Caderno Pesquisa Bio - Volume 16-1 - TSpace

Optimization of Hormonal Priming Techniques of Alleviation...

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OPTIMIZATION OF HORMONAL PRIMING TECHNIQUES FOR ALLEVIATION OF SALINITY STRESS IN WHEAT (TRITICUM AESTIVUM L.) Irfan Afzal* Shahzad Maqsood Ahmad Basra Nazir Ahmad Muhammad Farooq ABSTRACT An experiment was conducted to examine the effect of hormonal priming with abscisic acid (ABA), salicylic acid (SA), or ascorbic acid on wheat (Triticum aestivum cv. Auqab-2000) germination and seedling growth under normal (4 dS/ cm) and saline (15 dS/cm) conditions. During emergence test, emergence percentage was significantly increased by ascorbic acid and salicylic acid seed treatments but mean emergence time (MET) was unaffected by all priming treatments, however, root and shoot length, fresh and dry weight of seedlings were significantly increased by 50 ppm ascorbic acid and 50 ppm salicylic acid treatments under both normal and saline conditions. Priming with ABA failed to improve seedling growth under both conditions. But all hormonal priming treatments decreased the electrolyte leakage of steep water as compared to that of nonprimed seeds even after 12 h of soaking. Hormonal priming with 50 ppm SA induced maximum decrease in electrolyte leakage while an increase in electrolyte leakage was observed by 10 ppm ABA and 100 ppm ascorbic acid. It is concluded that hormonal priming has reduced the severity of the effect of salinity but the amelioration was better due to 50 ppm SA and 50 ppm ascorbic acid treatments as these showed best results on seedling growth, fresh and dry weights under nonsaline and saline conditions whereas hormonal priming with ABA as not effective in inducing salt tolerance under present experimental material and conditions.

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Abbreviations: Salicylic acid = SA, Abscisic Acid = ABA, Final emergence percentage = FEP, Mean emergence time = MET, Electrical conductivity = EC, Reduction percentage of emergence = RPE

RESUMO Experimentos foram conduzidos para avaliar o efeito do priming hormonal com ácido abscísico (ABA), ácido salicílico (SA), ou ácido ascórbico em trigo (Triticum aestivum cv. Auqab-2000) na germinação e crescimento de plântulas em condições normais (4 dS/cm) e salinas (15 dS/cm). Durante o teste, o percentual de emergência foi significativamente aumentado pelo tratamento das sementes com ácido ascórbico e ácido salicílico, mas o tempo médio de emergência (MET) não foi afetado por todos os tratamentos “priming”, entretanto, o comprimento da raiz e caule, peso fresco e seco das mudas foram significativamente maiores nos tratamentos com 50 ppm de ácido ascórbico e 50 ppm de ácido salicílico tanto em condição normal como salina. Priming com ABA não melhorou o crescimento de mudas em ambas as condições, mas todos os tratamentos com priming hormonal diminuíram a drenagem eletrolítica do steep water quando comparada com a de sementes sem priming, mesmo após 12 horas. Priming hormonal com 50 ppm de SA induziu a uma diminuição máxima da drenagem eletrolítica enquanto que um aumento na drenagem foi observado com 10 ppm de ABA e 100 ppm de ácido ascórbico. Conclui-se que o priming hormonal reduz os efeitos da salinidade sendo o melhor resultado obtido com tratamentos com 50 ppm de SA e 50 ppm de ácido ascórbico, que mostraram melhores resultados sobre o crescimento de plântulas, peso seco e fresco e sob condições salinas e não salinas. O priming hormonal com ABA não foi efetivo na indução de tolerância a sal sob as condições e material deste experimento. Palavras-chave: Priming hormonal, tolerância a salinidade, vigor de plântulas, sementes de trigo.

Keywords: Hormonal Priming, salinity tolerance, seedling vigor, wheat seed. ________________ * Department of crop physiology, University of Agriculture, Faisalabad, Pakistan; tel.: +92 300 9658671, fax: +92 41 9200183, e-mail: [email protected] Caderno de Pesquisa Sér. Bio., Santa Cruz do Sul, v. 17, n. 1, p. 95-109, jan./jun . 2005

INTRODUCTION Salinity is one of the major and increasing problems in irrigated agriculture in Pakistan, particularly in wheat and rice grown areas. The areas affected by Caderno de Pesquisa Sér. Bio., Santa Cruz do Sul, v. 17, n. 1, p. 95-109, jan./jun . 2005


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varying degrees of salinity are reported at around 6.3 M ha within Canal Command areas, of which half is cultivable or cultivated to some extent (RAFIQUE, 1990). GHASSEMI et al. (1995) estimated about 14 % of irrigated land to be badly affected by salinity in Pakistan. The adverse effects of high concentration of salts for plants are due to the osmotic retention of water and to specific ionic effects on the protoplasm. Water is osmotically held in salt solutions, so as the concentration of salt increased water becomes less and less accessible to the plant. Poor germination and seedling establishment are the results of soil salinity. It is an enormous problem adversely affecting growth and development of crop plants and results into low agricultural production (GARG & GUPTA, 1997). Wheat is grown on all type of soils and is classified as a moderate, salt tolerant crop (MASS & HOFFMAN, 1977). Yield losses on salt affected soils of Pakistan average about 64%. The effect of salinity at seedling stage of wheat range from reduction in germination percentage, fresh and dry weight of shoots and roots to the uptake of various nutrient ions. Pre-sowing seed treatments have been shown to enhance stand establishment in non-saline areas (KHAN, 1992) and have potential in saline areas as well (ASHRAF & RUAF, 2001; BASRA et al., 2005). Prior to selecting these alternatives, it seems necessary to examine seed vigor enhancement techniques leading to better and synchronized stand establishment under stress conditions. Physiological treatments to improve seed germination and seedling emergence under various stress conditions have been intensively investigated in the past two decades (BRADFORD, 1986). It is thought that the depressive effect of salinity on germination could be related to a decline in endogenous levels of hormones (DEBEZ et al., 2001)). However, incorporation of plant growth regulators during presoaking, priming and other pre-sowing treatments in many vegetables crops have improved seed performance. Typical responses to priming are faster and closer spread of times to germination and emergence over all seedbed environments and wider temperature range of germination, leading to better crop stands, and hence improved yield and harvest quality, especially under suboptimal and stress condition growing conditions in the field (HALMER, 2004). Plants produce proteins in response to abiotic and biotic stress and many of these proteins are induced by phytohormones such as ABA (JIN et al., 2000) and salicylic acid (HOYOS & ZHANG. 2000). Salicylic acid is an endogenous growth regulator of phenolic nature, which influence a range of diverse processes in plants, including seed germination (CUTT & KLESSIG, 1992), stomatal closure (LARQUESAAVEDA, 1979), ion uptake and transport (HARPER & BALKE, 1981),

membrane permeability (BARKOSKY & EINHELLIG, 1993), photosynthetic and growth rate (KHAN et al., 2003). SA is also important signal molecule for modulating plant responses to environmental stress. SA is known to provide protection against a number of abiotic stresses (SENARATNA et al., 2000). Presoaking seeds with optimal concentration of phytohormones has been shown to be beneficial to growth and yield of some crop species growth under saline conditions by increasing nutrient reserves through increased physiological activities and root proliferation (SINGH & DARA, 1971). Concerted attempts have been made to mitigate the harmful effects of salinity by application of plant growth regulators (DATTA et al. 1998). Thus the detrimental effects of high salts on the early growth of wheat seedlings may be reduced to some extent by treating seeds with the proper concentration of a suitable hormone (DARRA et al., 1973). To our knowledge, little research has been done on the use of SA, ABA and ascorbic acid as hormonal priming agent, however, these are abundantly used in stress conditions as a foliar application during different growth stages of crop plants. The present study is therefore, conceived with to investigate the effects of presoaking of wheat seeds in varying concentrations of ABA, SA and ascorbic acid upon their germination and subsequent growth under saline conditions. The research is important because it can reveal the role of hormones that impart stress resistance and provide insight into the potential for wheat plants to adapt to saline conditions.

Caderno de Pesquisa Sér. Bio., Santa Cruz do Sul, v. 17, n. 1, p. 95-109, jan./jun . 2005


MATERIALS AND METHODS Seed materials Seeds of wheat (Triticum aestivum L.) cv. Uqab-2000 were obtained from Punjab Seed Corporation, Faisalabad, Pakistan. Before the start of experiment, seeds were surface sterilized in 1% sodium hypochlorite solution for 3 min, then rinsed with sterilized water and air-dried. Hormonal Priming Hormone solutions of appropriate concentrations were prepared. 250 gram of seeds were soaked in 500mL of aerated solution for 12 h and redried near to original weight with forced air under shade (SUNDSTROM et al., 1987). Seedling Vigor Evaluation Before the start of the experiment, salinity was developed in each plastic


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pot by giving the first irrigation of 15 dS/cm saline water (USDA Salinity Lab. Staff, 1954). Control and treated seeds were sown in plastic tubs having moist sand and were placed in a net house. After sowing the seed in sand at the depth of 3 cm, the pots were placed in growth chamber at temperature of 25 ± 2 oC. Half strength Hoagland solution was applied when the sand began to dry out, but there was no excess water visible. Weather data recorded during the course of studies is given in Table 1. Emergence was recorded daily according to the Seedling Evaluation Handbook of Association of Official Seed Analysts (1990). The experiment was preceded for three weeks. Seedlings were harvested and washed with deionized water after harvest. Washed seedlings were separated into root and shoot for the determination of their fresh and dry weight. Dry weight was determined after oven drying the samples at 65 oC. During this, mean germination / emergence time (MGT) or (MET) was calculated according to the equation of ELLIS & ROBERTS (1981). The reduction percentage of emergence (RPE) was calculated as quoted by MADIDI et al. (2004): RPE = (1- Nx / Nc) x 100 “Nx” is the number of germinated seedlings under salt treatments and “Nc” is the number of germinated seedlings under control. Electrical conductivity of seed leachates After washing in distilled water, 5 g seeds were soaked in 50 mL distilled water at 25 ºC. Electrical conductivity of steep water was measured 0.5,1.0,1.5,2.0,6.0,12.0 and 24.0 h after soaking using conductivity meter (Model Twin Cod B-173) and expressed as mS/cm (BASRA et al., 2002). The data collected was analyzed using the Fisher’s analysis of variance technique under completely randomized block design (CRD) and the treatment means were compared by Least Significant Difference (LSD) test at 0.05 probability level (STEEL & TORRIE, 1984).

RESULTS FEP, MET and RPE were significantly affected by hormonal priming under both normal and saline conditions (Fig. 1). Maximum emergence was achieved in Caderno de Pesquisa Sér. Bio., Santa Cruz do Sul, v. 17, n. 1, p. 95-109, jan./jun . 2005

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seeds primed with 50 ppm ascorbic acid, which was statistically similar to all the remaining treatments except non-primed seeds under normal conditions however salinity drastically inhibited emergence percentage (Fig. 1a). Under saline conditions, enhanced emergence was observed in seeds primed with ascorbic acid and salicylic acid, but ABA treatments failed to improve emergence percentage. Priming with 50 ppm ascorbic acid and salicylic acid took minimum time to emerge as compared to control (Fig. 1b). Maximum emergence time was recorded in seeds primed with various concentrations of ABA including non-primed seeds. Similarly, maximum reduction in emergence percentage was observed in seeds primed with 10 or 50 ppm ABA as compared to non-primed seeds (Fig. 1c). All the priming treatments showed a significant effect on root and shoot length, root shoot ratio under both normal and saline conditions (Fig. 2). Priming with 50 ppm salicylic acid followed by 50 ppm ascorbic acid showed maximum shoot length as compared to control as compared to ABA and non-primed seeds under normal and saline conditions (Fig. 2a & b). Minimum shoot and root length were recorded in seeds primed with various concentrations of ABA as compared to control. Root shoot ratio was unaffected by most of priming treatments under both conditions (Fig. 2c) Priming treatments significantly affected fresh and dry weight of seedlings under both normal and saline conditions (Fig. 3). Fresh weights of seedlings was drastically decreased due to salinity stress but seedlings raised from seeds primed with various concentrations of ascorbic acid and salicylic acid improved fresh weight of seedlings as compared to control under normal and saline conditions (Fig. 3a & b). Minimum shoot and root fresh weights were recorded in seedlings raised from seeds primed with 10, 30 or 50 ppm ABA and 100 ppm salicylic acid treatments. All the hormonal priming treatments failed to improve shoot dry weight under normal conditions but under saline conditions, shoot dry weight was significantly decreased and maximum dry weight was recorded in seedlings raised from seeds primed with 50 ppm salicylic acid, which was statistically at par with various concentrations of ascorbic acid treatments (Fig. 3c). All the priming treatments failed to improve root dry weight under normal as well as saline conditions (fig. 3d). The electrolyte conductivity of seed leachates was significantly decreased with the application of hormonal priming treatments on wheat seeds (Fig. 4). Generally the electrolyte leakage was increased with increasing imbibition period including all treatments and control. After a longer period of imbibition ranging from 1h to 24h all the priming treatments lowered down the electrolyte leakage than control. An increase in electrolyte leakage was observed in seeds treated with 10 Caderno de Pesquisa Sér. Bio., Santa Cruz do Sul, v. 17, n. 1, p. 95-109, jan./jun . 2005


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ppm ABA and 100 ppm ascorbic acid as compared to remaining treatments including control on all measuring periods. Maximum decrease in electrolyte leakage was induced by 50 ppm salicylic acid after 24 h of soaking period. Overall, all the priming treatments except 10 ppm ABA and 100 ppm Ascorbic acid were effective in decreasing electrical conductivity of seed leachates.

DISCUSSION Salinity markedly affected seedling growth (Fig. 1-3). These results are strongly in accordance with CICEK & CAKIRLAR (2002) who reported that salinity reduced shoot length, fresh and dry weight of maize seedlings. There are several possible causes for increased emergence percentage and seedling growth. First, greater tolerance of emergence may result from a lower uptake of NaCl by intact seeds and hence lower concentrations in the embryo axis. Secondly, the increase in emergence percentage in seeds primed with 50 ppm acorbic acid and salicylic acid under saline conditions may be due to enhanced oxygen uptake, increased a- amylase activity and the efficiency of mobilizing nutrients from the cotyledons to the embryonic axis (KARTHIRESAN et al., 1984). Thirdly, concentrations of SA and ascorbic acid declined in response to salinity and the role of SA in alleviating salinity stress and ascorbic acid as an antioxidant scavenging enzyme during oxidative stress is well documented in the literature. With the application of SA and ascorbic acid to seeds will helpful in minimizing the damaging effect of salinity stress. Salinity tolerance in seeds primed with 50 ppm salicylic acid might be due to increased activities of alpha amylase and proteinase in endosperm and the contents of soluble sugar, protein and free amino acids under stress conditions (ZHANG et al., 1999). Salt tolerance was increased in seeds subjected to 50 ppm SA and 50 ppm ascorbic acid as indicated by shoot and root length, shoot fresh and dry weight. These results are in agreement with those obtained by other authors, showing that salt tolerance is induced in seedlings raised from seeds primed with ascorbic acid and salicylic acid (ROY & SRIVASTAVA, 1999; TARI et al. 2002). These results further relate with the studies of ANGRISH et al. (2001) who reported that amelioration of salinity was due to enhanced N status and nitrate reductase activity through pre-sowing wheat seeds with plant growth regulators. These observations are in consistent with those of KHODARY (2004) who reported that SA increases the fresh and dry weight of shoot and roots of stress maize plants. Caderno de Pesquisa Sér. Bio., Santa Cruz do Sul, v. 17, n. 1, p. 95-109, jan./jun . 2005

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Maximum EC of seed leachates was recorded in untreated seeds (Fig. 4). All the seed treatments resulted in lower EC of seed leachates compared with check. Minimum EC of seed leachates was noted in seeds subjected to 50 ppm salicylic acid followed by 50 ppm ascorbic acid. The reduced EC of seed leachates from SA treated seeds might be related to induction of antioxidant responses that protect the plant from oxidative damage. An increase in electrolyte leakage was observed by 10 ppm ABA at all soaking periods which was probably due to the loss of ability to reorganize cellular membranes rapidly and completely (MCDONALD, 1980). Our experiments indicate that phytohormones play critical roles in plant responses to salinity and it can be concluded that hormonal priming with 50 ppm ascorbic acid and 50 ppm salicylic acid increase the ability of what to grow successfully under saline conditions whereas hormonal priming with ABA were not effective in inducing salt tolerance. Finally, in future, these hormonal priming treatments may be used for improving plant growth and yield in saline areas.

LITERATURE CITED ANGRISH, R.; KUMAR, B.; DATTA, K. S. Effect of gibberellic acid and kinetin on nitrogen content and nitrate reductase activity in wheat under saline conditions. Indian Journal of Plant Physiology, 6, p. 172-177, 2001. ASHRAF, M.; RAUF, H. Inducing salt tolerance in maize (Zea mays L.) thorugh seed priming with chloride salts: Growth and ion transport at early growth stages. Acta Physiologia Plantarum, 23, p. 407-417, 2001. ASSOCIATION OF OFFICIAL SEED ANALYSIS (AOSA). Rules for testing seeds. Journal of Seed Technology, 12, p. 1-112, 1990. BARKOSKY, R. R.; EINHELLIG, F. A. Effects of salicylic acid on plant water relationship. Journal of Chemical Ecolology, 19, p. 237-247, 1993. BASRA S. M. A.; AFZAL I.; RASHID, R. A.; HAMEED, A. Inducing salt tolerance in wheat by seed vigor enhancement techniques. International Journal Biotechnology and Biology, 1, p.173-179, 2005 BASRA, S. M. A.; ZIA, M. N.; MAHMOOD, T., AFZAL, I.; KHALIQ, A. Comparison of different invigoration techniques in wheat (Triticum aestvum L.). Pakistan Journal of Arid Agriculture, 5, p. 325-329, 2002. BRADFORD, K. J. Manipulation of seed water relations via osmotic priming to Caderno de Pesquisa Sér. Bio., Santa Cruz do Sul, v. 17, n. 1, p. 95-109, jan./jun . 2005


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improve germination under stress conditions. Horticultural Science, 21, p. 11051112, 1986.

induced changes in protein synthesis in tomato roots. Plant Cell and Environment, 23, p. 51-60, 2000.

CICEK, N.; CAKIRLAR, H. The effect of salinity on some physiological parameters in two maize cultivars. Bulgarian Journal of Plant physiology, 28, p. 66-74, 2002.

KATHIRESAN, K.; KALYANI, V.; GNANARETHIUM, J. L. Effect of seed treatments on field emergence, early growth and some physiological processes of sunflower (Helianthus annus L.). Field Crops Research, 9, p. 255-259, 1984.

CUTT, J. R.; KLESSIG, D. F. Salicylic acid in plants. A changing perspective. Pharmacetical Technology, 16, p. 25-34, 1992.

KHAN, A. A. Preplant physiological seed conditioning. Horticultural Review, 14, p. 131-181, 1992.

DARRA, B. L.; SETH, S. P.; SINGH, H.; MENDIRATTA, R. S. Effect of hormone-directed presoaking on emergence and growth of osmotically stressed wheat (Triticum aestivum L.). Agronomy Journal, 65, p. 292-295, 1973.

KHAN, W.; PRITHIVIRAJ, B.; SMITH. Photosynthetic responses of corn and soybean to foliar application of salicylates. Journal of Plant Physiology, p. 18, 2003.

DATTA, K. S.; VARMA, S. K.; ANGRISH, R.; KUMAR, B.; KUMARI, P. Alleviation of salt stress by plant growth regulators in Triticum aestivum L. Biologia Plantarum, 40, p. 269-275, 1998.

KHODARY, S. E. A. Effect of salicylic acid on the growth, photosynthesis and carbohydrate metabolism in salt-stressed maize plants. International Journal of Agriculture and Biology, 6, p. 5-8, 2004.

DEBEZ, A.; CHAIBI, W.; BOUZID, S. Effect du NaCl et de regulatoeurs de croissance sur la germination d’ Atriplex halimus L. Cahiers Agricultures, 10, p.135-138, 2001.

LARQUE-SAAVEDA, A. Stomatal closure in response to salicylic acid treatment. Z. Pflanzenphysiology, 93, p. 371-375, 1979.

ELLIS, R. A.; ROBERTS, E. H. The quantification of ageing and survival in orthodox seeds. Seed Science and Technology, 9, p. 373-409, 1981.

MADIDI, S. E.; BAROUDI, B. E.; AAMEUR, F. B. Effects of salinity on germination and early growth of barley (Hordeum vulgare L.) Cultivars. International Journal of Agriculture and Biology, 6, p.767-770, 2004.

GARG, B. K.; GUPTA, I. C. Plant relations to salinity. In: Saline wastelands environment and plant growth., p. 79-121. Scientific Publishers, Jodhpur, 1997.

MASS, E. V.; HOFFMAN, G. J. Crop salt tolerance current assessment. Journal of Irrigation and Drainage, 103, p. 115-134, 1977.

GHASSEMI, F.; JACKMAN, A. J.; NIX, H. A. Salinization of land and water resources. CAB international, Wallingford, UK, p. 526, 1995.

MCDONALD, Jr. M. B. Assessment of seed quality. Horticultural Science, 15, p. 784-788, 1980.

HALMER, P. Methods to improve seed performance in the field. In: Handbook of Seed Physiology; Application to Agriculture. BENECHARNOLD, R. L.; SANCHEZ, R. A. (eds.). New York: The Haworth Press, p, 125-165, 2004.

RAFIQUE, M. Soil resources and soil related problems in Pakistan. In: Soil Physics Application under Stress Environments. AHMAD, M. (ed.): BARD, PARC, Islamabad, 1990.

HARPER, J. P.; BALKE, N. E. Characterization of the inhibition of K+absorption in oat roots by salicylic acid. Plant Physiology, 68, p.1349-1353, 1981.

ROY, N. K.; SRIVASTAVA, A. K. effect of presoaking seed treatment on germination and amylase activity of wheat (Triticum aestivum L.) under salt stress conditions. Rachis, 18, 46-51, 1999.

HOYOS, M. E.; ZHANG, S. Q. Calcium-independent activation of salicylic acidindcued protein kinase and a 40-kilodalton protein kinase by hyperosmotic stress. Plant Physiology, 122, p. 1355-1363, 2000.

SENARATNA, T.; TOUCHELL, D.; BUMM, E.; SIXON, K. Acetyl salicylic (Aspirin) and salicylic acid induce multiple stress tolerance in bean tomato plants. Plant Growth Regulation, 30, p.157-161, 2000.

JIN, S.; CHEN, C. C. S.; Plant, A. L. Regulation by ABA of osmotic stress

SINGH, H.; DARA, B. L. Influence of presoaking of seeds with gibberellin and



auxins on growth and yield attributes of wheat (Triticum aestivum L.) under high salinity, sodium adsorption ratio and boron levels. Indian Journal of Agricultural Sciences, 41, p. 998-1003, 1971. STEEL, R. G. D.; TORRIE, J. H. Principles and Procedures of Statistics. A Bionetrical Approach. Singapore: 2nd Ed. McGraw Hill Book Co. Inc., p. 172-177, 1984.

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SUNDSTROM, F. J.; READER, R. B.; EDWARDS, R. L. Effect of seed treatment and planting method on Tabasco pepper. Journal of American Society of Horticultural Sciences, 112, p. 641-644, 1987. TARI, I.; CSISZAR, J.; SZALAI, G.; HORVATH, F.; PCSVARADI, A.; KISS, G.; SZEPESI, A.; SZABO, M.; ERDEI, L. Acclimation of tomato plants to salinity stress after a salicylic acid pre-treatmemt. Acta Biologica Szegediensis, Proceedings of the 7th Congress on plant physiology, 46, p. 55-56, 2002.

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ZHANG, S.; Gao, J.; Song, J.; Zhang, S. G.; Gao, J. Y.; Song, J. Z. Effects of salicylic acid and aspirin on wheat seed germination under salt stress. Plant physiology communications, 35, p. 29-32, 1999.

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Fig. 1 - Effect of different hormonal priming techniques on final emergence (a), MET (b) and RPE (c) of wheat growing under normal and saline conditions during emergence test. Caderno de Pesquisa Sér. Bio., Santa Cruz do Sul, v. 17, n. 1, p. 95-109, jan./jun . 2005



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Fig. 2 - Effect of different hormonal priming treatments on root length (a), shoot length (b) and root shoot ratio (c) of wheat during emergence test.

Fig. 3 - Effect of different hormonal priming techniques on Shoot fresh weight (a), root fresh weight (b), root dry weight(c) and shoot dry weight (d) of wheat growing under normal and saline condition during emergence test.




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Caderno Pesquisa Bio - Volume 16-1 - TSpace

Caderno Pesquisa Bio - Volume 16-1 - TSpace

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