soil analysis was performed for Determination of fertilizer content. Planting was accomplished after several ploughs. Fertilizers were applied to the field according to the soil analysis. The plant density was 400 seeds .The experimental plots received similar management practices such as land preparation, weed control and etc. Measurement of traits Plants of two middle rows (in each plot 1

) were harvested at harvest time

Number of spikes per plot At the final harvest, the number of spikes in each plot was counted. Number of grain per spike After plants harvest, 100 spikes were removed from each plot and grain were counted. Finally average of them for number of grains per spike was determined. 1000 kernel weight 1000 seeds were isolated and weighted by a precision digital scale. Grain weight per gram was calculated. Grain yield After crop maturity and completion of harvest process, the seeds were separated and yield per plot was determined. Grain yield per ha was calculated. Biological Yield Plants that harvested from each plot after drying, were weighed and biological yield per ha was measured. Harvest index Harvest index was calculated using the following formula.Harvest index (%)=(Grain yield / Biological Yield)×100 Statistical analysis Analysis of variance of split plot and randomized complete blocks (RCB) was performed by SAS ver. 9.1 software. In addition, Excel software was used for charts adjustments as well. It should be pointed out for means

Intl ntl J Agri Crop Sci. Sci Vol., 5 (1), ( 69-79,, 201 comparison we applied DunCan's Multiple Range Test at 0.05 and 0.01 probability levels using SAS and MSTAT-C MSTAT so softwares. RESULTS AND DISCUSSION Number of fertile spike per In present study variance analysis demonstrates that number of fertile spike per was significant at 5% level (Tab.1). (Tab . Results indicate that highest number of fertile spike per was relating to PISHTAZ and SHIRZ cultivars with average value (605 and 615 spike per ), respectively. It should be pointed that DARAB2 and NIKNEJAD cultivars were in same statistical class (Fig.1). With consideration that cutting different organs of plants treatments was accomplish after pollination stage,, the application treatments had no effect on number of spike. Zhenlin et al. (1998) reported that removing of all leaves declined partially the the grain number of wheat 3 to 6%. In a study with 20 cultivars and lines of wheat Alam et al. (2008) asserted that number of grain per spike decreased significantly by removal of all leaves after anthesis. Table1.summary of analysis of variance(mean of squares) squares) for yield and yield componenent Harve st index (%) 5.139n s 179.27 * 35.654 61.06*

Grain yield (ton/ha)

Biologic al yield (ton/ha)

Number of grain per spike

42.59ns

1000 kernel weight( g) 22.58ns

5.01ns

d

34.649 18.02ns

Number of fertile spike per 2 m 20832.3 ns 454889.58 * 85195.57 1236.69ns

82.02*

214.17*

176.08*

160.44**

16.789 10.85*

45.364 89.08*

7.86ns

1.53ns

16.67ns

36.662 138.22* * 7.71ns

15.66ns

4081.43ns

9.735

17.649

14624.212

1 2 3 2

12.771

2.072

18.105

9.31

15.44

17.47

8.09

12.47

15.66

103.19ns

sov

f

2

replication

3

cultivars

6 4

error Phonotypical manipulation C*p error c.v

no.fertile spike per m2

Ns ,* and **: non significant, significant at the 5% and 1 % levels of probability respectively

pishtaz

shiraz

darab

niknejad

Cultivars

Figure ure1.Effect 1.Effect of cultivars on number of fertile spike

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Number of grain per spike In present study variance analysis illustrate that number of grain per spike was significant at 5% level (Tab.1). the result showed that the highest number of grain per spike was belongs to SHIRZ and DARAB2 and NIKNEJAD cultivars with average value (35.1 and 33.1 and 32.1), respectively. It should be pointed that lowest number of grain per spike belongs to PISHTAZ cultivar with average value (29.88) (Fig.2). With consideration that cutting different organs of plants treatments was accomplish after pollination stage, the application treatments had no effect on number of grain per spike. These results were in agreement with Borras et al. (2004) (2004) reported that under most conditions grain growth in wheat was more sink-limited. sink limited. Ahmadi et al. (2009) suggested that the relative limitation of yield by source or sink is influenced by several factors and varies in different environments.

Figure 2.Effect 2.Effect of cultivars on number of grain per spike

Biological yield In present study variance analysis state that biological yield was significant at 5% level (Tab.1). The results showed the maximum biological yield was belongs to DARAB2 cultivar with average value (12.70 ton/ha) otherwise results said that there was significant difference (at 5% level) between in manipulating phenotypic treatments (fig (fig.3). However, Awns cutting and flag cutting and spike covering with average value (89.87 (89.87 and 10.11 and 11.16 ton/ha), respectively were in in same statistical class. It should be pointed the maximum biological yield belongs to Cutting of the leaves which is below the flag leaf treatment with average value (9.15 ton/ha) was obtained (fig.4 4). In similar study scientists conclude that in n cereals, Biological yield (BY) Y) is dependent on Plant source ⁄ sink relationship. The top two leaves are the primary source, and the florets are primary rimary sink for photosynthesis (Ahmadi (Ahmadi et al., 2009). 2009 The importance of sourcesource-sink sink relationship in the formation of yield and its components has been studied by Herzog (1982), Lafitte and Travis (1984) and Ashraf et al. (1994). In rice, the upper leaves are the main source of assimilates for grain filling (Yoshida (Yoshida 1981). Large sink size is a prerequisite for high yield and high harvest index (Ashraf et al. 1994).

Intl ntl J Agri Crop Sci. Sci Vol., 5 (1), ( 69-79,, 201

Fig Figure3. Effect of cultivars on total dry mater

Figure4.Effect 4.Effect of phonotypical manipulation on total dry mater

Grain Yield Variance analysis demonstrates that between all cultivars was significant at 5% level (Tab.1). (Tab.1). In recent study, the maximum grain yield was belongs to DARAB2 and NIKNEJAD cultivars with average value (7.47 and 7. 7 ton/ha), respectively. Result illustrated average value (6.72 7.27 (6. 2 and 6.42 6. 2 ton/ha) was belongs to PISHTAZ and SHIRAZ cultivars.(fig.5) cultivars. .However However result indicates indicate that there was significant difference (at 5% level) between in manipulating phenotypic treatments (Tab.1)(fig.6). (Tab.1) In addition addition with consideration about means at seed Yield trait, all treatments were in separate statistical groups. Therefore each one had different ratio in seed yield. Assimilate supply is closely associated with both final grain weight and grain-filling grain percentage, and consequently with grain yield (Egli 1998; Kobata et al. 2000). The flag leaf is often regarded as the most important source of the assimilateassimilate supply to the ear, and was associated with spikelet sterility, grains with high-density, high density, 10001000-grain n weight and grain yield in wheat and rice (Hsu and Walton 1971; Herzog 1982; Ghosh et al. 1990). Richards (1996) also suggested

Intl ntl J Agri Crop Sci. Sci Vol., 5 (1), ( 69-79,, 201

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that reducing the size of the flag leaf may increase grain number and yield because of an increase in assimilates to the developing developing ear in wheat. Secondly, it is often observed that negative correlation occurs between leaf area and photosynthetic rate (Herzog 1982; Bhagsari and Brown 1986). Grain weight is determined by both source and sink (Reynolds et al. 1999). The ratio of leaf area to spikelet number represents the available source per spikelet and could be a critical physiological parameter influencing grain weight. The capacity of the conducting tissue could limitthe amount of assimilates accumulated in the grains during the filling period, especially under environmental conditions favorable for both photosynthesis and a large sink capacity (Natrova and Natr 1993). The relationship of vascular bundles to yield traits such as filled grain number, grain weight and grain yield yield per panicle was established in oat and wheat (Peterson et al. 1982; Li et al.1999).

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Fig Figure5. Effect of cultivars on grain yield

Figure 6.Effect of phonotypical manipulation on grain yield

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Intl ntl J Agri Crop Sci. Sci Vol., 5 (1), ( 69-79,, 201

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Harvest index In present study variance analysis demonstrates that between all cultivars was significant at 5% level (Tab.1). In recent study, the maximum Harvest index was belongs to DARAB2 and NIKNEJAD cultivars with average value (41.5 and 40.7 ton/ha), respectively. respectively. Result illustrated average value (37.7 and 38.8 ton/ha) was belongs to PISHTAZ and SHIRAZ cultivars. However result indicates that there was significant difference (at 5% level) between in manipulating phenotypic treatments (Tab.1). In addition with consideration consideration about means at harvest index trait, Awns cutting, flag cutting, Spike covering, cutting other leaves treatments were in statistical groups. Lafitte and Travis (1984) reported that sink to source ratios can be genetically altered for increasing harvest arvest index and grain yield. Results from this study suggest that transport tissue to source and sink ratios should also be considered in the genetic manipulation of morpho-physiological morpho physiological traits for improving crop yield potential. This suggests that more attention attention should be paid to the integration of source, sink and transport tissue with wholewhole system viewpoints, rather than only to individual source, sink or transport tissue.

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Fig Figure7. Effect of cultivars on harvest index

Figure8. Effect of phonotypical manipulation on harvest index

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Intl J Agri Crop Sci. Vol., 5 (1), 69-79, 201

Relatively ratio of different plant organs on 1000-kernel weight Relatively ratio of different plant organs on 1000-kernel weight in wheat was showed(Table.2). On the other hand relatively ratio in 1000-kernal weight was relating to photosynthesis spike and minimum relatively ratio in this trait was relating to cutting of the leaves which is below the flag leaf treatment. At least, result was obtained from (Tab.2) illustrated that with manipulating phenotypic 1000-kernel weight was reduced. This subject was showed that none of cultivars sink limitation, but all of them were source limitation. Grain weight has been a most important factor in increasing yield potential (Liu and Meng, 1994). However, grain weight potential of such cultivars was not always realized due to their lowgrain fill rate (GFR). Grain filling is quite often interrupted under unfavorable weather conditions during grain filling stage. According to source/sink theory, grain filling rate can be limited by source or sink, including sink size (grain number per hectare) and sink strength (example, enzyme activity, phloem unloading, hormone control etc.) (Farrar,1993). By using two wheat cultivars with different grain size and grain filling rate, this study aims to elucidate the possible role of photosynthate supply and utilization in limiting grain filling rate in wheat. Yasari et al (2009) reported that the comparison of different levels of leaf and flower elimination at flowering stage of the plant also showed that 33 % of flower elimination resulted in maximum 1000 seed weight. Table2. Relatively ratio of different wheat organs on 1000-kernel weight(%) pishtaz 10.8 15.9 11.6

shiraz 10.4 15.4 12.6

Darab2 11 13.2 9.1

Niknejad 11.2 14.1 10.5

15.4

15.2

13.9

14.9

control Awns cutting Flag cutting Cutting of leaves Spike covering

Relatively ratio of different plant organs on grain yield Relatively ratio of different plant organs on seed yield in wheat was showed. On the other hand relatively ratio in seed yield was relating to photosynthesis spike and minimum relatively ratio in this trait was relating to cutting of the leaves which is below the flag leaf treatment (Tab.3). In cereals, grain yield (GY) is dependent on the plant source ⁄ sink relationship. The top two leaves are the primary source,and the florets are the primary sink for photosynthesis (Hirota et al., 1990; Sicher, 1993). Slafer et al. (1994) reported that breeders have increased wheat yield potential mainly through increasing the number of grains per m2 (sink size) rather than through increasing individual grain mass. Blade and Baker (1991) also reported that large-seeded cultivars are more sensitive to assimilated supply. Proulx and Nave, (2007) decelerated under sink-limited conditions, yield is correlated with seed number but not with seed size, although seed size is generally larger than the control. Table3. Relatively ratio of different wheat organs on grain yield(%) pishtaz 10.02 11.79 7.87

shiraz 9.59 12.9 10.17

Darab2 11.1 14.2 8.61

Niknejad 10.54 13.08 8.72

15.89

17.29

16.19

17.19

control Awns cutting Flag cutting Cutting of leaves Spike covering

CONCLUSION In summary, the results suggested that the grain yield of wheat cultivars and also photosynthesis inhibition of sources at the beginning of GF is more controlled by source than sink limitation. With respect to the future requirements for the production of wheat cultivars with higher grain yield, among the different sources of assimilates, spike (ear) photosynthesis had the main role in grain filing and should be more considered in future breeding programs. Another main strategy for higher grain yield stability must be the selection of genotypes with greater amounts of carbohydrates storage in stem with higher remobilization rate to the growing grains before anthesis stage.Therefore, it is strongly suggested that for the efficient improvement of plant matter (biomass) production, well balanced improvement of source and sink would be essential. Further studies are desired for

Intl J Agri Crop Sci. Vol., 5 (1), 69-79, 201 deeper and more comprehensive understanding of the regulatory mechanism of photosynthetic source-sink balance including the regulatory mechanism for leaf photosynthesis under excessive photosynthetic source capacity. One of the ways for increasing photosynthesis is sink demand. The sink demand will be increased when there are more seeds, thus the leaves will have more photosynthesis and considering that radiation rate for photosynthesis is more in climate condition of Firoz abad/Iran, so further seed number may increase the sink demand and yield. In this research, our results indicate that relatively ratio of different plant organs on 1000-kernel weight and seed yield in wheat was showed. On the other hand relatively ratio in 1000-kernal weight and seed yield was relating to photosynthesis spike and minimum relatively ratio in this trait was relating to cutting of the leaves which is below the flag leaf treatment.There was significant difference between in manipulating phenotypic and control treatments was illustrated .Although result indicate awn cutting, flag leaf and spike covering cause1000kernel weight, seed yield, biological yield and harvest index were decreased. Also, it should be pointed that if each parts of plan organs cut off with the reasons of pests, diseases, drought stress and (etc).these factors will be considerable effect on grain yield. REFERENCE Aggarwal PK, Fischer RA, Liboon SP. 1990. Source-Sink relation and effects of post anthesis canopy defoliation in wheat at low latitudes. J Agric Sci 114:93-99. Ahmadi A, Joudi M, Janmohamadi M. 2009. Late defoliation and wheat yield: little evidence of post anthesis source limitation. 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