Due to diverse human activities zinc (Zn) may reach phytotoxic levels in the soil. Here, we evaluated the differential sensibility of three Brazilian tree species from the Fabaceae to increasing soil ...Zn concentrations and its physiological response to cope with excess Zn. A greenhouse experiment was conducted with the species: Mimosa caesalpiniaefolia, Erythrina speciosa and Schizolobium parahyba, and the addition of 0, 200, 400 and 600 mg Zn kg−1 to the soil. Plants were harvested after three months of cultivation, and growth, root symbiosis, biochemical markers and elemental composition were analyzed. Soil Zn addition reduced seedling growth, irrespective of the species, with a strong reduction in M. caesalpiniaefolia. Regarding root symbiosis, in N2-fixing species, nitrogenase activity was reduced by the highest Zn concentrations. Zn addition caused plants nutritional imbalances, mainly in roots. The content of photosynthetic pigments in leaves decreased up to 40%, suggesting that high Zn contents interfered with its biosynthesis, and altered the content of foliar polyamines and free amino acids, depending on the species and the soil Zn concentration. Zn toxicity in M. caesalpiniaefolia plants was observed at available soil Zn concentrations greater than 100 mg kg−1 (DTPA-extractable), being the most sensitive species and E. speciosa was moderately sensitive. S. parahyba was a moderately tolerant species, which seems to be related to polyamines accumulation and to mycorrhizal association. This last species has the potential for revegetation of areas with moderately high soil Zn concentration and for phytostabilization purposes. Future research evaluating the tolerance to multiple metal stress under field conditions should confirm S. parayba suitability in Zn contaminated areas of tropical regions.
•Soil Zn addition reduced growth of seedling of tropical tree species.•Soil Zn caused nutritional imbalances, mainly in roots.•In N2-fixing species high Zn concentrations reduced nitrogenase activity.•Polyamine accumulation may be related to the tolerance to zinc toxicity.•Schizolobium parahyba was a moderately tolerant tree species.
•Plants respond to nutrient deficiency with different signaling mechanisms.•Recent studies in plants have focused on detecting long-distance signals.•Local and systemic signaling pathways coordinate ...adaptive responses to nutritional stress.•Phytohormones, RNAs, peptides, and proteins are part of the signaling pathways.•Split root, grafting, and girdling are useful techniques in signaling studies.
Plant growth is related to the amount of nutrients that it can acquire and it can be limited by poor root development and nutrient uptake, and low efficiency of nutrient use. Nutrients are not distributed evenly throughout the soil around roots, causing plants to put in action the functioning of the various local and systemic signaling pathways to coordinate adaptative responses to the most diverse types of stresses, among them nutritional limitation. A coordinated array of long-distance signaling mechanisms integrates the communication between shoots and roots, which provide photoassimilates and nutrients, respectively. The use of techniques to study signaling among the most diverse plant species has gained prominence. The main techniques for studying nutrient signaling between shoots and roots are split-root, grafting and girdling. The split-root system is characterized by separating a single root system in two independent compartments, with a common shoot. Split-root has been used for analyzing transcriptional, biochemical, and physiological changes in roots in response to nutritional challenges. Grafting has stood out as an important method concerning signaling mechanisms studies. It still follows the basic principle of cutting and fitting two parts (scion = bud and rootstock = root) from different plants, which merge, grow and develop as a single plant. Most recent studies have been in detecting long-distance signals, their transport, and the factors involved in signaling mechanisms, with particular attention to the role of phytohormones, RNAs, peptides, and proteins. Girdling is an important technique widely used in fruit trees. It consists of the removal of a strip of bark from branches or trunk, affecting different stages of reproductive growth, including flowering and fruiting, development, ripening, and nutritional quality of fruits. The increase in the amount of carbohydrates above the cut induces the expression of genes involved in the metabolism of carbohydrates, favoring the respiratory potential of the stem and branches, as well as the leaf mass per area. The techniques reviewed here allow the monitoring and study of long-distance signaling and relate it to plant development through simple, efficient, and reproducible approaches. They permit researchers to make inferences about the existence, direction, and intensity of the cross-talk between long-distance signaling and nutrients, suggesting that mobile signals and their interactions with individual nutrients exist.
ABSTRACT The coffee sector is estimated to have a retail market value in excess of USD 83 billion, and over 125 million jobs have been created in the global coffee chain. The coffee specialty market ...has recently increased significantly, generating opportunities to certify coffee beans produced by sustainable practices. This avoids practices potentially harmful to the environment. Agroforestry, organic farming, intercropping, and soil conservation strategies are examples of sustainable alternatives in the production of coffee. In this review, we focus on practices for the sustainable management of coffee plantations that can help farmers fight problems caused by global warming. More specifically, we address soil organic matter and microbiota, the use of Urochloa grass as intercrop in coffee plantations, shading systems (including agroforestry), and organic coffee production. We concluded that from the agronomic viewpoint, we already have production techniques that can replace traditional ones with significant advantages accruing to the quality of coffee orchard ecosystems. Nevertheless, we need scientific research efforts to deal with the existing gaps and the engagement of the whole coffee chain as a means of guaranteeing an adequate profit to those smallholders who adopt and maintain sustainable practice and are capable of bringing several positive changes to the coffee crop, including the use of microbia-based commercial products and new organic sources of nutrients to complement chemical fertilizers and improve coffee quality.
Manganese (Mn) is a nutrient that can cause phytotoxicity if above a threshold concentration. Acid soils are prone to excessive Mn levels that under certain environmental conditions may increase ...availability and exacerbate deleterious effects on plants. Apart from oxidative stress, excess Mn usually affects photosynthetic apparatus. Nonetheless, some plants are known to tolerate high Mn contents without negative consequences. We carried out a greenhouse experiment with two eucalypt species (
Eucalyptus globulus
and
Corymbia citriodora
), treated with four Mn additions in the soil substrate (0, 50, 150 and 300 mg kg
−1
) for 18 weeks. Before harvest, shoot height and the chlorophyll
a
fluorescence parameters were assessed, then leaves, stems and roots were sampled, weighted and nutrients determined. Manganese addition increased height for both species while biomass production remained unchanged, even though foliar concentrations ranged from 600 to 800 mg kg
−1
at the highest Mn in soil. High root-to-shoot translocation of Mn was observed, yet—contrary to our hypothesis—photochemical efficiency of photosystem II was barely affected, except for the slight decrease in
C. citriodora
under 300 mg kg
−1
Mn. The capacity to accumulate high Mn in photosynthetic tissues without chlorophyll damage seems to be a feature of Mn tolerant species. Nutritional imbalances such as magnesium decrease due to Mn exposure was observed, but not enough to cause deficiency. Both eucalypt species were therefore tolerant to high Mn concentrations in soil, especially
E. globulus
, and have the potential to be employed in reforestation/afforestation of lands with high risk of Mn phytotoxicity.
Eucalypts and low phosphorus availability Bulgarelli, Rafaela Gageti; de Oliveira Silva, Franklin Magnum; Bichara, Samir ...
Plant and soil,
12/2019, Letnik:
445, Številka:
1/2
Journal Article
Recenzirano
Odprti dostop
Background and aims
Twenty-four species of eucalypts were studied regarding their ability to grow under low P and their responsiveness to P inputs.
Methods
Growth and photosynthesis-related ...parameters were evaluated.
Results
Growth of all species was influenced by low P availability. No significant correlation was found between leaf P concentration and biomass, indicating that P concentrations in leaves cannot be solely considered an indication of the responsiveness to P in eucalypts. Species responsive to P-input (high agronomic P efficiency values, APE) were those with low P use efficiency - PUE (here assessed as relative efficiency of P-use, REP) and low P uptake efficiency (PUpE). But, non-responsive species were related to higher P-efficiency under low soil P-availability.
Eucalyptus tereticornis
,
E. cladocalyx
,
E. globulus
and
E. camaldulensis
were efficient under low-P availability. Whereas,
E. crebra
and
E acmenoides
were the most responsive species, with high APE, suggesting that for these species P-inputs are needed to guarantee plant growth. The root:shoot ratio remained constant at different P availabilities, suggesting that biomass allocation towards the root in response to P and greater investment in roots were not correlated with greater PUE. Under limited P,
E. robusta
and
E. botryoides
exhibited low foliar P contents and higher root:shoot ratios than those of other species with higher P contents, indicating that greater root investment does not necessarily result in greater PUE.
Conclusion
The results suggest that the divergence among species is probably related to different mechanisms, which may improve P-use efficiency.
Endophytic fungi are those that inhabit within organs and tissues without causing damage, while mycorrhizal fungi develop hyphal complexes called pelotons within cortical cells of orchid roots. ...Although abundant and frequent in all plant organs, the role of endophytic fungi has been neglected in relation to orchid's early development.
Cogn. is an aclorophyllated and mycoheterotrophic (MH) orchid. This study aimed at i) investigating the endophytic fungal community in organs of
and its mycorrhizal fungi associated; ii) evaluating the ability of isolated fungus in the
germination of the seeds of the species, and iii) describing the development of
protocorm, analyzing the ultrastructure of the infected cells. Six genera of fungi were isolated and identified through the partial sequencing of the internal transcribed spacer region, all belonging to the phylum Ascomycota. Also, Tulasnellaceae was identified through uncultured technique as potentially mycorrhizal in this MH orchid. Some isolates of the genera
,
, and especially
presented germinative potential on
seeds, causing rupture of the external tegument. The protocorms showed complete absence of peloton formation, but fungal hyphae were clearly observed within living cells. This is the first report of germination of a MH and aclorophyllated orchid species stimulated by the presence of non-mycorrhizal endophytic fungi isolated from fruits and roots of the same species.
In regions of low soil phosphorus (P) availability, such as many tropical and subtropical regions, the cultivation of eucalypts is common due to their adaptation to P-constrained soils. As in other ...trees, the molecular mechanisms underlying the phosphate starvation response (PSR) in eucalypts remain poorly understood. This study aimed to elucidate the molecular responses associated with PSR and assess the efficiency of P acquisition in five eucalypt species:
Eucalyptus acmenoides
,
E. grandis
,
E. globulus
,
E. tereticornis
, and
Corymbia maculata
. A greenhouse experiment was carried out in soil/substrate with low resin-extractable P (4.5 mg kg
−1
, Low P) and sufficient P (10.8 mg kg
−1
, Sufficient P) availability. After nine months growing in such conditions, various parameters were assessed, such as biomass production, P concentrations, P uptake efficiency (PUpE), and the expression of PSR-related genes. Overall, eucalypt plants exhibited a relatively weak response to low P availability, with slight variations in biomass production, P concentration, and PSR gene expression.
C. maculata
plants exhibited the highest PUpE under low P, while
E. globulus
exhibited the lowest. Among PSR-related genes, LPR1/2 in the roots of
E. grandis
, PDR2 in the roots of
C. maculata
, and phosphate transporters
PHT1;6
and
PHT1;8
in the roots of
E. globulus
, along with
PHT1;12
in the roots of
E. tereticornis
, were induced under low P availability. Elevated
PHT1
transcripts in the roots under sufficient P conditions, despite adequate leaf P concentrations, suggest potential interactions with other nutrient availability such as nitrogen, magnesium, and calcium, as well as symbiotic associations. Additionally, the upregulation
SQD1
gene involved in membrane lipid remodeling in leaves of
E. tereticornis
,
E. acmenoides
, and
C. maculata
under low P suggests an improved P utilization efficiency. This study reveals the intricate and multifaceted nature of eucalypt responses to soil P availability. Despite the low P concentrations, eucalypt plants maintained foliar concentrations similar to those in the P-sufficient treatment suggesting a complex interplay of factors influencing PSR including nutrient balance.
•We studied the effects of forest cover and seasonality on fine-root production and AMF.•Soil samples were collected in four different forest covers and contrasting seasons.•The most suitable time ...interval for collecting fine roots in Montane Forests was over three months.•Restoration forest post-pasture produced more fine-root biomass in the rainy season.•Most AMF traits were affected by forest cover type and the rainy season.
Tropical Montane Forests are unique climate-influenced ecosystems with a vital role for some ecosystem services, of which one of the most important is soil carbon storage. Changes in forest cover affect forest structure, composition and functioning, but little is known about how such changes influence the belowground carbon content. In this study, we addressed this issue by evaluating whether fine-root production differed between forest-cover types and contrasting seasons after controlling arbuscular mycorrhizal fungi (AMF) traits, and what the minimum time required to detect such differences is. We also determined whether AMF-related traits were affected by distinct forest cover and seasons after controlling fine-root production. The objects of study were four forests with distinct degradation histories in the Atlantic Forest: Old-growth, Post-selective logging, Post-clear-cut and Post-pasture forests. Data were collected in four 2500-m2 plots installed in each area and analyzed through multivariate statistics. Fine-root production differed significantly between forest covers, and marginally between seasons, as it was greater in the post-pasture area and in the rainy season. Some AMF traits also differed between forest covers and seasons, especially the abundance of viable spores in the dry season. We found that the shortest period necessary to identify differences in the production of fine roots was over three months. This study shows that forests with different degradation histories and annual climatic variations significantly affect fine-root production and AMF dynamics in Tropical Montane Forests. In particular, ecosystems that have been more perturbed tend to invest more in fine-root production (post-pasture). Our results help to better understand belowground interactions and biomass investment under different managed ecosystems.
The influence of jack bean
Canavalia ensiformis (L.) D.C. mycorrhization, by the arbuscular mycorrhizal (AM) fungus
Glomus etunicatum, in response to increasing Cu concentrations in soil (0, 50, 150 ...and 450
mg
dm
−3) was studied. In the highest Cu dose, mycorrhiza decreased Cu concentrations in plant organs and promoted biomass accumulation. In addition, mycorrhizal colonization was not affected by Cu suggesting certain tolerance of the inoculated AM fungus to this metal. Cu-induced proline accumulation and an increase in soluble amino acid contents in leaves, with higher proline contents in AM plants. Marked differences in foliar soluble amino acid composition were also observed in response to Cu in the soil. The activity of key antioxidant enzymes increased mainly in the leaves of non-AM plants, indicating increased production of reactive oxygen species. However, changes in malondialdehyde content were not observed suggesting an effective antioxidant system. Independent of mycorrhization, glutathione content in leaves decreased as Cu increased in the soil. Phytochelatins were detected in the leaves of both Cu treated and untreated plants, and quantitative and qualitative differences were observed due to mycorrhization. In summary, the AM fungus was able to maintain an efficient symbiosis with jack bean plants in soil containing high Cu concentrations. A combination of physiological and nutritional changes caused by the symbiotic association that might be of interest for phytoremediation strategies in Cu-contaminated soils.
Phosphorus (P) is a vital nutrient for plant growth. P availability is generally low in soils, and plant responses to low P availability need to be better understood. In a previous study, we studied ...the growth and physiological responses of 24 species to low P availability in the soil and verified of eucalypts, five (
Eucalyptus acmenoides
,
E. grandis
,
E. globulus
,
E. tereticornis
, and
Corymbia maculata
) contrasted regarding their efficiency and responsiveness to soil P availability. Here, we obtained the metabolomic and lipidomic profile of leaves, stems, and roots from these species growing under low (4.5 mg dm
–3
) and sufficient (10.8 mg dm
–3
) P in the soil. Disregarding the level of P in the soils, P allocation was always higher in the stems. However, when grown in the P-sufficient soil, the stems steadily were the largest compartment of the total plant P. Under low P, the relative contents of primary metabolites, such as amino acids, TCA cycle intermediates, organic acids and carbohydrates, changed differently depending on the species. Additionally, phosphorylated metabolites showed enhanced turnover or reductions. While photosynthetic efficiencies were not related to higher biomass production,
A
/
C
i curves showed that reduced P availability increased the eucalypt species’
Vcmax, Jmax
and
photosynthetic P-use efficiency
. Plants of
E. acmenoides
increased galactolipids and sulfolipids in leaves more than other eucalypt species, suggesting that lipid remodelling can be a strategy to cope with the P shortage in this species. Our findings offer insights to understand genotypic efficiency among eucalypt species to accommodate primary metabolism under low soil P availability and eventually be used as biochemical markers for breeding programs.
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