Interaction effects of zinc and manganese on growth, uptake response and chlorophyll content of sweet corn (Zea mays var. saccharata)

Manganese (Mn) and Zinc (Zn) interact with each other and this interaction can result in impacts on the yield of corn plants. This study was conducted to examine the effect of different levels of Mn and Zn on the yield, Mn and Zn concentration, root growth parameters and chlorophyll contents of corn plants. Sweet corn was grown in nutrient culture containing all combinations of Zn and Mn at levels of 0.0, 0.1, 1.0 and 10.0 mg L-1 as ZnSO4.7H2O and MnSO4.H2O, respectively and harvested at 28 days after transplanting. Mn and Zn concentrations in roots and shoots increased with increasing Mn and Zn concentration in nutrient solution. Zn concentration in both roots and shoots enhanced with increasing Mn levels. Mn concentration in shoots did not show any correlation with Zn concentration in nutrient solution, but Mn concentration in roots decreased with increasing levels of Zn. Zn0Mn1 treatment produced the highest yield. The lowest dry weight of young corn plants was recorded under Zn10Mn0 treatment due to Mn deficiency. Chlorophyll content decreased with high Zn application and this can be attributed to the interaction of Zn with iron in the growth medium. Different levels of Zn and Mn in nutrient solution did not have any significant effect on root parameters

Species-specific effects of mycorrhizal symbiosis on Populus trichocarpa after a lethal dose of copper

Poplars have been identified as heavy metals hyperaccumulators and can be used for phytoremediation. We have previously established that their symbiosis with arbuscular mycorrhizal fungi (AMF) may alter their uptake, tolerance and distribution to excess concentrations of heavy metals in soils. In this study we hypothesised that mycorrhizal symbiosis improves the tolerance of poplars to lethal copper (Cu) concentrations, but this influence may vary among different AMF species. We conducted an experiment in a growth chamber with three Cu application levels of control (0 mg kg-1), threshold-lethal (729 mg kg-1) and supra-lethal (6561 mg kg-1), and three mycorrhizal treatments (non-mycorrhizal, Rhizophagus irregularis, and Paraglomus laccatum) in a completely randomized design with six replications. The poplars did not grow after application of 729 mg Cu kg-1 substrate, and mycorrhizal symbiosis did not help plants to tolerate this level of Cu. This can be explained by the toxicity suffered by mycorrhizal fungi. Translocation of Cu from roots to shoots increased when plants were colonised with R. irregularis and P. laccatum under threshold-lethal and supra-lethal applications of Cu, respectively. This result shows that mycorrhizal mediation of Cu partitioning in poplars depends on the fungal species and substrate Cu concentration. Multi-model inference analysis within each mycorrhizal treatment showed that in plants colonised with R. irregularis, a higher level of mycorrhizal colonisation may prevent Cu transfer to the shoots. We did not observe this effect in P. laccatum plants probably due to the relatively low colonisation rate (14%). Nutrient concentrations in roots and shoots were impacted by applied substrate Cu levels, but not by mycorrhizas. Magnesium (Mg), potassium (K), and manganese (Mn) concentrations in roots reduced with enhancing applied substrate Cu due to their similar ionic radii with Cu and having common transport mechanism. Synergistic effect on shoot concentration between applied substrate Cu levels and Mg, K, calcium, iron (Fe), and zinc was observed. Root Cu concentration was inversely related with root K and Mn concentrations, and shoot Cu concentration had a positive correlation with shoot Fe and K concentrations. Overall, mycorrhizal symbiosis has the potential to enhance plant health and their resilience to Cu toxicity in contamination events. However, it is important to note that the effectiveness of this symbiotic relationship varies among different mycorrhizal species and is influenced by the level of contamination

Revealing soil legacy phosphorus to promote sustainable agriculture in Brazil

Exploiting native soil phosphorus (P) and the large reservoirs of residual P accumulated over decades of cultivation, namely "legacy P", has great potential to overcome the high demand of P fertilisers in Brazilian cropping systems. Long-term field experiments have shown that a large proportion (> 70%) of the surplus P added via fertilisers remains in the soil, mainly in forms not readily available to crops. An important issue is if the amount of legacy P mobilized from soil is sufficient for the crop nutritional demand and over how long this stored soil P can be effectively 'mined' by crops in a profitable way. Here we mapped the spatial-temporal distribution of legacy P over the past 50 years, and discussed possible agricultural practices that could increase soil legacy P usage by plants in Brazil. Mineral fertiliser and manure applications have resulted in ~ 33.4 Tg of legacy P accumulated in the agricultural soils from 1967 to 2016, with a current annual surplus rate of 1.6 Tg. Following this same rate, soil legacy P may reach up to 106.5 Tg by 2050. Agricultural management practices to enhance soil legacy P usage by crops includes increasing soil pH by liming, crop rotation, double-cropping, inter-season cover crops, no-tillage system and use of modern fertilisers, in addition to more efficient crop varieties and inoculation with P solubilising microorganisms. The adoption of these practices could increase the use efficiency of P, substantially reducing the new input of fertilisers and thus save up to 31.8 Tg of P fertiliser use (US$ 20.8 billion) in the coming decades. Therefore, exploring soil legacy P is imperative to reduce the demand for mineral fertilisers while promoting long-term P sustainability in Brazil

A critical review of Pongamia pinnata multiple applications: from land remediation and carbon sequestration to socioeconomic benefits

Pongamia pinnata (L.) Pierre (Pongamia) is a tree native to Southeast Asia. Recently, interest in Pongamia focused on its potential as a biofuel source as its seeds contain around 40% oil. However, Pongamia has multiple applications beyond biofuel production. It is a legume, can form symbiotic associations with mycorrhizal fungi, has been shown to be tolerant to drought, salinity, and heavy metals in soil, and has potential to mitigate climate change. Additionally, Pongamia oil has medicinal properties, can be used as biopesticide, insect repellent, to produce soap, and as a source of edible grade vegetable oil. The seed cake can be used as a source of bioenergy, food and feed protein, and organic fertiliser, and the flowers are a good source of pollen and nectar. Pongamia can also bring socio-economic benefits as its ability to restore degraded and contaminated land provides opportunities for local communities through novel valorisation pathways. These multiple applications have potential to form part of a circular bioeconomy in line with sustainable development goals. Although research on the multiple applications of Pongamia has grown considerably, knowledge gaps remain and these need to be addressed so that the full potential of Pongamia can be achieved. Further understanding of the mechanisms underlying its resilience to abiotic stresses, phytoremediation potential and biotic interactions should be a priority, and co-ordinated breeding efforts will be key. Here, we critically review the available literature on Pongamia and highlight gaps in knowledge in which future research should focus on to ensure that the full potential of this versatile tree can be achieved. We conclude that Pongamia can potentially form part of a circular bioeconomy and that harnessing the multiple applications of Pongamia in a holistic manner, with collaboration among key stakeholders, is crucial for the successful application of its benefits far beyond biofuel production

Partitioning of environmental and taxonomic controls on Brazilian foliar content of carbon and nitrogen and stable isotopes

The Neotropics harbor some of the most diversified woody species in the world, and to understand the nutrient dynamics in these ecosystems, it is crucial to understand the role of plant taxonomy. In addition, biological nitrogen (N) fixation (BNF) in the tropics is one of the key processes affecting the global N cycle. Our objective was to (i) investigate the role of taxonomy and sampling site as predictors of foliar carbon (C) and N concentration and its stable isotopes (i.e., δ13C and δ15N); (ii) assess differences in foliar N, C:N ratio, and δ15N among three functional groups: species of N2-fixers and non-fixers of the Fabaceae family, as well as non-Fabaceae species; and (iii) examine the effect of wood density on tree foliar properties. We hypothesized that Fabaceae specimens in symbiosis with N2-fixers would possess a higher foliar N than non-fixing plants, including those of the Fabaceae family, as well as high-density trees would have higher foliar C and C:N ratio relative to low-density trees, where the latter invest in nutrients instead of structural C. We used a data set composed of 3,668 specimens sampled in three main biomes of Brazil: Amazon, Atlantic Forest, and Cerrado. The partitioning of variance had a higher influence of taxonomy on leaf C, N, and C:N ratio. Conversely, foliar δ13C and δ15N were environmentally constrained. While family was the most important taxonomy level for C, N, and C:N ratio, species played a major role for δ13C and δ15N. Foliar N followed the pattern fixers > non-fixers > non-Fabaceae, while C:N ratio had an opposite trend. In addition, foliar C was correlated with wood density, where high-density > medium-density and low-density woods. The large variability of δ15N was observed among Fabaceae species, demonstrates the complexity of using δ15N as an indicator of BNF. The higher foliar N of Fabaceae non-fixers than non-Fabaceae specimens support the hypothesis that an N-demanding lifestyle is an inherent pattern in this family. Lastly, although observed in some studies, the prediction of foliar properties using wood density is challenging, and future research on this topic is needed

Agronomic and biochemical expression of Zinc, Manganese, and Phosphorus interaction in sweet corn plants (Zea mays L Var. Saccharata (sturtev.) L. H. Bailey)

Zinc and phosphorus have antagonistic effects on the absorption and translocation of each other in plants. Phosphorus-induced Zn deficiency is more common than Zn-induced P deficiency because growers commonly apply large amounts of P fertilizer as compared to Zn fertilizer. Manganese and Zn also interact with each other and this interaction can affect the yield of corn plants. This research was conducted to examine the effects of different levels of Zn, Mn, and P on the yield, Zn, Mn, and P concentrations and uptake, the ultrastructure of chloroplast, physiological characteristics, root growth parameters, and chlorophyll contents of sweet corn plants. Sweet corn was grown in nutrient culture containing all combinations of Zn as ZnSO4.7H2O at levels of 0.0, 5.0, 10.0, and 20.0 mg L-1 and of P as KH2PO4 at levels of 0.0, 20.0, 40.0, and 80.0 mg L-1. The treatment Zn0P20 produced the highest yield and the yields decreased with P application in combination with Zn. The lowest dry weight of young corn plants was recorded under Zn0P80 treatment at both harvesting times due to both Zn deficiency and P toxicity. Chlorophyll content decreased with high Zn and P applications and this can be attributed to the interactions of Zn and P with iron in the growth medium. The study has shown that Zn deficiency can enhance P uptake and translocation to such an extent that P may accumulate to toxic level in leaves. Sweet corn was grown in nutrient culture containing all combinations of P at levels of 0.0 and 80.0 mg L-1 as KH2PO4 and Zn at levels of 0.0 and 20.0 mg L-1 as ZnSO4.7H2O, and harvested at 14 and 28 days after transplanting. Phosphorus and Zn concentrations in leaves increased with increasing P and Zn concentration in nutrient solution. Zinc supply did not affect P concentration but Zn concentration reduced with increasing P supply in nutrient solution at both harvests. Carbonic anhydrase activity in leaves was enhanced with increasing Zn levels and decreased with increasing P levels at both harvest times. Carbonic anhydrase activity is a better indicator of Zn nutritional status than Zn concentration alone. The ultrastructure of chloroplast was affected by P and Zn supply. Sweet corn was grown in nutrient culture containing all combinations of Zn and Mn at levels of 0.0, 0.1, 1.0, and 10.0 mg L-1 as ZnSO4.7H2O and MnSO4.H2O, respectively and harvested at 28 days after transplanting. Manganese and Zn concentrations in roots and shoots increased with increasing Mn and Zn concentration in nutrient solution. Zinc concentration in both roots and shoots was enhanced with increasing Mn levels. Manganese concentration in shoots did not show any correlation with Zn concentration in nutrient solution but Mn concentration in roots decreased with increasing levels of Zn. The lowest dry weight of young corn plants was recorded under Zn10Mn0 treatment due to Mn deficiency. Sweet corn grown in pot culture containing all combinations of Zn at levels of 0.0, 5.0, and 10.0 mg kg-1 soil and P at levels of 0.0, 50.0, 100.0, and 200.0 mg kg-1 soil as ZnSO4.7H2O and KH2PO4, respectively and harvested at 28 days after transplanting showed dry matter yield increased with P supply, while Zn application did not show any significant effect on this parameter. Zinc and P uptake by shoots increased with increasing Zn and P application to the soil. Zn concentration in shoots decreased with increasing P supply, but P concentration and uptake was enhanced. Phosphorus-induced Zn deficiency in this study is mostly related to the dilution effect. The percentage of P derived from fertilizer reduced with increasing Zn application, although P uptake by shoots was unchanged

Soil characteristics and fertility of the unique jarrah forest of Southwestern Australia, with particular consideration of plant nutrition and land rehabilitation

The jarrah forest is a natural ecosystem with significant endemism in the flora and fauna. The forest stands on the western edge of the ancient Great Plateau of Western Australia on the granitic shield of the Yilgarn craton (2.5 Gya). The long-term migration of soluble iron and aluminium led to the formation of bauxite ore. The regolith ore is bound by surficial topsoil and deep pallid zone kaolinite clays, primarily used in land rehabilitation. We investigated the chemical fertility of the substrates, along with key physical properties. We found the capacity of these soils to provide a stable growth medium differed considerably in their ability to retain and supply nutrients. These substrates are deficient in nitrogen, phosphorus, and micronutrients. In the topsoil, 15% of total P is plant-available, while in the pallid zone layer, only 1% of total P is available. 31P-NMR showed no organic P in the pallid zone, whereas the topsoil had significant organic P and, consequently, a supply of phosphate ions. This shows the importance of organic P in the topsoil for ecosystem nutrition when inorganic fertilisers are not applied in state-of-the-art restoration schemes

Combined effect of salinity and zinc nutrition on some physiological and biochemical properties of rosemary

Salinity and reducing its destructive effects on plant, soil, and water is among the most important challenges in agricultural lands. This study aims to evaluate the effect of zinc (Zn) and salinity on some physiological and biochemical properties of rosemary. A greenhouse experiment with two levels of Zn (0 and 20 mg kg−1) and salinity of sodium chloride (0, 60, and 120 mM) in a completely randomized design was used. Salinity decreased dry weight and concentrations of K, Ca, Mg, and Zn in rosemary shoots. However, it increased electrolyte leakage, shoot sodium concentration, phenolic compounds, and catalase activity. Zinc application increased rosemary dry weight by 13% and 9% under salinity levels of 0 and 60 mM NaCl, respectively. However, at higher salinity level (120 mM), it could not ameliorate the negative impact of salinity. Zinc improved the growth of rosemary under salinity stress by increasing the cell membrane stability, increasing shoot K, Ca, Mg, and Zn concentrations, and decreasing shoot Na concentration. The concentration of phenolic compounds in the leaves of rosemary grown under the salinity levels of 0 and 60 mM NaCl increased under the influence of Zn application. Nevertheless, the phenolic content remained unchanged under 120 mM NaCl salinity level. In this study, Zn addition increased catalase activity under all salinity levels. According to the results, optimum soil Zn application can be considered as an efficient and rapid solution for increasing rosemary growth and its tolerance to salinity stress

Purslane (Portulaca oleracea L.) salt tolerance assessment

The present study was aimed to evaluate the effect of irrigation water salinity on some agronomic and physiological attributes of purslane (Portulaca oleracea L.) and its tolerance to salinity stress. The treatments included seven levels of electrical conductivity of irrigation water (0.6 (control), 3, 6, 9, 12, 15, and 18 dSm−1) arranged in the form of a completely randomized design with three replications. The results showed that salinity stress successively decreased agronomic attributes such as root, shoot, and stem dry weight, plant height and leaf area. Physiological attributes such as relative water content as well as ion leakage differently responded to salinity stress. Relative water content response to salinity followed a quadratic regression model with the maximum of 81% at electrical conductivity of 6.87 dSm−1 and the minimum of 65% at highest salinity level of 18 dSm−1. Following an exponential regression model, ion leakage remained relatively the same till irrigation water salinity of 15 dSm−1 and reached to the maximum of 78% at highest irrigation water salinity of 18 dSm−1. In addition, shoot potassium content of purslane under non saline conditions equaled to 11% that was around 10 times more than the typical of potassium sufficient concentration for adequate growth. Moreover, with increasing salinity stress, shoot potassium content decreased to 7% at highest salinity level of 18 dSm−1 of irrigation water. However, with increasing irrigation water salinity, sodium shoot content of purslane was increased from 1.9% at the lowest salinity stress to 6.7% at the highest salinity stress. Based on the linear and nonlinear models, 10% of purslane biomass reduction occurred at soil electrical conductivity of around 10 dSm−1. In addition, 25 and 50% yield reduction observed at 16 and 25 dSm−1 of electrical conductivity of soil saturated paste. Therefore, purslane can be considered as a very salt tolerant plant, halophyte, and can successfully grow in soils with electrical conductivities not suitable for most crops