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Journal of Stress Physiology & Biochemistry, Vol. 11 No. 1 2015, pp. 29-38 ISSN 1997-0838 Original Text Copyright © 2015 by Allahverdiyev
ORIGINAL ARTICLE
Effect of drought stress on some physiological traits of durum (Triticum durum Desf.) and bread (Triticum aestivum L.) wheat genotypes
Tofig Allahverdiyev
Research Institute of Crop Husbandry, Ministry of Agriculture, Pirshagi, Sovkhoz-2, Baku AZ1098, Azerbaijan
*E-Mail: tofig 1968@mail.ru
Received December 18, 2014
Drought is a wide-spread problem seriously influencing wheat production and quality worldwide. We aimed to study adaptive changes in physiological parameters of 6 durum and 7 bread wheat genotypes under drought stress. Water stress caused reduction of leaf gas exchange parameters-photosynthesis rate, stomatal conductance, intercellular CO2 concentration, transpiration rate as well leaf area, dry mass, relative water content, and chlorophyll content. Photosynthesis rate, chlorophyll content were higher in flag leaf of bread wheat genotypes. Photosynthesis rate positively correlated with leaf area, dry mass and relative water content.
Key words: leaf area, photosynthesis rate, stomatal conductance, wheat
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Effect of drought stress on some physiological traits...
Wheat (Trticum durum Desf. and Triticum aestivum L.) is one of the major crop plants in the human nutrition, is a sources of energy from carbohydrates and proteins. Drought is the most important limiting factor for wheat production in arid and semiarid regions of the world. Under field conditions important stages of wheat development (stem elongation, heading-flowering, grain filling) is accompanied with increase of water deficit in the soil. Wheat is one of the widely cultivated crops in Azerbaijan, where drought is the main limiting factor for its production (Aliyev, 2001).
Moderate to severe water stress drastically affects various morpho-physiological traits in wheat, such as dry matter production, assimilating area, relative water content, and chlorophyll content. Photosynthesis, which is the most significant process influence crop production, is also inhibited by drought stress. The effects can be direct, as the decreased CO2 availability caused by diffusion limitations through the stomata and the mesophyll (Flexas et a/., 2004) or the alterations of photochemical reactions (Tang et a/., 2002) and photosynthetic metabolism (Lawlor and Cornic, 2002). Under field conditions, stomatal regulation of transpiration was shown as a primary event in plant response to water deficit leading to decrease of CO2 uptake by the leaves (Chaves, 1991, 2002; Cornic and Massacci, 1996). Strengthening of drought during growth period lead to inhibition of photosynthesis through the reactive oxygen species damage to photosynthetic pigments, photosystems I and II, and electron transport proteins. Reduced plant
size, leaf area, and leaf area index are a major mechanism for moderating water use and reducing injury under drought stress (Mitchell et a/., 1998). It is revealed that varieties, with higher leaf turgor and RWC under stress conditions are more droughts tolerant and gave higher yield than others (Akram, 2011; Khakwani et al., 2011). The present study aims to determine soil water deficit effects on leaf gas exchange, area, dry biomass, chlorophyll and relative water content of six durum wheat (Triticum durum Desf.) and seven bread wheat (Triticum aestivum L.) genotypes and to determine the relationships between some physiological traits, to identify morpho-physiological traits as indicators of drought tolerance in wheat genotypes.
MATERIALS AND METHODS
Field experiment was carried out in the research area of Plant Physiology and Biotechnology Department of Research Institute of Crop Husbandry located in Absheron peninsula, Baku, during the 2012-2013 growing season. Six durum wheat genotypes (Garagylchyg 2, Vugar, Shiraslan 23, Barakatli-95, Alinja- 84, Tartar), seven bread wheat genotypes (Gobustan, Giymatli-2/17, Gyrmyzygul 1, Azamatli-95, Tale-38, 12nd FAWWON№97, 4th FEFWSN№50) were used for this study. Genotypes grown in 10 m2 plots (1mx10m) with three replications both under irrigated and rain-fed conditions Given in manuscript physiological parameters were measured during grain formation stage. Photosynthesis rate (Pn), stomatal conductance (gs), intercellular CO2
concentration (Q), transpiration rate (Tr) measured
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with a Portable Photosynthesis System LI-6400 XT (LI-COR Biosciences, Lincoln, NE, USA). Photosynthetic pigments content determined following the method of Lichtenthaler (1987) with little modifications. About 0,1 g fresh leaves were ground in 96% ethanol for the extraction of chlorophyll and carotenoids. Absorbance of the supernatant was recorded at 664, 648 and 470 nm
spectrophotometrically (Genesys 20, Thermo Scientific, USA). Pigments content calculated by the following formulas:
Chl a=(13,36^A664-5,19^A648)^25/DW;
Chl b=(27,43^ A64s-8,12^A664)^25/DW Chl(a+b)=(5,24^A664+22,24^ A^^/DW Car(x+c)=(4,785^A470+3,657^A664-12,76^A64e)^25/DW Leaf area (LA, sm2) measured with an area meter (AAC-400, Hayashi Denkon Co., LTD, Japan). Leaf dry mass was then determined, and Leaf Specific Mass (LSM, leaf dry mass per unit leaf area, mg mm2) was calculated. The relative water content (RWC) determined gravimetrically. Immediately after cutting at the base of lamina, leaves were preserved within plastic bags and in time transferred to the laboratory. Fresh mass (FW) was determined after removal and turgid mass (TW) was measured after saturating leaves in distilled water for 24 h at room temperature. After saturating, leaves were carefully blotted dried with tissue paper. Dry mass (DW) was measured after oven drying the leaves samples at 105°C for 24 h. RWC was calculated by using the following formula: RWC(%)= (FW-DW)/(TW-DW)x100. Soil moisture content was determined in the 0-20, 20-40, 40-60 cm
depths and expressed as percentage of the field moisture capacity, was about 60% in irrigated plots and 30% in non-irrigated plots. Correlations among parameters, standard errors of means were calculated by SPSS software.
RESULTS
Water deficit significantly affected leaf gas exchange parameters (Table 1). The high Pn observed in flag leaf of durum wheat genotypes Alinja 84 and Tartar, bread wheat genotypes Gyrmyzy gul1, Azamatli 95, Tale 38, 4thFEFWSN№50. Deep
reduction of Pn detected in genotypes Gobustan (61%), Gyrmyzy gul1(57%), Azamatli 95 (62%), Tale 38 (58%), 12ndFAWWON№97 (45%). The high gs
defined in flag leaf of genotypes Barakatli 95, Gobustan, Gyrmyzy gul 1, Azamatli 95, Tale 38, 4thFEFWSN№50. The gs decreased in the range of 45-85%, slight reduction was detected in flag leaf of genotype Vugar. The Q reduction was 7-27% and 845% among genotypes of durum and bread wheat genotypes, respectively. Strong reduction of Ci was determined in flag leaf of genotypes Gobustan, Gyrmyzy gul 1, and 12ndFAWWON№97. The durum wheat genotypes Shiraslan 23, Barakatli 95, Alinja 84 and all bread wheat genotypes were characterized with high Tr under irrigated condition. Water stress caused strong reduction of Tr in genotypes Shiraslan 23 (60%), Barakatli 95 (58%). Gobustan (74%), Gyrmyzy gul 1 (71%), Azamatli 95 (61%),
12ndFAWWO N №97(70%), slight reduction in
genotypes Garagylchyg 2, Vugar and Tartar. The mesophyll conductance (gm) was calculated as the ratio of Pn to Ci, water use efficiency (WUE) was
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Effect of drought stress on some physiological traits...
calculated as the ratio of Pn to Tr. As well the gm decreased under the influence of soil drought, deeper decrease was observed in genotypes Azamatli 95 and Tale 38. The WUE increased under the influence of drought in most genotypes that can be explained to a more reduction in Tr than in Pn. Table 2 shows correlation between gas exchange parameters under irrigated and rain-fed conditions. Positive and significant correlations were found between Pn and gs, Pn and Tr, Pn and gm. There was more strong correlation between the Pn and gm, than the Pn and gs, indicating the dominance of gm in reducing of Pn. The Q negatively correlated with Pn, gm, and WUE, but positively correlated with gs.
Higher RWC was observed in genotypes Barakatli -95, Alinja- 84, Tartar, Gyrmyzygul- 1, Tale -38, 12ndFAWWON№97, and 4thFEFWSN№50 (Fig.1). The genotypes Tartar, Gyrmyzygul-1, Tale- 38, 12ndFAWWON№97, and 4thFEFWSN №50 were late heading, and their flag leaves contained relatively more water. Under the influence of water stress significant reduction of RWC was found in genotypes Garagylchyg- 2 (12%), and Giymatli - 2/17(14%). The difference in RWC of irrigated and rain-fed plants was almost imperceptible in genotype Tartar.
A significant decrease in the LA observed in all genotypes (Fig.2). More profound reduction of LA observed in genotypes Shiraslan 23 (44%) and Vugar (35%), Gyrmyzy gul 1(37%), Tale 38 (34%), Garagylchyg 2 (31%), Barakatli 95 (31%),
4thFEFWSN№50 (30%), 12ndFAWWON№97 (28%), Tartar (28%). Deep reduction can be explained to the fact that the formation of the flag leaf of late- heading
wheat genotypes (Vugar, Shiraslan 23, Tartar, Gyrmyzy gul 1, Tale 38, 4thFEFWSN№50, and 12ndFAWWON№97) occurs during a severe water shortage.
Water scarcity causes a decrease in DM of flag leaf (Fig.3). As in the case of LA, strong reduction of DM observed in all genotypes of durum wheat, with exception of Alinja 84, in bread wheat genotypes Gyrmyzy gul 1, Tale 38, 12ndFAWWON№97,
4thFEFWSN№50. A more profound reduction of flag leaf dry mass was detected in genotypes Vugar (44%) and Tale 38 (43%).
It was revealed an increase of LSM under water stress in most wheat genotypes (Figure 4). Such an increase in the LSM is probably adaptive response to drought and is due to the relatively greater reduction in LA than the DM. A reduction of LSM was observed in genotypes Vugar and Tale 38, because of the greater reduction in DM. A higher LSM observed in genotypes Barakatli 95, Gyrmyzy gul 1, Giymatli 2/17, Tale 38, 4thFEFWSN№50, Garagylchyg 2.
In general, water stress caused significant declines in photosynthetic pigments content, in the ratio of Chl(a+b)/Car(x+c) and increase in the ratio of Chla/b (Table 3). Photosynthetic pigments were higher among genotypes of bread wheat than durum wheat. Higher decrease of chlorophyll content was observed in genotypes Vugar (35%), Shiraslan 23 (29%), Barakatli 95 (21%), Gobustan (29%), Giymatli 2/17 (31%), Azamatli 95 (37%), and 4thFEFWSN№50 (28%). A slight decrease was observed in genotypes Gyrmyzy gul 1, 12ndFAWWON№97, Alinja 84, Tale 38 and Garagylchyg 2. An increase in Chl a/b could be
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due to more reduction in Chlb than Chla by water deficit.
Table 4 shows correlations between studied physiological parameters. The Pn was positively and significantly correlated with RWC, LA, and DW. The relationship between Pn and Chl content was positive,
but non-significant. The RWC positively and significantly correlated with Chl content. Correlation between LA and DW was positive and significant, correlation between LA and Chl was positive but nonsignificant.
Table 1. Effect of water stress on gas exchange parameters (Data are mean of 8 measurements)
Wheat genotypes Experime nt condition Pn, pmolCO2m-2 s-1 gs, molH2O m-2 s-1 Ci, pmolCO2 mol-1 Tr,mmolH2 Om-2 s-1 gm, molCO2 m2 s-1 WUE, pmolCO2 mmol-1H2O
Garagylchyg 2 Irr. 10,5 0,218 299 3,82 0,035 2,74
R-f 7,26 0,119 279 2,95 0,026 2,46
Vugar Irr. 13,4 0,164 285 4,4 0,047 3,04
R-f 9,17 0,134 257 3,52 0,035 2,61
Shiraslan 23 Irr. 14,9 0,289 282 6,71 0,052 2,22
R-f 9,56 0,100 213 2,68 0,044 3,56
Barakatli 95 Irr. 15,1 0,469 331 7,91 0,045 1,91
R-f 9,32 0,133 260 3,31 0,035 2,81
Alinja 84 Irr. 17,9 0,303 259 6,34 0,069 2,82
R-f 11,1 0,112 207 3,82 0,053 2,90
Tartar Irr. 18,5 0,235 232 5,35 0,079 3,46
R-f 13,8 0,134 170 4,27 0,081 3,23
Gobustan Irr. 18,6 0,481 287 9,2 0,064 2,02
R-f 7,32 0,07 159 2,4 0,046 3,05
Giymatli-2/17 Irr. 18,7 0,311 252 7,88 0,074 2,37
R-f 11,9 0,107 179 3,97 0,066 2,99
Gyrmyzy gul 1 Irr. 20,1 0,476 291 8,48 0,069 2,37
R-f 8,6 0,073 175 2,42 0,049 3,55
Azamatli 95 Irr. 19,8 0,499 274 8,54 0,071 2,31
R-f 7,54 0,112 253 3,36 0,029 2,24
Tale-38 Irr. 19,8 0,482 276 8,42 0,071 2,35
R-f 8,32 0,121 249 3,63 0,033 2,29
12ndFAWWON №97 Irr. 14,6 0,351 290 7,11 0,050 2,05
R-f 8,16 0,068 180 2,17 0,045 3,76
4thFEFWSN №50 Irr. 20,1 0,593 294 9,72 0,068 2,06
R-f 12,7 0,180 246 4,72 0,051 2,69
Note: Irr.-irrigated; R-f- rain fed
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Effect of drought stress on some physiological traits...
Table 2. Correlation coefficients between gas exchange parameters gm, and WUE.
Irrigated Parameters Pn gs Ci Tr gm WUE Rain-fed
Pn 1 0,433** -0,070 0,819** 0,778** 0,058
gs 0,341** 1 0,592** 0,592** 0,019 -0,271*
C -0,459** 0,500** 1 0,156 -0,594** -0,399**
Tr 0,800** 0,366** -0,305* 1 0,535** -0,445**
gm 0,975** 0,196 -0,622* 0,766** 1 0,244*
WUE 0,130 -0,161 -0,228 -0,458** 0,163 1
**, Correlation is significant at the 0,01 level; *, Correlation is significant at the 0,05
Table 3. Changes of photosynthetic pigments content of wheat genotypes under water stress.
Wheat genotypes Chl a mg g-1dw Chl b mg g-1dw Chl (a+b) mg g-1dw Car (x+c) mg g-1dw Chl a/b Chl (a+b)/Car (x+c)
T. durum Desf.
Garagylchyg 2 irr. 7,14 3,34 10,48 1,76 2,14 5,96
r-f 5,50 3,06 8,56 1,18 1,80 7,25
Vugar irr. 6,02 2,93 8,95 1,45 2,06 6,16
r-f 4,00 1,86 5,86 0,98 2,15 5,97
Shiraslan 23 irr. 5,68 2,68 8,36 1,41 2,12 5,93
r-f 4,08 1,89 5,97 1,02 2,15 5,84
Barakatli 95 irr. 6,08 2,81 8,89 1,54 2,16 5,76
r-f 4,83 2,19 7,02 1,15 2,21 6,09
Alinja 84 irr. 5,10 2,66 7,76 1,24 1,92 6,26
r-f 4,46 2,01 6,47 1,16 2,22 5,57
Tartar irr. 4,90 2,51 7,41 1,17 1,96 6,34
r-f 6,23 2,69 8,92 1,58 2,32 5,66
T. aestivum L.
Gobustan irr. 6,78 3,30 10,08 1,58 2,06 6,37
r-f 5,08 2,57 7,65 1,20 1,98 6,35
Giymatli 2/17 irr. 5,85 2,68 8,53 1,38 2,18 6,17
r-f 4,07 1,84 5,91 1,12 2,21 5,26
Gyrmyzygul 1 irr. 7,19 3,22 10,41 1,86 2,23 5,60
r-f 7,17 3,06 10,24 1,93 2,34 5,31
Azamatli 95 irr. 6,68 3,70 10,38 1,38 1,81 7,50
r-f 4,43 2,06 6,49 1,12 2,15 5,82
Tale 38 irr. 7,68 3,54 11,22 1,84 2,17 6,08
r-f 6,44 3,13 9,57 1,60 2,06 5,99
12ndFAWWON №97 irr. 6,80 3,57 10,37 1,67 1,98 6,21
r-f 6,68 3,29 9,97 1,65 2,03 5,98
4thFEFWSN №50 irr. 7,14 3,49 10,63 1,80 2,04 5,92
r-f 5,20 2,49 7,69 1,34 2,08 5,75
Note: irr.-irrigated; r-f.-rain-fed
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Table 4. Correlations between different physiological parameters
Parameters Pn RWC LA DW LSM Chl
Pn 1
RWC 0,527** 1
LA 0,798** 0,321 1
DW 0,674** 0,116 0,845** 1
LSM -0,171 -0,327 -0,201 0,330 1
Chi 0,274 0,623** 0,113 -0,043 -0,235 1
**. Correlation is significant at the 0, 01 level
100 |--
Figure 2. Effect of water stress on flag leaf area. Data are mean of five replications.
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Effect of drought stress on some physiological traits..
0.25 -г
"у i-Л qP q> ■,£ <£> оЛ oh -ft <Л
/ V/ * " </>V V/
■ irrigated
■ rain-f e d
Figure 3. Effect of water stress on flag leaf dry biomass. Data are mean of five replications.
0.07 -
0.06 -
■ irrigated ■rain-fed
<r 4-
Figure 4. Effect of water stress on LSM.
DISCUSSION
Soil water deficit causes decrease of leaf gas exchange parameters. Our result is in agreement with results of Changhai et al., (2010), Wu and Bao, (2011), Shan et al., (2012). The Pn was higher among
genotypes of bread wheat than durum wheat. The gs regulate Pn, Tr and Q. According to correlation studies the gm has a dominance role in the regulation of Pn. This result is in agreement with result of Siddique et al., (1999). Despite the fact that the leaf gas exchange
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parameters, LA and DM strongly influenced by drought, RWC remained relatively high. Stomatal responses are more closely linked to soil moisture content than to leaf water status. Although LA and DM was positively correlated with Pn and were relatively higher in genotypes Barakatli 95, Giymatli 2\17, Tale 38 and 4thFEFWSN№50 under irrigated condition, strongly affected by drought stress. Therefore, large LA may be good selection trait under irrigated condition. In breeding retains a large LA that is conducive to greater yield potential, then when stress occurs a large part of this LA, which is a dry matter investment, will be irreversibly desiccated and lost (Blum, 2005). In genotypes with early heading period (Garagylchyg 2, Alinja 84, Gobustan, Giymatli 2/17, Azamatli 95) LA reduction was greater than DM, as a result LSM increased. Our result is in agreement with result of Witkowski and Byron (1991). Drought stress more affected on DM of late heading genotypes. Photosynthetic pigments are important to plants mainly for harvesting light and production of reducing powers (Anjum et a/., 2011). The decrease in Chl content under drought stress may be the result of pigment photo-oxidation and degradation. Drought stress leads to more reduction of Chl b than Chl a. This may be due to the fact that Chl b is a main component of photosystem II, disruption of electron flow and formation of oxidizing radicals under drought stress results in the more decrease of this pigment. The RWC, Chl (a+b) content of genotypes Tartar, Gyrmyzy gyl 1did not reduce significantly, we can consider these genotypes as drought resistant.
CONCLUSION
Physiological traits of wheat genotypes are strongly influenced under soil water deficit. Wheat genotypes survive water scarcity by adaptive changes in morphological traits and in the course of physiological, biochemical processes. Grain formation stage is very sensitive to water scarcity. Traits, such as optimal heading time, high RWC, photosynthesis rate, and chlorophyll content can be used as good selection criteria for breeding of wheat genotypes under rain-fed condition.
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