Main Conclusion
Plant growth-promoting bacteria association improved the enzymatic and non-enzymatic antioxidant pathways in Neotropical trees under drought, which led to lower oxidative damage and ...enhanced drought tolerance in these trees.
Water deficit is associated with oxidative stress in plant cells and may, thus, negatively affect the establishment of tree seedlings in reforestation areas. The association with plant growth-promoting bacteria (PGPB) is known to enhance the antioxidant response of crops, but this strategy has not been tested in seedlings of Neotropical trees. We evaluated the effects of inoculation with two PGPB (
Azospirillum brasilense
and
Bacillus
sp.) on the antioxidant metabolism of
Cecropia pachystachya
and
Cariniana estrellensis
seedlings submitted to drought. We measured the activity of antioxidant enzymes and the content of non-enzymatic antioxidants in leaves, and biometrical parameters of the seedlings. In both tree species, drought decreased the activity of antioxidant enzymes and the content of non-enzymatic antioxidant compounds. For
C. pachystachya,
the enzymatic and non-enzymatic pathways were mostly influenced by
A. brasilense
inoculation, which enhanced ascorbate peroxidase (APX) and superoxide dismutase activities and positively affected the level of non-enzymatic antioxidant compounds. In
C. estrellensis
,
A. brasilense
inoculation enhanced APX activity. However,
A. brasilense
and
Bacillus
sp. inoculation had more influence on the non-enzymatic pathway, as both bacteria induced a greater accumulation of secondary compounds (such as chlorogenic acid, gallic acid, rutin and synapic acid) compared to that in non-inoculated plants under drought. For both species, PGPB improved biometrical parameters related to drought tolerance, as specific leaf area and leaf-area ratio. Our results demonstrate that PGPB induced antioxidant mechanisms in drought-stressed Neotropical trees, increasing drought tolerance. Thus, PGPB inoculation provides a biotechnological alternative to improve the success of reforestation programmes.
Despite the important role played by nitric oxide (NO) in plants subjected to abiotic stress, NO donors application to induce drought tolerance in neotropical tree seedlings has not yet been tested. ...It is also worth investigating whether NO bioactivity in drought-stressed seedlings could be potentiated by NO donors nanoencapsulation. The aim of the current study is to evaluate the effects of chitosan nanoparticles (NPs) containing S-nitroso-mercaptosuccinic acid (S-nitroso-MSA) on drought-stressed seedlings of neotropical tree species Heliocarpus popayanensis Kunth in comparison to free NO donor and NPs loaded with non-nitrosated MSA. Nanoencapsulation slowed down NO release from S-nitroso-MSA, and nanoencapsulated S-nitroso-MSA yielded 2- and 1.6-fold higher S-nitrosothiol levels in H. popayanensis roots and leaves, respectively, than the free NO donor. S-nitroso-MSA has prevented drought-induced CO2 assimilation inhibition, regardless of nanoencapsulation, but the nanoencapsulated NO donor has induced earlier ameliorative effect. Both NO and MSA have decreased oxidative stress in H. popayanensis roots, but this effect was not associated with antioxidant enzyme induction, with higher seedling biomass, or with proline and glycine betaine accumulation. Nanoencapsulated S-nitroso-MSA was the only formulation capable of increasing leaf relative water content in drought-stressed plants (from 32.3% to 60.5%). In addition, it induced root hair formation (increase by 36.6% in comparison to well-hydrated plants). Overall, results have evidenced that nanoencapsulation was capable of improving the protective effect of S-nitroso-MSA on H. popayanensis seedlings subjected to drought stress, a fact that highlighted the potential application of NO-releasing NPs to obtain drought-tolerant tree seedlings for reforestation programs.
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•S-nitroso-MSA protected neotropical tree seedlings from drought stress.•S-nitroso-MSA nanoencapsulation improved NO availability to drought-stressed plants.•Nanoencapsulation boosted NO-induced improvement of photosynthesis.•Only the nanoencapsulated NO donor avoided leaf water content decrease.•The nanoencapsulated NO donor has induced unique changes in root morphology.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Key message
High nitrogen supply prevents dynamic photoinhibition in
Guazuma ulmifolia
seedlings and improves their morphophysiological quality during the high-light acclimation in the nursery.
...Acclimation under full sun is an important step in the production of tree seedlings in nurseries because it increases plant resistance to stressful conditions. Thus, the development of management techniques that improve high-light acclimation could facilitate the production of higher-quality seedlings. Given the importance of nitrogen (N) for plant growth and photosynthetic metabolism, here we evaluated whether supplementation with high N levels (HN) could positively affect the high-light acclimation of seedlings of
Guazuma ulmifolia
Lam., a tree species widely used in reforestation programs in the neotropics. We compared the morphophysiological parameters of seedlings transferred from the shaded sector of the nursery to full sun that were supplemented with or without HN. HN supply prevented the midday depression of both photosystem II (PSII) activity and the CO
2
assimilation rate, suggesting the avoidance of dynamic photoinhibition by HN. This effect was related to HN-induced increases in the electron transport rate of PSII, carboxylation efficiency and mesophyll conductance to CO
2
and not to reduced stomatal limitation. A decrease in excess excitation energy in PSII resulting from energy-demanding N assimilation, as suggested by increases in the light saturation points of the CO
2
assimilation and PSII electron transport rates, might also contribute to the protective effect of N. In addition, HN treatment increased seedling biomass accumulation and stem base diameter, enhancing the Dickson quality index of the acclimated seedlings. Overall, these results indicate that HN supply during high-light acclimation in the nursery improves the morphophysiological quality of
G. ulmifolia
seedlings.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The input of large amounts of fertilizers in agricultural areas may result in nitrogen (N) leakage to nearby forest fragments, which can impact the physiology and growth of trees. The current study ...aimed to assess the effects of soil N addition on seedlings of four tree species in the Brazilian Atlantic Forest: Croton floribundus and Astronium graveolens (pioneer), Guarea kunthiana and Aspidosperma polyneuron (non-pioneer). The experiment was carried out in a greenhouse condition with three treatments: reference (soil without addition of nutrients), N addition (N: soil with addition of ammoniacal-N), and complete (C: soil with addition of ammoniacal-N and other macro and micronutrients). Croton floribundus seedlings presented higher shoot growth with N addition, mainly in treatment C, and only this treatment increased net photosynthesis. There was great variation in the metabolic responses induced by treatments N and C, with accumulation of nitrate in the leaves and xylem sap only in seedlings in treatment N. In A. graveolens, there was a decrease in transpiration in response to treatments N and C. However, water use efficiency, leaf area, and dry mass increased only in seedlings subjected to treatment C. Regarding metabolic parameters, A. graveolens was little responsive to the treatments. In G. kunthiana seedlings, the treatments decreased net photosynthesis and increased leaf total N. Only treatment N led to decreased stem dry mass and increased nitrate contents in leaves and xylem sap. Aspidosperma polyneuron exhibited no change in growth, but there was an accumulation of N compounds in the leaves for both treatments N and C, which suggests that this species could be a good bioindicator of N addition to the soil. Although influencing different parameters, the results indicate that soil N addition affects the performance of both pioneer and non-pioneer species. Finally, the implications of these results for biomonitoring of N availability in the soil of forest fragments are discussed.
Phenotypic plasticity occurs when plants acclimatize to contrasting conditions. Herein, we test the hypothesis that seedlings of a light-demanding species have greater phenotypic plasticity compared ...to seedlings of a shade-tolerant species under high irradiance. Thus, we investigate the growth, anatomical, and leaf gas exchange responses of
Citharexylum myrianthum
, a light-demanding species, and
Poecilanthe parviflora
, a shade-tolerant species, under full light and 60% shading. Under full light, the seedlings of both species were shorter, showed lower photosynthetic rates and specific leaf area, and thicker palisade parenchyma. In the same conditions,
C. myrianthum
showed increased number of leaves, and
P. parviflora
reduced leaf area and increased number of stomata and allocation of phloem and cortical parenchyma. Lower photosynthetic rates may negatively affect biomass allocation and growth, although
C. myrianthum
seems to show a higher tolerance to irradiance since it produced more leaves.
P. parviflora
seems to optimize heat dissipation, reduce water loss, and improve the allocation of photoassimilate transport and storage, which could increase performance during establishment in field conditions. The plasticity index of both species was similar. Thus, generalizations about the species plasticity and ecological group to which they belong should be avoided. Species-related responses of growth, anatomical, and gas exchange parameters were found, indicating that generalizations about the performance of functional groups should also be avoided. These findings may contribute to the success of forest restoration projects.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In selectively logged forests, trees are more likely to expand their diameters (D) at the expense of height (H) growth, resulting in variations in H:D relationships. This study examines how selective ...logging affects the H:D allometric relationships of five common tree species and whether the effects vary with functional groups (shade-intolerant or shade tolerant) in seasonal semi-deciduous forests. Individuals of five species in a 3000 m
2
(0.3 ha) plot were marked and heights and diameters recorded. Most of the species, with one exception, showed greater investment in diameter per increment of height compared to an unlogged forest, possibly because of the greater light available. This study shows the effects of selective logging on species populations as evidenced by increases in H:D ratios. Comparison of forest fragments with different degrees of human impact is important because it allows us to understand the differences in architectural characteristics caused by selective logging.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Leaf plasticity to light can affect species distribution in areas with contrasting light availability. Plants can acclimate to prevailing light conditions according to their optimal growth ...conditions. Our goal was to assess differences in the morphophysiological plasticity of leaves of two woody species (
Inga vera
subsp.
affinis
and
Psychotria carthagenensis
) that occur in a riparian forest (low irradiance) and in the ecotone between the riparian forest and a savanna-like formation (high irradiance) in the Southern Pantanal, Brazil. Both species showed lower specific leaf area and higher concentration of carotenoids per leaf area in the ecotone. Moreover, the maximum quantum yield of photosystem II decreased at midday in the ecotone, suggesting the induction of dynamic photoinhibition.
Psychotria carthagenensis
showed a sharp decrease in leaf water potential at midday in both sites. The light saturation point and non-photochemical quenching of
Inga vera
increased in the ecotone. Both species had thicker cuticles and mesophyll in the ecotone, and the palisade to spongy parenchyma ratio of
P. carthagenensis
increased at the same site. Additionally, in the ecotone, the concentration of proteins per leaf area was higher. The results indicate that these species showed different patterns of leaf plasticity, with
I. vera
presenting increased photosynthetic capacity and
P. carthagenensis
showing more plasticity in morphoanatomical traits. Therefore, our results suggest that the high potential of photosynthetic use of light by
I. vera
may help to explain its broader distribution in sites with higher irradiance.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Key message
The inoculation of seeds from neotropical tree species with PGPB revealed an active role of inoculant strains in modulating the germination and physiology of seedlings, although the ...specific responses were subject to specific plant–bacteria and genotype–genotype combinations.
Beneficial microbial species encompass different phylogenetic groups, and growth-promoting mechanisms can be direct (nutritional effects) or indirect (resistance against biotic and abiotic stresses). Seed inoculation with plant growth-promoting bacteria (PGPB) can increase the growth and productivity of agricultural crops. However, few studies have been conducted to determine these effects on the seed germination and seedling growth of neotropical tree species. Thus, this study aimed to determine the effects of inoculation with PGPB on the germination, initial development and activities of the enzymes phenylalanine ammonia-lyase and polyphenol oxidase of seedlings of neotropical tree species. Shade-intolerant (
Cecropia pachystachya
,
Heliocarpus popayanensis
and
Trema micrantha
) and shade-tolerant tree species (
Cabralea canjerana
,
Cariniana estrellensis
and
Trichilia elegans
) were inoculated with different species of PGPB (
Azospirillum brasilense
,
Bacillus
sp. and
Azomonas
sp.) and allowed to germinate and grow for 45 days under greenhouse conditions. Inoculation of
C. pachystachya
with all types of PGPB increased the percentage of germinated seeds (GS) and the vigor index (VI), while the mean time to germination (MTG) decreased. The VI of
T. micrantha
increased in response to
Bacillus
sp. and
Azomonas
sp. inoculation.
Cabralea canjerana
showed a decreased GS and VI and an increased MTG when inoculated with PGPB and increased activity of phenylalanine ammonia-lyase and polyphenol oxidase when inoculated with
Azomonas
sp. Inoculation of PGPB interfered with seed germination and seedling physiology, and shade-intolerant species were more likely to benefit from inoculation. Inoculation with PGPB can modulate the seed germination patterns of neotropical tree species, with indications that the ecological group may be involved in the magnitude of the response.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract This study aimed to determine the tree structure, floristic composition and species diversity in the Araucaria State Park, southern Brazil. We allocated 100 plots of 100 m2 (1 ha) each one, ...and we recorded all trees with diameters at breast height ≥ 5 cm. We sampled 1368 individuals of 106 species, 75 genera and 44 families. Fabaceae, Lauraceae and Myrtaceae showed the greatest richness of species. The diversity of tree species was high (H ‘= 3.96), although the observed richness was less than the estimated one. The basal area was 46.88 m2 ha-1. We observed an intrinsic association between Araucaria angustifolia and Nectandra megapotamica, and a predominance of secondary and zoochorous (> 70%) species. Endangered and vulnerable species in the Santa Catarina state, such as Araucaria angustifolia, Cedrela fissilis, Dicksonia sellowiana and Ocotea porosa were sampled in the Park, highlighting its importance for the conservation of the Mixed Ombrophylous Forest.
Water deficiency has been recognized as a major abiotic stress that causes losses in maize crops around the world. The maize crop is very important due to the range of products that are derived from ...this plant. A potential way to reduce the damages caused by water deficiency in maize crops is through the association with plant growth-promoting bacteria (PGPB) and arbuscular mycorrhizal fungi (AMF). To define the mechanisms developed by associative PGPB and AMF in maize that are involved in protection against moderate drought (MD), this study evaluated the biometrical, anatomical, biochemical, and physiological parameters of maize grown under MD and inoculated with different PGPB (Azospirillum brasilense strain Ab-V5 and Bacillus sp. strain ZK) and with AMF. The relative water content did not change in the treatments. The association with ZK increased the shoot:total ratio, total dry weight, maximum quantum yield of photosystem II, vascular cylinder thickness, and vascular cylinder area. The Ab-V5 inoculation led to an increment in root dry weight, the area of metaxylem vessel elements, and nitrate reductase activity. The AMF association did not lead to changes in the measured parameters. The results indicate that the association with PGPB is a relevant alternative to contribute to reducing losses in maize crops under drought. However, AMF is not indicated for this crop under drought.
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