The rate of germination, radicle and plumule length, fresh and dry mass of maize seedlings were increased as Ca2+ was added to the nutrient solution, which contained different levels of Cd2+, especially at low concentration of Ca2+ (5 mM) and high concentrations of Cd2+ (1.4 and 1.8 mM). The biosynthesis of pigments, respiration rate and content of soluble saccharides in endosperm were reduced sharply as the concentration of Cd2+ in the medium increased. This effects was alleviated by Ca2+ addition. Cd2+ content in seedlings was increased as the Cd2+ concentration in medium was increased and decreased sharply as Ca2+ was present in the culture medium. The study suggests liming of soil with CaCO3 to improve the yield of many crops.

The ameliorative effect of salicylic acid (SA: 0.5 mM) on sunflower (Helianthus annuus L.) under Cu stress (5 mg l –1 ) was studied. Excess Cu reduced the fresh and dry weights of different organs (roots, stems and leaves) and photosynthetic pigments (chlorophyll a, b and carotenoids) in four-week-old plants. There was a considerable increase in Chl a/b ratio and lipid peroxidation in both the roots and leaves of plants under excess Cu. Soluble sugars and free amino acids in the roots also decreased under Cu stress. However, soluble sugars in the leaves, free amino acids in the stems and leaves, and proline content in all plant organs increased in response to Cu toxicity. Salicylic acid (SA) significantly reduced the Chl a/b ratio and the level of lipid peroxida- tion in Cu-stressed plants. Under excess Cu, a higher accumulation of soluble sugars, soluble proteins and free amino acids including proline occurred in plants treated with 0.5 mM SA. Exogenous application of SA appeared to induce an adaptive response to Cu toxicity including

The response of wheat seedlings germinated under salinity stress to exogenous abscisic acid was discussed. Exogenous ABA acid induces two characteristic proteins of high molecu- lar weights ( 109.4 and 84.0 kDa) in addition to the new protein set formed under high salinity levels. ABA, also induces synthesized forms of guaiacot peroxidase in seedlings treated with 200 mM NaCI. The induction and/or accumulation of peroxi- dase isoforms in ABA-treated seedlings, may reduce the active oxygen produced by salinity. The changes in gene expression and peroxidase isoforms may be selected to adaptation of wheat seedlings to NaCl-salinity.

The effect of sewage water on some physiological activities of cyanobacteria was studied. Metal-tolerant cyanobacterium (Nostoc linckia) and metal-sensitive (Nostoc ri6ularis) were grown at three levels of sewage water (25, 50 and 75%). The growth rate showed significant stimulation in low and moderate levels (50% for N. linckia and 25% for N. ri6ularis). Not only the number of cells was elevated but also, the time required to reach the exponential and the stationary phases was reduced. Also, low levels of sewage water increased chl.a content, photosynthetic O2-evolution, respiration and protein content. Similarly, heterocyst frequency as well as nitrogenase activity were increased in cyanobacteria grown at low and moderate levels (25 and 50% sewage). On the other hand, the high level of waste (75%) reduced growth and metabolic activities of the two species. N. linckia accumulated about 30-fold of Zn and ten-fold of Cd than those of growth medium (50% sewage water). Also, N. ri6ularis accumulated about ten-fold of Zn and two-fold of Cd. The distribution of Cd and Zn in cells were investigated. About 65–60% of Cd or Zn were found in pellets (sediment) as insoluble form in the two species. The soluble form (cytosolic fraction) after being fractionated on sephadex G-(75-100) revealed two peaks with molecular weights of 70–75 and 40–45 kDa. These peaks were in coincidence with Cd and Zn maxima. Nostoc ri6ulais showed more sensitivity to heavy metals than N. linckia, and accumulated less amount of metal-binding proteins. Nostoc linckia seems to be tolerant to heavy metals (Zn and Cd) and is able to accumulate this metal by adsorption on the pellets (cell surface) and:or through sequestration via metal-binding protein. Therefore it can be recommended it to be employed in the purification of waste contaminated with these heavy metals. © 2000 Elsevier Science B.V. All rights reserved.

The effect of sewage water on some physiological activities of cyanobacteria was studied. Metal-tolerant cyanobacterium (Nostoc linckia) and metal-sensitive (Nostoc ri6ularis) were grown at three levels of sewage water (25, 50 and 75%). The growth rate showed significant stimulation in low and moderate levels (50% for N. linckia and 25% for N. ri6ularis). Not only the number of cells was elevated but also, the time required to reach the exponential and the stationary phases was reduced. Also, low levels of sewage water increased chl.a content, photosynthetic O2-evolution, respiration and protein content. Similarly, heterocyst frequency as well as nitrogenase activity were increased in cyanobacteria grown at low and moderate levels (25 and 50% sewage). On the other hand, the high level of waste (75%) reduced growth and metabolic activities of the two species. N. linckia accumulated about 30-fold of Zn and ten-fold of Cd than those of growth medium (50% sewage water). Also, N. ri6ularis accumulated about ten-fold of Zn and two-fold of Cd. The distribution of Cd and Zn in cells were investigated. About 65–60% of Cd or Zn were found in pellets (sediment) as insoluble form in the two species. The soluble form (cytosolic fraction) after being fractionated on sephadex G-(75-100) revealed two peaks with molecular weights of 70–75 and 40–45 kDa. These peaks were in coincidence with Cd and Zn maxima. Nostoc ri6ulais showed more sensitivity to heavy metals than N. linckia, and accumulated less amount of metal-binding proteins. Nostoc linckia seems to be tolerant to heavy metals (Zn and Cd) and is able to accumulate this metal by adsorption on the pellets (cell surface) and:or through sequestration via metal-binding protein. Therefore it can be recommended it to be employed in the purification of waste contaminated with these heavy metals. © 2000 Elsevier Science B.V. All rights reserved.

Identification of common signals of nodulation control among legume species will facilitate progress in enhancing symbiotic nitrogen fixation of legumes in sustainable agriculture system. Grafting experiments between soybean and common bean were carried out to evaluate whether a common shoot signals control the expression of hypernodulation among the tow species. Grafting of a hypernodulating soybean mutant NOD1-3 shoots to three cultivars of normally nodulating common bean roots resulted in hypernodulation on roots of three tested cultivars of common bean. The shoot control of hypernodulation may be causally related to differential root isoflavonoid levels, which are also controlled by shoot factors. Isoflavonoid analysis from root extracts of grafted plants showed that NOD1-3 shoots had markedly higher root isoflavonoid concentrations in roots of both NOD1-3 and common bean cv. Adzuki compared with self-grafts of common bean Adzuki. Exogenous application of daidzein, genistein, coumestrol, glycitein and in combination at concentration of 10 µmol to the nutrient solution significantly increased the nodule numbers of common bean cv. Adzuki. Therefore, the control of hypernodulation expression by isoflavonoid signal molecules translocated from shoot is common among legume species.

A rhizobial isolate was recovered from the root nodule of the faba bean (Vicia faba L.) grown in sludgecontaminated fields in Upper Egypt. The isolate was identified as Rhizobium leguminosarum bv. viciae on the bases of phenotypic characteristics and sequences of the gene encoding 16S rRNA. The isolate was resistant to heavy metal stress in decreasing order Ba2þ (80 ppm), Zn2þ (70 ppm), Co2þ (50), Al3þ (40 ppm), Ni2þ (30 ppm), and Cd2þ (10 ppm). The rhizobial isolate was used as an efficient biosorbent for Cd2þ and Co2þ removal from aqueous solutions. The maximum adsorption capacities for Cd2þ and Co2þ biosorption calculated from the Langmuir adsorption isotherm were 135.3 and 167.5 mg g1, respectively. The adsorption isotherm for both heavy metals fit well with the Langmuir isotherm rather than the Freundlich model with correlation coefficient (r2>0.98). This study indicates that the R. leguminosarum bv. viciae isolate STDF-Egypt19 can be useful as an inexpensive and efficient bioremediation technology to remove and recover heavy metal ions from an aqueous solution.

A rhizobial isolate was recovered from the root nodule of the faba bean (Vicia faba L.) grown in sludgecontaminated fields in Upper Egypt. The isolate was identified as Rhizobium leguminosarum bv. viciae on the bases of phenotypic characteristics and sequences of the gene encoding 16S rRNA. The isolate was resistant to heavy metal stress in decreasing order Ba2þ (80 ppm), Zn2þ (70 ppm), Co2þ (50), Al3þ (40 ppm), Ni2þ (30 ppm), and Cd2þ (10 ppm). The rhizobial isolate was used as an efficient biosorbent for Cd2þ and Co2þ removal from aqueous solutions. The maximum adsorption capacities for Cd2þ and Co2þ biosorption calculated from the Langmuir adsorption isotherm were 135.3 and 167.5 mg g1, respectively. The adsorption isotherm for both heavy metals fit well with the Langmuir isotherm rather than the Freundlich model with correlation coefficient (r2>0.98). This study indicates that the R. leguminosarum bv. viciae isolate STDF-Egypt19 can be useful as an inexpensive and efficient bioremediation technology to remove and recover heavy metal ions from an aqueous solution.

A rhizobial isolate was recovered from the root nodule of the faba bean (Vicia faba L.) grown in sludgecontaminated fields in Upper Egypt. The isolate was identified as Rhizobium leguminosarum bv. viciae on the bases of phenotypic characteristics and sequences of the gene encoding 16S rRNA. The isolate was resistant to heavy metal stress in decreasing order Ba2þ (80 ppm), Zn2þ (70 ppm), Co2þ (50), Al3þ (40 ppm), Ni2þ (30 ppm), and Cd2þ (10 ppm). The rhizobial isolate was used as an efficient biosorbent for Cd2þ and Co2þ removal from aqueous solutions. The maximum adsorption capacities for Cd2þ and Co2þ biosorption calculated from the Langmuir adsorption isotherm were 135.3 and 167.5 mg g1, respectively. The adsorption isotherm for both heavy metals fit well with the Langmuir isotherm rather than the Freundlich model with correlation coefficient (r2>0.98). This study indicates that the R. leguminosarum bv. viciae isolate STDF-Egypt19 can be useful as an inexpensive and efficient bioremediation technology to remove and recover heavy metal ions from an aqueous solution.

This study was devoted for H2 production from rotten fruits of date palm (Phoenix dactylifera L.) by three fermentation stages. A facultative anaerobe, Escherichia coli EGY was used in first stage to consume O2 and maintain strict anaerobic conditions for a second stage dark fermentative H2 production by the strictly anaerobic Clostridium acetobutylicum ATCC 824. Subsequently, a third stage photofermentation using Rhodobacter capsulatus DSM 1710 has been conducted for the H2 production. The maximum total H2 yield of the three stages (7.8 mol H2 mol
1 sucrose) was obtained when 5 g L
1 of sucrose was supplemented to fermentor as rotten date fruits. A maximum estimated cumulative H2 yield of the three stages (162 LH2 kg
1 fresh rotten dates) was estimated at the (5 g L
1) sucrose concentration. These results suggest that rotten dates can be efficiently used for commercial H2 production. The described protocol did not require addition of a reducing agent or flashing with argon which both are expensive.