Effects of seed size on seedlings characteristics of five barley cultivars

Transcription

1 In vitro growth of Stevia rebaudiana Bertoni 265 Effects of seed size on seedlings characteristics of five barley cultivars Bagher Gharoobi* Agriculture Group (Cultivation), Agriculture Faculty, Saveh Branch, Islamic Azad University, Saveh, Iran Abstract If a seed could germinate earlier and form bigger and stronger seedlings, this would positively affect its yield. Seed size affects the features and quality of seedlings of crop; therefore, farmers can select suitable and favorite size of seed and increase performance and stability of the crop. In the present study, we considered effects of three seed sizes on seedling characteristics of five barley cultivars. The study was carried out in a randomized design with four replications in Horticulture Laboratory of Faculty of Agriculture, Islamic Azad University, Saveh Branch, Iran. The variables considered in the study included five cultivars of barley and three seed sizes (2, 2.5 and in width). Results suggested that the speed of germination, percentage of germination, speed of growth, root length, shoot length and seedling dry and fresh weight were generally influenced by cultivars and seed size. Seed size did not affect percentage of germination, speed of germination, root and shoot length in most of the cultivars. However, in 3 variables, namely, seedling growth rate, fresh weight and dry weight meaningful changes were observed in 3 cultivars. Keywords: seedlings; growth rate; germination; dry weight; shoot length Gharoobi, B 'Effects of seed size on seedlings characteristics of five barley cultivars'. Iranian Journal of Plant Physiology 1 (4), Introduction Successful crop production requires the use of high quality seeds to achieve better stand establishment and higher crop yield. High quality seeds are demanded by the end user to assure maximum seedling emergence and stand establishment in the field (Tekrony, 2006). A positive relationship between seed weight or size and germination percentage has been found in different plant seeds in a number of studies (Larsen and Andreasen, 2004; Turk and Tawaha, *Corresponding author E mail address: pazhooheshgar2010@yahoo.com Received: July, 2011 Accepted: September, ; Kalakanavar and Shashidhara, 1989). Previous studies have shown that success in seed emergence is achieved when seed could prevail over the adverse environmental conditions and show appropriate reaction (Guillen Portal et al., 2006; Waldron et al., 2006). Certainly this reaction to the environmental conditions will be varied (Hakizimana et al., 2000; Hall and Wiesner, 1990). Seed size could be affectd by environment during the seed filling (Egil, 1998). Therefore, stand establishment and primary growth are considered as a positive factor on crop yield (Acevedo et al., 1991; Ludlow and Muchow, 1990). Different factors could reduce stand population and in many environmental conditions more attention has been paid to initial

2 266 Iranian Journal of Plant Physiology, Vol (1), No (4) growth of the seedlings (Ludlow and Muchow, 1990). This preference particularly under drought stress and low temperature is more effective than other conditions (Willenborg et al., 2005; Cisse and Ejeta, 2003; Turk and Tawaha, 2002). Also some studies have shown that seedlings from large seeded cultivars have higher rates of survival than seedlings from smallseeded cultivars under natural conditions (Moles and Westoby, 2004; Peterson et al., 1989). Aprico et al. (2002) indicated that there was a significant correlation between seed size of wheat and its pre ripening growth and development. Accordingly, growth rate and the first leaf area could be affected by seed size. Other studies about the role of seedlings vigor on other plant`s characteristics showed that seed size affected the stand establishment and total yield of wheat (Guillen Portal et al., 2006; Stougaard and Xue, 2004; Lafond and Baker, 1986). In some studies, medium size seeds had higher germination percentage than both smaller and larger seeds (Mian and Nafziger, 1994; McKersie et al., 1981). In contrast, Willenborg et al. (2005) indicated that planting large oat seed improved oat germination characteristics, particularly where spring soil moisture was limited. Turk and Tawaha (2002) also observed increased germination percentage as well as greater speed for two barley cultivars under moisture stress. Moles and Westoby (2004) reported that there was a strong positive relationship between seed mass and the percentage of seedlings surviving through the first week of establishment across 113 cultivars from around the world. Thus, seedlings from large seeded cultivars had higher survival rates than seedlings from small seeded cultivars (Moles and Westoby, 2006). Studies of the relationship between seed weight or size and germination speed have provided various conclusions. However, the general trend suggests a positive relationship between seed size, germination rate and emergence speed (Moles and Westoby, 2004; Singh and Singh, 2003; Aprico et al., 2002; Fenner and Kitajima, 2000). Therefore, it was discussed that some of the seedling characteristics such as percentage of seedling emergence, emergence rate index, fresh weight and dry weight of root and shoot and their lengths were heritable (Khan et al., 2002). The objective of this research was to determine the relationship between seed size and seed vigor index in various types of barley cultivars. Table 1 The Germination percentage of 5 cultivar of Barley 92.5± ± ± ± ± ± ± ± ± ± ±2.5 90± ± ± ±2.887 Table 2 The Germination speed ( germination per day) of 5 cultivar of Barley 2.374± ± ± ± ± ± ±0.06 2± ± ± ± ± ± ± ±0.072

3 Effects of seed size on seedlings characteristics of barley 267 Furthermore, response surface analysis and linear regressions have been undertaken to analyze the data. Materials and Methods Experimental design This experiment was conducted to evaluate the effects of seed size of barley cultivars on seed vigor indicators. It was carried out at the Islamic Azad University, Saveh Branch. A factorial experiment was carried out based on completely randomized design with four replications. The factors included cultivars and seed size. Temperature in the germination chamber was set at 28 C. Vigor index in this experiment was considered as speed of germination, percentage of germination, seedling growth rate, root length, shoot length and seedling dry and fresh weight. Seedling growth rate was calculated through the following equation (Ellice and Roberts, 1980): Seedling growth rate = X= number of germinated seeds Y= total dry weight of normal seedlings a= number of unusual seedlings b= number of dead seeds. Root and shoot length were measured. Fresh weights of seedlings were measured and put in foil for measurement of seedling dry weight and then placed in the oven at 80 C for 24 hours. Samples were weighed with 0.01 g error of measurement. Statistical analysis The data were submitted to statistical analysis using SPSS software with Duncan test to compare the means. Results Percentage of germination In this research no meaningful relationship was observed between percentage of germination except cultivars of (Karun Dar Table 3 Seedling Fresh Weight of 5 cultivar of Barley (g/seedling) 0.4± ± ± ± ± ± ± ± ± ± ± ± ± ± ±0.07 Table 4 Seedling Dry Weight of 5 cultivar of Barley (g/seedling) 0.15± ± ± ± ± ± ± ± ± ± ± ± ± ± ±0.009

4 268 Iranian Journal of Plant Physiology, Vol (1), No (4) Kavir) with code 1 which had smaller seed size and higher germination rate. It may occur because of Genotype effects (Table 1). It is thought that, according to the results of the experiment. The size of the seed does not affect the percentage of germination for these five types of the plant of barley. But this result might not be for the other types and the growing size of the seed could have a positive or negative effect on the percentage of germination. increased, so did the fresh weight. In Kavir cultivar (code 2), also meaningful relationship was found between size fresh weight. Similarly, in Reyhan 03 and particularly in cultivar, significant positive relationships were observed between fresh weight and seed size. Thus, the seed has a great effect on the fresh weight of the seedling. Dry weight Speed of germination No meaningful relation was not found between seed size and seedling speed of germination. The result of our experiments did not show any positive or negative effect of the seed size on the speed of germination among the barley cultivars under study (Table 2). Fresh weight Positive relationship was observed between seed size and fresh weight in barley cultivars (Table 3). In Karun Dar Kavir (code 1) cultivar, highly significant relationship was detected between all sizes. As seed size An interesting finding of the study was the highly significant relationship observed between seed size and dried weight in the for burley cultivars under study (P<0.01). Increase in seed size resulted in increase in dried weight (Table 4). Seedling growth rate of grain Table 5 Seedling Growth Rate of 5 cultivar of Barley(mg dry weight) / Germinated seeding) 0.02± ± ± ± ± ±0.003 The seedling growth rate is one of the most important characteristics of the seedling to have a very good crop. The results of this experiment have showed that, with an increase in seed size, seedling growth rate increased. In Kavir cultivar (code 2) meaningful relationship was 0.013± ± ± ± ± ± ± ± ±0.002 Table 6 Root Length of 5 cultivar of Barley (cm/seedling) 16.72± ± ± ± ± ± ± ± ± ± ± ± ± ± ±2.59

5 Effects of seed size on seedlings characteristics of barley 269 Table 7 Shoot Length of 5 cultivar of Barley (cm/seedling) 89.7± ± ± ± ± ± ± ± ± ± ± ± ± ± ±1.86 recorded between seed size and seedling growth rate. Similarly, in Reyhan 03 a meaningful relationship was observed between seed size and seedling growth rate. In cultivar Triticale meaningful difference was also observed between treatment 1 and treatment 2 (Table 5). Root and shoot Length Only in one cultivar a meaningful relationship was found between seedling growth rate and seed size. These experiments have generally shown no specific relationship between the size of the seed and the length of the root (Table 6 ) and shoot (Table 7). Discussion This study confirmed that the impact of environment and seed size on three indexes, namely, seedling growth rate of grain, fresh weight and dry weight of seedlings were significant. This is in line with a number of studies reported earlier (e.g., Aprico et al., 2002 ; Willenborg et al., 2005). The findings also suggests that among the seven characteristics of the barley plants in this experiment, only seedling fresh weight, seedling dry weight and seedling growth rate were influenced by size of the seed. This means that percent of germination, speed of germination, root and shoot length are not affected by seed size. It can therefore be concluded that using larger seeds, farmers can achieve a better crop and final yield without using more materials and chemical fertilizers. Acknowledgement Thanks to Dr Khalaj Zadeh the Head of Agriculture College, Islamic Azad University, Saveh Branch and also Dr Farzamisepehr for her help in managing the research project. References Aprico, N., D. Villegas, J. L. Araus and R. R. C. Blanco 'Seedling development and biomass as affected by seed size and morphology in durum wheat'. J. Agric. Sci. Cabb. 139: Cisse, N. D. and G. Ejeta ' Genetic variation and relationships among seedling vigor traits in sorghum'. Crop Sci. 43: Egil, D. B Seed Biology and the Yield of Grain Crops. 1st Ed. CABI Publishing: Wallingford. Fenner, M. and K. Kitajima, 'Ecology of seedling regeneration'. In Seeds: The Ecology of Regeneration in Plant Communities. Fenner, M. (Ed.). CABI Publishing: Wallingford. Guillen Portal, F. R., R. N. Stougaard, Q. Xue and K. M. Eskridge 'Compensatory mechanisms associated with the effect of spring wheat seed size on wild oat competition'. Crop Sci. 46: Hakizimana, F., S. D. Haley and E. B. Turnipseed 'Repeatability and genotype environment interaction of coleoptiles length measurements in winter wheat'. Crop Sci. 40:

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