Nutrient Solution Experiments Research Articles

Effects of grafting on growth, root morphology and leaf physiology of pepino (Solanum muricatum Ait.) as affected by salt stress under hydroponic conditions

In this study, grafted and ungrafted pepino (Solanum muricatum Ait.) plants were tested under different saline conditions. The nutrient solution experiment was conducted within October – November 2016, by employing the technique of Deep-Water Culture (DWC) in an entirely operated automatically climate chamber found in the Plant Physiology Laboratory of Erciyes University, Agriculture Faculty, Kayseri, Turkey. Plants were examined under three various salt levels (i.e., 1 dS m-1, 4 dS m-1 and 8 dS m-1) by growing them in a 8 liter pots loaded constantly in an aerated Hoagland solution. The study was organized with completely randomized block design through three repetitions. The climate chamber study was performed to investigate effects of salt stress on plant growth, shoot- root fresh- dry weights, photosynthesis, leaf area formation, chlorophyll content of leaf (SPAD), leaf and root electrolyte leakage, total length of root, volume of root, and diameter of root in grafted and ungrafted pepino plants. The results showed that shoot growth, root morphological and leaf physiological responses were considerably (p<0.001) influenced by various levels of salt conditions at the nutrient solution. Increased salt level of the nutrient solution decreased significantly root and shoot growth, area of leaf, photosynthetic activity of both grafted and ungrafted plants. Irrespective of being grafted, significant declines were observed in shoot fresh weight (23.6%, 52.1%), root fresh weight (24.8%, 52.8%), leaf area (21.3%, 51.9%), shoot dry weight (24.3%, 53.0%), root dry weight (15.4%, 45.1%), SPAD (5.7%, 18.7%), photosynthesis rate (24.6%, 42.1%), total root length (6.7%, 16.4%), and root volume (3.8%, 5.8%) of pepino plants under 4 dS m-1 salt applications and 8 dS m-1 salt applications, respectively. Grafting promoted growth of plant in pepino plants under both control and saline conditions, furthermore it was noticed that under saline conditions biomass production of both grafted and ungrafted ones were significantly depressed.Grafted plants produced 54.1%, 43.0% and 9.6% higher shoot fresh weight; 52.0%, 42.0% and 12.8% higher root fresh weight; 52.5%, 40.7% and 8.7% higher leaf area; 60.0%, 46.6% and 11.1% higher shoot dry weight; 68.8%, 36.0% and 29.3% higher root dry weight; 19.9%, 9.2% and 8.2% higher SPAD; 8.0%, 5.1% and 10.8% higher photosynthesis rate; 8.6%, 3.6% and 6.6% higher total root length; 3.1%, 6.7% and 2.4% higher root volume than ungrafted plants under 1 dS m-1, 4 dS m-1 and 8 dS m-1 salt applications, correspondingly. Overall, our study showed that the effectiveness of grafting with respect to expansion of plants growth and development under salinity. Grafting was demonstrated to be an effective mean to achieve this goal.

Elevated zinc concentrations did not induce thiols in spinach (Spinacia oleracea) and parsley (Petroselinum crispum)

AbstractBackgroundPlants evolved various mechanisms to cope with metal stress. Cadmium (Cd) exposure specifically induces the synthesis of thiol‐rich substances such as phytochelatins. Due to the chemical similarity of Cd and zinc (Zn), similar detoxification mechanisms for both metals are under discussion.AimWe conducted a nutrient solution experiment to investigate thiol accumulation of parsley (Petroselinum crispum) and spinach (Spinacia oleracea) cultivars at different metal toxicity levels in vivo.MethodsThree metal treatments were applied: 1 µM Zn (control), 10 µM Zn, and 1 µM Zn + 1 µM Cd. After 10 days, thiol accumulation in parsley and spinach cultivars, which differ in their Zn tissue tolerance, was measured.ResultsSpinach and parsley cultivars differed in metal uptake, translocation, and resistance. In spinach, Cd application induced more severe toxicity symptoms and biomass reduction than Zn. Cadmium toxicity was more pronounced in spinach than in parsley due to higher Cd translocation of spinach cultivars. Despite comparable Zn tissue concentrations, parsley did not show any Zn toxicity symptoms. Due to lower Cd tissue concentrations, only a slight browning of parsley roots was found after Cd treatment. Whereas Cd application induced thiol synthesis in both plant species, Zn excess did not.ConclusionAs elevated Zn concentrations in plant tissues did not induce thiol synthesis, a contribution of phytochelatins to Zn homeostasis and detoxification was excluded.

Growth, root morphology and leaf physiology of watermelon as affected by various rates and forms of nitrogen in the hydroponic system

The aim of this study was to determine the effects of different rates and forms of nitrogen (N) on shoot growth and root morphological and leaf physiological responses of watermelon (cv. Crimson Tide F1) under hydroponic growth condition. The nutrient solution experiment was conducted between January - March in 2018 by using an aerated Deep Water Culture (DWC) technique in a fully automated climate room placed in the Plant Physiology Laboratory of Erciyes University, Faculty of Agriculture, Kayseri in Turkey. Plants were tested under two N-Rates (N1: 1000 and N2: 2000 µM N) and three different N-Forms (Am-N: NH4+, Nit-N: NO3-, 50% mixture of both N-Forms Mix-N: NH4+NO3) by growing in 8 L pots filled continuously aerated nutrient solution (modified Hoagland). The experiment was conducted with a completely randomized block design with four replications. From each pot two plants were harvested 42 days after treatment (DAT) by separating into stem, leaf and root fractions. The results indicated that shoot growth, root morphological and leaf physiological responses were significantly (p<0.001) affected by N-Rate, N-Form and N-Rate x N-Form interaction. The lowest performance under sole Am-N supply was achieved, since it severely reduced shoot and root growth and leaf area development as compared to sole Nit-N and Mix-N treatments. Irrespective of N rates, best growth performance in shoot growth was achieved under Mix-N supply, while root growth significantly improved under sole Nit-N supply. All these clearly indicate that the application of sole ammonium (1000 µM N) is detrimentally toxic for hydroponically grown watermelon plants. On the other hand, a 50% mixed of ammonium with nitrate even at a higher dose (N2: 2000 µM ammonium N) can be more advantageous for the growth and development of watermelon plants grown in the hydroponic system. Furthermore, our study showed that the effects of N-Form (Nit-N and Mix-N) on the improvement of shoot growth, root morphology and leaf physiological development and photosynthesis were significantly higher than the effects of N-Rate. Therefore, the application of nitrogen fertilizers in the form of Mix-N could be a useful N management strategy for growth and yield of watermelon plants under hydroponic conditions.

Interactions between cadmium and zinc in uptake, accumulation and bioavailability for Salix integra with respect to phytoremediation

The willow (Salix spp.) is a potential accumulator of cadmium (Cd)/zinc (Zn), and the interaction between Cd and Zn is an important factor influencing their phytoextraction potentials. In this study, interactions between Cd and Zn in uptake, accumulation and bioavailability for Salix integra clone SI63 were investigated through nutrient solution and soil culture methods. The result of the soil culture showed that Cd had additive effects for Zn-caused biomass reduction. The result from nutrient solution indicated that added Zn showed antagonistic (low Cd level) or synergistic (moderate and high Cd levels) effects on shoot Cd accumulation and antagonistic effects on root Cd accumulation. Irrespective of nutrient solution or soil culture experiment, Cd addition always had antagonistic effects on Zn accumulation in both shoots and roots. Under Cd10Zn50 condition, the clone accumulated higher Cd and Zn concentrations (95 μg g−1 Cd and 165 μg g−1 Zn) in shoots. Cd slightly increased bioavailable Zn in the rhizosphere, and EDTA well predicted bioavailable Cd and Zn in the rhizosphere. Interactions of Cd–Zn markedly changed their respective phytoextraction potentials, especially for Zn. This result will provide a new insight into improving phytoextraction potentials of both Cd and Zn using willows through applying metal interactions.

Tolerance and recovery of the annual pasture legumes Melilotus siculus, Trifolium michelianum and Medicago polymorpha to soil salinity, soil waterlogging and the combination of these stresses

This study evaluated the responses to and recovery from soil waterlogging, soil salinity and the combination of these stresses of the annual pasture legumes Melilotus siculus cv. Neptune, Trifolium michelianum cv. Frontier and Medicago polymorpha cv. Scimitar. The major aim was to test the tolerance of these plants to salinity and waterlogging in soil inoculated with rhizobia, adding to previous controlled-environment studies, which have used nutrient solution cultures, as well as to examine post-stress recovery. Plants were grown in pots of soil inoculated with their appropriate species-specific rhizobia. Drained non-saline controls, and waterlogged non-saline, drained saline (100 mM NaCl) and waterlogged saline treatments were imposed for 3 weeks, followed by a 4 week recovery period. In the waterlogged saline soil, shoot dry mass of M. siculus was 63% of the control, compared to 10% for T. michelianum and 5% for M. polymorpha, and after the recovery phase was 75% of the control for M. siculus, 58% for T. michelianum and 4% for M. polymorpha. Foliar Na+ concentrations of T. michelianum and M. polymorpha were 2.8-fold higher than for M. siculus. The greater tolerance of M. siculus can be attributed to regulation of leaf Na+ concentrations in saline conditions and the formation of aerenchymatous phellem to enhance O2 supply to roots in waterlogged soils. This controlled glasshouse study using pots of soil supports earlier nutrient solution experiments and field observations that M. siculus possesses greater tolerance of combined waterlogging and salinity, than T. michelianum and M. polymorpha.

Sources and doses of aluminum in experiments with rice in nutrient solution

ABSTRACT The aluminum source to produce toxicity in upland rice in nutrient solution experiments is not yet well established, althought the aluminum potassium sulfate has been utilized source to produce aluminum toxicity. However, in recent studies have used aluminum chloride. The aim of this study was to evaluate the capacity of aluminum sources and doses to produce toxicity in upland rice plants grown in nutrient solution. The experiment was arranged in a block randomized design, in a 2 x 5 factorial scheme and four repetitions. The treatments were two aluminum sources (aluminum potassium sulfate - AlK(SO4)2.12H2O and aluminum chloride - AlCl3.6H2O) and five aluminum doses in nutrient solution (0, 370, 740, 1100 and 1480 μmol L-1). The experiment was conducted in a greenhouse in Botucatu city, São Paulo state, Brazil, starting in April 2012, and was carried out for 56 days from transplanting of the seedlings. Using aluminum chloride, the rice plants show lower production of root and total dry weight, area and root volume, medium and thick root length, potassium and sulfur contents and accumulations. Using aluminum potassium sulfate, there are lower aluminum activity and availability, besides the formation of large amount of aluminum compounds non-toxic to the plants (aluminum sulfate) in the nutrient solution. The aluminum doses between 1100 to 1480 µmol L-1, corresponding to aluminum activity of 336.8 to 429.0 µmol L-1 of aluminum chloride as source, are more effective to produce aluminum toxicity in upland rice plants grown in nutrient solution.

Effects of different levels of glycine in the nutrient solution on the growth, nutrient composition, and antioxidant activity of coriander (Coriandrum sativum L.)

A nutrient solution experiment was performed using sand culture to evaluate the effects of different glycine levels on the growth and nutrient uptake of coriander (<em>Coriandrum sativum</em> L.). Different glycine concentrations of 0, 5, 10, 20, or 40 mg L<sup>−1</sup> were applied to plants via Hoagland’s nutrient solution in a completely randomized design with four replications and under greenhouse conditions. The results showed that leaf SPAD (soil and plant analysis development; an indicator of leaf greenness) value, stem diameter, and fresh and dry weights of shoots and roots were significantly increased by 10 mg L<sup>−1</sup> glycine in comparison to the control plants. Application of glycine at 40 mg L<sup>−1</sup> reduced many plant growth parameters, whereas leaf proline concentration was increased. All glycine levels except for 40 mg L<sup>−1</sup> increased root fresh weight. Leaf protein content was increased by glycine applied at 10 or 20 mg L<sup>−1</sup>, whereas leaf antioxidant activity was increased at all glycine levels. Application of glycine increased leaf concentrations of nitrogen and potassium (at 10 mg L<sup>−1</sup>), magnesium (at 5 mg L<sup>−1</sup>), and zinc (at all glycine levels) compared to the control plants. The results indicate that moderate level of glycine (10 mg L<sup>−1</sup>) in the nutrient solution can improve the growth and nutritional quality of coriander.

Characterization of nutrients uptake and enzymes activity in Khatouni melon (Cucumis melo var. inodorus) seedlings under different concentrations of nitrogen, potassium and phosphorus of nutrient solution

A nutrient solution experiment was done to evaluate effects of different concentrations of nitrogen (N), phosphorus (P) and potassium (K) on leaf mineral concentrations and some enzymes activity of melon seedlings (Cucumismelo var. inodorus subvar. Khatouni). Different levels of these nutrients including 0, 53, 105, 158 and 210 mg L−1 N; 0, 8, 16, 23 and 31 mg L−1 P; 0, 59, 118, 176 and 235 mg L−1 K, all corresponding to 0, 25, 50, 75 and 100% of their concentrations in Hoagland nutrient solution, were applied to plants. The results showed that the highest leaf nitrate reductase (NR) activity was observed at highest N and P levels, whereas the three highest K levels showed the highest NR activity. The highest leaf peroxidase activity was observed at 8 mg L−1 P, 59 mg L−1 K and 158 mg L−1 N. The leaf catalase activity was highest at zero concentration of P, 158 mg L−1 N and 176 mg L−1 K; however, catalase activity was decreased by increasing P levels. Leaf protein content showed an increasing trend with increasing N, P and K levels of nutrient solution, while there was no significant difference between 158 and 210 mg L−1 N. The highest leaf concentrations of N, P, K and Mg were observed at highest nitrogen, potassium and phosphorus levels of nutrient solution, whereas the highest leaf concentration of Ca were obtained at 53 or 105 mg L−1 N, 176 mg L−1 K and 23–31 mg L−1 P. The highest iron concentration of leaves was obtained from 23 to 31 mg L−1 P, 176 mg L−1 K and 210 mg L−1 N.

Effects of different magnesium levels on some morphophysiological characteristics and nutrient elements uptake in Khatouni melons (cucumis melo var. inodorus)

A nutrient solution experiment was carried out to evaluate effects of different magnesium (Mg) concentrations (0, 25, 50, 75 and 100 percent of magnesium concentration of Hoagland solution) on growth and physiological characteristics of Iranian melons (Cucumis melo var. inodorus subvar. Khatouni). The experiment was done based on completely randomized design using plastic pots and sand culture. The results showed that SPAD value of leaves, plant leaf number, stem diameter, shoot fresh and dry weight, root fresh weight, chlorophyll b, carotenoids, protein, catalase and peroxidase activities were constantly increased by increasing Mg levels of nutrient solution until 75 or 100% Mg levels, while leaf area, petiole length, internodes length were highest in lower levels of Mg compared to full Mg of nutrient solution. Moreover, the leaf concentrations of nitrogen (N), phosphorus (P), potassium (K), magnesium, and iron (Fe), but not calcium (Ca), were increased by increasing magnesium concentration to full Hoagland nutrient solution Mg level.

Genotypic Variation and Biofortification with Selenium in Brazilian Wheat Cultivars.

Selenium is essential to human and animal health, as it regulates glutathione peroxidase activity. Although not considered essential to plants, it may be beneficial to plant growth and development at low concentrations. This study evaluated the effect of selenate application on Se biofortification, macro- and micronutrient content, and the expression of genes involved in Se uptake and assimilation in 12 Brazilian wheat ( L.) cultivars. This nutrient-solution experiment was performed in a greenhouse and consisted of a complete 12 × 2 factorial randomized design, with 12 wheat cultivars in the absence or presence of Se in solution (13 μmol), with three replicates. The presence of Se in solution did not affect growth and yield of wheat cultivars. Selenium content and accumulation in the grain varied significantly among the different cultivars. The presence of Se affected macronutrient content more than micronutrient content, and selenate application increased S content in the shoots of eight cultivars and in the grains of five cultivars. Examination of gene expression did not allow identification of responses within the two groups of cultivars-with high or low Se contents-after selenate application. Our findings are relevant to the design of Se biofortification strategies for wheat in tropical and subtropical agroecosystems.

Growth and Fruit Biochemical Characteristics of Three Strawberry Genotypes under Different Potassium Concentrations of Nutrient Solution

Abstract A nutrient solution experiment was performed to evaluate the growth, yield and fruit biochemical characteristics of strawberry under different potassium levels of nutrient solution. Potassium concentrations including 235 (control), 350, 450 and 600 mg L-1 were applied to three strawberry genotypes of Camarosa, Selva and Parus under hydroponic culture. In the three genotypes, the maximum leaf area was observed at 350 mg L-1 K, and the maximum shoot fresh weight was either at 350 mg L-1 (in Camarosa and Parus) or at 400 mg L-1 (in Selva). In Selva, higher yield was produced by higher K concentrations than control (17-33%) and in Camarosa, the maximum yield was produced at 350 mg L-1 (16%), whereas fruit yield in Parus was not affected by K concentrations. In Selva and Parus application of 350 mg L-1 potassium produced more fruits than control. The maximum fruit vitamin C content in Camarosa and Selva was at 350 mg L-1, and in Parus at 450 mg L-1, while the significant lowest in three genotypes was at 600 mg L-1. Fruit titratable acidity and pH in Camarosa and Selva, and fruit TSS in Parus were not affected by K levels. Fruit total soluble solids (TSS) in Camarosa and Selva were maximum in 350 and 450 mg L-1. Increasing K concentrations of nutrient solution increased leaf and fruit K concentration than control. The results indicate that overall plant growth and fruit quality of three strawberry genotypes were increased by 350 mg L-1 potassium, while application of 600 mg L-1 reduced most traits than control. The Selva genotype had also a better response to higher concentration of K than two other genotypes.

Effects of melatonin on the growth and cadmium characteristics of Cyphomandra betacea seedlings.

To determine whether the melatonin (MT) could reduce cadmium (Cd) accumulation in Cyphomandra betacea seedlings, different concentrations of MT were added to the nutrient solution and soil to study its effects on the growth and Cd characteristics of C. betacea seedlings. Fifty micromoles per liter (μmol/kg) of MT increased the biomass of C. betacea seedlings, but 100-200μmol/L (μmol/kg) MT decreased seedling biomass in both the nutrient solution and soil cultivation experiments. The photosynthetic pigment contents showed no significant changes compared with the control when the MT dose was 150μmol/L (μmol/kg) or less, while 200μmol/L (μmol/kg) MT decreased the photosynthetic pigment contents. Low levels of MT improved the antioxidant enzyme activities of C. betacea seedlings, whereas high MT levels reduced them. MT increased the Cd contents in different organs of C. betacea seedlings in the nutrient solution cultivation experiment, but only 50μmol/kg MT increased the Cd contents in stems, leaves, and shoots of C. betacea seedlings in the soil cultivation experiment. Therefore, only low levels of MT can promote the growth of C. betacea seedlings, and MT is not suitable for reducing Cd accumulation in C. betacea seedlings.

The Effect of Foliar-Applied Manganese in Mineral and Complex Forms with Amino Acids on Certain Defense Mechanisms of Cucumber (Cucumis sativus L.) Against Powdery Mildew

Manganese (Mn) is an essential micronutrient with positive effects on enhancing plant tolerance against fungal diseases. On the other hand, it has been suggested that metal–amino acid complexes are more effective than mineral sources in supplying Mn and improving the translocation and distribution of these metal nutrients in plants. Meanwhile, certain amino acids, that is, lysine and methionine, play an important role in crop resistance to biotic stresses. Little information is, however, available regarding the effect of foliar-applied Mn in mineral and complex forms with amino acids on crop tolerance to powdery mildew caused by Podosphaera fuliginea. In this nutrient solution experiment, the effect of foliar-applied Mn, in the form of MnSO4, Mn-methionine (Mn-Met) and Mn-lysine (Mn-Lys), on certain defense mechanisms of cucumber (Cucumis sativus L. cv. Espadana RZ) against powdery mildew was investigated. Different Mn sources were applied as foliar spray 4 days before and 6 days after inoculation with P. fuliginea. The results revealed that Mn application prior to pathogen inoculation decreased the disease in the treated and newly growing leaves; however, the efficiency of Mn–amino acid complexes in disease suppression was greater than that of MnSO4. Post-inoculation spray of Mn had no effect on the disease reduction of the newly growing leaves, but all Mn sources diminished disease severity equally in the treated leaves. In such leaves, regardless of the application time, the higher content of cell wall lignin was found in the plants treated with MnSO4, in comparison with those treated with Mn–amino acid complexes. In the newly growing leaves, the foliar application of Mn–amino acid complexes before inoculation resulted in a significant increase of leaf cell wall lignin content, whereas MnSO4 was ineffective. Pre-inoculation spray of MnSO4 led to increasing PO and PPO activities in the treated leaves, whereas Mn–amino acid complexes had no significant effect on the activity of these enzymes in the same leaves. Application of Mn-Met and Mn-Lys after pathogen inoculation led to a significant decrease of PPO activity in the treated leaves. In general, the results of the present study revealed that the time of Mn foliar application could have a considerable effect on controlling cucumber powdery mildew. Foliar application of Mn before infection with P. fuliginea could strengthen the defensive structures of the plant and help to prevent the disease incidence.

Comparison of Selenium Toxicity in Sunflower and Maize Seedlings Grown in Hydroponic Cultures.

Several studies have demonstrated that selenium (Se) at low concentrations is beneficial, whereas high Se concentrations can induce toxicity. Controlling Se uptake, metabolism, translocation and accumulation in plants is important to decrease potential health risks and helping to select proper biofortification methods to improve the nutritional content of plant-based foods. The uptake and distribution of Se, changes in Se content, and effects of various concentrations of Se in two forms (sodium selenite and sodium selenate) on sunflower and maize plants were measured in nutrient solution experiments. Results revealed the Se content in shoots and roots of both sunflower and maize plants significantly increased as the Se level increased. In this study, the highest exposure concentrations (30 and 90 mg/L, respectively) caused toxicity in both sunflower and maize. While both Se forms damaged and inhibited plant growth, each behaved differently, as toxicity due to selenite was observed more than in the selenate treatments. Sunflower demonstrated a high Se accumulation capacity, with higher translocation of selenate from roots to shoots compared with selenite. Since in seleniferous soils, a high change in plants' capability exists to uptake Se from these soils and also most of the cultivated crop plants have a bit tolerance to high Se levels, distinction of plants with different Se tolerance is important. This study has tried to discuss about it.

Konstitusi Genetik dan Karakter Fenotipik Galur-galur Padi Pup1 Turunan Varietas Situ Bagendit

<p>Acidity, phosphorus deficiency, and drought<br />stress are major problems in Indonesia’s Ultisol rice farming.<br />Development of rice lines tolerant to those stresses is<br />expected to be able to reduce the consumption of P<br />fertilizer. The objectives of the research were to evaluate<br />genetic constitutive of rice lines (BC2F6 population) derived<br />from Situ Bagendit x Kasalath and Situ Bagendit x NIL-C433<br />crossings, and to evaluate responses of those lines to<br />Yoshida nutrient solution under P deficiency and Al stress<br />condition. The research was conducted at Molecular Biology<br />Laboratory and Greenhouse of ICABIOGRAD, from<br />November 2011 to May 2013. The result of foreground<br />analysis showed that Pup1 locus has been integrated into<br />the genome of BC2F6 rice lines, eventhough some lines (SK5,<br />SK6, SK7, SK8, SK9, SK10, SK19, and SK20) showed<br />incomplete integration. Background analysis indicated that<br />majority (95.7%) of the Situ Bagendit background has been<br />recovered in BC2F6 rice lines. Al stress evaluation showed SN<br />lines were more tolerant to P deficiency and Al stress than<br />that of SK lines. Pup1 locus showed good expression under<br />low P and no Al stress. Based on genome proportion and<br />Yoshida nutrient solution experiments, a total of three lines,<br />namely SK13, SN2, and SN9, have potential good<br />characteristics. Molecular analysis within a marker-assisted<br />backcrossing (MAB) experiment should be carried out at<br />each generation of lines for gaining fully gene segment in<br />advanced generations.</p>

Assessment and comparison of selenium-enriched maize with sodium selenite and sodium selenate

Selenium is an element of environmental interest owing to the narrow range between its nutritionally required and toxic concentrations in many organisms. Its mobility and bioavailability differ greatly depending on individual Se species. In this regard, in present study, the uptake and distribution of Se, the changes in Se content, and the effects of different concentration of Se in two forms of sodium selenite and sodium selenate on maize plants were measured in nutrient solution experiments to clarify their response to the two forms of Se. The results revealed that the Se content in shoots and roots of maize plants significantly increased as the Se level increased. Two Se forms behaved differently and the effects of toxic damage in samples which had been treated with selenite were much more than in the selenate treatments.

Differences in Aluminium Accumulation and Resistance between Genotypes of the Genus Fagopyrum

Aluminium (Al) toxicity is a major factor reducing crop productivity worldwide. There is a broad variation in intra- and inter-specific Al resistance. Whereas the Al resistance mechanisms have generally been well explored in Al-excluding plant species, Al resistance through Al accumulation and Al tolerance is not yet well understood. Therefore, a set of 94 genotypes from three Fagopyrum species with special emphasis on F. esculentum Moench were screened, with the objective of identifying genotypes with greatly differing Al accumulation capacity. The genotypes were grown in Al-enriched peat-based substrate for 21 days. Based on the Al concentration of the xylem sap, which varied by a factor of five, only quantitative but not qualitative genotypic differences in Al accumulation could be identified. Aluminium and citrate and Al and Fe concentrations in the xylem sap were positively correlated suggesting that Fe and Al are loaded into and transported in the xylem through related mechanisms. In a nutrient solution experiment using six selected F. esculentum genotypes differing in Al and citrate concentrations in the xylem sap the significant correlation between Al and iron transport in the xylem could be confirmed. Inhibition of root elongation by Al was highly significantly correlated with root oxalate-exudation and leaf Al accumulation. This suggests that Al-activated oxalate exudation and rapid transport of Al to the shoot are prerequisites for the protection of the root apoplast from Al injury and thus overall Al resistance and Al accumulation in buckwheat.

Aluminum-TolerantPisolithusEctomycorrhizas Confer Increased Growth, Mineral Nutrition, and Metal Tolerance toEucalyptusin Acidic Mine Spoil

Ectomycorrhizal fungi (ECM) may increase the tolerance of their host plants to Al toxicity by immobilizing Al in fungal tissues and/or improving plant mineral nutrition. Although these benefits have been demonstrated inin vitro(pure culture) or short-term nutrient solution (hydroponic) experiments, fewer studies have examined these benefits in the field. This study examined the growth, mineral nutrition, and Al levels in twoEucalyptusspecies inoculated with threePisolithusecotypes that varied in Al tolerance (in vitro) and grown in mine spoil in the greenhouse and field. All three ecotypes ofPisolithusimprovedEucalyptusgrowth and increased host plant tolerance to Al in comparison to noninoculated plants. However, large variations in plant growth and mineral nutrition were detected among thePisolithus-inoculated plants; these differences were largely explained by the functional properties of thePisolithusinoculum. Seedlings inoculated with the most Al-tolerantPisolithusinoculum showed significantly higher levels of N, P, Ca, Mg, and K and lower levels of Al than seedlings inoculated with Al-sensitive ecotypes ofPisolithus. These findings indicate an agreement between the fungal tolerance to Alin vitroand performance in symbiosis, indicating that both ECM-mediated mineral nutrient acquisition and Al accumulation are important in increasing the host plant Al tolerance.

Effects of chain length and pH on the uptake and distribution of perfluoroalkyl substances in maize (Zea mays)

Maize is the most important grain crop grown for human nutrition, animal fodder and biogas production worldwide. Nonetheless, no systematic studies have been undertaken on these plants to examine the uptake mechanisms for perfluoroalkyl substances (PFASs) dependent upon chain length and pH value. The aim of the present study was therefore to determine the influence of chain length (C4 to C10) and pH value (pH 5, pH 6, pH 7) on the uptake and distribution of seven perfluoroalkyl carboxylic acids (PFCAs) and three perfluoroalkane sulfonic acids (PFSAs) by maize in nutrient solution experiments under controlled conditions in a climate chamber. A pH-dependent uptake was observed for perfluorodecanoic acid (PFDA) with an uptake rate of 2.51μgg−1 at pH 5 compared to 1.52μgg−1 root dry weight (DW) per day (d) at pH 7. Perfluorobutanoic acid (PFBA) had the highest uptake rate within the group of PFCAs with an average of 2.46μgg−1 root DWd−1 and perfluorooctane sulfonic acid (PFOS) had the highest uptake rate (3.63μgg−1 root DWd−1) within the group of PFSAs. The shoot:root ratio for shorter-chain PFCAs (⩽C7) and PFBS (C4) was >2.0, which indicates that shorter-chain PFASs are transferred predominantly and at higher concentrations to the shoot. In contrast, long-chain PFCAs such as perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) as well as the PFASs perfluorohexane sulfonic acid (PFHxS) and perfluorooctane sulfonic acid (PFOS) accumulated at higher concentrations in the roots of maize plants with a shoot:root ratio of <1.0.

Manganese in substrate clays—harmful for plants?

AbstractMixtures of peat and substrate clays are commonly used as growth media for horticultural plant production. A quality protocol for substrate clays defines a threshold value of active manganese (Mnact = sum of exchangeable and easily reducible Mn) in substrate clays of &lt; 500 mg kg–1 to prevent toxic reactions of plants. This threshold value was tested in experiments with peat‐clay blends under various growth conditions, and nutrient solution experiments were additionally conducted to investigate the effects of silicic acid and dissolved organic matter on the occurrence of Mn toxicity. Common bean (Phaseolus vulgaris L.) and hydrangea (Hydrangea macrophylla) plants were cultivated in different peat‐clay substrates and in peat under different moisture and pH levels. The clays varied in their Mnact content from 4–2354 mg kg–1. The results of the substrate experiments reveal that a threshold value for Mn in substrate clays is not justified, as plants grown in all peat‐clay substrates did not develop any Mn toxicity even at high substrate moisture or low pH conditions which are known to increase the Mn availability. The extraction of active Mn did not well reflect the Mn concentrations in plant dry matter and substrate solution. As plants tolerated high Mn concentrations in the substrate solution compared to the nutrient solution without toxicity symptoms, the influence of silicic acid and dissolved organic matter (DOM) on Mn toxicity was characterized in a nutrient‐solution experiment. Manganese toxicity was clearly diminished by silicic acid application, but not by DOM. The former effect probably explains the tolerance of bean plants in peat substrates where high silicon concentrations in the substrate solution were observed. Peat‐clay blends even provided up to five times more silicon to plants than pure peat.