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The Effect of Water Stress and Polymer on Water Use Efficiency, Yield and several Morphological Traits of Sunflower under Greenhouse Condition

Hossein NAZARLI, Mohammad Reza ZARDASHTI, Reza DARVISHZADEH, Solmaz NAJAFI

Urmia University, Department of Agronomy and Plant Breeding, Urmia, Iran; [email protected]

Abstract

In many part of Iran, the reproductive growth stages of sunflower (Helianthus annuus L.) are exposed to water deficit stress. Therefore, the investigation of irrigation management in the farm conditions is a necessary element for increasing irrigation efficiency and decreasing water losses. The objective of present study was to investigate the effect of different rates of super absorbent polymer and levels of water stress on water use efficiency (WUE), yield and some morphological traits of sunflower (cultivar ‘Master’). Factorial experiment was carried out in completely randomized design with 3 replications. Factors were water stress in three levels (irrigation in 0.75; 0.50 and 0.25% of field capacity) and super absorbent polymer in five levels (0; 0.75; 0.150; 2.25; 3 g/kg of soil). Super absorbent polymer was added in eight leaves stage of sunflower to pots in deepness of roots development. Water stress treatment was also applied in this growth stage of sunflower. For stress application, pots were weighted every day and irrigated when soil water received to 0.75; 0.50 and 0.25 of field capacity, respectively. The results of ANOVA indicated that the effect of different rates of super absorbent polymer and different rates of consumed water in all traits were significant (P<0.001). ANOVA also revealed that the interactive effects of two mentioned factors were significant (P<0.001) except for seed yield trait. Polynomial model based on the ANOVA results was fitted for each trait.

The results indicated that water stress significantly convert in decreasing the number of leaves per plant, chlorophyll content, 100 weight of seeds, seed yield and WUE in sunflower, whereas the application of super absorbent polymer moderated the negative effect of deficit irrigation, especially in high rates of polymer (2.25 and 3 g/kg of soil). The above mentioned rates of polymer have the best effect to all characteristics of sunflower in all levels of water stress treatment. The findings strongly suggest that the irrigation period of sunflower cultivation can be increased by application of polymer.

Keywords: sunflower, water stress, polymer, yield

Introduction

The objective of well-regulated deficit irrigation is to save water by subjecting crops to periods of moisture stress with minimal effects on yields. Iran has arid and semi arid climate, so the drought stress is considered as one of the main problems of production in this country. Water short- age is usually one of the important reasons for the reduc- tion of performance in the unit area of arid and semi arid areas. Since 75% of our country’s regions have a rainfall of less than 250 mm in year, the danger of drought is con- sidered serious. Low water potential caused by a soil water deficit is one of the major natural limitations of the pro- ductivity of natural and agricultural ecosystems, resulting in large economic losses in many regions. In the past, ir- rigation has been a key solution to resolving this problem, but due to the increasing societal demands to water, today it is not a reasonable alternative and it increase financial cost (Wu and Cosgrove, 2000). Thus, the implementa- tion of research programs for planning proper irriga- tion management is essential. Causing stress in a stage of plant’s growth without loosing its performance from the point of view of saving water and irrigation for the arid

and semi arid areas is one of the favorite research areas for researchers. On the other hand, the use of super absorbent polymers can be a general solution for the farming in the arid and semi arid areas of our country. Super absorbent polymers can hold 400-1500 g of water per dry gram of hydro gel (Boman and Evans, 1991). The use of super ab- sorbent polymers has a great importance for their role in the increase of absorption capacity and retention of water in soil and for the fight against water shortage conditions and the decrease of bad effects of drought stress (Chatzo- poulos et al., 2000). Sunflower (Helianthus annuus L.) is one of the most important oil crops and due to its high content of unsaturated fatty acids and a lack of cholesterol, the oil benefits from a desirable quality (Razi and Assad, 1998). Although sunflower is known as a drought tolerant crop or grown under dry land conditions, substantial yield increases are achieved by irrigation and many researchers have reported its performance decrease under water stress conditions (Erdem et al., 2006; Nezami et al., 2008). This experiment was carried out with the aim of investigating the effect of super absorbent polymer A200 and water stress on the chlorophyll content of leaves, the number of the leaves per plant, the 100 weight of seeds, seed yield

Received 12 August 2010; accepted 28 October 2010

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Statistical analysis was carried out through SAS soft- ware version 9.0. The graphs were designed by using Mi- crosoft Office Excel 2007 software.

Results and discussions The chlorophyll content

The analysis of variance on chlorophyll content data revealed significant difference among super absorbent polymer and water treatments at 1% probability level (Tab. 1). The regression equation showing relationships between chlorophyll content and the amount of water and super absorbent polymer was determined as the following order:

This equation is polynomial in which I show irriga- tion and P shows the super absorbent polymer amount.

Chlorophyll content in plants is an important factor in determining photosynthetic capacity. Decreasing chloro- phyll content during drought stress depends on duration and severity of water stress. By using the above mentioned equation, one can found the appropriate amount of poly- mer corresponding to each water treatment stress in order to estimate the best level of chlorophyll that need to stop the significant reduction of photosynthesis. The results of this study showed that the chlorophyll content increased as amount of polymer increased, and in the severe stresses in which no polymer exist with the irrigation of 25% of the field capacity, the chlorophyll of the leaves showed severe reduction. With the use of the polymer treatment (1.5 g per 1 kg of soil) the impact of water stress on the amount of chlorophyll has modified to some extent, in other words, in more moderate stresses the amount of chlorophyll has slightly increased. Also the results showed that the impact of polymer is less visible in high amounts of irrigation treatments (Fig. 1). Drought stress results in the decrease of the amount of chlorophyll and protein, and also results in the cell membrane damage and lack of balance between nutrient substances in ‘SH222’ cultivar of sunflower. Thus, it results in the aging of cells and un matured seeds (Santos et al., 2002). Even, low water deficit stress (FC=15%) re- sulted in significant decrease in the chlorophyll content of wheat’s leaves (Ahmadi and Baker, 2000).

Seed yield

The analysis variance on seed yield data showed that the effect of different amounts of polymer and different amounts of irrigation on this character is significant at 1% probability level. But the interaction effect of the two mentioned factors on seed yield did not turned out signifi- and water use efficiency (WUE) in sunflower under green-

house condition.

Materials and methods

Factorial experiment was carried out in completely ran- domized design with 3 replications on sunflower (Cultivar Master) in the summer of 2008 in the research greenhouse of Urmia University, Iran. The primary factor included three irrigation regimes including irrigation at 25%, 50%

and 75% of field capacity and secondary factor included four amounts of super absorbent polymer including 0, 0.75, 1.5, 2.25 and 3 g polymer per 1 kg of soil. The super absorbent polymer A200 was provided from Rahab Rezin Company, Institute of Polymer Research, Karaj, Iran. Ac- cording to the manufacturing company’s protocol this substance had a maximum seven years of durability in soil and its practical capacity of water absorption was equal to 220 g.

Some properties of super absorbent polymer A200:

• Water content (%) = 5-7

• Grain size (i m) = 50-150

• Density (g/cm3) = 1.4-1.5

• Ph = 6-7

The net weight of soil of each pot was cosidered 9 kg and the plantation of the pot took place in 10 June. The polymer was added to pots around the roots at the stage of eight leaves of sunflower with making ten centimeter holes in pots and right after that the pots was irrigated. Then the intended water stress was started from the stage of 8 leaves. The pots were put at distances from each other that triggered no competition for light taking. Before the ir- rigation, the pots were weighted by a sensitive balance and appropriate amount of water corresponding to each water stress treatment was added to pots and recorded.

In order to measure the performance of seed in capi- tol, first the capitol were dried in fluent air and the seeds were separated from them. The performance of seed in the capitol was calculated on the basis of 10 percent of the moisture. The weight of 100 seeds with 10 percent of the moisture was measured for each treatment combina- tion per replication. Chlorophyll content was assessed us- ing a chlorophyll meter (SPAD-502, Minolta) and mea- surements were done at three points of each leaf (upper, middle and lower part). Average of these three readings was considered as SPAD value. After pollination and with the start of seeds filling time, the number of the leaves per plant was measured. At counting time, some of the old leaves of the plants were fallen due to low irrigation; by their trace on the stem, these leaves were also considered and counted. Before the start of each irrigation interval, the amount of the used water by each treatment combina- tion per replication was measured with graduated cylinder and recorded. Then the total performance was computed and was finally water use efficiency determined through the following formula:

Chlorophyll content = -10.96+70.68I-37.9I2+7.85P- 0.037P3-8.5IP

(The general performance/ the used water) x 100 = Water Use Efficiency (g.lit)

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cant (Tab. 1). The results showed that the highest amount of seed yield was achieved form high amounts of polymer (2.25, 3 g polymer per 1 kg soil) and also under the condi- tion of no drought stress but the lowest amount of per- formance was related to the treatment of severe drought stress without using polymer (Fig. 1). According to the regression analysis, the follow equation was fitted among seed yield as response variable and polymer as well as water amount as predictor variables:

The equation shows the relation between the amounts of the used polymer at different levels of irrigation and the seed yield. Nezami et al. (2008) reported that the dry mat- ter of sunflower increased with the increase of irrigation and the maximum dry matter earned from well watered condition. Allahdadi et al. (2007) reported that the use of polymer under drought stress resulted in general higher performance of soybean. They observed that some soy- bean yield components and yield of soybean was linearly increased by increasing the amount of polymer in drought conditions which is in accordance with our results in this study. The application of the super absorbent polymer in soil resulted in the increase of sugar beets budding roots growth, and roots performance (Dexter and Miyamoto, 1995).

Number of leaves per plant

The analysis of variance on the number of leaf data showed that this characteristic is significantly affected by

the amounts of polymer and water. The regression equa- tion is:

There was a decrease in the number of leaves in low amounts of polymer and water deficit combination. In low amounts of polymer with severe drought stress com- bination it was observed the old leaves of the plant were dried and the shrubs were weaken and lost their growth power. But in high amounts of polymer and good irriga- tion, the soil of pots were able to provide enough water for the growth of the plants. Long periods of severe soil water deficit at any growth period cause leaf-drying with subsequent reduction in seed yield. As a result, long leaf area durability (LAD) in high amounts of polymer and good irrigation resulted in the opening of stomas for long time, subsequently good CO2 fixation that resulted in the increase of the dry matter of the plant. In sunflower the leaves are the primary source of the production of pho- tosynthetic substances that needed for the filling of the seeds. Any stress resulting in decrease of photosynthetic substances, will result in the decrease of performance.

Water Use Efficiency (WUE)

The Tab. 1 describe the analysis of variance for effi- ciency of water usage and there was a significant differ- ence between the treatments of super absorbent polymer and different amounts of irrigation. Also the interaction between amounts of polymer and irrigation levels on this characteristic was significant, too. The high amounts of Yield = -7.64+43.73I+0.35P+3.37P2-0.981P3-2.79I2P

NL = 2.63+41.04I-23.45I2+2.82P-1.50IP-0.062I2P3

Tab. 1. Analysis of variance for the effect of drought stress and super absorbent polymer on water use efficiency (WUE), yield and some morphological traits of sunflower (Helianthus annuus L.) in greenhouse condition

MS df S.O.V

WUE YP W100A NL Chl

1707.49ns 25.94** 0.069ns 0.86ns 3.45ns 2 Replication

2392415.79** 1470.10** 15.71** 216.6** 404.58** 2 Irrigation

3422089.75** 2930.40** 31.41** 410.7** 753.003** 1 Linear(L)

1362741.83** 9.80ns 0.013ns 22.5** 56.169** 1 Quadratic (Q)

292663.32** 79.27** 3.26** 47.27** 158.01** 4 Polymer

1081160.16** 256.37** 11.39** 184.9** 544.644** 1 Linear(L)

391.56ns 18.51* 0.27ns 1.34ns 0.167ns 1 Quadratic (Q)

88802.35** 22.30** 1.38* 1.87ns 78.96** 1 Cubic(C)

299.21ns 19.91* 0.000022ns 0.99ns 8.29ns 1 Quadratic (Qt)

76341.40** 5.40ns 0.91** 2.37* 23.36** 8 Irrigation × Polymer

25738.80* 9.20ns 1.39* 8.81** 152.32** 1 LI×LP

2354.58ns 0.66ns 1.02* 0.58ns 9.73ns 1 LI×QP

1969.05ns 0.81ns 1.43* 0.60ns 0.17ns 1 LI×CP

2921.63ns 0.0095ns 1.69* 0.46ns 1.46ns 1 LI×QtP

525563.86** 19.53* 0.02ns 0.45ns 2.88ns 1 QL×LP

1908.88ns 2.95ns 1.70* 2.48ns 0.590ns 1 QL×QP

46582.48** 1.72ns 0.01ns 4.35* 4.802ns 1 QL×CP

3691.89ns 8.28ns 0.04ns 1.26ns 14.98ns 1 QL×QtP

df: degree of freedom; MS: mean of square; Chl: chlorophyll content; W100A: weight of 100 achens; NL: number of leaves per plant; YP: yield of plant; WUE: water use efficiency; *,** significant at 0.05 and 0.01 probability levels, respectively; ns: non significant

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polymer contributed to the highest usage of water effi- ciency, the lowest efficiency of water use was related to the treatment of severe drought stress without using polymer in which the addition of polymer increased water use ef- ficiency. Polymer stored the water and released it on the right time which resulted in saving of the used water, also resulted in the improvement of physical conditions and probably proper access to nutrient elements and as a re- sult the performance of dry matter has increased. In order

to obtain precise results the regression analysis on inter- active effects was carried out and the equation related to this characteristic was written with taking the significant effects into consideration:

WUE = -353.43+1904.26I-679.63I2-598.68P-3.56P3 +3568.75IP-3533.12I2P+8.63I2P3

0 5 10 15 20 25

0 0,75 1,5 2,25 3

POLYMER (gr)

NUMBER OF LEAVES

0,25 0,5 0,75

0 1 2 3 4 5 6 7

0 0,75 1,5 2,25 3

POLYMER (gr)

WEIGHT OF 100 ACHENE (gr)

0,25 0,5 0,75

0 1 2 3 4 5 6 7 8 9

0 0,75 1,5 2,25 3

POLYMER (gr)

WUE (gr/lit)

0,25 0,5 0,75

0 5 10 15 20 25 30

0 0,75 1,5 2,25 3

POLYMER (gr)

CHOLOROPHIL CONTENT(mg/g FW)

0,25 0,5 0,75

0 5 10 15 20 25 30 35

0 0,75 1,5 2,25 3

POLYMER (gr)

YIELD (gr)

0,25 0,5 0,75

Fig. 1.The effect of water stress and polymer (A200) on water use efficiency (WUE), yield and some morphological traits of sun- flower under greenhouse condition

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weight of 100 seeds of sunflower in drought stress show significant reduction. In a research work, when the mois- ture of soil decreased from 100% to 30% of field capac- ity the weight of 100 seeds showed a decrease of 32.7%

(Nezami et al., 2008). Drought stress results in the closure of the foramen and decrease of leaf area index and photo- synthesis. It also reduces the filling period. This will lead to weak transfer of the amounts of carbohydrates to the seed (Bieloria and Hopmans, 1975). Drought stress results in significant reduction of 37% in the weight of 100 seeds in comparison with standard plants (Igbal et al., 2005).

Based on the results of this study, it can be concluded that the application of polymer can increase irrigation in- tervals for sunflower, thus it can be planted in regions suf- fering limited sources of water and irrigation.

References

Ahmadi, A. and D. A. Baker (2000). Stomatal and nonstomatal limitations of photosynthesis under water stress conditions in wheat plant. Iranian Journal of Agriculture Science 31:

813-825.

Allahdadi, I., F. Yazdani, G. A. Akbari and S. M. Behbahani (2005). Evaluation of the effect of different rates of superabsorbent polymer (superab A200) on soybean yield and yield component (Glysin max L.), 20-32 pp. 3rd Specialized training course and seminar on the application of superabsorbent hydrogel in agriculture, IPP, Iran.

Bieloria, H. and P. A. M. Hopmans (1975). Recovery of leaf water potential, transpiration and photosynthesis of cotton during irrigation cycles. Agronomy Journal 67: 629-632.

Boman, D. C. and R. Y. Evans (1991). Calcium inhibition of polyacrylamide gel hydration is partially reversible by potassium. Hortic. Sci. 26: 1063-1065.

Chatzopoulos, F., J. L. Fugit, I. Quillon, F. Rodriguez and J. Taverdet (2000). Etude du function de differences parameters, de l‘absorbtion et de la desorbation d‘eau par un copolymer acrlamid-acrylate de sodium reticule. European Polymer Journal 36:51-60.

Dexter, S. T. and T. Miyamoto (1995). Acceleration of water uptake and germination of seedballs by surface coatings of hydrophilic colloids. Agronomy 51:388-389.

Erdem, T., Y. Erdem, A. H. Orta and H. Okursoy (2006). Use of a crop water stress index for scheduling the irrigation of sunflower (Helianthus annuus L.). Turkish Journal of Agriculture Forestry 30:11-20.

Huttermann, A., M. Zommorodi and K. Reise (1990). Addition of hydro gels to soil for prolonging the survival of Pinus halepensis seedlings subjected to drought. Soil and Tillage Research, 50:295-304.

Igbal, N., M. Y. Ashraf and M. Ashraf (2005). Influence of water stress and exogenous glycinebetaine on sunflower achene weight and oil percentage. Int. J. Environ. Sci. Tech. l2: 155- 160.

This equation shows the relation between the amount of polymer usage at different irrigation intervals and wa- ter usage. This equation is polynomial and the amount of the used water can be obtained through putting different amounts of polymer and so stop unreasonable use of water.

The high amount of WUE for high amounts of polymer can be related to the role of polymer in the increase of re- taining capacity of moisture and the used water in soil. The performance of the dry matter and the efficiency of water use in grass sorghum were affected by the amount of poly- mer. By increasing polymer amount, the performance of dry matter and water use efficiency were increased (Karimi and Naderi, 2007). The application of polymers results in the absorption and retaining of the irrigated water that will be released little by little, which increased the time that the plant has access to moisture and so irrigation efficiency increased (Hutterman et al., 1990). Our results were con- firmed with those obtained. The efficiency of water us- age did not have a significant difference in mild drought stress but, significantly decreased in severe conditions of drought stress. This condition was observed both for the plants grown in environment with normal CO2 density and CO2 densities with higher than normal environment (Tezara et al., 2002). The application of polymer in soil increased the amount of absorbed water in red bean and silken oak. This was because of the increase in the amount of leaves transpiration and the increase in CO2 absorption (Specht and Harvey-Jones, 2000).

Weight of 100 seeds

The results of the experiment showed that the effect of different amounts of irrigation and the application of polymer on this characteristic was significant in 1% proba- bility level and even the interactive effect of the two above factors was also significant (Tab. 1). In this experiment the lowest amount of seed index was related to standard plant having no polymer under severe drought stress and the highest weight of 100 seeds was for 2.25 and 3 g poly- mer per 1 kg of soil with no drought stress. The regression equation is:

The weight of 100 seeds depends on length and rate of seed filling period. Reduction of moisture during the growth period especially in the genesis stage results in low photosynthesis rate and the length of seed filling period.

Thus a significant reduction happens in the weight of 100 seeds in such situation. But the application of polymer provided moisture for the soil which in turn increased the rate and length of this period. The effect of the amounts of polymer on the weight of 100 soybean seeds was statisti- cally significant and by application of polymer, the weight of 100 soybeans increased linearly (Allahdadi et al., 2007).

Our results were confirmed with those obtained. The W100A = 0.71+6.35I+1.72P-0.086P3-7.092IP+

6.27IP2-2.47I P3

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Santos, C., G. Pinto, J. Loureiro, H. Oliveira and A. Costa (2002). Response of sunflower cells under Na2SO4. I.

Osmotic adjustment and nutrient responses and proline metabolism in sunflower cells under Na2SO4 stress. J. Plant Nut. Soil Sci. 165:366-372.

Specht, A. and J. Harvey-Jones (2000). Improving water delivery to roots of recently transplanted. Forest Research 1:117- 123.

Tezara, W., V. Mitchall, S. P. Driscoll and D. W. Lawlor (2002).

Effects of water deficit and its interaction with CO2 supply on the biochemistry and physiology of photosynthesis in sunflower. J Exp Bot. 375:1781-1791.

Wu, Y. and D-J. Cosgrove (2000). Adaption of roots to low water potentionals by changes in cell wall extensibility cell wall proteins. J. Exp. Bot 51:1543-1553.

Karimi, A. and M. Naderi (2007). Yield and water use efficiency of forage corn as influenced by superabsorbent polymer application in soils with different textures. Pajouheshe Keshvarzi 3:187-198.

Muro, J., I. Irigoyen, A. F. Militino and C. Lamsfus (2001).

Defoliation effects on sunflower yield reduction. Agron. J.

93:634-637.

Nezami, H., R. Khazaei, Z. Boroumand Rezazadeh and A.

Hosseini (2008). Effect of drought stress and defoliation on sunflower (Helianthus annuus L.) in controlled conditions.

Desert 12:99-104.

Razi, H. and M. T. Asad (1998). Evaluation of variation of agronomic traits and water stress tolerant in sunflower conditions. Agricultural and Natural Resources Sciences 2:31-43.

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