Effect of Source Restriction and Drought Stress during Grain Growth ...

International journal of Agronomy and Plant Production. Vol., 4 (5), 1048-1059, 2013 Available online at http:// www.ijappjournal.com ISSN 2051-1914 ©2013 VictorQuest Publications

Effect of Source Restriction and Drought Stress during Grain Growth on Grain Yield and its Components of Winter Bread Wheat Cultivars 1*

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Majid Abdoli , Mohsen Saeidi , Saeid Jalali-Honarmand , Sirus Mansourifar and Mohammad-Eghbal 2 Ghobadi 1- Young Researchers and Elite Club, Zanjan Branch, Islamic Azad University, Zanjan, Iran 2- Department of Agronomy and Plant Breeding, Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran *Corresponding Author: Majid Abdoli Abstract In order to examine the effects of source restriction and drought stress on grain yield and its components of wheat cultivars, a greenhouse experiment was carried out at department of plant breading and agronomy, campus of agricultural and natural resource, Razi university in Kermanshah state in the west of Iran, during 2010-2011. The wheat cultivars were included Bahar, Parsi, Pishtaz, Pishgam, Chamran, Zarin, Sivand and Marvdasht and DN-11. The source manipulation treatments including Control (C), Defoliation of flag leaf (T1), Defoliation of all leaves except the flag leaf (T 2), De-awning (T3) and Ear shaded (T4), were imposed at anthesis. Results showed that post anthesis water deficiency stress caused 18 and 22 percent reduction in grain yield and thousand grain weight in average respectively, but had no significant effect on of biomass. Zarin and Marvdasht cultivars was more sensitive to drought stress than the other cultivars. In all cultivars drought stress decreased Harvest Index at the similar level of defoliation treatments yield significantly but in Chamran decreasing rate was less than the other -1 cultivars. The highest grain yield was observed in de-awning treatment (1.77 g spike ) and in terms of ranking the control treatment was in the next level. In addition ear -1 shaded treatment was the lowest grain yield (1.18 g spike ). Also, highest thousand grain weight was observed in Control treatment (37.7 g) and lowest was investigated in the ear shaded treatment (27.2 g). Results showed that the effect defoliation of flag leaf, defoliation of all leaves except the flag leaf, de-awning and ear shaded treatmants on the grain yield due to decrease 9.3, 14.7, 4.4 and 32.9% in the well watered candition, also 13.4, 8.5, 5.8 and 27.1% in the drought stress candition. But on the thousand grain weight due to decrease 2.2, 3.9, 0.2 and 30.2% in the well watered candition and 7.1, 3.5, 2.3 and 25.2% in the drought stress candition. Current photosynthesis of spike had a significant role in grain filling formation more than flag leaf and other leaves. Keywords: wheat, drought stress, grain yield, source, flag leaf, ear, awn. Introduction Wheat is regarded as the most important cereal crop of the world in view of both areas under cultivation and production level (Royo et al., 2005). Drought is the most important limiting factor for crop production (Chaves et al., 2003) and increasingly severe problem in many regions of the word (Passioura, 2007). Among the stressors, Drought, salinity, cold and warm, Drought is the most yield of crops by up to 50 percent decrease (Mittler, 2006; shao et al., 2007). There is real source-sink relationship between leaves and development of grains in wheat because healthy grain formation depends upon the potential assimilation of carbon dioxide (CO2) and accumulation of photosynthates during grain filling period (Li et al., 2006). Although the lower leaves also supply assimilates to grain, but the detachment of flag leaf considerably influenced the grain yield (Khaliq et al., 2008). Thus, the flag leaf is the primary source of assimilates for grain filling and grain yield due to its short distance from the spike and it also stays green for longer time than other leaves (Briggs and Aytenfisu, 1980; Khaliq et al.,

Intl. J. Agron. Plant. Prod. Vol., 4 (5), 1048-1059, 2013

2004). Moreover, Gelang et al. (2000) reported that leaf area duration was positive associated with grain weight and grain filling duration. Awns are plays a dominant role as an important transpiration and photosynthetic organs, which act as source of assimilates for grain formation because they are the nearest plant parts to the developing grains in spikelets. The removal of awns showed a considerable effect on grain yield because these parts can significantly enhance the proportion of net photosynthesis of wheat spike resulting in greater value of grain dry matter (Khaliq et al., 2008). In addition awns play a dominant role in carbohydrate production during the grain-filling stages (Li et al., 2006). It is observed in wheat that the varieties having awns give higher yield and heavier kernel than awn less varieties (Olugbenim et al., 1976). The presence of awns affects grain yield positively, with an average increase of 10-16% (Motzo and Giunta, 2002). The studies of Khaliq et al. (2008) revealed that the detachment of both flag leaf and awns together at post emergence stage cause more reduction in grain yield as compared to removal of flag leaf and awns individually. Mahmood and Chowdhry (1997) and Khaliq et al. (2008) reported 34.5% and 18.32% decrease in grain yield respectively due to the detachment of flag leaf blade. Moreover, the removal of these organs influence the yield contributing characters like grains per spike, grain weight per spike and thousand grain weight (Mahmood and Chowdhry, 1997; Birsin, 2005; Khaliq et al., 2008). In some previous studies, Mahmood and Chowdhry (1997), Birsin (2005) and Khaliq et al. (2008) reported that flag leaf and awns play a positive role for higher grain yield, which gave a good insight regarding positive effects of these organs on grain yield in wheat. But their reports were unable to establish the source-sink relationship between these organs and grain yield components during grain filling stage. In addition, the organs directly involved in photosynthesis during grain development (flag leaf blade and awns) were not correlated with grain yield and its components. These reports did not show the effects of removal of these photosynthetic organs on the variation among grain yield components. So, the objective of this study was to establish source-sink association between grain yield along with its components and the photosynthetic organs mainly contributing towards grain development, filling and ultimately to grain yield. Additionally, this relationship was supported by correlation analysis between these photosynthetic organs and grain yield attributes and how their removal affects the variability among genotypes for grain yield attributes. Materials and Methods The present study was conducted during 2010-2011 in the field research of the Department of plant breading and agronomy, campus of Agricultural and Natural Resource, Razi university in Kermanshah state in the west of Iran (47º, 9′/E; 34º, 21′/ N), 1319 meter elevated from sea level. The research was in a field where the previous crop was a corn. The soil was a clay loam (36.1% clay, 30.7% silt) and the experiment was laid out in a split–plot factorial arranged in a randomized complete blocks design with three replications. Evaluated treatments were included that moisture regimes and different improved bread wheat cultivars (Triticum aestivum L.). Two levels of moisture regimes (includes: Irrigation in all stages of plant growth normally and post anthesis water deficiency with withholding of irrigation) as the main-plot and different improved cultivars (includes: Bahar, Parsi, Pishtaz, Pishgam, Chamran, Zarin, Sivand, Marvdasht and DN11) along the source manipulation treatments including Control (C), Defoliation of flag leaf (T1), Defoliation of all leaves except the flag leaf (T2), De-awning (T3) and Ear shaded (T4) were imposed at anthesis (GS65, Zadoks et al., 1974) as sub-plot were considered (Fig 1).

Control

Defoliation of all De-awning Ear shaded leaves except the flag leaf Fig 1. Diagrams showing the experimental set-up for the defoliation, awn removal and ear shading, all the treatments in both experiments were imposed three-five days after anthesis. Shading of the ear (upper diagram) was made with a perforated aluminum foil. 1049

Defoliation of flag leaf


These cultivars were chosen because of their contrasting grain yield productivity and the highest area under cultivation in the west of Iran. Also, occurred almost every year of post anthesis water deficit in cultivated area in these regions, was the most reason for selection of these treatments. Date of anthesis was determined from middle rows in each plot when 50% of the spikes had extruded anthers (Ehdaie et al., 2006 a). Each plot included 54 rows 20 cm apart, 4 meter long, 4 and 3 meter distances were taken between test -2 th plots and replicates, respectively. Seeds were sown at a density of 400 seeds m on 12 October. Based on soil analysis, nitrogenous fertilizer as urea (CO(NH2)2) was applied prior to planting, as topdressing at tillering stage and at flowering stage, 80 kg N/ha in each stage. In order to measuring biomass, grain yield and yield components such as: thousand grain weight and number of grains per spike, 20 plants randomly selected and measurements were performed. Harvest index was measured by dividing grain yield to biomass production. Statistical analyses were performed using EXCEL and SAS software. Mean comparisons were also performed using LSD test (p < 0.05). Mean temperature and precipitation during the crop season is presented in Table 1. Table 1. Minimum and Maximum of temperature and relative humidity also precipitation in the Kermanshah region in the west of Iran during 2010-2011 Average of temperature Average of relative humidity Monthly total of precipitation Month (°C) (%) (mm) minimum maximum minimum maximum Oct. 10.6 30.3 1 13.2 46.4 Nov. 4.5 21.9 31 22.8 66.8 Dec. -1.5 16.8 24 26.5 62.4 Jan. -2.2 9.6 50 47.1 91.0 Feb. -2.7 8.0 65 52.1 94.2 Mar. 0.6 15.4 21 28.1 82.0 Apr. 4.5 20.1 47 24.6 78.8 May. 9.5 23.6 128 33.6 87.4 Jun. 12.8 33.8 0 11.3 51.1 Jul. 17.1 38.5 0 6.6 32.1 Aug. 18.1 39.5 0 6 27.7 Sep. 13.8 34.6 0 7.8 32.0 Results Effects of water regimes on yield and its components Grain Yield The results obtained from mean comparison analysis of grain yield and its components are shown in Tables 2, 3 and 4. showed that post anthesis water deficiency stress caused 18 and 22 percent reduction in grain yield and thousand grain weight in average respectively, but had no significant effect on no of biomass. The averages of grain yield and thousand grain weight of different cultivars in controlled condition were 1.68 -1 g spike and 39.2 g respectively, while under water deficiency stress these values significantly reduced to -1 1.37 g spike and 30.5 g. In all cultivars drought stress decreased Harvest Index at the similar level of defoliation treatments yield significantly but in Chamran decreasing rate was less than the other cultivars (Tables 2 and 3). The grain -1 yield in Sivand cultivar declined drastically by source restriction from 1.84 in Control to 1.53 g spike (17.3% -1 reduction) in defoliation of flag leaf under well-watered and from 1.35 in Control to 1.14 g spike (16.3% reduction) in defoliation of flag leaf under drought stress condition. Zarin and Marvdasht cultivars was more sensitive to drought stress than the other cultivars (Tables 2 and 3). In both of the irrigation regimes in other cultivars except the Marvdasht, Zarin and Parsi cultivars there were significant differences among de-awning treatment effect on grain yield (Tables 2 and 3). -1 The highest grain yield was observed in de-awning treatment (1.77 g spike ) and in terms of ranking the control treatment was in the next level. In addition ear shaded treatment was the lowest grain yield (1.18 g -1 spike ). Also, highest thousand grain weight was observed in Control treatment (37.7 g) and lowest was investigated in the ear shaded treatment (27.2 g) (Table 2 and 3). A point to note in this connection was that de-awning treatment was due to thousand grain weight reduction, but more number of grain per spike the grain yield of its was addition rathe than control treatment. Harvest Index The harvest index can be expressed as ability of plants to allocate photosynthetic material to produce economic yield. In terms of this trait under control and post anthesis water deficiency stress, there was 1050


significant variation between cultivars. Post anthesis water deficiency stress significantly decreased harvest index in most cultivars (Table 3). In well watered condition, Pishgam cultivar had the highest (54.4%) and Parsi and Chamran cultivars the lowest (48.6 and 48.5%, respectively) harvest index. Also, in drought stress condition, Pishgam cultivar had the highest (49.4%) and Zarin and Marvdasht cultivars the lowest (41.4 and 41.3%, respectively) harvest index. Significant reduction in harvest index under post anthesis water deficiency stress showed that dehydration stress as shown in Table 3. According to results means comparision showed that the defoliation of flag leaf treatment, defoliation of all leaves except the flag leaf and de-awning treatments no significant with harvest index by control. But, harvest index decrease from 47.8% in control to 37.9% in ear shaded treatment. Maybe, the reason of harvest index decrease influence of ear shaded treatment is decrease of grain yield (Table 2 and 3). Thousand Grain Weight Maximum thousand grain weight was observed in control treatment of Sivand (47.5 g) and Pishtaz (46 g) under well-watered condition (Table 2). Also, Maximum thousand grain weight was observed in control treatment of Chamran (37.9 g) and Pishgam (36.8 g) under drought stress condition (Table 3). In all cultivar thousand grain weight decreased under drought stress compared to well-watered condition in a similar level of defoliation. However, decreasing rate of thousand grain weight in Zarin, Marvdasht and Sivand cultivars was significantly more than the other cultivars (32.2, 28.5 and 28%, respectively) under drought stress conditions. Among the source manipulation treatments under well watered condition, Ear shaded in Sivand and deawning in Marvdasht had the highest (39.6%) and lowest (0.3%) reduction of thousand grain weight, respectively (Table 2). Also, under drought stress condition, (Ear shaded in Sivand and defoliation of flag leaf in Zarin had the highest (32.6%) and lowest (2.2%) reduction of thousand grain weight, respectively (Table 3). Number of Grain per Spike It can be seen from the data in Table 2. that significant differences were found among cultivars in terms of -1 grains spike . In term of the number of grain per spike, Zarin, Pishgam and Marvdasht cultivars had the -1 -1 highest (53, 52.3 and 51.4 grain spike , respectively) and Chamran cultivar (35.9 grain spike ) had the lowest values. -1 The highest number of grain per spike was observed in de-awning treatment (48 grain spike ) and in defoliation of flag leaf treatmant and defoliation of all leaves except the flag leaf treatmant was the lowest -1 number of grain per spike (42 grain spike ) (Table 4). Effects of source restriction on yield and its components Flag leaf Results showed that the effect defoliation of flag leaf treatmant in the well watered and drought stress canditions due to decrease on the grain yield (9.3 and 13.4%, respectivity), biomass (7.9 and 11.4%, respectivity), harvest index (1.6 and 2.3%, respectivity), thousand grain weight (2.2 and 7.1%, respectivity) and number of grain per spike (7.5 and 7.2%, respectivity) (Table 4). Defoliation of flag leaf treatmant was due to increase of grain yield of the Chamran and Pishgam cultivars (4.8 and 3.7%) but decrease of the Pishtaz, Sivand and DN-11 cultivars (17.9, 17.3 and 17.3%, respectivity) under well watered condition (Table 1). Also, Chamran cultivar were the least reduction (0.1%) but in Parsi and Marvdasht cultivars had the mast reduction (25.3 and 24.1%, respectively) of grain yield under drought stress conditions. (Table 3). Defoliation of flag leaf treatmant was due to increase of thousand grain weight of the Pishgam and Marvdasht cultivars (4.2%, In both of the cultivar) but Zarin and Bahar cultivars had the mast reduction (6.8 and 6.1%, respectivity) under well watered condition (Table 2). Too, Bahar cultivar were the increase (2.6%) but in Pishgam and Parsi cultivars had the decrease (14 and 12.5%, respectively) of thousand geain weight under drought stress conditions. (Table 3). Source restriction decreased number of grain per spike significantly in Marvdasht cultivar from 56.5 in Control to 45.6 (19.2% reduction), DN-11 cultivar from 44.9 in Control to 37.8 (15.7% reduction) and Pishtaz cultivar from 38.3 in Control to 32.2 (15.9 % reduction) in defoliation of flag leaf treatment, under well watered condition (Table 2). On the other hand, Parsi and Pishgam cultivars had the least reduction (0.1 and 1.3%, respectively) but in Chamran and Bahar cultivars had the increase (6.5 and 1.5%, respectively) of number of grain per spike under defoliation and well watered conditions. (Table 2). Also, in the Marvdasht cultivar from 55.2 in Control to 44.9 (18.6% reduction) in defoliation of flag leaf treatment, under drought stress condition (Table 3). On the other hand, Pishgam cultivar were the least reduction (4.9%) but in Pishtaz, DN-11 and Chamran cultivars had the increase (2.9, 2.9 and 2.7%, respectively) of number of grain per spike under defoliation of flag leaf and drought stress conditions. (Table 3). 1051


Leaves except the flag leaf Effect defoliation of all leaves except the flag leaf treatmant on the grain yield, biomass, harvest index, thousand grain weight and number of grain per spike due to decrease 14.7, 13.7, 1.2, 3.9 and 11% respectivity in the well watered condition, also 8.5, 8.8, 0, 3.5 and 5.1% respectivity in the drought stress condition (Table 4). Defoliation of all leaves except the flag leaf treatmant was due to Chamran cultivar were the least reduction (5.5%) but in Zarin, Pishtaz and Marvdasht cultivars had the mast reduction (26.3, 19 and 18.7%, respectively) of grain yield under well watered conditions. (Table 2). In addition, Pishtaz cultivar had the increase (1.1%) and this treatmant on the Chamran cultivar was neutral, but Bahar cultivar was the mast reduction (17%) of grain yield under drought stress conditions. (Table 3). Defoliation of all leaves except the flag leaf treatmant was due to increase of thousand grain weight of the Marvdasht and Parsi cultivars (13.8 and 2.7%) and Zarin cultivar had the mast reduction (13.2%) under well watered condition (Table 2). Also, Zarin and Bahar cultivars was the increase (1.8 and 0.8%, respectivity) but in Sivand and Parsi cultivars had the decrease (7.3 and 6.6%, respectively) of thousand geain weight under drought stress conditions. (Table 3). Source restriction decreased number of grain per spike significantly in Marvdasht cultivar from 56.5 in Control to 41.8 (26% reduction) but in Chamran cultivar had the least reduction (3.9%, respectively) of number of grain per spike under defoliation of all leaves except the flag leaf and well watered conditions. (Table 2). Also, in the Bahar cultivar from 51.2 in Control to 42.5 (17.1% reduction) in defoliation of all leaves except the flag leaf treatment, under drought stress condition (Table 3). On the other hand, Marvdasht cultivar were the least reduction (2.1%) but in Pishtaz, DN-11 and Chamran cultivars had the increase (7.1, 4.4 and 3.7%, respectively) of number of grain per spike under defoliation of all leaves except the flag leaf and drought stress conditions. (Table 3). Awn Results showed that the effect de-awning treatmant on the grain yield, biomass and number of grain per spike due to increase 4.4, 6.4 and 4.8% respectivity in the well watered condition, otherwise 5.8, 6.1 and 7.8% respectivity in the drought stress condition. But harvest index and thousand grain weight were decrease, 1.8 and 0.2% respectivity in the well watered condition, also 0.7 and 2.3% respectivity in the drought stress condition (Table 4). De-awning treatmant was due to increase of grain yield of the all cultivars, in the Pishgam cultivar had the mast increase (19.6%) but Zarin and Marvdasht cultivars were the mast reduction (10.3 and 7.5%, respectively) under well watered condition (Table 2). Also, De-awning treatmant in the Sivand cultivar had the mast increase (14.9%) but Parsi and Marvdasht cultivar were the mast reduction (7.5 and 5.2%, respectively) under drought stress conditions. (Table 3). Results showed that the effect de-awning treatmant was due to increase of thousand grain weight of the Pishgam, Pishtaz, Bahar and Parsi cultivars (8, 4.4, 2.2 and 0.7%, respectively) and Chamran and Zarin cultivars had the mast reduction (8 and 6.9%, respectively) under well watered condition (Table 2). Also, Zarin, Bahar, Sivand and DN-11 cultivars was the increase (6.3, 4.3, 1.3 and 0.3%, respectivity) and Marvdasht cultivar had the decrease (9%) of thousand geain weight under drought stress conditions. (Table 3). Source restriction decreased number of grain per spike significantly in Marvdasht, Zarin and Pishtaz cultivars had the reduction (7.2, 3.8 and 0.8%, respectively) but in other cultivars had the increase of number of grain per spike under de-awning and well watered conditions. (Table 2). Also, source restriction decreased number of grain per spike significantly in Zarin cultivar from 56.3 in Control to 54.5 (3.1% reduction) but in other cultivars had the increase of number of grain per spike under de-awning and drought stress conditions. (Table 3). Ear Effect ear shaded treatment on the grain yield, biomass, harvest index, thousand grain weight and number of grain per spike due to decrease 32.9, 13.3, 22.3, 30.2 and 2.8% respectivity in the well watered condition, also 27.1, 9.5, 19, 25.2 and 2.3% respectivity in the drought stress condition (Table 4). Effect ear shaded treatmant on the grain yield of the Zarin, Sivand and Bahar cultivars had the mast reduction (43.2, 39.4 and 39.1%) and Chamran cultivar had the least reduction (8.4%) under well watered condition (Table 2). Also, Chamran cultivar were the least reduction (10.5%) and in Marvdasht, Bahar and Pishgam cultivars were the mast reduction (33.7, 31.2 and 31%, respectively) of grain yield under drought stress conditions (Table 3).

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Table 2. Effect of source restriction on yield and some related characteristics of wheat cultivars under wellwatered condition. Cultivars Bahar

Parsi

Pishtaz

Pishgam

Chamran

Zarin

Sivand

Marvdasht

DN-11

LSD

Treatments

Yp

C T1 T2 T3 T4 C T1 T2 T3 T4 C T1 T2 T3 T4 C T1 T2 T3 T4 C T1 T2 T3 T4 C T1 T2 T3 T4 C T1 T2 T3 T4 C T1 T2 T3 T4 C T1 T2 T3 T4

1.84 1.75 1.66 2.06 1.12 1.61 1.56 1.48 1.77 1.25 1.77 1.45 1.43 1.82 1.14 2.15 2.23 1.99 2.57 1.44 1.43 1.50 1.35 1.61 1.31 2.41 2.11 1.78 2.16 1.37 1.84 1.53 1.53 1.93 1.12 2.00 1.68 1.63 1.85 1.29 1.82 1.51 1.54 1.86 1.29 0.07

R (%) -5.1 -9.9 11.6 -39.1 -3.2 -8.2 9.7 -22.7 -17.9 -19.0 2.8 -35.5 3.7 -7.4 19.6 -33.0 4.8 -5.5 12.3 -8.4 -12.4 -26.3 -10.3 -43.2 -17.3 -16.9 4.8 -39.4 -15.9 -18.7 -7.5 -35.7 -17.3 -15.4 2.3 -29.1

B 3.54 3.45 3.28 4.05 2.82 3.31 3.12 2.89 3.58 3.07 3.35 2.92 2.79 3.57 2.92 3.96 4.10 3.73 4.67 3.58 2.95 3.09 2.73 3.43 3.03 4.64 4.11 3.59 4.35 3.68 3.67 3.07 3.07 3.73 3.04 3.88 3.31 3.17 3.73 3.30 3.60 3.13 3.16 3.87 3.10 0.11

R (%) -2.7 -7.5 14.2 -20.5 -5.6 -12.8 8.2 -7.1 -12.8 -16.5 6.7 -12.9 3.8 -5.6 18.1 -9.5 5.1 -7.3 16.5 2.8 -11.4 -22.7 -6.2 -20.7 -16.5 -16.4 1.6 -17.1 -14.6 -18.3 -3.9 -15.0 -13.1 -12.3 7.5 -14.1

HI 52.0 50.8 50.5 50.8 39.5 48.6 49.9 51.2 49.4 40.6 52.7 49.7 51.2 50.8 39.2 54.4 54.3 53.3 55.1 40.2 48.5 48.4 49.4 46.6 43.7 51.9 51.5 49.4 49.7 37.1 50.3 49.7 50.0 51.9 36.8 51.6 50.9 51.3 49.7 39.0 50.4 48.0 48.6 48.1 41.6 0.9

R (%) -2.4 -2.8 -2.4 -23.9 2.7 5.3 1.7 -16.5 -5.7 -2.7 -3.5 -25.6 -0.2 -2.0 1.3 -26.1 -0.3 1.9 -4.0 -10.0 -0.8 -4.8 -4.2 -28.4 -1.1 -0.5 3.2 -26.9 -1.4 -0.5 -3.8 -24.4 -4.8 -3.5 -4.7 -17.5

TGW 40.7 38.2 38.3 41.6 28.5 43.3 41.9 44.5 43.6 31.5 46.0 45.0 41.8 48.1 29.4 41.6 43.4 40.1 45.0 26.5 43.8 43.3 43.5 40.3 41.1 41.9 39.1 36.4 39.0 27.2 47.5 45.0 43.0 45.1 28.7 35.4 37.0 40.3 35.4 23.5 40.6 39.8 38.2 40.3 29.6 1.3

R (%) -6.1 -6.0 2.2 -30.1 -3.2 2.7 0.7 -27.2 -2.3 -9.3 4.4 -36.1 4.2 -3.7 8.0 -36.3 -1.3 -0.7 -8.0 -6.2 -6.7 -13.2 -6.9 -35.2 -5.4 -9.5 -5.0 -39.6 4.2 13.8 -0.3 -33.7 -1.9 -5.8 -0.6 -27.0

NGS 45.2 45.9 43.4 49.4 39.3 37.2 37.2 33.2 41.0 39.5 38.3 32.2 34.3 38.0 38.8 52.0 51.3 49.7 57.2 54.3 32.6 34.7 31.3 40.0 32.3 57.5 54.2 48.8 55.3 50.3 38.8 33.8 35.8 42.8 38.9 56.5 45.6 41.8 52.4 54.7 44.9 37.8 40.3 46.2 43.5 1.6

R (%) 1.5 -4.0 9.1 -13.1 -0.1 -10.7 10.3 6.2 -15.9 -10.6 -0.8 1.3 -1.3 -4.5 9.9 4.3 6.5 -3.9 22.7 -0.9 -5.7 -15.1 -3.8 -12.4 -12.8 -7.7 10.3 0.2 -19.2 -26.0 -7.2 -3.1 -15.7 -10.2 2.9 -3.2

Y: Grain Yield (g/spike), B: Biomass (g/plant), HI: Harvest Index (%), TGW: Thousand Grain Weight (g), NGS: Number of Grain per Spike. R: Reduction (%) due to Treatments in comparison with control.  Control (C), Defoliation of flag leaf (T1), Defoliation of all leaves except the flag leaf (T2), de-awning (T3) and Ear shaded (T4). All the treatments in both experiments were imposed three-five days after anthesis. Shading of the ear (upper diagram) was made with a perforated aluminum foil.

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Table 3. Effect of source restriction on yield and some related characteristics of wheat cultivars under drought stress condition. Cultivars Bahar

Parsi

Pishtaz

Pishgam

Chamran

Zarin

Sivand

Marvdasht

DN-11

LSD

Treatments

Ys

C T1 T2 T3 T4 C T1 T2 T3 T4 C T1 T2 T3 T4 C T1 T2 T3 T4 C T1 T2 T3 T4 C T1 T2 T3 T4 C T1 T2 T3 T4 C T1 T2 T3 T4 C T1 T2 T3 T4

1.57 1.40 1.30 1.72 1.08 1.45 1.08 1.26 1.34 1.02 1.37 1.24 1.38 1.54 1.02 1.95 1.59 1.67 2.03 1.34 1.34 1.34 1.34 1.52 1.20 1.61 1.44 1.44 1.66 1.13 1.35 1.14 1.20 1.56 0.98 1.40 1.06 1.33 1.32 0.93 1.49 1.44 1.47 1.63 1.17 0.07

R (%) -10.5 -17.0 10.0 -31.2 -25.3 -12.9 -7.5 -29.5 -9.8 1.1 12.4 -25.7 -18.4 -14.5 4.4 -31.0 -0.1 0.0 13.3 -10.5 -11.1 -10.7 2.6 -30.0 -16.1 -11.8 14.9 -27.3 -24.1 -4.9 -5.2 -33.7 -3.5 -1.9 8.8 -21.8

B 3.54 3.15 2.89 3.81 2.94 3.33 2.64 2.93 3.15 2.89 3.01 2.86 3.01 3.26 2.81 3.92 3.38 3.52 4.18 3.38 2.94 2.93 2.84 3.34 2.98 3.87 3.48 3.30 3.87 3.42 3.02 2.65 2.76 3.46 2.95 3.37 2.56 3.14 3.40 2.86 3.26 3.17 3.23 3.63 3.14 0.11

R (%) -10.9 -18.5 7.7 -17.1 -20.6 -11.9 -5.3 -13.0 -5.0 0.0 8.4 -6.6 -13.9 -10.4 6.5 -13.8 -0.3 -3.4 13.3 1.1 -10.1 -14.7 0.0 -11.6 -12.1 -8.4 14.8 -2.2 -24.2 -6.9 0.8 -15.1 -2.8 -1.1 11.2 -3.6

HI 44.0 44.6 45.0 45.0 36.8 43.4 40.7 42.8 42.3 35.3 45.2 42.8 45.9 47.2 36.4 49.4 46.9 47.4 48.4 39.7 45.5 45.8 47.1 45.6 40.4 41.4 41.0 43.7 42.7 32.8 44.5 42.5 42.6 44.8 33.4 41.3 41.4 41.9 38.8 32.3 45.6 45.4 45.4 44.6 37.1 0.9

R (%) 1.4 2.3 2.3 -16.4 -6.0 -1.2 -2.4 -18.6 -5.3 1.6 4.4 -19.5 -5.0 -3.9 -1.9 -19.6 0.6 3.4 0.1 -11.3 -0.9 5.5 3.1 -20.7 -4.4 -4.3 0.6 -24.9 0.3 1.6 -5.9 -21.8 -0.5 -0.5 -2.2 -18.8

TGW 30.5 31.3 30.8 31.8 24.4 35.5 31.1 33.1 32.5 25.6 35.8 31.6 34.5 34.5 24.8 36.8 31.6 35.8 35.0 26.0 37.9 37.0 36.6 35.8 33.5 28.4 27.8 29.0 30.2 21.6 34.2 31.3 31.7 34.7 23.1 25.3 23.6 24.3 23.0 17.9 33.1 31.1 31.3 33.2 25.9 1.3

R (%) 2.6 0.8 4.3 -20.1 -12.5 -6.6 -8.4 -27.8 -11.6 -3.6 -3.5 -30.8 -14.0 -2.5 -4.8 -29.2 -2.5 -3.5 -5.6 -11.6 -2.2 1.8 6.3 -24.0 -8.5 -7.3 1.3 -32.6 -7.0 -3.9 -9.0 -29.1 -5.9 -5.5 0.3 -21.9

NGS 51.2 45.3 42.5 54.0 44.3 40.5 34.8 38.0 41.3 39.8 38.1 39.2 40.8 44.9 41.4 52.6 50.1 46.8 57.8 51.4 35.4 36.4 36.7 42.7 36.3 56.3 51.3 49.6 54.5 52.0 39.6 36.0 37.4 44.8 42.6 55.2 44.9 54.0 57.1 51.5 45.0 46.3 47.0 49.0 45.1 1.6

R (%) -11.6 -17.1 5.5 -13.6 -14.1 -6.2 1.8 -1.8 2.9 7.1 17.9 8.7 -4.9 -11.0 9.8 -2.3 2.7 3.7 20.6 2.4 -8.8 -11.8 -3.1 -7.6 -8.9 -5.6 13.2 7.8 -18.6 -2.1 3.4 -6.7 2.9 4.4 9.0 0.3

Y: Grain Yield (g/spike), B: Biomass (g/plant), HI: Harvest Index (%), TGW: Thousand Grain Weight (g), NGS: Number of Grain per Spike. R: Reduction (%) due to Treatments in comparison with control.  Control (C), Defoliation of flag leaf (T1), Defoliation of all leaves except the flag leaf (T2), de-awning (T3) and Ear shaded (T4). All the treatments in both experiments were imposed three-five days after anthesis. Shading of the ear (upper diagram) was made with a perforated aluminum foil.

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Table 4. Mean modification (%) for grain yield and some related characteristics under different photosynthesis inhibiting (Defoliation of flag leaf, Defoliation of all leaves except the flag leaf, de-awning and ear shaded) and drought stress treatment. Conditions Well-watered

Drought stress

Well-watered Drought stress

Treatments

Y

C T1 T2 T3 T4 C T1 T2 T3 T4

1.88 1.70 1.60 1.96 1.26 1.50 1.30 1.38 1.59 1.10 1.68 1.37

R1 (%)

R2 (%)

-9.3 -14.7 4.4 -32.9 -13.4 -8.5 5.8 -27.1

-19.8 -23.4 -13.9 -18.7 -12.8 -18.1

B 3.66 3.37 3.16 3.89 3.17 3.36 2.98 3.07 3.57 3.04 3.45 3.20

R1 (%)

R2 (%)

-7.9 -13.7 6.4 -13.3 -11.4 -8.8 6.1 -9.5

-8.0 -11.5 -2.8 -8.2 -4.0 -7.1

HI 51.1 50.3 50.5 50.2 39.7 44.5 43.4 44.6 44.4 36.0 48.4 42.6

R1 (%)

R2 (%)

-1.6 -1.2 -1.8 -22.3 -2.3 0.4 -0.2 -19.0

-13.1 -13.7 -11.7 -11.6 -9.4 -12.0

TGW 42.3 41.4 40.7 42.0 29.6 33.1 30.7 31.9 32.3 24.8 39.2 30.5

R1 (%)

R2 (%)

-2.2 -3.9 -0.7 -30.2 -7.1 -3.5 -2.3 -25.1

-21.9 -25.8 -21.6 -23.1 -16.3 -22.1

NGS 44.8 41.4 39.8 46.9 43.5 46.0 42.7 43.6 49.6 44.9 43.3 45.4

R1 (%)

R2 (%)

-7.5 -11.0 4.8 -2.8 -7.2 -5.1 7.8 -2.3

2.7 3.1 9.5 5.6 3.3 4.8

Y: Grain Yield (g/spike), B: Biomass (g/plant), HI: Harvest Index (%), TGW: thousand Grain Weight (g), NGS: Number of Grain per Spike. R (1) and (2): Reduction (%) due to Treatment in comparison with control and application of water stress after anthesis in comparison with water control, respectively.  Control (C), Defoliation of flag leaf (T1), Defoliation of all leaves except the flag leaf (T2), de-awning (T3) and Ear shaded (T4). All the treatments in both experiments were imposed three-five days after anthesis. Shading of the ear (upper diagram) was made with a perforated aluminum foil. In each column, compared to the 5% level of LSD method is used. Results showed that the effect ear shaded treatmant on the thousand grain weight of the Sivand, Pishgam and Pishtaz cultivars had the mast reduction (39.6, 36.3 and 36.1%, respectively) and Chamran cultivar had the least reduction (6.2%) under well watered condition (Table 2). Also, Sivand and Pishtaz cultivars had the mast reduction (32.6 and 30.8%, respectivity) and Chamran cultivar had the least reduction (11.6%) of thousand geain weight under drought stress condition (Table 3). Source restriction decreased number of grain per spike significantly in Bahar cultivar from 45.2 in Control to 39.3 (13.1% reduction) and Zarin cultivar from 57.5 in Control to 50.3 (12.4% reduction) in ear shaded treatment, under well watered condition (Table 2). On the other hand, Chamran cultivar had the least reduction (0.9%) but in Parsi, Pishgam, Pishtaz and Sivand cultivars had the increase (6.2, 4.3, 1.3 and 0.2%, respectively) of number of grain per spike under ear shaded and well watered conditions (Table 2). Also, in the Bahar cultivar from 51.2 in Control to 44.3 (13.6% reduction) in ear shaded treatment, under drought stress condition (Table 3). On the other hand, Parsi cultivar were the least reduction (1.8%) but in Pishtaz, Sivand, Chamran and DN-11 cultivars had the increase (8.7, 7.8, 2.7 and 0.3%, respectively) of number of grain per spike under ear shaded and drought stress conditions (Table 3).

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Discussion The results showed that post anthesis water deficiency stress reduced grain yield and thousand grain weight in average respectively. The findings from (Saeidi et al., 2010), when they imposed water deficit at different stages of grain growth separately, showed that significant reduction in grain yield production in these conditions may be result of reducing the production of photo-assimilates (source limitation) for grain filling, reducing the sink power to absorb of photo-assimilates and reducing the grain filling duration. They also reported that probably, the early processes of grain growth (cell division and formation of sink size) are less affected by water deficiency. Therefore, grain weight and grain yield reduction under post anthesis water deficiency may be more reflects the lack of photoassimilates supply for grain filling. These findings also are in agreement with Yang and Zang (2006), Ahmadi et al. (2009), Abdoli and Saeidi (2012) and Radpour et al. (2013). The results showed that post anthesis water deficiency stress reduction in harvest index. is largely due to more significant reduction in grain yield production than biomass production (Shafazadeh et al., 2004). In Richards et al. (2002) demonstrated that for this reason that harvest index is indicators of the genetic potential of plant to produce economic yield, high harvest index under control treatment can be accompanied with high grain yield under water stress. The findings of the current study are consistent with those of Reynolds et al. (2009) who found wheat cultivars that have high biological yield and harvest index, most likely have high grain yield under stress and control conditions. A point to note in this connection was that Chamran cultivar under post anthesis water deficiency with lowest reduction (6.2%) in harvest index had also the lowest reduction in grain yield production and Zarin and Marvdasht with highest reduction (20.2 and 20.1%, respectively) in harvest index had also the higher reduction in grain yield production. The findings of the current study are consistent with those of Moral et al. (2002) who found that also negative correlation between these two traits. They concluded that this negative correlation is related to compensation effect of yield components on each other. In this situation, by increasing the -1 number grain spike , plants cannot fill all of them and then this is caused shrinking of grains and finally caused weight loss of the grains. This phenomenon is more serious under water deficiency stress. Flag leaf area is the main source of photosynthetic activity contributing towards grain filling as the lower leaves are quickly lacking of chlorophyll contents. Therefore, grain yield is associated with photosynthetic ability of different plant parts. Gelang et al. (2000) suggested that the contribution of the flag leaf blade to grain filling increased over time. Also, Foulkes et al. (2007) reported that longer green flag leaf area duration was related with the ability to maintain yield under drought. However, in drought conditions optimum flag leaf area is important for optimum photosynthetic activity as more area causes more transpiration losses (Ali et al., 2009). In the past scientists also remained interested in determining the role of flag leaf blade towards grain yield and its attributes. Mahmood and Chowdhry (1997) reported 34.5%, while Khaliq et al. (2008) revealed 18.32% decrease in yield due to the detachment of flag leaf blade. Defoliation of leaves treatmant decreased number of grain per spike significantly. Also, Mohamadtaheri et al. (2010) in their study on the wheat cultivars, reported that effect leaves removed on the number of grain per spike was significantly and decreas its. Similarly, Birsin (2005) and Alam et al. (2008) reported that flag leaf removal also resulted in significant reduction in the yield attributes like number of grains per spike, grain weight per spike and thousand grain weight. In this study observated that source limitation treatment, decrease of thousand grain weight due to reduction ot grain yield. The reason for this maybe is remove of source that lack of filling grain and consequent the product grains was weak. Photosynthesis taking place in ear produces assimilates, which are directly deposited in the grains at grain filling stage. The awns increase the capability of the plant to capture more radiations light energy and facilitate more CO2 fixation in the plants (Li et al., 2006). Awns amplify the surface area of the spike up to 36-59%, which in turn increases amount of intercepted light on an average of 4% (Motzo and Giunta, 2002). The physiological role of awns has long been of interest because under certain climatic conditions awned varieties out yield awnless ones (Olugbenim et al., 1976). Transpiration and photosynthesis are considered to be promising functions of awns in contributing to grain yield and their removal resulted in considerable decline in grain yield and its components. Removal of awns 10 days after anthesis might cause a reduction of 3-9% in grain yield however; grain yield declined 8.32% by removal of awns at head emergence stage. The removal of awns also affected number of grains per spike, grain weight per spike and thousand grain weight. These studies are in accordance with the reports of Birsin (2005) and Khaliq et al. (2008). 1056


Furthermore, removal of both photosynthetic machineries (flag leaf + awns) exerted the most declining effects on grain yield and its related parameters especially thousand grain weight as compared to detachment of awns and flag leaf individually. The report of Khaliq et al. (2008) also demonstrated more decrease in grain yield, when both of the photosynthetic organs were removed at post emergence stage. No decrease of some traits under effect source limitation such as grain yield and thousand grain weight in som cultivars, perchance throught increase of photosynthesis of other plant parts (Chanishvili et al., 2005; Mohamadtaheri et al., 2010) and/or cause a increase remobilization of store mater in stem to grain supply is being developed (Noshin et al., 1996; Janmohammadi et al., 2010). The importence of spikes association of grains filling agreement with many researcher, becuase of suitable light conditions for photosynthesis, more period of photosynthesis after anthesis than leavs and their promimity to grains (Evans et al., 1972; Biscoe et al., 1975). Ear shaded treatment in under study cultivars was cause a reduction of grain yield, biomass, harvest index, thousand grain weight and number of grain per spike. In this case, Maydupa et al. (2010) and Saeidi et al. (2011) reported that role of photosynthesis spike on the grain yield is more than photosynthesis of leavs. Agreement with the results of this study, Abbad et al. (2004) reported that in the well watered conditions, the total spike photosynthesis is more than flag leaf and at drought stress the spike photosynthesis was less reduction than fleg leaf. Wich is becuase of more relative water contant (RWC) and better osmotic adjusment (Tambussi et al., 2005). Conclusion In summary, the results suggested that the grain yield of wheat cultivars under water deficiency and also photosynthesis inhibition of sources at the beginning of grain filling is more controlled by source than sink limitation. The results showed that, post anthesis water deficiency significantly decreased grain yield (18.1%) and grain weight (22.1%). Removing of photosynthetic sources of assimilates reduced grain yield via grain weight reduction. In this case the role of spike photosynthesis in grain filling (27.7%) was higher than the flag leaf (4.7%) and lower leaves (3.7%). Awns had the lowest role in grain filling (1.5%). ear photosynthesis might represent to maintain grain yield under source limitations (e.g. defoliation, water stress conditions), and could have an important role even without stress, because an incipient ‘source’ limitation might be emerging in modern cultivars of bread wheat. Acknowledgments The authors would like to thank their colleagues in Agricultural and Natural Resource, University of Razi, Kermanshah. Also, the authors are extremely thankful to Mr. Hadi Hashemzade, Mr. Abolfazl Abdolahzade and Mrs. Mariam Rezaei for excellent technical assistance in some phases of this study. References Abbad H, Samir ELJ, Jordi B, Jose-Luis A, 2004. Comparison of flag leaf and ear photosynthesis with biomass and grain yield of durum wheat under various water conditions and genotypes. J Agro. 24: 19-28. Abdoli M, Saeidi M, 2012. Using different indices for selection of resistant wheat cultivars to post anthesis water deficit in the west of Iran. Ann Bio Res. 3(3): 1322-1333. Ahmadi A, Joudi M, Janmohammdi M, 2009 b. Late defoliation and wheat yield: little evidence of post anthesis source limitation. Field Crops Res. 113: 90-93. Ahmadi A, Joudi M, Tavakoli A, Ranjbar M, 2009 a. investiation of yield and its related morphological traits responses in wheat genotypes under drought stress and irrigation conditions. J Sci Tech Agri Nat Res. 12(46): 155-166. Alam MS, Rahman AHM, Nesa MN, Khan SK, Siddquie NA, 2008. Effect of source and/or sink restriction on the grain yield in wheat. Euro J App Sci Res. 4(3): 258-261. Ali MA, Niaz S, Abbas A, Sabirv W, Jabran K, 2009. Genetic diversity and assessment of drought tolerant sorghum landraces based on morph-physiological traits at different growth stages. Plant Omi J. 2: 214-227 Birsin MA, 2005. Effects of Removal of Some Photosynthetic Structures on Some Yield Components in Wheat. Tar Bili Der. 11: 364-367.

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