Microbiol. Res. (1994) 149, 317 - 320 Microbiological Research

© Gustav Fischer Verlag Jena

Effect of biological treatments on growth and some metabolic activities of barley plants grown in saline soil

A. A. Issa, M. H. Abd-Alla, A.-L. E. Mahmoud

Botany Department, Faculty of Science, Assiut University, Egypt

Accepted: April 15, 1994

Abstract

The ability of different microorganisms to alleviate the noxious effect of salinity was tested. Barley grains were planted under salt stress and were inoculated with cyano­bacteria, Pseudomonas fluorescens and Dunaliella tertiolec­tao All tested microorganisms improved growth of barley plants as indicated by dry weight, photosynthetic pigments and vitality of the plants. Cyanobacterial inoculant was the most effective and significantly diminished the adverse effect of salinity. Results of the present study hold promise for use of such microorganisms to cultivate plants in saline soils.

Key words: Barley - Cyanobacteria - Dunaliella -Pseudomonas - Salt Stress

Introduction

Soil salinity in arid and semi-arid regions of the world is a major detrimental factor for crop production (Epstein 1978). To achieve an integrated approach toward economic utilization of saline soils, traditio­nal approaches of drainage and reclamation should be supplemented with genetic improvement in salini­ty tolerance of group plants (Epstein and Rains 1987).

Many methods including both, chemical and bio­logical amendments, have been recommended to alleviate the negative effect of salinization and/or to increase the plants' tolerance to salinity stress (Lumin and Gallatin 1965, Saubern et at. 1968; Malik 1978; Ahmed et al. 1989 a; Abdel-Alla 1992).

Corresponding author: A.-L. E. Mahmoud

Therefore, the objective of this study was to examine the influence of some biological treatments on various characteristics of barley plants grown under saline conditions.

Materials and methods

Plant culture and experimental conditions. Surface­sterilized barley seeds were planted into plastic pots of 17 cm diameter and 22 cm depth containing 3 kg sterilized clay soil. The clay soil had the following characteristics: pH7.8; total soluble salts, 0.2%; organic matter content, 2% and total nitrogen, 0.1 %. Seedlings were thinned to 5 per pot after 5 days. Plants were cultivated under the conditions as pre­viously described (Abd-Alla 1992). Pots were divided into two groups according to salinity levels. Group I received 0.25% NaCI (w/w) and group II received 0.5% NaCI (w/w). Each plant-soil combination was a seperate completely randomized experiment consist­ing of 5 treatments. The treatments were: control (0.0% NaCI), salinity level (0.25% or 0.5% NaCI), application of cyanobacteria (a commercially-avail­able soil inoculant, blue-green algae 200 g/feedan), application of 20 ml of Pseudomonas jluorescens (approx. 2.3 x 107 cell/ml), an application of Duna­liella tertiolecta at the same rate. The experiments were done three times with three replicates for each treatment. Plants were irrigated with tap water when the soil began to dry and were harvested 35 days after planting. The photosynthetic pigments, chlorophyll a, chlorophyll band carotenoids were determined using the spectrophotometric method recommended by Metzner et al. (1965). Soluble carbohydrates were

Microbiol. Res. 149 (1994) 3 317

estimated according to Dubois et al. (1956) and soluble protein was determined by means of the Lowry method (Lowry et al. 1951). Free amino acids and proline were evaluated according to Lee and Takahanshi (1966) and Bates et al. (1973), respective­ly. Percentage of vitality was estimated according to Lorenzen (1967). Dry weight per plant was recorded.

Statistical analysis. Statistical analysis of data was made by means of one-way analysis of variance (Pc-state computer program). Means were separated by the Duncans multiple-range test.

Results and discussion

The results in Table 1 reveal that the dry weight of barley plants was significantly reduced at both salini­ty levels. Application of N rfixing cyanobacteria, Pseudomonas jluorescens or Dunaliella tertiolecta inoculants significantly improved the dry weight of the salt-treated plants compared with uninoculated plants under the same salinity conditions.

The data for the mean chlorophyll content of barley plants growing at varying salt concentrations are given in Table 1. Analysis of variance of these data shows that both concentrations ofNaCI signifi­cantly reduced chlorophyll a. However, chlorophyll b and c were inversely proportional to the NaCI concentration. Inoculation of salt-treated plants with the tested microorganisms significan.tly reduced the adverse effect of salinity on chlorophyll a.

With respect to the vitality of barley plants grow­ing under different treatments, vitality (%) was

generally increased compared with the uninoculated plants.

Results of the present study clearly indicate that N rfixing cyanobacteria were more effective on plant growth than Pseudomans jluorescens and Dunaliella tertiolecta.

Data in Tab. 2 show that soluble carbohydrates, soluble protein, free amino acids and proline contents of shoots of all salt-treated non-inoculated plants were higher than the control. These results confirm with those of several authors who found that soluble carbohydrates, soluble protein, free amino acids, and proline values were increased in plants under salt stress (Handa et al. 1983; Fukutoku and Yamada 1984; Ramagopal1987; Ahmed et al. 1989a; Shaddad and Zidan 1989; Shaddad 1990; Valluri et al. 1989). However, data obtained in the present investigation show that these parameters decreased by inoculating the salt-treated plants with the tested microorganisms. Apparently, microorganisms inoculants could reduce the toxicity effect of salinity. Similar to these results, Ojala et at. (1983) found that mycorrhizal fungi improved growth and yield of onion in saline soils.

The results indicate that N 2-fixing cyanobacteria have the ability to prevent the adverse effect of salinity. This could be attributed to extracellular production of different amino acids (Kerby et al. 1987). Palfi et al. (1974) and Abdel-Samad (1987) reported that the injury effect of salinity can be reduced by addition of certain amino acids.

Fogg and Pattanaik (1966) reported that ammo­nium and amid nitrogen accounted for most of the

Table 1. Effect of biological treatments on growth of barley, grown under salt stress. Each value represents the mean of three replicates*

Treatments Dry weight Chlorophyll (mg/plant) Vitality % NaCl (w/w) (mg/plant) a b c %

0.00 235a L05e 0.44e 0.58c 86.3 0.25 201 b 0.82f 1.12b O.72b 62.6 0.50 175c 0.50g L74a L85a 58.9 0.25 + Dunaliella 215a L26d 0.62c 0.65bc 65.03

tertiolecta 0.50 + Dunaliella 182c l.35cd 0.55cd O.64bc 60.30

tertiolecta 0.25 + Pseudomonas 225a L42cd 0.51d 0.63c 69.2

fluorescens 0.50 + Pseudomonas 203b L49bc 0.50d 0.61c 72.18

fluoresens 73.11 0.25 + Cyanobacterial 227a 1.92a 0.45e 0.23F

inoculant 0.50 + Cyanobacterial 210ab L62b 0.40e 0.58c 79.04

inoculant

* Numbers in the same column followed by the same letter(s) are not significantly different at the 5% level by Duncans multiple range test.

318 MicrobioL Res. 149 (1994) 3

Table 2. Effect of biological treatments on some metabolic activities of barley, grown under salt stress. Each value represents the mean of three replicates*)

Treatments Soluble Soluble Free Proline % NaCl (w/w) sugars proteins amino acids

(mg/plant)

0.0 35.6g 38.91 9.3h 0.7f 0.25 46.5d 57.7b l1.8de 2.67c 0.50 63.1a 60.6a 15.04a 3.05a 0.25 + Dunaliella 42.ge 49.6e 11.1 ef 1.89 cd

tertiolecta 0.50 + Dunaliella 59.7b 53.4c 13.9b 2.68b

tertiolecta 0.25 + Pseudomonas 41.7ef 51.6d 10.5fg 1.65d

fluorescens 0.50 + Pseudomonas 48.6c 46.0f 12.3cd 2.58b

fluorescens 0.25 + Cyanobacterial 40.99f 44.2g 9.56gh 1.22e

inoculant 0.50 + Cyanobacterial 45.6d 40.1h 13.1 bc 1.71d

inoculant

*) Numbers in the same column followed by the same letter(s) are not significantly different at the 5% level by Duncans mUltiple range test.

total extracellular nitrogen produced by N rfixing cyanobacteria. Ahmed et al. (1989b) found that the addition of nitrogen fertilizers to saline soil dimin­ished the negative effects of salinity.

The results of the present study agree also with those of Nanda et al. (1991) who reported that the metabolites of N 2 -fixing cyanobacteria promoted seed germination and their subsequent growth and development.

Pseudomonas fluorescens was the second microor­ganism in the ability to reduce the adverse effect of salinity. This ability may be due to the production of plant growth regulators such as auxins, gibberellin, and cytokinin-like substances as well as vitamins (Barea et al. 1976, Baya et al. 1981). Seed inoculation with this organism has proved to be a powerful technique to enhance plant growth and yield (Brown 1974; Chanway and Nelson 1990; Kumar and Dube 1991). Singh et al. (1973), Radi et al. (1988 and 1989) and Shaddad et al. (1990) reported th,at addition of some plant growth regulators and vitamins to salt­treated plants reduced the injury effect of salinity.

The inoculant of the halo tolerant alga (Dunaliella tertiolecta) also significantly reduced the injury effect of salinity. This may be attributed to the ability of this organism to accumulate relatively massive amounts of organic compounds, which may act as osmoregu­lators as well as vitamins (Ben-Amotz and Avron 1980, 1983).

The results of the present study suggest that the application of such microorganisms in agronomic

practice could have a potential for the cultivation of plants in saline soil.

The use of such inoculants offers an alternative to plant breeding programmes for the selection of salt tolerant plants.

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