Comparative response of poppy (Papaver somniferum L.) and eight crop and vegetable species to manganese excess in solution culture

The relative response of poppy (Papaver somniferum L.) and eight crop and vegetable species to excess manganese was investigated in a glasshouse, solution culture experiment. Plant yields and manganese concentrations were measured after two and six weeks growth at five levels of manganese (10–800 μM).

Poppies were highly sensitive to manganese toxicity in solution culture and reductions in shoot yield occurred at lower manganese levels in solution and at lower shoot manganese concentrations than that for the following sensitive species, ranked in order of increasing tolerance : brussels sprout, barley, green beans, lucerne and grean pea. In contrast lupins, oats and sugar beet were relatively tolerant producing about 80% or more of maximum shoot yield at the highest solution manganese level (800 μM Mn).

In this study the sensitivity of poppy, and brussels sprout, to manganese excess was attributed to their low shoot manganese “toxicity threshold values”; and their capacity to partition a high proportion of total plant manganese and dry matter to the shoot at solution manganese levels ≥ 100 μM.

The application of these results to field grown poppy is discussed in relation to interactions between manganese and other elements which modify plant tolerance to manganese excess.     

Inoculation treatments affect the migration and colonisation of rhizobia in alfalfa (Medicago sativa L.) plants

Purpose: The purposes of this study were to characterise the migration and the colonisation dynamics of two different fluorescent-tagged rhizobia in various alfalfa tissues (especially in seeds); and also to develop efficient inoculation treatments to promote colonisation ability of target rhizobia in elite seed varieties.

Materials and methods: Four treatments (root drench, root damaging and drench, root drench with matrine, and flower spray) were applied to inoculate alfalfa with two fluorescent-tagged rhizobia, Ensifer meliloti LZgn5f (gn5f) and Ensifer meliloti 12531f (12531f), at three different growth stages; bud, flower and pod stages. The migration and colonisation dynamics of the two fluorescent tagged rhizobia strains were monitored using UV lamp detection and a stereo fluorescence microscopy.

Results: The results showed that both rhizobia strains mainly colonised the roots and could migrate to aerial tissues. In aerial tissues, when alfalfa plants were inoculated during the bud stage, both rhizobia strains mainly colonised the leaves and stems; during the flower stage, a spray inoculation treatment resulted in more 12531f colonising reproductive tissues, while during the pod stage, more rhizobial strains gn5f colonised seeds using the root drench with matrine treatment.

Conclusions: These results indicate that endophytic rhizobia are natural inhabitants of internal regions of roots, stems, leaves and that the endophytes may arise from reproductive tissues, such as seeds. Understanding the population dynamics of endophytic rhizobia in alfalfa would considerably improve the survival of target rhizobia during seed transfer. Combining target endogenous rhizobial species with good alfalfa seed varieties may lead to the development of a novel breeding method.     

Carbohydrate status in response to ion regulation of two rice varieties (Oryza Sativa L.) grown in saline medium

Two experiments were conducted to test varietal salt tolerance differences in the growth of rice and to identify initial ion‐specific salinity effects on ion regulation and carbohydrate metabolism.

The tillering growth stage of sensitive Giza 35 was more depressed due to high NaCl salinization than tolerant Giza 159. At low external K/Na there were no significant varietal differences in ion regulation. Reducing sugars generally were little affected by salinity. Salinization increased the low sucrose level in shoots of Giza 35 considerably, whereas the high sucrose level of Giza 159 was of little change. KC1 was most stimulative; sulfate had little effect in Giza 35 but decreased sucrose in Giza 159. Salinity Increased shoot starch content more in Giza 35 than in Giza 159, KC1 was most effective, whereas there was no change due to sodium sulfate treatment.

Possible interactions of ion regulation and carbohydrate metabolism in response to varietal salt tolerance of the two rice varieties were discussed. It is assumed that differences within the carbohydrate metabolism contribute to metabolic tolerance of rice varieties when grown in saline environment.     

Effect of moisture stress on Nitrate Reductase Activity (NRA) in PEA (Pisum sativum L.) [C3] and sorghum (Sorghum vulgare Pers.) [C4] plants

Nitrate reductase activity (NRA) was studied in pea, a C₃ plant, and sorghum, a C₄ plant, at various stages of growth and development. Influence of moisture stress and nitrogen application was also observed since these factors have profound influence on growth and development.

In pea, NRA was maximum at pod maturity stage and minimum at flowering stage. In sorghum plant there was gradual increase in NRA upto grain formation followed by a fall in activity at maturity.

Nitrogen treatment as nitrate and ammonia significantly increased nitrate reductase activity over control in both pea and sorghum. Treatment with potassium nitrate was found to stimulate more NRA in pea than with ammonium sulphate. In sorghum, both forms of nitrogen did not differ much in their influence on NRA.

Influence of moisture stress in reducing NRA was more clear in sorghum, a C₄ plant than in pea, a C₃ plant. In general, control plants recorded low NRA in both the crops when compared to nitrogen treated plants except at pod formation stage in pea.     

Book review

Trace elements in plants by M. Ya. Shkolnik

Elsevier Science Publishers P. O. Box 330 1000 AH Amsterdam The Netherlands

Elsevier Science Publishing Company 52 Vanderbilt Ave. New York, New York 10017     

Incidence of P,Mn and B deficiencies on the levels of the whole and individual flavonoid groups in tomato leaves

Alterations occur in the normal content of total and individual flavonoids with P, Mn and B deficiencies, in tomato leaves.

P and Mn deficiencies do not alter the total flavonoid level. Nevertheless, these deficiencies lead to different contributions of each flavonoid group (flavonols, flavones and flavanones) to the whole content.

B deficiency produces a very significant increase in total flavonoid content. Compounds that contribute the most to this accumulation are flavones.     

Resistance breeding and biocontrol of Striga asiatica (L.) Kuntze in maize: a review

Purpose: The aims of this article are to highlight pre-breeding procedures for identifying primary sources of Striga-resistance genes and to summarize complimentary breeding techniques that enhance partial resistance of maize varieties against Striga species.

Materials and methods: The paper presented a comprehensive account of Striga screening and controlling techniques and highlighted the potential of integrating partial resistance with FOS to boost maize production and productivity in SSA.

Results: Striga infestation is a major constraint to maize production and productivity in Sub-Saharan Africa (SSA). A lack of Striga-resistant maize varieties and the limited adoption of other control methods hinder effective and integrated control of the parasitic weed in maize and related cereal crops globally. Genetic resistance of maize should be complemented with the use of Fusarium oxysporum f.sp. strigea (FOS), a biocontrol agent known to suppress Striga.

Conclusions: A combined use of genetic resistance and FOS has remained largely unutilized in controlling Striga in Africa. A combination of conventional and molecular Striga-resistance breeding tools as well as the use of FOS are promising methods to effectively control Striga in SSA.     

Sulfur nutrition effects on dinitrogen fixation of seedling alfalfa

Greenhouse experiments with alfalfa (Medicago sativa L. cv. ‘Apollo') were performed to evaluate the effect of varied nutrient solution concentrations of S on the yield, nodulation, dinitrogen fixation, N and S concentration, and the partitioning of N and S into shoots and roots.

Sulfur treatments consisted of four levels (0, 1, 2.5, and 25 mg S/L) of added S. The experimental design was a randomized complete block, with three replications. Seeds were inoculated with commercial inoculum, planted in plastic containers of acid‐washed sand, and irrigated with nutrient solution for one minute, at 2 h intervals.

Sulfur application increased the yield of all treatments. The results demonstrated that the addition of 2.5 mg S/L to the nutrient solution, besides providing the highest total dry matter yield (12 g/72 plants), showed the highest percent yield increase (19%), acetylene reduction rate (0.426 umole ethylene/mg nodule dry wt/h), total N content (306 mg/72 plants), percent recovery of S (3.8%), and percent increase in N due to dinitrogen fixation (32%).

N:S ratios obtained were different for shoots and roots, with S application decreasing the N:S ratios. The N:S ratios of 16:1 (shoots), and 9:1 (roots) obtained in the 2.5 mg S/L treatment were found to be adequate for normal growth and development.

These data indicated that the 2.5 mg S/L treatment (2.7 mg total S/L) was optimal for alfalfa seedling development.     

The relative efficiency of ionic iron(III) and iron(II) utilization by the rice plant

Uptake of iron by rice plants was equally rapid when supplied as ionic iron(II) or iron(III) at pH 3 and 4. Iron(III) uptake was reduced at pH 5 and uptake of iron when supplied as FeEDTA was relatively low at all three pH levels.

At pH 4 in the presence of plant roots, reduction of iron(III) to iron(II) occurred as indicated by Fe²⁺ BPDS formation. BPDS in a 3:1 ratio to iron(III) suppressed iron uptake by about 70%. The reduction was observed to be located in the endodermis of young roots and exodermis of older roots.

A capacity to oxidize iron(II) at the root surface was also observed under local anaerobic and relatively high pH conditions.

The significance of these two counteracting processes in affecting the oxidation state of iron at the root surface is discussed.     

Low-P solution culture can be used for screening root growth vigor in soil for high nutrient uptake of spring wheat varieties

Purpose: Root and root hairs of plants have been intensively studied in solution culture; however, correlation of such measurements in solution culture with development in soil is poorly understood. Therefore, the aim of this study is to study whether root and root hairs grown in solution culture can predict their behavior in soil and their correlation with macro- and micronutrients uptake of wheat genotypes.

Materials and methods: The growth of roots and root hairs as well as uptake of macro- and micronutrients of six spring wheat varieties was compared in solution culture under P stress and P abundance and in a low fertility soil.

Results and conclusions: Root length and surface area under P stress were significantly positively correlated with that in the low fertility soil, while no such correlation was apparent for root hair length and density. In absolute terms, the root length, surface area, root hair length and density of spring wheat varieties were substantially higher in soil than in solution culture, while the concentration and uptake of macro- and micronutrients in soil differed from solution culture in a complex way. The early uptake of macro- and micronutrients was intimately associated with root length and surface area as well as root hair length and density in soil but not in solution culture. Therefore, root length rather than root hair traits in low-P solution may be used to screen early root growth vigor in soil and thereby high nutrient uptake of wheat in low fertility soil.     

Arbuscular mycorrhizal colonization of selected herbaceous plants under arid protected area in Tunisia

Arbuscular mycorrhizal fungi (AMF) play an important role in plants growth and soils dynamic in all most ecosystems. The main objective of the present study was to evaluate the plant-AMF interactions on soil functions under arid protected area ‘Zarat-Gabès’ in Tunisia.

AMF colonization was evaluated by visual observation of AMF in fine roots of eight herbaceous plants. The level of mycorrhizal colonization varied between plants. Astragalus corrugatus and Hippocrepis areolata showed the highest mycorrhizal performance. The relative spore number was significantly different across rhizosphere soils. Statistical analysis showed a clearly positive correlation between the number of spores and plant-mycorrhizal intensity.

For microbiological parameters, our results showed that mycorrhizal plants improved significantly the various microbiological parameters. Rhizosphere soils of Astragalus corrugatus and Hippocrepis areolata presented the necessary microbial densities and microorganisms more stable compared to unplanted soil. This study allowed obtaining a new result that challenges us about the need for efficient management of natural resources in the objective of nature conservation.     

Effect of nitrogen and sulphur fertilizers and seed inoculation with rhizobium phaseoli on the nitrogen‐sulphur relationships of bean (phaseolus vulgaris L.)

A greenhouse experiment with beans (Phaseolus vulgaris L.) was performed in order to investigate the effect of nitrogen and sulphur application and seed inoculation on the yield, leaf area, distribution of different nitrogen and sulphur fractions and N/S ratio in shoot, fruit and root.

Inoculation of plants together with nitrogen or sulphur application produces an increase in the concentration of total nitrogen and a decrease in the accumulation of nitrate‐nitrogen and sulphate‐sulphur in shoot, fruit and root. Leaf area increased more with nitrogen than with sulphur application while the highest amounts of fruit dry matter were obtained with sulphur application.

N: S ratios obtained were different according to the part of the plant tested. Sulphur fertilization decreased the N: S ratios in shoot, fruit and root. The data obtained indicate that and adequate N: S ratio can insure maximum production of yield.     

Iron nutrition of sunflower(Helianthus annuus L.) as affected by various levels of p and ZN

The effects of various P and Zn levels on iron nutrition of sunflower (Helianthus annuus L.c.v. Record) were studied in two separate experiments in nutrient solution under greenhouse conditions.

In the first experiment, sunflower was grown in nutrient solutions containing four levels of P(1.5, 2.5, 3.5 and 4.5 mM/l) and three levels of Fe(0.25, 0.75, and 1.5 ppm) as FeCl₃ or FeEDDHA. In the second experiment (following the first experiment), the treatments were three P levels (0.75, 1.50 and 3.00 mM/l), three Fe levels (0.25, 0.75 and 1.5 ppm) as FeEDDHA and three Zn levels (0.1, 0.2 and 0.4 ppm).

The plants receiving Fe‐chelate, except for 0.25 ppm Fe, showed no symptoms of iron chlorosis. With inorganic Fe treatments, iron chlorosis appeared after 7–10 days depending on P level, but except for 0.25 ppm Fe which remained chlorotic, plants recovered completely within 3–4 days thereafter due to pH regulating mechanism of sunflower under iron stress condition. With both sources of Fe, chlorosis was associated with high P:Fe ratio.

Increased P and Fe levels in nutrient solution resulted in general increases in the dry weights of roots and shoots. The Fe concentration of shoots, except in few instances, was not affected by P levels, indicating that the sunflower cultivar used in this experiment could utilize inorganic Fe as well as Fe‐chelate under our experimental conditions.

Increasing P levels caused significant increases in Mn content of the shoots as 0.25 and 0.75 ppm inorganic Fe³⁺. Increased Fe levels increased shoot Mn content with inorganic Fe and decreased it with Fe‐chelate. The effects of P, Fe and Zn on sunflower indicated an antagonistic effect of Zn on 1.5 ppm Fe for all P levels. Increased Zn levels in nutrient solution generally increased Zn content of the shoots without having any marked effect on their Mn content.     

Breeding rice for rice yellow mottle virus resistance in Sub-Saharan Africa: a review

Rice is the world’s second most produced staple cereal crop after wheat. Currently, rice production and consumption have steadily increased in Sub-Saharan Africa (SSA). To date, rice is the largest imported commodity crop in the region. The low productivity is due to a number of biotic and abiotic stresses, and socio-economic constraints. Among the biotic constraints, rice yellow mottle virus (RYMV) is the most important constraint to rice in SSA. In SSA, RYMV causes yield losses ranging from 20% to 100%. Various control strategies (host resistance, cultural practices and chemicals) have been recommended to manage RYMV epidemics. RYMV disease management through generic crop protection chemicals is not economic nor is it successful due to the presence of a large number of vector species disseminating the virus. In addition, cultural practices are ineffective against RYMV because the virus is spread by several agents, including insect vectors. The use of RYMV resistant cultivars remains the most effective, economic and environmentally friendly method for resource poor farmers. However, RYMV resistant varieties have not yet been developed and deployed in SSA. The aim of this review was to present the main components in the development of rice cultivars with RYMV disease resistance. The paper provides a comprehensive review on the genetic variability of the RYMV, its epidemiology and control measures, and the gene action responsible for RYMV resistance.

The review also summarises complementary genomic tools useful in RYMV disease resistance breeding.

Successful breeding of rice for RYMV resistance depends on the availability of genes for stable resistance, knowledge of the genetics of the host and, the availability of efficient phenotyping and pathotyping methods, and understanding of the genes involved and their pattern of inheritance. Information presented in the review can serve as a reference guide for rice breeding emphasising RYMV resistance, high yields and farmers-preferred traits.     

Phosphorus uptake rate and growth characteristics of wheat roots 1

Phosphorus uptake by plant roots is influenced by the plant root properties and solution P supply characteristics. These properties included (i) the relation between nutrient concentration and uptake rate, (ii) the change in uptake rate with plant age and with root age.

Information on the size of nutrient flux values and their change with increasing plant age can be used to determine the nutrient levels needed in the soil to supply nutrients rapidly enough to the root surface to minimize deficiencies. The objective of this research was to determine the relation between plant age and P absorption properties and root growth characteristics of wheat (Triticum vulgare L.) cv. Era.

Wheat was grown for periods up to 42 days in solution culture in a controlled climate chamber. Sequential harvests were made and P uptake and root morphology were measured. Shoot growth was exponential with time to 32 days and linear thereafter. Root dry weights increased linearly with time at a slower rate than shoot dry weights. Root length increased logarithmically with time (r² = 0.95; log y = 0.069x + 1.85).

With increasing plant age there was a reduction in average P uptake rate by wheat roots.     

Influence of extreme K:Na ratios and high substrate salinity on plant metabolism of crops differing in salt tolerance.VII. Relations between carbohydrates and degradative enzymes in salt tolerant and salt sensitive cotton genotypes during initial salinity stress

The effects of salinity on carbohydrates in leaves and roots of different salt tolerant cotton genotypes Glza 45 (salt tolerant) and Dandara (salt sensitive) during the initial salinity stress are investigated. Changes of starch and sucrose in relation to soluble amylases, phosphorylase and invertase in young leaves are studied. The plants are grown in water culture under controlled conditions.

Starch and sucrose accumulation is rapidly stimulated in leaves of Dandara, particularly due to extreme potassium sulfate supply, while in Giza 45 the amount of starch and sucrose declines except for extreme potassium sulfate treatment. The low sucrose value in roots of Dandara increases extremely, especially as a result of potassium chloride treatment. In contrast, the higher sucrose content in roots of Giza 45 is little affected. Amylase activity changes considerably in positive correlation with the starch content, whereas the low specific activity of phosphorylase is little affected. The sucrose content in the leaves is directly controlled by a high level of invertase activity of both cotton varieties.

Possible interactions of carbohydrate metabolism and genotyplcal ion regulation in response to the different salt tolerance of the genotypes are discussed. It is concluded that genotypical differences in the carbohydrate metabolism could be effective mechanisms for salt tolerance in cotton.     

Assessing the impact of soil amendments made of processed biowaste digestate on soil macrofauna using two different earthworm species

Fermentation in combination with subsequent composting of biowaste is a preferred method for municipalities to recycle organic byproducts and transform them into useful end products for soil amelioration or plant fertilization. These compost products, especially if obtained from household wastes, can be a source of hazardous components, e.g. heavy metals, pathogens, synthetic chemicals or toxic organic compounds. An avoidance test with two earthworm species (Eisenia fetida and Aporrectodea caliginosa) was conducted to assess the impact of differently processed biowaste based digestate products on soil invertebrates. Body weight changes were recorded, as well as differences in effects on adult versus juvenile earthworms.

While E. fetida showed no avoidance towards the digestate products (negative avoidance, meaning that the tested products were preferred, of 80 to 100 %), A. caliginosa rejected the crude biowaste digestate compost in higher concentrations (avoidance of 45 %), but not the agglomerated or pelletized variants. A clear weight gain of up to 25 % was observed only for individuals of E. fetida. The developmental stages of the worms were not crucial for the outcome of the avoidance test.

Based on the results of this study the application of biowaste products on arable land cannot be recommended without constraints.     

Animal-based organic nutrition can substitute inorganic fertigation in soilless-grown grape tomato

Purpose: In recent years, interest in plant nutrition research has arisen with a strong focus on organic forms. The aim of this study was to determine the effect of different organic fertilizers on growth, yield, fruit quality and polyphenol content in soilless grown grape tomatoes under greenhouse conditions.

Materials and methods: Tomato plants were subjected to three organic nutrient solutions, which consisted of different mixtures of several OMRI (Organic Materials Review Institute) certified nitrogen fertilizers of industrially processed residues: Treatment I: solid and soluble liquid fertilizers of animal raw materials, natural potassium sulphate-non-synthetic, and calcium chloride; Treatment II: solid and soluble liquid fertilizers of animal raw materials, by-product of marine raw material (soluble liquid), natural potassium sulphate-non-synthetic, and calcium chloride; and Treatment III: solid fertilizers of animal raw materials, natural potassium sulphate-non-synthetic, and calcium chloride to 100% [0-30 days after transplanting (DAT)], 125% [31-80 DAT], and 150% [>81 DAT]. The Steiner solution (SS) was used as a control (Treatment IV).

Results: Yield did not differ between organic and conventional treatments, ranging from 3.04 to 3.35 kg m^-2 while fresh weight in organic treatments was 3.14 compared to 3.2 kg m^-2 in plants fed with the SS. No significant differences in plant height or fruit quality were found. The application of organic fertilizers positively affected the total hydrolysable and condensed polyphenols of tomato fruits compared to the control. Twelve phenolic compounds were identified, highlighting 3-Caffeoylquinic acid, salvianolic acid and 5,6-Dihydroxy-7,8,3’,4’-tetramethoxyflavone (Treatment I) and Medioresinol (Lignan) (Treatment II).

Conclusions: The results indicated that organic fertilization through animal-based fertilizer application is a feasible alternative for grape tomato production under greenhouse conditions.     

Aluminum effects on uptake and translocation of nitrogen in sorghum (Sorghum bicolor,L. Moench)

The effects of aluminum on the uptake and translocation of N in two hybrid cultivars of sorghum with differential tolerance to aluminum were studied.

Aluminum decreased the amount of N accumulated and the % of N in the aerial parts of the plants. In the roots the amount of N accumulated also decreased but the % of N increased, in both cultivars. Besides an effect on dry matter yield, Al probably reduces the uptake of N and its translocation to the aerial parts of the plant. Apparently, this impairment on N translocation resulted from Al effects on the root pressure.

Aluminum not only reduced the amount of N translocated but also changed the sap composition. The % of NO₃ ‐N decreased while the % of amino acid‐N increased suggesting an Al effect on N uptake and also on protein degradation. Asparagine and glutamine contributed about 80% of the free amino acid fraction; however, their proportions changed in presence of Al. Therefore, Al also interfered with the synthesis and/or interconversion of these amino acids.     

Differential Tolerances of Amaranthus Strains to High Levels of Aluminum and Manganese in Acid Soils

Species of Amaranthus are grown extensively as leafy green vegetables in tropical Africa and Asia and as high yielding grain crops in Western South America, Central America, Northern India, Western Nepal, and Pakistan. The crop is often grown on acid, marginal soils, under subsistence conditions, where liming even the soil plow layer may not be economically feasible. Hence, the identification or development of strains with high tolerance to acid soils would be beneficial. Aluminum and Mn toxicities are the most important growth‐limiting factors in many acid soils. The objective of our research was to determine the tolerances of selected Amaranthus strains to high levels of these elements in acid soils.

Fifteen strains, representing five species, were grown in greenhouse pots of an acid, Al‐toxic Tatum soil limed to pH 4.8 and 5.8. Strains differed significantly in tolerance to the acid soil. Relative yields (pH 4.8/pH 5.8%) ranged from 50.1 to 6.3% for tops and from 54.5 to 5.7% for roots. Four strains of A. tricolor L. (vegetable type) were significantly more tolerant than six strains of A. cruentus L. (seed and vegetable type). Strains of A. hypochondriacus L. and A. caudatus L. studied were intermediate in tolerance.

Twelve strains, representing four species, were grown on an acid, Mn‐toxic Zanesville soil at pH 4.6 and 6.3. Strains also differed significantly in tolerance to this acid soil; however, overall growth was better and strain differences were smaller than on Al‐toxic Tatum soil at pH 4.8. On Zanesville soil the relative top yields (pH 4.6/pH 6.3%) ranged from 74.1 to 18.6%. The most tolerant group included three strains of A. tricolor and one strain of A. hypochondriacus, but four strains of A. cruentus were also fairly tolerant. The sensitive end of the scale included one strain of A. cruentus and two strains of A. hypochondriacus.

In general, strains that were most tolerant to the Al‐toxic Tatum soil were also among the most tolerant to the Mn‐toxic Zanesville soil. Likewise, those most sensitive to the high Al soil were most sensitive to the high Mn soil. But some strains that were sensitive to excess Al in Tatum soil were fairly tolerant to high Mn in Zanesville soil.

Results suggest that superior strains of Amaranthus can be selected or developed for use on acid soils.