PRE-SOWING SEED TREATMENTS TO IMPROVE GERMINATION AND SEEDLING GROWTH IN WHEAT (TRITICUM AESTIVUM L.) RESUMO

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1 Pre-Sowing Seed Treatments to Improve Germination and Seedling PRE-SOWING SEED TREATMENTS TO IMPROVE GERMINATION AND SEEDLING GROWTH IN WHEAT (TRITICUM AESTIVUM L.) ABSTRACT Shahzad M. A. Basra 1 Irfan Afzal Rashid Ali Rashid M. Farooq An experiment was conducted to study the germination, emergence and seedling establishment of wheat (Triticum aestivum L.) cv. Auqab Wheat seeds were subjected to hydropriming for 24h or hardening for 12h (one cycle) or matriconditioning with pressmud for 24h or halopriming with 100 mol m -3 CaCl 2, 50 mol m -3 NaCl, 25 mol m -3 Ca(NO 3 ) 2 for 24h. Both primed and unprimed seeds were subjected to germination, emergence and electrical conductivity test. In germination test hydropriming, hardening and matriconditioning were found better as expressed by all the invigoration parameters. But no significant effect of Ca(NO 3 ) 2 and NaCl treatments was noted in final germination percentage, T 50 and mean germination time. In case of seedling evaluation in emergence test, hydropriming and hardening treatment were the most effective treatments as expressed by final emergence percentage, root and shoot dry weight, root and shoot length and root / shoot ratio. While seed priming with NaCl resulted in minimum final emergence percentage, seedling dry weight and minimum fresh weight of seedling, root and shoot length, root / shoot ratio and shoot fresh weight except control. All the treatments showed maximum seed invigoration than the control. Higher electrical conductivity of seeds treated with CaCl 2, non-primed seeds and Ca(NO 3 ) 2 were recorded as compared to seeds treated with NaCl, matriconditioning, hydropriming, and hardening treatments. These results support the hypothesis that wheat seed vigor can be enhanced when treated with distilled water for 24 h or hardening for 12h (one cycle). Keywords: hydropriming, matriconditioning, halopriming, seedling vigor, wheat. 1 Department of crop physiology, University of Agriculture, Faisalabad, Pakistan E- mail: irita76@yahoo.com RESUMO Um experimento foi conduzido para estudar a germinação, emergência e estabelecimento de plântulas de trigo (Triticum aestivum L.) cv. Auqab Sementes de trigo foram sujeitas a hidrocondicionamento por 24 horas ou hardening por 12h (um ciclo) ou matricondicionamento com bagaço por 24h ou halocondicionamento com 100 mol m -3 CaCl 2, 50 mol m -3 NaCl, 25 mol m -3 Ca(NO 3) 2 por 24h. Tanto sementes com e sem o condicionamento foram submetidas ao teste de germinação, emergência e condutividade elétrica. No teste de germinação o hidrocondicionamento, hardening e matricondicionamento foram considerados os melhores como foi expressado em todos os parâmetros de envigoramento. Mas nenhum efeito significante nos tratamentos com Ca(NO 3) 2 e NaCl foi notado na percentagem final de germinação, T 50 e tempo médio de germinação. No caso da avaliação de plântulas em testes de emergência, os tratamentos de hidrocondicionamento e hardening foram os mais efetivos como foi expressado pela percentagem final de emergência, peso seco e comprimento da raíz e parte aérea e razão raiz/parte aérea. Enquanto que o condicionamento da semente com NaCl resultou numa percentagem de emergência final, peso seco e fresco da plântula, comprimento da raiz e parte aérea, relação raiz/parte aérea e peso fresco da parte aérea em valores mínimos, exceto no controle. Todos os tratamentos apresentaram envigoramento máximo da semente em relação ao controle. Foram conseguidos as maiores condutividades elétricas de sementes tratadas com CaCl 2, sementes não condicionadas e Ca(NO 3) 2 se comparadas com as sementes tratadas com NaCl, matricondicionamento, hidrocondicionamento e hardening. Estes resultados suportam a hipótese de que o vigor da semente de trigo pode ser aumentado quando tratado com água destilada por 24 h ou hardening por 12 h (um ciclo). Palavras-chave: hidrocondicionamento, Matricondicionamento, Halopriming, vigor de plântulas, trigo. INTRODUCTION Seed invigoration is a term used in the scientific literature to describe beneficial treatments applied on the seeds after harvest, but prior to sowing in

2 Pre-Sowing Seed Treatments to Improve Germination and Seedling order to improve the germination or seedling growth (TAYLOR et al., 1998). Many seed invigoration treatments are being used in many parts of the world to improve the germination or to get synchronized germination and less mean germination time (LEE AND KIM, 2000). These include water soaking (RUDRAPAL and NAKAMMA, 1988), hardening (NATH et al., 1991; ADAM, 1999; LEE and KIM, 2000) and Seed priming. (KHAN, 1992; LEE et al., 1998a). The beneficial effects of seed hardening are primarily due to pre-enlargement of the embryo (AUSTIN et al., 1969), biochemical changes like enzyme activation (VILLIERS and EDGCUMBE, 1975), and improvement of germination rate particularly in old seeds (GRAY and STECKEL, 1977; LEE et al., 1998a). Soon et al. (2000) reported that hydropriming was best in promoting germination. The best priming treatment was found to be hydropriming for 24 h by BASRA et al. (2003) followed by matriconditioning with gunny bags for 24 h. Another approach to control seed hydration is the use of solid matrix carriers with low matrix potentials (KUBIK et al., 1988; CATLIFFE, 1997). Solid matrix priming is a term used for pre-sowing treatment in which a solid matrix instead of an osmotic solution is used to enhance germination. It is a process that uses solid matrix materials, water and seed in combination to control water, oxygen and temperature effects on germination. The process controls seed hydration to level that allows pre-germination activity but prevents radical emergence. Matric-priming (HARDGREE, 1994) or Matriconditioning (KHAN et al., 1995) was proposed as an alternative term to solid matrix priming (CANTLIFFE, 1997). Salts or nonpenetrating organic solutes in liquid medium or matrix solutions are used to establish equilibrium water potential between seed and osmotic medium needed for conditioning (KHAN, 1993). The objective of the present experiment was to study whether priming with water, osmotica or solid matrix carrier results in enhancement of seed vigor in wheat. Further to develop suitable invigoration techniques for wheat seeds under our local ecological conditions and genetic material. MATERIALS AND METHODS The experiment was conducted to study the influence of different seed priming techniques on growth and vigor of wheat in the seed laboratory, Department of Crop Physiology, University of Agriculture, Faisalabad during the year Seeds of wheat (Triticum aestivum L.) cv. Uqab-2000 were obtained from Punjab seed corporation, Faisalabad. Before the start of experiment, seeds were surface sterilized in 10% sodium hypochlorite solution for 10 minutes, then rinsed with sterilized water and air-dried. Following pre-sowing seed treatments were included T 1 = Control T 2 = Hydropriming for 24 h T 3 = Hardening for 12 h (One cycle) T 4 = Matriconditioning with Pressmud for 24 h T 5 = 100 mol m -3 CaCl 2 for 24 h T 6 = 50 mol m -3 NaCl for 24 h T 7 = 25 mol m -3 Ca(NO 3 ) 2 for 24 h A weighed quantity (250 g) of wheat seeds was used in each treatment in plastic beakers containing 500 ml of respective solution for 24 hours for hydropriming and halopriming. Solid matrix priming was carried out with pressmud in which seeds were mixed with one kg sterilized pressmud and 350 ml of distilled water in closed plastic container. The container was placed under shade at room temperature for 24h. The partially hydrated seeds then were screened from the pressmud (AFZAL et al., 2002). After all the treatments, seeds were given three surface washings with distilled water (KHAN et al., 1992) and re-dried to the original weight with forced air under shade. For hardening treatment this cycle was repeated twice for 12h in distilled water. These seeds were sealed in polythene bags and stored in a refrigerator at 7 o C for further studies. Yhe treated seeds were compared with control ones for vigor by germination, emergence and electrical conductivity tests. Vigor evaluation Germination test: Germination of controlled and treated seeds was evaluated between two layers of moist filter paper in petridishes (ASHRAF et al., 1999). Twenty-five seeds per petridish were sown and the experiment was replicated thrice. The petridishes were covered with lids and placed in an incubator at 25 o C. The data of final germination percentage (%), days to 50% germination (T 50 ) (days) and mean germination time (MGT) (days) were recorded up to 3 days after sowing. Emergence test: The experiment was carried out in pots filled with sand. 25 seeds were sown per pot at the depth of 3cm and the experiment was replicated thrice. The pots were placed in the net house. The data regarding the final emergence percentage (%), days to 50% emergence (E 50 ) (days) and mean

3 Pre-Sowing Seed Treatments to Improve Germination and Seedling emergence time (MET) (days) were recorded after the start of experiment. The data for the shoot length (cm), root length (cm), root / shoot ratio, fresh weight of seedling (g) and dry weight of seedling (g) was recorded after 8 days of sowing. Electrical conductivity test: Four-gram seeds of each treatment were soaked on plastic beaker having distilled water at 25 o C. Electrical conductivity of seed leachates was measured after 0.5, 1.0, 1.5, 2, 6, 12, and 24 hours of soaking (ASHRAF et al., 1999) using the conductivity meter (Model Twin Cod B-173) and expressed as ms / cm / g. The experiment was replicated thrice. 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 and TORRIE, 1984). RESULTS AND DISCUSSION In germination test (Fig. 1), the comparison of treatment means elaborates that 100% germination percentage was recorded from non-primed seeds subjected to hydropriming, seed hardening, matriconditioning or CaCl 2 priming while halopriming with NaCl and Ca(NO 3 ) 2 resulted in lower and statistically similar germination percentage (92.00). Minimum T 50 was recorded in hardening, which is statistically similar to that of hydropriming and matriconditioning. Maximum mean germination time was recorded in control. While in emergence test (Table 1), the results indicate that hydropriming and hardening treatments significantly reduced the germination time and increased the emergence rate and seedling vigor despite the seed lot selected was already of high vigor (100% emergence of uncontrolled seeds). It shows that priming (hydropriming and hardening) can not only improve the performance of low vigor seeds but can also invigorate and induce early, synchronized and healthier crop stand. The minimum emergence time was recorded in seeds subjected to NaCl. Significantly minimum E 50 was recorded in hydroprimed seeds which was statistically at par to that of hardening, matriconditioning, and Ca(NO 3 ) 2. Statistically maximum E 50 was recorded in control, which results that all seed treatments resulted in earlier and faster emergence. Maximum shoot length was observed in seeds subjected to hardening which was similar to hydroprimed seeds. Longest roots were measured in seed subjected to hardening. The minimum root length was recorded in non-primed seeds which may be due to ion toxicity. Hardening treatment showed maximum seedling dry weight which is similar to hydropriming, matriconditioning, CaCl 2 and Ca(NO 3 ) 2 treatments. Minimum dry weight was shown by control treatment. The overall results showed that the halopriming of wheat seeds by CaCl 2, Ca(NO 3 ) 2, and NaCl could not invigorate the wheat seeds rather these reduced the vigor and increased the germination time. Halopriming might succeed in low vigor seeds. However, no extra ordinary depressing effect of growth was observed by halopriming which negate the possibility of salt toxicity during priming. Non-viable or deteriorated seeds have been reported to leak more solutes when placed in water than viable or vigorous seeds. The fig.2 Shows the effect of different pre-sowing seed treatments on solute leakage of wheat seeds. Hardening treatment had minimum electrical conductivity on all measuring periods than all other treatments. Maximum EC was recorded by 50 mol m -3 CaCl 2 treatment. Overall results of EC test shows that EC of seed leachates was decreased by most of pre-sowing treatments. 50 mol m -3 CaCl 2 treated seeds had greater EC, which shows the toxic behaviors of ionic salts. Penetration of CaCl 2 in the seed tissues, which resulted increasing the EC of seed leachates. Decreased leakage of solute in hydropriming treatment than control may be because of better membrane repair during hydration. Greater membrane integrity in treated seeds of eggplant and radish are reported by RUDRAPAL and NAUKAMURA (1998) and AFZAL et al. (2002) for hybrid maize. However, our results are not in line with the findings of AGERICH and BRADFORD (1989) for tomato seeds and BASRA et al. (2002) for wheat seeds. Reduction in germination percentage of seeds subjected NaCl might be due to accumulation of salts in tissue, which cause toxicity (SMITH and COBB, 1991). Decrease in T50 by hydropriming may be due to faster production of germination metabolites and better genetic repair i.e., earlier and faster synthesis of DNA, RNA and protein (BRAY et al., 1995). These findings are in agreement with the results of Lee et al. (1998) and LEE and KIM (2000) who reported that hardening treatment reduces the T 50 in rice seeds. Reduction in emergence percentage of seeds might be due to accumulation of salts in tissue, which cause toxicity (SMITH and COBB, 1991). These findings are in accordance with the finding of BASRA et al. (2002) in wheat. The decrease in E 50 by various priming tools might be due to controlled hydration by priming which results in better structural and genetic repair (BRAY et al., 1989). Increased dry weight of seedling in treated seeds attributed to more synchronize germination, which resulted in early stand establishment. Our results confirm the findings of BASRA

4 Pre-Sowing Seed Treatments to Improve Germination and Seedling et al. (2002). CONCLUSION Wheat seeds genotype Auqab-2000 respond to different pre-sowing seed treatment and hydropriming for 24h treatment showed the maximum invigoration followed by hardening for 12h (one cycle) than all other treatments including control. Table 2 - Influence of seed priming on vigor of wheat cv. Auqab-2000 in emergence test Treatments Final emergence (%) E 50 (days) MET (days) Shoot length (cm) Root length (cm) Root shoot ratio Fresh weight (g) Dry weight (g) Control 100 a a a c b b d c Hydropriming 100 a c c a a a ab a Hardening 100 a bc bc a a a b a Matriconditioning b bc bc b b b a ab d b b b b b b CaCl 2 ab e bc bc b b b c b NaCl c bc bc b b b b Ca(NO 3 ) 2 ab Solute leakage (us/cm/g) Control Soaking period (h) FIGURE 2 - Solute leakage of wheat cv. Uqab-2000 as affected by various presowing treatments. REFERENCES Hydrpriming Hardening Matriconditioning Calcium Chloride Sodium Chloride Calcium Nitrate ADAM, R. Germination of callitris seeds in relation to temperature, water stress, priming and hydration-dehydration cycles. Journal of Arid Environment, 43, p , AFZAL, I.; BASRA, S. M. A.; AHMAD, N.; CHEEMA, M. A.; WERRAICH, E. A.; KHALIQ, A. Effect of priming and growth regulator treatment on emergence and seedling growth of hybrid maize (Zea mays). International journal of Agriculture and Biology, 4, p , ASHRAF, M.; AKHTAR, N.; TAHIRA, F.; NASEEM, F. H. Effect of NaCl pretreatment on the germination and emergence of seven cultivars of wheat seeds. Pakistan Journal of Agricultural Sciences, 2, p , AUSTIN, R. B.; LONGDEN, P. C.; HUTCHINSON, J. some effects of hardening carrot seed. Annals of Botany, 33, p , BASRA, S. M. A.; ZIA, M. N.; MAHMOOD, T.; AFZAL, I.; KHALIQ, A. Comparison of different invigoration techniques in wheat (Triticum aestivum L.). Pakistan Journal of Arid Agriculture, 5, p , 2002.

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