EFFECT OF WATER STRESS ON IMBIBITION, GERMINATION AND SEEDLING GROWTH OF MAIZE CULTIVARS

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1 Sarhad J. Agric. Vol.25, No.2, 2009 EFFECT OF WATER STRESS ON IMBIBITION, GERMINATION AND SEEDLING GROWTH OF MAIZE CULTIVARS ABDUL KABIR KHAN ACHAKZAI Department of Botany, University of Balochistan, Quetta, Pakistan ABSTRACT A Laboratory experiment was conducted to evaluate the effect of four level of water potential (ψ) viz., 0.00, -4.09, -8.18, and bars on the imbibitions (water absorption), germination, and seedling growth of six cultivar of maize (Zea mays L.). Mannitol was used as an osmoticum. Results showed that water stress treatments significantly (P<0.05) influenced the root-shoot length, their fresh and dry weights (except root oven dry weight) of different cultivars of maize i.e., Agaithi-72, Azam, Composite-15, Ehsan, Synthetic-551 and Yousafwala E.V Similarly, significant variations in seedling growth were obtained among cultivars. However, interactions between water stress and cultivars for root-shoot length, and shoot fresh & dry weights were also found as highly significant (P<0.01). Results also showed that increase in water stress level decreases imbibition, germination and seedling growth. Reduction in imbibition, germination and root-shoot fresh and dry weights were recorded in the highest water stress level ( bars). Results further exhibited that on the basis of total or cumulative drought tolerance index, maize cv. Azam could be ranked as drought tolerant and cv. Agaithi-72 as drought sensitive. While cultivars viz., Composite-15, Synthetic-551, Ehsan and Yousafwala E.V were ranked as drought intermediate in response, respectively. Key Words: Water stress, maize, Imbibition, Germination, Seedling growth Citation: Achakzai, A.K.K Effect of water stress on imbibition, germination and seedling growth of maize cultivars. Sarhad J. Agric. 25(2): INTRODUCTION Maize (Zea mays L.) is an important multipurpose cereal crop used as food, feed, fodder, fuel and in the manufacture of industrial product (Clark, 1977; Anonymous, 1997; Liu et al. 2001). In Pakistan, it is grown on over 1042 thousand hectare with a total production of 3109.ousand tons or 2984 kg ha -1 (Anonymous, ). Research points to the effect that this crop has high potential in the country by producing 8.93 t ha -1 in experimental fields, but its average grain yield is very low i.e., 1.42 t ha -1 in farmers field (Anonymous, 1993; Mahmood, 1994). Among various constraints responsible for low grain yield, inadequate supply of water at its critical development stage and high sensitivity of different maize cultivars to water stress are of immense importance (Link et al. 1999; Shakhatreh et al. 2001). To find out the extent or level of drought tolerance preliminary studies on the effect of water stress on germination, growth and endogenous level of some metabolites (proline accumulation, cations and anions uptake) of a species are prerequisite or having prime importance. In Pakistan, very little work has been done on this aspect. Ashraf and Mehmood (1990) studied the response of four brassica species to drought stress and determined their drought tolerance. Saeed et al. (1997) found significantly decreased growth rate of two maize cultivars. Some post graduate students of University of Balochistan, Quetta also studied the effect of water stress on germination of four varieties of maize (Jabbar, 1985), Mungbean (Akhtar, 1985), eight species of Agropyron (Batool, 1988) and six exotic species (Ali, 1988). In Balochistan large area is lying as wasteland, only a small portion of its total area is being utilized for crop growing, forestation and grazing purposes. Even in these areas the production is very low and uneconomical. These wastelands can be used for crop production, forestation and range managements, either by the provision of good quality irrigation water or by growing drought tolerant species. The present study was therefore, mainly aimed to evaluate the drought tolerance of maize during its preliminary stages of growth and also to choose a maximum drought tolerant cultivar among these six cultivars.

2 Abdul Kabir Achakzai. Effect of water stress on imbibition, germination and seedling growth of maize 166 MATERIALS AND METHODS The work presented here deals with the effect of four level of water potential (Ψ) i.e., 0.00, -4.09, -8.18, and bars on the imbibitions (water uptake), germination, and seedling growth of six cultivar of maize (Zea mays L.) viz., Agaithi-72, Azam, Composite-15, Ehsan, Synthetic-551 and Yousafwala E.V The water potential treatments (S) were prepared by dissolving calculated amount of mannitol (C 6 H 14 O 6 ) in deionized water, using the formula as described by Ting (1980). The treatments were then designated as,,, and. Ψ (bars) = x M x T 273 Where: Ψ = Water potential in bars M = Molar concentration of solution T = Room temperature ( 0 C) + Absolute temperature (K) 273 = Absolute temperature bars = Osmotic potential of one molar solution In biological practice, solutions of known molarity are prepared, because it is important that concentration (and, hence, the osmotic potential) of the solution may not change significantly during the course of experiment. The solute used to prepare the solutions should be one that is not readily taken up by the tissue. Sorbitol, mannitol [D(-)- Mannit], and polyethylene glycol (PEG) are commonly used for this purpose (Hopkins, 1995). Therefore, in present study mannitol, which is a monosaccharide is used to maintain the osmotic potential of the prepared solutions. Experimental Setup A. Imbibition Imbibitions (water absorption) in response to various level of water potential (i.e., S 0,,, and ) for each cultivar of maize were studied in Petri dishes of 9.0 cm in diameter. Each treatment was triplicated. Maize seeds were initially treated with 1.0% mercuric chloride solution for few seconds. A double layer of blotting paper was laid down in each Petri dish, and thereafter 10 healthy treated seeds of uniform size were placed at an equal distance on blotting paper. Before placing, each seed was initially weighed (W1) and numbered from 1 to 10. In each Petri-dish 10 ml solution of respective treatment was added slowly. These Petri dishes were then placed in an Incubator at 30 0 C by arranging them in a Completely Randomized Design (CRD). After 24 hours, seeds were reweighed (W2) one by one. Water absorption was calculated with the following formula: Water absorption, % = W2 W1 x 100 W1 B. Germination For germination studies, another set of 10 treated healthy seeds were placed on filter paper in Petri-dishes by repeating the aforementioned procedure. Filter papers were replaced after every 48 hours to minimize the risk of fungal attack. The observations regarding germination were made after every 24 hours, and continued till the completion of germination. The emergence of radical and plumule was taken as an indicator or measure of germination. After 15 days the germination % was calculated by the formula given below: Germination, % = Total number of seeds germinated in each treatment x 100 Total number of seeds soaked in each treatment C. Seedling Growth After 15 days of germination, a set of plant from each Petri dish was taken out and the following growth measurements were made: (i) Root and shoot length, cm. (ii) Root and shoot fresh weight, g. (iii) Root and shoot oven dry weight (g) at 80 0 C. D. Drought Tolerance Index (%) The given formulae were used for the determination of drought tolerance indices (DTI):

3 Sarhad J. Agric. Vol.25, No.2, DTI for germination = Final germination or growth in x 100 Total germination or growth in Cumulative Drought Tolerance Index (%) = Average of all growth parameters in x 100 Average of all growth parameters in Data obtained for seedling growth were also statistically analyzed, following the procedure as described by Steel and Torrie (1980). MSTAT-C computer software package was used for the purpose. RESULTS AND DISCUSSION In the present work (Table I), as the water stress increases (0.0 to bars), there was a gradual reduction in imbibition (water uptake) by maize seeds of all varieties except cv. Synthetic-551. This reduction might be due to the fact that water moves from high potential to low potential due to differences in the free energy content. The gradient of water potential between dry seeds and pure water (0.0 bars) decreased rapidly with the addition of any soluble substances (mannitol in the present study) in water. The decrease in water potential gradient between seed and media will prevent the seeds to absorb the desired amount of water. Similar results were also reported in case of few cultivars of maize (Jabbar, 1985), four varieties of mungbean (Akhtar, 1985), and eight species of Agropyron (Batool, 1988). Based on drought tolerance index of imbibition, maize cv. Synthetic-551 could be rated as drought tolerant and cv. Agaithi-72 as drought sensitive. Table I. Imbibition (%) of maize cultivars in response to varying level of imposed water stress treatments Maize Cultivars Water stress (bars) Agaithi-72 Azam Composite-15 Ehsan Synthetic-551 Yousafwala E.V ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 0.35 Mean ± SE. Results presented in Table II indicated that water stress did not impose any considerable change in the final germination of maize cultivars. However, a significant delay in the initiation and completion of germination was observed in water stress treatments. Tesche (1975) stated that under water stress conditions, delay in completion of germination is a common response, because seeds require more time to absorb sufficient amount of water, which is vital for the act of initiation of germination. Gul and Allan (1976) also reported that germination time increased to 8 folds in 93 lines of wheat, when water potential of seed was reduced to bars. In conformity to present study similar trend of results have been also reported by many other researchers (Freeman, 1975; Wood and Nash, 1976; Hogon and Chan, 1977). The decreased germination in response to water stress is not uniform in all cultivars. This might be due to differences in their range of drought tolerance. Therefore, based on drought tolerance index of germination, maize cv. Ehsan could be rated as drought tolerant and cv. Yousafwala E.V as drought sensitive. While remaining four cultivars were found as drought intermediate. Reports of varietal differences in other crops subjected to salinity were also found in literature (Mass and Hoffman, 1977; Khan and Naqvi, 1984).

4 Abdul Kabir Achakzai. Effect of water stress on imbibition, germination and seedling growth of maize 168 Table II. Germination (%) of maize cultivars in response to various levels of water stress Cultivars/ Water (bars) DAS Agaithi-72 Azam Composite-15 Ehsan Synthetic-551 Yousafwala E.V Mean ± SE DAS = Days after sowing ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 8.82 Nil Nil ± ± ± ± ± ± ± 0.00 Results presented in Table III exhibited that in relation to various levels of water (A) root-shoot length, root-shoot fresh weight and root dry weight as well as different cultivars of maize (B) responded significantly (P<0.05). Whereas interactions between A x B was also found significant at P<0.01 except for root fresh and dry weight. Data presented in Table IV & V depicted that as water stress increases both the root and shoot length significantly decreased. Statistically higher reduction in root length (2.33 cm) and shoot length (1.47 cm) was recorded in highest water stress levels ( bars). However, shoot was comparatively more affected than root. Research revealed that water stress affects critically every aspect of plant growth, by modifying the anatomy, agronomy, physiology and biochemistry (Kramar, 1969; Saeed, et al. 1997). The present decrease in growth was expected because the rate of growth of plant cells and the efficiency of their physiological processes are highest when the cells are at higher turgidity. Plants subjected to water stress ( to ) have turgor pressure of the cell lower than the maximum value. Cell and leaf growth are highly sensitive to water stress, because cell expansion is caused by the action of turgor pressure upon cell walls (Greacen and Oh, 1972; Burstrom, 1975). They further revealed that even mild water stress conditions, when turgor pressure is reduced by only few bars would result a significant decrease in growth. The reduction in growth is a primary effect of every stress, which may be due to different metabolic disturbances. Similar results have been reported in wheat genotypes (Ashraf and Naqvi, 1995; Ashraf et al and 1996). This decrease depends upon the sensitivity of crops and even cultivars/lines to stress. Therefore,

5 Sarhad J. Agric. Vol.25, No.2, based on cultivars response in respect of both of their root and shoot length subjected to various water stress treatments, maize cv. Agaithi-72, cv. Synthetic-551 and cv. Azam could be rated as drought tolerant and cv. Composite-15 as drought sensitive. Whereas remaining cultivars could be ranked as drought intermediate in response. However, contrasting results are obtained by Mahmood, et al. (2004) in the field grown crops. Data presented in Table VI and VII enumerated that water stress conditions significantly (P<0.05) and linearly decreased the root and shoot moist weight. A maximum reduction (i.e., and mg plant -1 ) in both attributes was recorded at highest level of imposed water stress (i.e., bars), respectively. Similarly, cultivar to cultivar response toward water stress was also statistically found significant. Therefore, based on cultivars response in respect of their root and shoot moist weight, maize cv. Composite-15 and cv. Azam could be rated as drought tolerant, and cv. Agaithi-72 and cv. Composite-15 as drought sensitive. Results pertaining to root and shoot oven-dry weight (Table VIII and IX) showed that in relation to water stress root dry weight had no response, while shoot dry weight exhibited significantly positive response up to bars. A maximum shoot dry weight is obtained in level of water stress. These findings are in conformity with those described by Ashraf et al. (1996). However, varietal means had significant variations for both parameters. Maize cv. Agaithi-72 and cv. Ehsan were ranked as drought tolerant and cv. Yousafwala E.V as drought sensitive. Results regarding cumulative drought tolerance index (Fig. 1) indicated that maize cv. Azam could be rated as drought tolerant and cv. Agaithi-72 as drought sensitive. While remaining cultivars i.e., Composite-15, Synthetic-551, Ehsan and Yousafwala E.V were rated as middle degree drought resistance. Table III. Variables Analysis of variance (ANOVA) for seedling growth of maize cultivars (Zea mays L.) in response to imposed water stress levels Levels (A) Sum of Squares Mean Squares F-value of variables at an error of 48 Cultivars (B) Levels (A) Cultivars (B) A (Df=3) B (Df=5) A x B (Df=15) Root length, cm plant -1 Shoot length, cm plant -1 Root fresh weight, mg plant -1 Shoot fresh weight, mg plant -1 Root oven dry weight, mg plant -1 Shoot oven dry weight, mg plant ** ** ** ** ns ** * ** ** ** ** ** ** ** ns ** ns ** * and ** are significant at P<0.05 and P<0.01, respectively. While ns stands for non-significant at both probability levels and Df for degree of freedom. Table IV. Effect of four different level of imposed water-stress on root-length (cm plant -1 ) of six cultivar of Maize (Zea mays L.) 6.56 a 4.50 de 3.48 fghi 5.91 ab 3.23 ghij 3.19 ghijk 4.51 de 3.75 efgh 3.16 ghijk 4.86 cd 3.79 efgh 3.60 fgh 5.56 bc 3.90 efg 4.16 def 4.58 de 3.90 efg 4.10 def 1.75 m 1.81 lm 2.33 klm 3.01 hijk 2.42 jklm 2.67 ijkl a b b ab a ab **Cf.V = 13.93%; LSD (for cv) = 0.432; LSD (for S) = 0.353; LSD (for S x cv) = a b b c

6 Abdul Kabir Achakzai. Effect of water stress on imbibition, germination and seedling growth of maize 170 Table V. Effect of four different level of imposed water-stress on shoot-length (cm plant -1 ) of six cultivar of Maize (Zea mays L.) 7.34 b 4.20 efgh 2.35 klm a 3.72 fghij 3.05 ijkl 4.32 efg 4.72 ef 2.16 lmn 4.88 de 4.10 efghi 3.58 ghij 5.92 cd 4.17 efgh 3.24 hijk 6.27 c 4.63 efg 2.94 jkl a b c d 1.34 mn 1.43 mn 1.29 n 1.54 mn 1.47 mn 1.77 mn b a c bc b b **Cf.V = 16.39%; LSD (for cv) = ; LSD (for S) = ; LSD (for S x cv) = Table VI. Effect of four different level of imposed water-stress on root moist weight (mg plant -1 ) of six cultivar of maize (Zea mays L.) a b c d 13 l e d a bc cd b **Cf.V = 18.61%; LSD (for cv) = 9.456; LSD (for S) = 7.721; LSD (for S x cv) = Table VII. Effect of four different level of imposed water-stress on shoot moist weight (mg plant -1 ) of six cultivar of Maize (Zea mays L.) 342 b 156 jk 98 lmn a 201 ghi 164 ijk 82 mn 231 defg 237 cdefg 123 klm 69 no 267 cde 224 efgh 186 hij 81 mn 279 c 216 fgh 161 ijk 103 lmn 271 cd 251 cdef 138 kl 89 mn a b c d c a c b b b **Cf.V = 13.96%; LSD (for cv) = 21.64; LSD (for S) = 17.67; LSD (for S x cv) = Table VIII. Effect of four different level of water-stress on root oven dry weight (mg plant -1 ) of six cultivar of Maize (Zea mays L.) b a a ab ab a **Cf.V = 92.75%; LSD (for cv) = 27.51; LSD (for S) = 22.47; LSD (for S x cv) = 55.03

7 Sarhad J. Agric. Vol.25, No.2, Table IX. Effect of four different level of water-stress on shoot oven dry weight (mg plant -1 ) of six cultivar of Maize (Zea mays L.) fgh gh gh c cd cd cd cd cd def cd cde def a a cd cd def b a b c 5.00 h def cde efg cd fg d b b c a bc **Cf.V = 27.23%; LSD(for cv) = 13.13; LSD (for S) = 10.72; LSD (for S x cv) = Drought tolerance index (%) Aga-72 Azam Comp-15 Eshan Synth-551 Yous.1081 Cultivars Fig. 1. Cumulative drought tolerance index (%) of six cultivars of Zea mays. CONCLUSION It can be concluded that in relation to various levels of induced water stress, the root-shoot length, rootshoot fresh weight and root dry weight of 6 different cultivars of maize responded significantly (P<0.05). Results also showed that increase in water stress level decreased the imbibition, germination and seedling growth. Generally maximum reduction in imbibition, germination and root-shoot fresh and dry weights were recorded in the highest water stress level ( bars). Results further exhibited that based on cumulative or total drought tolerance index, maize cv. Azam was ranked as drought tolerant and cv. Agaithi-72 as drought sensitive. While cultivars viz., Composite-15, Synthetic-551, Ehsan and Yousafwala E.V were ranked as drought intermediate in response. REFERENCES Akhter, S Effects of water stress on germination of four varieties of mungbean (Vigna mungo L.) Hepper] M.Sc. Thesis Bot. Deptt. Univ. Balochistan, Quetta, Pakistan. Ali, Z Effects of different levels of water potential on germination and seedling growth of six exotic species. M.Sc. Thesis Bot. Deptt. Univ. Balochistan, Quetta, Pakistan. Anonymous, Economic Survey. Govt. Pakistan (GOP), Finance Div. Econ. Advisor s Wing, Islamabad. pp Anonymous, Agricultural Statistics of Pakistan. Statistics Div., GOP, Islamabad, Pakistan. Anonymous, Agricultural Statistics of Pakistan. Statistics Divi., Govt. Pakistan (GOP), Islamabad, Pakistan. 18p. Ashraf, M. and S. Mehmood Response of four Brassica species to drought stress. Envir. & Expt. Bot. 1: Ashraf, M.Y. and S.S.M. Naqvi Studies on water uptake, germination and seedling growth of wheat under PEG-6000 induced water stress. Pak. J. Sci. & Indust. Res. 38: Ashraf, M.Y., A.R. Azmi, A.H. Khan, S.S.M. Naqvi and S.A. Ala Effect of water stress on some enzymatic activities of wheat. Acta Physiol. Plant. 17:

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