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Journal of Stress Physiology & Biochemistry, Vol. 9 No. 3 2013, pp. 61-71 ISSN 1997-0838 Original Text Copyright © 2013 by Ansari, Azadi, Sharif-Zadeh, Younesi
ORIGINAL ARTICLE
Effect of Hormone Priming on Germination Characteristics and Enzyme Activity of Mountain Rye (Secale montanum) Seeds under Drought Stress Conditions
Ansari O.1*, Azadi M.S.2, Sharif-Zadeh F.3, Younesi E.1
1 Department of Agronomy and Plant Breeding, Faculty of Agriculture, University of Tehran, Karaj, Iran.
2 Department of Agronomy and Plant Breeding, Islamic Azad University, Dezfoul Branch, Iran.
3 College of Agriculture and Natural Resources, University of Tehran, Iran.
E-Mail: Ansari_o@ut. ac. ir
Received February 15, 2013
Seed priming techniques have been used to increase germination, improve germination uniformity and seedling establishment under stressed conditions. Seed priming was used in Rye Mountain (Secale montanum) to increase seed germination and tolerance on stress exposure. Rye seeds were treated with various priming agents for different time and temperatures. The effect of priming was assessed on germination characteristics on subsequent exposure to drought (PEG -14 bar) stress for 7 days. Seed priming treatments significantly (p< 0.01) affected, Germination percentage (GP), normality seedling percentage (NSP), germination Index (GI), germination uniformity (GU), means time to germination (MTG), coefficient of velocity of germination (CVG), seedling vigour index (SVI) and coefficient of allometry(AC). Seed priming with gibberelic acid (GA) and salicylic acid (SA) (p< 0.01) increased germination characteristics as the compared to the unprimed. Seed priming with concentrations 25, 50 ppm of GA for 15 h at 10 C and 25 ppm of SA for 12 h at 10 C, may be considered as optimal treatment for priming of Secale montanum seeds in drought stress conditions. Also priming increased catalase (CAT) and ascorbate peroxidase (APX) as compared to the unprimed.
Key words: Hormone priming, Seed germination, Drought stress, Enzyme activity, Secale montanum.
ORIGINAL ARTICLE
Effect of Hormone Priming on Germination Characteristics and Enzyme Activity of Mountain Rye (Secale montanum) Seeds under Drought Stress Conditions
Ansari O.1*, Azadi M.S.2, Sharif-Zadeh F.3, Younesi E.1
1 Department of Agronomy and Plant Breeding, Faculty of Agriculture, University of Tehran, Karaj, Iran.
2 Department of Agronomy and Plant Breeding, Islamic Azad University, Dezfoul Branch, Iran.
3 College of Agriculture and Natural Resources, University of Tehran, Iran.
E-Mail: Ansari_o@ut. ac. ir
Received February 15, 2013
Seed priming techniques have been used to increase germination, improve germination uniformity and seedling establishment under stressed conditions. Seed priming was used in Rye Mountain (Secale montanum) to increase seed germination and tolerance on stress exposure. Rye seeds were treated with various priming agents for different time and temperatures. The effect of priming was assessed on germination characteristics on subsequent exposure to drought (PEG -14 bar) stress for 7 days. Seed priming treatments significantly (p< 0.01) affected, Germination percentage (GP), normality seedling percentage (NSP), germination Index (GI), germination uniformity (GU), means time to germination (MTG), coefficient of velocity of germination (CVG), seedling vigour index (SVI) and coefficient of allometry(AC). Seed priming with gibberelic acid (GA) and salicylic acid (SA) (p< 0.01) increased germination characteristics as the compared to the unprimed. Seed priming with concentrations 25, 50 ppm of GA for 15 h at 10 C and 25 ppm of SA for 12 h at 10 C, may be considered as optimal treatment for priming of Secale montanum seeds in drought stress conditions. Also priming increased catalase (CAT) and ascorbate peroxidase (APX) as compared to the unprimed.
Key words: Hormone priming, Seed germination, Drought stress, Enzyme activity, Secale montanum.
The perennial Mountain Rye (Secale Montanum) is a native wild species in southern Europe, Morocco, Iran and Iraq (De Bustos & Jouve 2002). The value of S. Montanum as a pasture crop has been tested successfully in the United States
(Robert et al. 1988), Australia and New Zealand (Oram 1996). Montanum rye (Secale montane) is an important plant in world that has more feed uses.
Seed germination and rapid germination are usually essential processes in seedling
establishment and plant development to obtain seedling numbers those results in higher seed crop (Almansouri et al., 2001; Murungu et al., 2003). In more crop species, seed germination and establishment are the most sensitive stages to abiotic stress (Patade et al 2011; Redmann, 1974). Abiotic stress such as: drought stress, salt stress and cold stress maybe delay seed germination and reduce the rate (Patade et al., 2011; Rouhi et al., 2011; Ansari et al., 2012). Seed priming is one of the methods that can be taken to counteract the adverse effects of abiotic stress (Patade et al., 2009; Ashraf and Foolad, 2005). The purpose of seed priming is to a partially hydrated with water, or various chemical solutions like polyethylene glycol (osmo priming) or salts like CaCl2, CaSO4 and NaCl (Halopriming) the seeds to a point where germination processes are begun but not completed (Asfraf and Foolad, 2005), followed by drying of seeds to the original moisture level (McDonald, 2000). Seed priming techniques have been used to increase germination, improve germination uniformity, improve seedling establishment and stimulate vegetative growth in more field crops such as: wheat (Iqbal and Ashraf, 2007), sunflower seeds (Kaya et al., 2006), Chickpea (Kaur et al., 2002), Capsicum (Patade et al., 2011), lenti (Saglam et al., 2011) and soybean (Sadeghi et al., 2011), under stressed conditions. Also similarity indicated, in maize (Foti et al., 2008), cucumber (Ghasemi-Golezani and Esmaeilpour, 2008). Priming has also been shown to induce nuclear DNA synthesis in the radicle tip cells in several plant species including: tomato (Liu et al., 1997), pepper (Capsicum annuum) (Lanteri et al., 1993), maize (Zea mays) (Garcia et al. 1995), and leek (Ashraf and Bray, 1993; Clark and James, 1991). Also, the priming strategies enhanced activities of free
radical scavenging enzymes such as CAT and SOD (Ansari et al., 2012). In addition, the hormone-priming increased the germination percentage and activities of glyoxylate cycle enzymes in Persian Silk Tree (Albizia julibrissin Durazz) (Sedghi et al., 2011). Although effect of seed priming in other field crops are documented, no reports are available on potential of various seed priming treatments and responses of the Mountain Rye seeds on subsequent exposure to drought stress. Therefore, the study aimed was to determine the effect of different priming treatments on germination seedling growth of Mountain Rye (Secale montanum), under drought stress and to find the best combination and time regime in different materials priming.
MATERIALS AND METHODS
The study was conducted in the seed laboratory of Natural Resources Faculty, University of Tehran, Iran.
Determine the critical drought potential: Drought tolerance of Mountain Rye (Secale Montanum) seeds was tested by using solutions of
0, -2, -4, -6, -8, -10, -12, -14 and -16 bar Polyethylene glycol (PEG-6000) concentrations. Four replicates of 50 seeds for each treatment were used. Rye seeds were germinated in 10 cm glass Petri dishes containing 6 ml PEG6000 solution in a germinator at 20±1°C, in dark condition for 7 days. Germinated seeds were recorded every 24 h for 7 days. After test time expiration, for Determine the critical drought potential, some germination indexes were evaluated such as: germination percentage (GP) and normal seedling percentage (NSP).
Seed priming: Seeds of were pretreated with salicylic acid and gibberellic acid. In hormone
priming treatments, seeds were exposure in 0, 25, 50, 75 and 100 ppm concentrations salicylic acid and gibberellic acid for 12 and 15 h at 10±1°C and 12 h at 15±1°C. Rye seeds were exposure in 20 cm glass petri dishes containing 15 ml solution. The imbibed seeds were then washed three times with tap water and dried on filter paper at 15±1°C for 24 h.
Seed germination test: Seeds of primed and unprimed, rye mountain (Secale montanum) for drought tolerance were placed in 10 cm glass petri dishes containing 6 ml, critical potential in a germinator at 20±1°C for 7 days. Four replicates of 50 seeds for each treatment were used. Seeds were considered germinated when a 2 mm length radicle protruded through the seed coat. Germinated seeds were recorded every 24 h for 7 days. After test time expiration, some germination indexes were evaluated such as: Germination percentage (GP), normal seedling percentage (NSP), germination Index (GI), germination uniformity (GU), means time to germination (MTG), coefficient of velocity of germination (CVG), seedling vigor index (SVI) and coefficient of allometry (AC).
Antioxidant enzymes assay: After the results of priming effects on investigated traits and determined elite treatment (25 ppm for 12h at 10°C for GA and SA) for Secale montanum, determination of antioxidant enzyme activity was performed. All extraction procedures were carried out at 4°C. The seed samples, weighting about 0.3 gr, were homogenized with 3 ml of tris (PH 7.8), followed by centrifugation of 20000 g for 20 min (Ansari and Sharif-Zadeh, 2012). The supernatants were used for determination of enzyme activity. The supernatants were used for determination of enzyme activity. Catalase (CAT, EC 1.11.1.6) activity was determined spectrophotometric ally following
H2O2 consumption at 240 nm (Bailly et al., 1996). Ascorbate peroxidase (APX, EC 1.11.1.7) activity was determined according to the procedures of Johnson and Cunningham (1972). The activities of APX and CAT were expressed per mg protein, and one unit represented 1 ^mol of substrate undergoing reaction per mg protein per min.
Statistical analysis: All data were analyzed statistically by analysis of variance using SAS Software. Data for germination and normal germination percentages were subjected to arcsine transformation before analysis of variance was carried out with SAS software. Mean comparisons were performed using an ANOVA protected least significant difference (Duncan) (P<0.01) test.
RESULTS
Critical drought tolerance test: The ability of seed drought tolerance was indicated by the germination percentage and normality seedling percentage, which showed the critical drought concentration for rye seeds. Seeds germination of Rye was significantly affected (P<0.01) by PEG concentrations (Figure 1). The highest germination percentage and normality seedling percentage was found in distilled water, followed by -2 and -4 bar PEG. The highest PEG concentrations (-14 and -16 bar PEG) showed substantial reduction in seed germination (Figure 1) and showed substantial reduction in normality seedling percentage (%) (Figure 1). The differences between the variants were significant and mathematically proven (P<0.01). However, none of the treatments had a statistically significant effect on seed germination and normality seedling until -6 bar PEG, whereas -
14 and -16 bar treatments significantly reduced the germination and normality seedling (Figure 1). Suffered a drastic decrease at -10 bar PEG. Rye
seeds were more sensitivity in a higher concentration of -10bar.
The effect of different treatments seed priming on germination characteristics and enzyme activity in response to drought stress:
Priming with gibberellic acid: Results showed
germination percentage (GP) (Figure 2) and
germination index (GI), were significantly improved
in Secale Montanum seeds primed with GA as
compared to the unprimed. The highest
Germination percentage (GP), germination index
(GI), normality seedling percentage (NSP) and
seedling vigour index (SVI), were attained from
treatment 25 ppm of GA at 10°C for 12 h (Table 1).
The minimum germination uniformity (GU) was
attained from 0 ppm at 10°C for 15 h (Table 1).
Coefficient of velocity of germination (CVG), was
significantly improved in Secale montanum seeds
primed with treatments, 0 ppm at 10°C for 12 and
15 h, 0 ppm at 15°C for 12 h, 25 ppm at 10°C for 12
h and 100 ppm at 10°C for 12 h (Table 1). The
minimum Means time to germination (MTG) was
attained from treatment, 50 ppm at 10°C for 12 h
and the highest coefficient of allometry (AC) was
attained from treatment, 0 ppm at 10°C for 15 h and 25 ppm at 15°C for 12 h (Table 1).
Priming with salicylic acid: Results for SA showed germination percentage (GP) (Fig 3) and germination index (GI), was significantly improved in seeds primed with concentration 25 ppm SA at 10°C for 12 h, normality seedling percentage (NSP) was significantly improved in seeds primed with concentrations 25 ppm SA at 10°C for 12 h as compared to the unprimed and other concentrations SA (Table 2). The highest seedling vigour index (SVI) and coefficient of velocity of germination (CVG) were attained from treatment, 75 ppm SA at 10°C for 12 h.. Germination uniformity (GU) was no significantly difference in Secale montanum seeds primed with all treatments SA as compared to the unprimed (Table 2). The highest and minimum means time to germination (MTG) was attained respectively from 50 ppm SA at 10°C for 15 h and 75 ppm SA at 10°C for 12 h (Table 2). The best treatment for Coefficient of allometry (AC) attained from treatments 0 ppm, at 10°C for 12, 15 h and 50 ppm SA at 15°C for 12 h (Table 2).
Figure 1: Changes of the germination percentage (GP) and Normality seedling percentage (NSP) of Rye mountain (Secale montanum), seeds under different PEG concentration solution.
Table 1. Effect of priming with gibberellic acid on germination percentage (GP), normality seedling percentage (NSP), germination Index (GI), germination uniformity (GU), means time to germination (MTG), coefficient of velocity of germination (CVG), seedling vigour index (SVI) and Coefficient of allometry (AC), under Critical potential.
Treatments GI NSP SVI GU CVG MTG AC
0ppm- 10°C- 12 h 7.63ab 14.5bc 26.7ed 0.3cde 4.65ab 0.25cd 0.51abc
0ppm- 10°C- 15h 7.65abc 13.5cd 19.33h 0.23e 4.59ab 0.23d 0.58a
0ppm- 15°C- 12 h 4.93c 'S 0 1 20.10f 0.27de 4.51abcd 0.22d 0.51abc
25ppm- 10°C- 12 h 8.96a 18ab 34.51c 0.32bcde 4.69ab 0.24cd 0.41abcd
25ppm- 10°C- 15h 6.75b 'S 0 1 20.95e 0.31bcde 3.50efg 0.27bcd 0.37abcd
25ppm- 15°C-12 h 7.48ab 6.5g 10.02g 0.26de 3.58efg 0.23cd 0.58a
50ppm- 10°C- 12 h 8.87a 13cde 30.91c 0.47a 2.83g 0.34a 0.31bcd
50ppm- 10°C- 15h LO 8. 20a 54.2a 0.33bcde 4.40abcd 0.26bcd 0.28d
50ppm- 15°C- 12 h 6. 7 cr 10.5de 21.70e 0.31bcde 3.84cde 0.26bcd 0.43abcd
75ppm- 10°C- 12 h 9.16a 15bc 31.86c 0.33bcde 3.49efg 0.28bcd 0.24d
75ppm- 10°C- 15h 7.53ab 14bcd 35.51b 0.36bcd 3.77de 0.29bc 0.44abcd
75ppm- 15°C- 12 h 7.97ab 7.5fg 1 9 0.28cde 3.72def 0.25cd 0.36abcd
100ppm- 10°C- 12 h 8. 15bc 30.6cd 0.38abc 3.00fg 0.31ab 0.38abcd
100ppm- 10°C- 15h 8.79a 13.5cd 22.49de 0.31bcde 3.76de 0.28bcd 0.46abcd
100ppm- 15°C- 12 h 7.68ab 14.5bcd 25.58e 0.29cde 4.90a 0.24cd 0.51abc
Unprimed 4.65c 0h 01 0.39ab 4.07bcde 0.26bcd 0.00e
Table 2. Effect of priming with salicylic acid acid on germination percentage (GP), normality seedling percentage (NSP), germination Index (GI), germination uniformity (GU), means time to germination (MTG), coefficient of velocity of germination (CVG), seedling vigour index (SVI) and Coefficient of allometry (AC), under Critical potential.
Treatments GI NSP SVI GU CVG MTG AC
0ppm- 10°C- 12 h 7.63cd 14.5b 26.69c 4.65a 0.25bcd 4.04abcd 0.51a
0ppm- 10°C- 15h 7.65cd 13.5b 19.33f 4.59a 0.23cd 4.41abc 0.58a
0ppm- 15°C- 12 h 4.90fg 10cd 20.10f 4.51a 0.22cd 4.51ab 0.51ab
25ppm- 10°C- 12 h 9.83ab 20a 37.42ab 4.90a 0.23bcd 4.28abcd 0.46abcd
25ppm- 10°C- 15h 6.71de 12.5bc 24.78c 4.42a 0.21d 4.66ab 0.41bcde
25ppm- 15°C-12 h 4.41g 7efg 14.23d 3.94a 0.23bcd 4.30abcd 0.35cde
50ppm- 10°C- 12 h 7.70cd 11.5bc 27.90b 4.60a 0.25bcd 4.03abcd 0.34de
50ppm- 10°C- 15h 6.54de 8.5de 13.95d 4.89a 0.21d 4.76a 0.45abc
50ppm- 15°C- 12 h 4.53g 5.5f 7.55e 4.48a 0.22cd 4.50ab 0.58a
75ppm- 10°C- 12 h 10.14a 19.5a 41.44a 4.10a 0.31a 3.28e 0.38bcde
75ppm- 10°C- 15h 5.91ef 4.5f 10.78d 4.22a 0.28abc 3.66cde 0.28e
75ppm- 15°C- 12 h 6.52de 9de 13.96d 3.94a 0.25bcd 4.02abcd 0.47abc
100ppm- 10°C- 12 h 8.87bc 13.5b 25.38c 4.52aa 0.28ab 3.61de 0.41bcde
100ppm- 10°C- 15h 6.47de 5f 11.09d 4.10a 0.28abc 3.68cde 0.33de
100ppm- 15°C- 12 h 5.59efg 5f 10.41d 4.51a 0.23bcd 4.31abcd 0.32e
Unprimed 4.65gf 0g 0g 4.07a 0.26abcd 3.91bcde f0 .0 0.
Figure 2. Effect of priming with gibberellic acid on germination percentage (GP) under Critical potential.
Figure 3. Effect of priming with salicylic acid on germination percentage (GP) under Critical potential.
Unprime
Treatment
Figure 4. Effect of priming on activity catalase (CAT) and ascorbate peroxidase (APX)
Antioxidant enzyme activity: Enzyme activity was significantly improved in Secale montanum seeds primed with as compared to the unprimed (Figure 4). CAT significantly improved in Secale montanum seeds primed with GA and SA as compared to the unprimed. Also APX significantly improved in Secale montanum seeds primed with GA and SA as compared to the unprimed (Figure 4).
Thus, seed priming with concentration 25, 50 ppm of GA for 15 h at 10 °C and concentration 25 ppm of SA for 12 h at 10 °C, maybe considered as optimal treatment for priming of Secale montanom seeds in drought stress.
DISCUSSION
In the present investigation, drought stress affected Germination percentage (GP), normality seedling percentage (NSP), germination Index (GI), germination uniformity (GU), means time to germination (MTG), coefficient of velocity of germination(CVG), seedling vigour index (SVI) and Coefficient of allometry (AC) in Secale montanum. The -6 bar PEG or higher concentration reduced the germination characteristics significantly. The results are in agreement with the earlier study Ansari et al (2012) who reported the significant reduction in the germination as well as growth of Rye. As the PEG concentration of -14 and -16 bar inhibited completely the normality seedling percentage therefore, -14 bar PEG was used to study the potential critical in Secale montanum. Seed germination and seedling growth are critical stages in the life cycle of a plant, especially under adverse abiotic stresses. Seed priming is one of the methods that can be taken to counteract the adverse effects of abiotic stress (Patade et al., 2009. Ashraf and Foolad, 2005). In the present study, effect of various seed priming agents was assessed on
germination and seedling growth, under control conditions, various seed priming, significantly increased germination index (GI) (data no shown). In agreement with the results, earlier reports (Patade et al., 2011; Ansari et al., 2012; Rouhi et al., 2011) have shown positive effect of priming in relation to seed performance, germination percentage and seedling indices. However, the priming treatments in the present investigation like GA and SA with appropriate concentration, temperature and time, improved germination characteristics. Seed priming with all prime materials in this experiment improved GP, NSP, GI, GU, SVI and other traits than unprimed expect some treatments for some traits. GA increase the synthesis of hydrolytic enzymes at aleuron layer and by the activity of these enzymes, storage compounds convert to transferable and transfer to emberyo (Sedghi et al., 2008). GA treatments may improve rapid and uniform seedling germination-emergence and plant development in nurseries and in greenhouses (Tzortzakis, 2009). Also, SA increased germination percentage and other germination indices as compared to unprimed. The promotive effect of SA on shoot and root parameters has been reported in wheat and barley (Singh and Usha, 2003; Hayat et al., 2005). Salicylic acid changes the balance of hormones in plants, increased IAA and ABA and prevented the reduction of Cytokinins under no stress conditions (Shakirova et al., 2003). Improved germination and seedling growth were recorded in wheat, when the seeds were subjected to pre-sowing seed-soaking treatment in salicylic acid (Shakirva; 2007). Treat of wheat seeds to ascorbic acid decreased bad effective's drought stress on fresh and dry weight of radical and plumule (Hamad and Hamada, 2001). Afzal et al. (2006) reported that ascorbate and
salicylic acid caused reduction of effectives salinity stress on the germination and seedling growth of wheat. It was identified that salicylic acid regulate cell division, cell extension and death (Zhang et al., 2002). In the present investigation priming increased catalase and ascorbat peroxidase as compared to the unprimed. Rouhi et al. (2012) and Ansari et al. (2012) showed that antioxidant enzyme activities in treated seeds of Berseem clover (Trifolium alexandrinum L) increased as compared to the unprimed. Priming improvement of ATPase activity, RNA and acid posphathase synthesis (Fu et al., 1998), also bye improve of amylases, lipases and protease synthesis (Ashraf and Foolad 2005). Thus Can Said, effect of treatments priming on germination and seedling growth at concentrate, time of priming, temperature for priming and plant species.
CONCLUSIONS
Seed priming treatments improved germination percentage (GP), normality seedling percentage (NSP) and seedling vigour index (SVI), and reduced germination uniformity (GU), means time to germination (MTG), coefficient of velocity of germination (CVG) in Secale montanum under stressed conditions. Also, priming increased CAT and APX, therefore can be said that improvement this germination characteristics of primed seeds could be results of increasing the antioxidant profile of treated seeds.
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