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Glycinebetaine and salicylic acid application improves the plant water relations, water use efficiency and yield of sunflower under different planting methods

Mubshar Hussain, Muhammad Farooq, and M. A. Malik

Department of Agronomy, University of Agriculture, Faisalabad-38040, Pakistan, *E-mail: mubashiragri@yahoo.com

Abstract

Different planting methods and exogenous application of glycinebetaine (GB) and salicylic acid (SA) has been found very effective in increasing water use efficiency (WUE). This two year field study examined the possible role of different planting methods and exogenous application of GB and SA in improving plant water relations, water use efficiency and the yield of hybrid sunflower (Helianthus annuus L.). Sunflower was sown by flat sowing (75 cm spaced rows) and ridge sowing (75 cm spaced ridges). GB and SA were applied exogenously at 100 and 0.724 mM respectively, each at the budding and at the flowering stage. Control plants received application of distilled water. Foliar application of GB at flowering improved the relative leaf water contents, leaf water potential, leaf osmotic potential and leaf turgor potential and achene yield during both the years and WUE during 2006. While improved leaf turgor, achene yield and WUE were observed in sunflower planted at ridges.

Key Words

Exogenous application; growth regulants; osmotic adjustment

Introduction

Water crisis is a severe threat for the productivity and sustainability of agricultural systems worldwide. Many options are being explored to tackle this global issue. The use of exogenous applications of compatible solutes may allow crops to be grown successfully with minimum water input (Hussain et al. 2008). Glycinebetaine (GB) has been shown to protect functional proteins, vital enzymes and photosynthetic machinery (Xing and Rajashekar 1999) and has been found to improve the crop water productivity under limited and well watered conditions (Hussain et al. 2008). Applications of salicylic acid (SA) reduced damage from salinity and water deficit on seedling growth and accelerated the restoration of growth processes in wheat (Sakhabutdinova et al. 2003). Seed priming with SA improved the low temperature tolerance in hybrid maize by activation of antioxidant system and maintenance of high tissue water content (Farooq et al. 2008).

Planting techniques to improve efficient water utilization are also being explored. Ridge sowing enhanced the achene yield of sunflower by providing favorable soil environments for plant growth. The loose fertile soil in case of ridge sowing enhanced the root growth, nutrient and water uptake and improved achene yield (Saleem et al. 2008). The present study was carried out with the objective to examine the effects of various planting methods and foliar application of GB and SA on water relations and water productivity of sunflower.

Methods

Site and experimental details

The study was conducted at the Agronomic Research Area, University of Agriculture, Faisalabad (31.25oN, 73.09oE and 183 m asl) in 2 consecutive years, 2006 and 2007. The experiment was laid out as a split plot, randomized complete block design with three replicates. The net plot size was 3m 5m. Planting methods and GB and SA applications were randomized in main plots and sub-plots, respectively. Planting methods included in the study were flat sowing (FS, with rows 75 cm apart) and ridge sowing (RS with ridges75 cm apart). Glycinebetaine and SA were each applied twice during the growing season, at budding (VGB and VSA, respectively) and flowering (FGB and FSA, respectively). Glycinebetaine was applied at as a solution of 100 mM while SA was applied at 0.724 mM. The control plots (CKF) did not receive either GB or SA.

A known amount of irrigation water was applied using a cut-throat flume (Buland et al. 1994). Both sowing methods received 300 mm of water, applied as 4 irrigations, each 75 mm. Sunflower (Hysun-33) was sown on 14th February 2006 and 17th February 2007 and sowing was done with the help of dibbler in the case of flat sowing and manual seeding was done in the ridge sowing treatment. Both planting systems used a seeding rate of 8 kg/ha, with a row to row distance of 75 cm and plant to plant distance of 25 cm.

Measurements

Leaf water potential (ψw) was measured with a pressure chamber (Soil Moisture Equipment Corp., Santa Barbara, CA) from the penultimate leaf. Leaf tissues were sampled and immediately frozen to measure osmotic potential (ψs). The frozen leaf tissues were thawed, sap expressed, centrifuged at 5,000 g and the ψs was determined with an osmometer (Digital Osmometer, Wescor, Logan, UT). Leaf pressure potential (ψp) was computed as the difference between ψw and ψs. Leaf relative water content was measured according to Schonfeld et al. (1988). Water use efficiency (WUE) was calculated as the ratio between achene yield and water used (Viets 1962). The crop was harvested when fully ripe to determine achene and biological yield, and harvest index. The achene yield was adjusted to 10% moisture content..

Statistical analysis

The data were statistically analysed using MSTAT-C. Analysis of variance was employed to test the overall significance of the data, while the least significant difference (LSD) was used to compare the differences among treatment means.

Results

The planting method had a non-significant effect on plant water relations in both the years except with leaf turgor potential which was significantly affected during 2007 only. During 2007, ridge sowing had higher leaf turgor potential compared with flat sowing (Table 1).

Table 1. Effect of planting methods on water relations, achene yield and water use efficiency of sunflower

TreatmentA

LRWC
(%)

Water
potential
(-MPa)

Osmotic potential
(-MPa)

Turgor potential
(MPa)

Achene yield
(kg ha-1)

WUE
(kg m-3)

2006

2007

2006

2007

2006

2007

2006

2007

2006

2007

2006

2007

Flat sowing

79.7

81.3

0.94

0.96

1.38

1.35

0.44

0.39 b

2367

2355

0.631

0.660

Ridge sowing

80.8

82.0

0.94

0.95

1.42

1.41

0.46

0.47 a

2778

2732

0.740

0.756

LSD 5%

NS

NS

NS

NS

NS

NS

NS

0.048

63.86

65.66

0.043

0.052

AFS = Flat sowing with 75 cm apart rows and RS = Ridge sowing with 75 cm apart ridges

Exogenous application of GB and SA significantly affected all the water relation parameters during both the years (Table 2). Maximum RWC were measured from a GB application at flowering (FGB) during both the years. In 2006, the RWC was greater than the other treatments, but in 2007, the value was not significantly different to the control treatment and VGB (Table 2). Maximum Ψs was recorded in a foliar application of SA at the budding, which was similar to GA applied at flowering in 2006 and with all other treatments except the control during 2007 (Table 2). The maximum leaf Ψs was recorded in the control and the minimum was measured in GB applied at flowering, which was similar to all other treatments except the control during both the years (Table 2). Maximum Ψp was observed when GB was applied at flowering during both the years, but it did not differ significantly from the other GB or SA treatments in both years (Table 2).

Maximum achene yield and WUE were recorded in ridge sown sunflower compared with flat sowing during both the years (Table 1). In 2006, maximum achene yield was recorded when GB was applied at flowering while the lowest yields were measured in the control treatment and with SA applied during flowering. In 2007, applying GB during budding and flowering tended to produce the highest yields, with the application at flowering increasing yields over the control (Table 2). Similarly, maximum WUE was measured from GB application at flowering (FGB) against the minimum from control in 2006 (Table 2). While in 2007, there was no significant difference in WUE among the treatments.

Table 2. Effect of exogenous applications of GB and SA on water relations, achene yield and water use efficiency of sunflower.

TreatmentA

LRWC
(%)

Water potential
(-MPa)

Osmotic potential
(-MPa)

Turgor potential
(MPa)

Achene yield
(kg ha-1)

WUE
(kg m-3)

2006

2007

2006

2007

2006

2007

2006

2007

2006

2007

2006

2007

CKF

78.6 b

82.3ab

1.03 a

1.01 a

1.37 b

1.33 b

0.38 c

0.31 b

2470 c

2410 b

0.660 e

0.690

VGB

79.4 b

82.3 ab

0.94c

0.93 b

1.41 a

1.39 a

0.47 ab

0.46 a

2599 b

2536 ab

0.690 b

0.723

FGB

84.2 a

85.0 a

0.91 cd

0.95 b

1.42 a

1.41 a

0.52 a

0.46 a

2698 a

2595 a

0.718 a

0.740

VSA

79.2 b

79.8 b

0.87 d

0.91 b

1.37 b

1.38 a

0.49 ab

0.47 a

2572 b

2496 ab

0.685 c

0.713

FSA

79.6 b

79.0 b

0.98 b

0.96 b

1.42 a

1.41 a

0.44 b

0.45 a

2530 bc

2431 b

0.675 d

0.695

LSD 5%

3.84

3.24

0.033

0.053

0.038

0.040

0.049

0.076

101.0

76.6

0.004

NS

ACKF = Control (distilled water application), VGB = Exogenous application of GB at budding stage, FGB = Exogenous application of GB at flowering stage, VSA = Exogenous application of SA at budding stage and FSA = Exogenous application of FSA at flowering stage

Discussion

Higher Ψpin ridge sowing during 2007 might be the result of improved soil environments (loose fertile surface soil), which promoted the root growth and thus increased the water availability. The exogenous application of GB and SA at vegetative and the flowering stages, but especially the exogenous application of GB at flowering stage, significantly improved the crop water relation parameters under both the sowing methods.

Higher achene yield in case of ridge sowing might be due to the favourable soil environments for plant growth by providing loose fertile soil. The loose fertile soil might improve the root growth, nutrient and water uptake. Saleem et al. (2008) earlier reported higher achene yield with ridge sowing compared to flat sowing. Improvement in the achene yield by foliar application of GB at flowering might be the result of maintenance of photosynthetic activity owing to GB application. Earlier, Agboma et al. (1997) reported that exogenous GB application protects the photosynthetic machinery in maize, wheat and sorghum thereby increasing the final yield. Increased WUE with ridge sowing and foliar application of GB at flowering stage might be due the increased achene yield as the same quantity of water was applied in both ridge and flat sown crop.

In conclusion, the planting methods did not significantly affect plant water relations during either of the two years except leaf turgor potential which was significantly improved by ridge sowing during 2007. Nevertheless GB application at flowering improved plant water relations and maintained high leaf turgor potential during both the years. Foliar application of GB at flowering and ridge sowing resulted in higher achene yield and WUE.

References

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Hussain M, Malik MA, Farooq M, Ashraf MY and Cheema MA (2008) Improving drought tolerance by exogenous application of glycinebetaine and salicylic acid in sunflower. Journal of Agronomy and Crop Science 194, 193-199.

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Xing W and Rajashekar CB (1999) Alleviation of water stress in beans by exogenous glycinebetaine. Plant Science 148, 185-195.

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