Reduced Plant Development Research Articles

Abiotic stress responses in crop plants: A multi-scale approach

Population stress has compelled the whole world to think about increasing, protecting, and finding ways to develop the best plant species for assured productivity in spite of all environmental odds. In addition to climate change, fluctuations in nature and human activities pose serious environmental degradation, threatening global food security through physical stress in the environment. Significant environmental constraints on agricultural yield worldwide include salt stress, water deficiency stress, nutritional imbalances (including mineral toxicity and deficiencies), and temperature extremes. Abiotic factors, such as agronomic factors, climatic factors, and nutrient availability in the soil, influence crop yield. Plants initiate and develop various possible stress mechanisms for their survival, which can be molecular, cellular and physiological. Abiotic stress has a high impact on crop growth and productivity, either in single forms or in combined forms. For example, drought stress causes a decrease in leaf area, plant height, and crop development. Cold stress reduces plant development and crop efficiency, resulting in productivity loss. Salinity stress not only contributes to water stress in plants, but it can also adversely influence cytosolic metabolism, cell development, membrane function, and increase reactive oxygen species (ROS) generation. Higher concentrations of CO2 could potentially improve global precipitation, resulting in increased rainfall, which can adversely affect crop development. Crops under excessive water stress have a lower percentage of amylose but a higher crude protein content. This in turn, affects the quality and quantity of crop production by hindering seed germination and causing growth damage due to the combined effects of higher osmotic potential and ion toxicity. In response to abiotic stress, plants evolve a variety of escape-avoidance and tolerance mechanisms, which include physiological adaptation and integrated cellular or molecular responses. Therefore, the main purpose of the current review paper is to investigate the effect of abiotic stress on morpho-physiological, biochemical and molecular activities in various crops. Moreover, we concentrate on crop inter-relativity with abiotic stress to react to and adapt to for survival, which can be a basic roadmap for the selection of species or the development of new tolerant species in the future.

Resilient Response to Combined Heat and Drought Stress Conditions of a Tomato Germplasm Collection, Including Natural and Ethyl Methanesulfonate-Induced Variants

Agricultural systems are currently facing significant issues, primarily due to population growth rates in the context of global climate change. Rising temperatures cause plant heat stress and impact crop yield, which in turn compromises global food production and safety. Climate change is also having a significant impact on water availability around the world, and droughts are becoming more frequent and severe in many regions. The combined effect of both heat and drought stresses increases plant damage, resulting in reduced plant development and productivity loss. Therefore, developing heat–drought-tolerant crop varieties is crucial for enhancing yield under these challenging conditions. Tomato (Solanum lycopersicum L.), a major vegetable crop highly appreciated for its nutritional qualities, is particularly sensitive to extreme temperatures, which have a significant negative impact on tomato fruit setting and cause male gametophyte abortion. In this work, a classical genetic approach was employed to identify tomato genotypes showing a resilient response to combined heat and drought stress conditions. A phenotype screening of a natural germplasm collection and an ethyl methanesulfonate (EMS) mutagenized population resulted in the identification of a significant number of tomato lines tolerant to combined heat and drought conditions, specifically 161 EMS lines and 24 natural accessions as tolerant. In addition, TILLING and Eco-TILLING analyses were used as proof-of-concept to isolate new genetic variants of genes previously reported as key regulators of abiotic stress responses in different species. The identification of these variants holds the potential to provide suitable plant material for breeding programs focused on enhancing tomato resilience to adverse climate conditions.

Fertilization during mineland rehabilitation may shift competitive outcomes toward invasive species

Managing invasive species is essential for achieving mineland rehabilitation goals and ensuring the long‐term provision of critical ecosystem services while preventing new dispersion sources to neighboring areas. Traditional techniques include chemical and manual weeding, but frequent reinvasion limits their long‐term success. Therefore, additional integrated tools, such as stimulating natural competitors, may become necessary, especially where sensitive ecosystems, e.g. the ferruginous savanna ecosystem (cangas) from the Carajás National Forest, Eastern Amazon, Brazil, are found nearby rehabilitation sites. Here, we investigate the influence of different substrates and fertilization levels on the biotic interactions between two native canga grasses (Axonopus longispicus and Paspalum cinerascens) and the invasive molasses grass (Melinis minutiflora), which is frequently found in anthropized and natural ecosystems in Latin America. Nutrient application significantly influenced the growth, resource use strategies, and competitive outcomes of M. minutiflora. Nutrient application has positive effects on the growth of native species when cultivated in isolation but reduces plant development when subjected to competition with molasses grass, potentiating the invader. Although neither of the tested native species exhibited competitive advantages over M. minutiflora, increased nitrogen availability favored the competitive ability of this invasive grass. Thus, eliminating fertilization during mineland rehabilitation may be important for reducing the cover of M. minutiflora in the Carajás region, as sensitive canga ecosystems lack natural barriers against invasion. This strategic approach mitigates the operational risks and costs associated with combating invasive species from rehabilitating minelands, reducing propagule pressure on neighboring canga areas.

Impact of phosphorus omission fertilizer on growth, nutritional status, biochemical and physiological parameters in a Pinus taeda L. plantation

Low availability of phosphorus (P) in the soil is one of the factors limiting the productivity of Pinus taeda plantations. Phosphate fertilizer application in Pinus shows divergence in growth responses. Thus, understanding the response of plant photosynthetic efficiency and growth in relation to phosphate fertilizer application can serve as a basis to guide management practices in Pinus taeda plantations. The study aimed to evaluate the impact of P omission fertilizer on growth parameters, nutritional, biochemical, and physiological status of a Pinus taeda L. plantation. The experiment was conducted on a Pinus taeda plantation subjected to P fertilization: Control - without addition of N, P and K; P–fertilized - with addition of N, P and K; and P–omission - addition of N and K, and P omission fertilizer. The parameters height, stem and canopy diameter and productivity factor, P concentration in needles, soil available P, electron transport rate (ETRm), maximum quantum yield of PSII (Fv/Fm), initial (Fo) and maximum (Fm) fluorescence, chlorophyll a, b and total, carotenoids, superoxide dismutase (SOD) and peroxidase (POD), hydrogen peroxide (H2O2), lipid peroxidation (TBARS), and acid phosphatase activity, were evaluated. P fertilized application increased soil available P, providing largest P uptake by roots and P concentration in needles. The increase in available soil P contributed to elevate photosynthetic parameters, such as ETRm, Fv/Fm, chlorophyll a, b and total, and carotenoids. These factors contributed to increase C assimilation, height, stem and canopy diameter and productivity factor parameters. On the other hand, the P–omission and control conditioned the growth of Pinus taeda under stress, elevating the values of Fo, Fm, SOD and POD, which reduced plant development.

Drought stress alleviation through nutrient management in Cyamopsis tetrogonoloba L.

Drought is one of the most serious issues since it reduces plant development and, as a result, yield significantly. This research is an attempt to provide an organic solution to combat the global issue of plant stress due to drought. To reduce the impact of drought on Cyamopsis tetragonoloba, the traditional preparation Panchagavya was used, and its effects on growth, photosynthetic and non-photosynthetic pigment synthesis, thylakoid protein composition, antioxidant activity, anatomy, and yield were investigated. Initially, drought had a negative effect on plant growth and other activities; however, as the duration of the treatment increased, the effect of drought decreased significantly. The plants that were under drought stress and were provided with nutrients, showed more plant growth and yield. Flavonoid and anthocyanin production was 50% higher in the plants under drought stress with nutrient supplementation than in the plants under drought stress and the control plants. The accumulation of 55, 47, 33, 27, and 20 kDa polypeptides of thylakoid protein also increased under nutrient conditions. Drought stress reduced overall fruit output by 10% relative to the control group (well irrigate plants). Nutrition management increased plant performance under stress conditions. Fresh & dry pod weights of control, drought stress, and drought with nutrients were recorded at 3.2 g & 0.6 g, 3 g & 0.52 g, and 4.5 g & 1.2 g, respectively. Under drought stress with nutrients, plants had more stomata per unit than control plants. This is the first study in which Panchagavya was used to alleviate drought. With the addition of beneficial nutrients, water use efficiency can be improved, and drought's negative impacts can be mitigated tangentially by activating plant physiological, biochemical, and metabolic processes. This study will add the crucial information required to determine the response of plants under drought stress conditions as well as how to alleviate its effects in a traditional organic way.

Assessment of Hexavalent Chromium Accumulation of Beta Vulgaris L. Var. Cicla and the Change of Its Antibacterial Activity

ABSTRACT Hexavalent chromium (Cr(VI)) is a frequently encountered heavy metal contaminant in agricultural soil and water sources resulting from industrial and agricultural applications, traffic, and urbanization. It is the most toxic form of chromium (Cr), which causes severe health problems. The accumulation capacity of Swiss chard (Beta vulgaris L. var. cicla) for hexavalent chromium and the effect of heavy metal accumulation on the antibacterial activity of plant extracts were evaluated in a pot experiment. The soil was treated with 10 mg kg−1 hexavalent chromium, 30 days prior to planting Swiss chard seedlings. After the harvest, macro- and micronutrient elements and Cr were measured using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES). Moreover, plant extracts were obtained by maceration in methanol and the extracts were tested against Gram-positive and Gram-negative bacteria. Cr was found to be uptaken and accumulated with a high concentration (54.7 ± 0.23 mg kg−1) in the aerial parts (transfer factor = 74.95). Cr toxicity reduced plant development and the macronutrient elements phosphorus and potassium in Swiss chard. The micronutrient elements iron and boron were found to be significantly increased in plant upon chromium in a synergistic manner with Cr. Additionally, the antibacterial activity of the extract of Swiss chard decreased against Staphylococcus aureus and Enterococcus faecalis around 50%. Moreover, the number of culturable bacteria decreased about 40% in soil after chromium treatment. The results suggested that this plant can accumulate a high amount of Cr in its aerial parts, which may decrease the health effects of the extracts.

The Dynamics of Immature Rubber Photosynthetic Capacities Under Macronutrients Deficiencies

Pará rubber produces natural latex which is essential for the industries. Rubber plant in immature phase is prone to macronutrient deficiencies due to improper management practices in the field and the nature of immature plants that have sensitive physiological responses under stress conditions. The study aimed to assess the effect of macronutrient limitation on immature rubber trees’ photosynthetic capacity and growth. The immature rubber was pot-grown inside the greenhouse with a completely randomized design experiment and nutrient limitations used as the treatments. The treatments consisted of 5 levels, namely, NPK; NP (-K); NK (-P); PK (-N); Control (-NPK). Photosynthetic capacity parameters (Vc max: maximum rate RuBisCO carboxylation, Jmax: RuBP regeneration rate, and TPU: Triose Phosphate Utilization), tree growth (plant height, flush number, leaf number, stem diameter), and leaf macronutrient (N, P, and K) concentrations were periodically measured. Welsch’s test (α = 0.05) continued with Games-Howell pairwise comparison, followed by Pearson’s correlation test and polynomial regressions were performed to describe the nutrient limitation and photosynthetic capacity relationships. Results showed that the leaf nutrient concentration corresponds with the given treatments, even though it was above the critical level for immature rubber. The limitation of N fertilization slightly reduced plant development and growth such as height, leaf number, flush number, relative growth rate, and photosynthetic capacities. However, the P and K limitation effect could not be observed clearly in the observation periods on growth and photosynthetic capacity parameters. Furthermore, the mobility rate of nutrients from the soil to the plants and its translocation inside plant organs played more essential role in plant growth and photosynthetic capacities. Prolonged observation periods on various rubber clones have to be performed to deeply understand the effects of nutrient deficiencies on immature rubber tree morphophysiological activities. HIGHLIGHTS Rubber plant in immature phase have sensitive physiological responses under stress conditions, and it is prone to macronutrient deficiencies due to improper management practices in the field Assessment of macronutrient limitation effect on immature rubber trees’ photosynthetic capacity and growth is essential to understand how the plants strive under the nutrient scarcity and providing a perspective which nutrient is more essential The N fertilization played more essential role compared to P and K, for immature rubber growth and photosynthetic activity GRAPHICAL ABSTRACT

Phosphorus Availability Affects the Photosynthesis and Antioxidant System of Contrasting Low-P-Tolerant Cotton Genotypes

Phosphorus (P) is an essential macronutrient, and an important component of plant metabolism. However, little is known about the effects of low P availability on P absorption, the photosynthetic electron transport chain, and the antioxidant system in cotton. This study used cotton genotypes (sensitive FJA and DLNTDH and tolerant BX014 and LuYuan343) with contrasting low-P tolerance in a hydroponic experiment under 15 µM, 50 µM, and 500 μM P concentrations. The results showed that low P availability reduced plant development and leaf area, shoot length, and dry weight in FJA and DLNADH, compared to BX014 and LuYuan343. The low P availability decreased the gas-exchange parameters such as the net photosynthetic rate, transpiration rate, and stomatal conductance, and increased the intercellular CO2 concentration. Chlorophyll a fluorescence demonstrated that the leaves' absorption and trapped-energy flux were largely steady. In contrast, considerable gains in absorption and trapped-energy flux per reaction center resulted from decreases in the electron transport per reaction center under low-P conditions. In addition, low P availability reduced the activities of antioxidant enzymes and increased the content of malondialdehyde in the cotton genotypes, especially in FJA and DLNTDH. Moreover, low P availability reduced the activity of PEPC and generated a decline in the content of ATP and NADPH. Our research can provide a theoretical physiological basis for the growth and tolerance of cotton under low-P conditions.

NaCl effect on Cd accumulation and cell compartmentalization in barley.

The effect of sodium chloride (NaCl) on cadmium (Cd) tolerance, uptake, translocation, and compartmentation was investigated in 3 barley genotypes. Seedlings were cultivated hydroponically in the absence of NaCl and Cd (control), in the presence of 50mM NaCl alone, in the presence of 10µM Cd alone, and in the combined addition of NaCl (50mM) and Cd (10µM). Plants were cultivated during one month under 16h light period at a minimal light intensity of 250µmolm-2s-1, a temperature of 25 ± 3°C, and 70-80% of relative humidity. Results showed that NaCl alone did not significantly affect plant development and biomass production; however, Cd alone reduced plant development rate leading to a decline in biomass production in Raihane and Giza 127 but did not affect that in Amalou. NaCl addition in Cd-treated plants accentuated the Cd effect on plant growth. NaCl limited Cd accumulation in the roots and in the shoots in all tested barley varieties by reducing Cd-absorption efficiency and the translocation of Cd from the root to the shoot. In all Cd-treated plants, cell Cd compartmentalization showed the following gradient: organelles < cell wall < vacuole. NaCl in the medium increased Cd accumulation in the soluble fraction and reduced that in organelle and cell wall fractions. Globally our results showed that, although NaCl reduces Cd accumulation in barley, it accentuates the Cd toxic effects, hence limiting the plant yield. We advise farmers to avoid barley cultivation near mine sites and its irrigation with moderately salty water, although this plant is considered as salt tolerant.

Effect of Indole-3-Acetic Acid on Tomato Plant Growth.

Plant growth-promoting bacteria have several abilities to promote plant growth and development. One of these skills is the synthesis of indole-3-acetic acid (IAA), which mainly promotes root and shoot development. The bacteria Bacillus subtilis and Azospirillum brasilense have been widely used in agriculture with this function. However, little is known about whether the joint inoculation of these bacteria can reduce plant development by the excess of IAA produced as a result of the joint inoculation. The objective of the present study was to verify the effect of IAA on the inoculation of B. subtilis and A. brasilense in three tomato genotypes. The Micro-Tom genotype without mutation for IAA synthesis, Entire, has high sensitivity to IAA, and the diageotropic genotype (dgt) has low sensitivity to IAA. The results show that the plant parameter most sensitive to microbial inoculation is the number of roots. No treatment increased the shoot dry mass parameters for the Micro-Tom genotype and dgt, root dry mass for the Micro-Tom genotype, plant height for the Micro-Tom and Entire genotypes, root area and root volume for the genotype dgt. The Azm treatment reduced plant height compared to the control in the dgt, the BS + Azw and BS + Azm treatments in the Micro-Tom genotype and the Azw + Azm treatment in the dgt genotype reduced the plant diameter compared to the control. BS and BS + Azw reduced the number of roots in the Micro-Tom. The results strongly support that the mixture of B. subtilis and A. brasilense can reduce some parameters of plant development; however, this effect is possibly an interference in the mode of action of growth promotion of each isolate and is not related to an excess of IAA produced by the bacteria.

Influence of microclimatic conditions during year-long storage of ‘Impresja’ potato tubers (Solanum tuberosum L.) on the emergence, growth, physiological activity and yield of plants

The natural lifespan of potato tubers (Solanum tuberosum L.) is influenced by several factors, including dormancy, tuber physiology, and conditions in the external environment, such as temperature, humidity, and air movement. We studied the effects of different periods of tuber storage (within 12 months) at 4 °C, followed by 14 d storage at 15–20 °C and 70–80% RH, on the germination, development, physiological activity, and yield of Impresja potato plants, as well as on the activity of catalase and N-acetyl-β-glucosaminidase. The tubers stored at 4–20 °C did not germinate until the beginning of December. Storage at 4 °C until September prevented sprouting and pathogen invasion. Depending on the period of storage, the time between planting and plant emergence gradually decreased, from 51 d (December) to 10 d (March–July), and the dynamics of shoot and root growth increased. Plants from tubers stored at 4 °C until May were the fastest to emerge and grow, whereas extended storage until July–September gradually reduced plant development. Transferring the tubers at the end of all storage periods from 4 °C to conditions of 15–20 °C and 70–80% RH for 14 d accelerated the emergence and growth of shoots and roots and increased chlorophyll content, net photosynthesis, transpiration, stomatal conductance, and the yield of new tubers. This additional storage period was most beneficial for tubers stored until March–July, but its effects decreased after prolonged storage until August–September and had almost disappeared by September. Regardless of the duration of storage, the plant vegetation periods were similar, although the growth of shoots and roots depended on the storage conditions and lighting in particular months. The storage technology presented here could increase the profitability of accelerated potato production.

Growth, Nutrient Accumulation, and Nutritional Efficiency of a Clonal Eucalyptus Hybrid in Competition with Grasses

Invasive grasses reduce resource availability, mainly nutrients in the soil, and the growth of eucalyptus plants. Efficient management to increase productivity depends on understanding levels of weed interference in eucalyptus plantations. The nutritional efficiency of eucalyptus plants in competition has been evaluated by plant tissue analysis. The objective was to evaluate the growth, relative accumulation of nutrients, and nutritional efficiency of the eucalyptus clonal hybrid I144 (Eucalyptus urophylla × Eucalyptus grandis), in competition with Megathyrsus maximus cv. BRS zuri, Urochloa brizantha cv. marandu, Urochloa decumbens cv. basilisk and in the control (eucalyptus plants without weed competition). The experiment was carried out with a completely randomized design, with four treatments and ten replications. The height, stem diameter, number of leaves, leaf area, dry matter of leaves and stem, nutrient content in leaves and uptake, transport, and N, P, and K utilization efficiency of the eucalyptus clonal hybrid were evaluated at 110 days after transplantation. The growth parameters and relative contents of macro and micronutrients in the eucalyptus clonal hybrid were lower in competition with M. maximus, U. brizantha and U. decumbens. The efficiency of N, P, and K uptake and transport by the eucalyptus clonal hybrid was 29.41 and 7.32% lower in competition with U. decumbens than in the control treatments, respectively. The efficiency of N, P, and K utilization by eucalypts was 13.73, 9.18, and 22.54% lower in competition with M. maximus, U. brizantha, and U. decumbens, respectively. The reduced growth and nutritional parameters of the eucalyptus clonal hybrid were more evident in competition with U. decumbens. Plant tissue analyses efficiently determined the level of competition for nutrients between species. Crop competition with grasses can decrease the efficiency and use of nutrients, which consequently reduces plant development and productivity.

PROLINE INDUCED CHANGES IN REDOX BALANCE AND PHOTOSYNTHETIC ACTIVITY OF WHEAT (TRITICUM AESTIVUM L.) UNDER SALINE CONDITIONS

Salinity is a major environmental constraint that reduces plant development, growth, and yield. To appraise the potential role of foliar-applied proline as an alternative shotgun approach to ameliorate the adverse effects of salinity on wheat, a pot experiment was conducted under controlled environmental conditions using two wheat cultivars (Galaxy-13 salt-sensitive) and (Pasban-90 salt-tolerant). The experiment was laid out in a completely randomized design with the factorial arrangement and four replications. After ten days of germination, the plants were thinned to maintain six plant seedlings in each pot and the germinating seedlings were irrigated weekly with full strength Hoagland’s nutrient solution and salinity stress (NaCl) was applied after three weeks of germination. Foliar spray of proline (100 mM) was applied with the treatment of salinity. Salinity stress caused a significant reduction in morphological attributes like lengths and fresh weights of root and shoot, number of leaves and leaf area as well as yield attributes like spike length, number of spikelets per spike, number of grains per spike, yield per plant and 100 seed weight. Furthermore, chlorophyll fluorescence, chlorophyll contents, quantum yield, and electron transport rate (ETR) were also reduced by salt stress. However, foliar spray of 100 mM proline was the most effective to ameliorate the toxic effects of salinity by improving biomass production, chlorophyll fluorescence, chlorophyll contents, and quantum yield in both the cultivars. The findings confirmed the ability of foliar spray of proline to stimulate salt tolerance in wheat plants.

Endemic Atlantic Forest species of Caryophyllales as inhibitors of viral infection in zucchini

ABSTRACT In Brazil, zucchini (Cucurbita pepo) is a socioeconomically important vegetable affected by damage caused primarily by zucchini yellow mosaic virus (ZYMV). Although the occurrence of cucumber mosaic virus (CMV) is less frequent, in C. pepo ‘Caserta’ plants it can cause symptoms such as mottle, mosaic, leaf and fruit distortion, as well as reduced plant development. To minimize the damage, the most widely used management technique is the preventive, albeit inefficient, application of insecticides, aimed at controlling aphids, the vectors of this virus. Thus, the search for more effective and less environmentally harmful control methods has been the target of investigations. The purpose of the present study was to assess the action of the extracts of four native Caryophyllales species, as inhibitors of infection by CMV and ZYMV in C. pepo, in addition to evaluating the possible induced resistance in this species. Fresh leaf extracts (LEs) of Guapira opposita, Pisonia ambigua (Nyctaginaceae), Gallesia integrifolia and Seguieria langsdorffii (Phytolaccaceae), previously assessed in the tobacco mosaic virus / Nicotiana glutinosa pathosystem, were submitted to progressive dilutions sprayed on cotyledonary C. pepo leaves 30 min before inoculation with CMV and ZYMV. Leaf extracts of G. integrifolia did not induce inhibition in any of the pathosystems assessed. Guapira opposita LEs inhibited the infection of plants inoculated with ZYMV below 50% but inhibited CMV infection by 70% at a concentration of 1:40. Given that leaf extracts of P. ambigua and S. langsdorffii induced high percentage inhibition, evident in the number of asymptomatic plants and confirmed by serological tests, these species were selected to assess induced resistance in pre-treatment experiments. The LEs were efficient in inhibiting ZYMV and CMV infection in C. pepo when applied up to 48 h before inoculation. The LEs of S. langsdorffii and G. opposita, also tested for this system, were efficient when applied up to 72 h before CMV inoculation. The LEs can be prepared from dry leaves and maintained at -20°C for at least three years, conserving their inhibitory activity. These results expand the possibilities for producers and consumers alike in the sustainable management of the main zucchini viruses, without damaging the environment.

Evaluating the potential of soil management to reduce the effect of Fusarium oxysporum f. sp. cubense in banana (Musa AAA)

Fusarium oxysporum f. sp. cubense (Foc) causes Fusarium wilt in banana (Musa AAA). Foc Race 1 devastated the subgroup Gros Michel during the first half of the twentieth century. The Gros Michel was largely replaced by the resistant subgroup Cavendish in the 1950s. However, in the 1980s, Foc Tropical Race 4 started to spread affecting Cavendish bananas. No proper control measures have been found to deal with the disease. This paper re-takes an important research line from the 1950s to evaluate the potential of soil management for Fusarium wilt management. The role of soil properties on Fusarium wilt in bananas was studied in two greenhouse experiments. It was evaluated whether the influence of two main soil properties (pH and N) on Fusarium wilt is similar for Race 1 and Tropical Race 4. Two soil pH levels (lower than 5.2 and higher than 6.0) respectively ensured through acidification and liming; and three levels of N (ammonium nitrate, 33.5% N) weekly doses (low:0 N g, medium: 0.08 N g and high: 0.25 N g per plant) were achieved. The first experiment in Costa Rica confirmed the earlier results about the influence of soil pH and nitrogen on Fusarium wilt (Race 1) on Gros Michel bananas. The second experiment in The Netherlands evaluated the influence of pH and N on interactions between Foc (both Race 1 and Tropical Race 4) and Cavendish bananas. Results in both experiments showed that soil pH affected crop development and the disease. Besides, the interaction of the lower pH x the higher N accelerated the infection and reduced plant development. As such, the results showed that soil management has the potential to reduce the impacts of Fusarium wilt while dealing with Race 1 and Tropical Race 4 although it requires confirmation and further evaluation under field conditions.

Organic acids as complexing agents for iron and their effects on the nutrition and growth of maize and soybean

ABSTRACT Synthetic chelating agents have high cost and low biodegradation in the environment; thus, the use of natural complexing agents for iron increases the sustainability in crop production. The aim of this study was to verify the efficiency of natural organic acids added to the nutrient solution on the Fe acquisition. For that purpose, two experiments were carried out using soybean and maize. Citric acid (CA), malic acid (MA), tartaric acid (TA), and oxalic acid (OA) were used as complexing agents for iron. Fe-EDTA (ethylenediaminetetraacetic acid) and FeSO4 were also tested. Soluble Fe and chemical speciation in a nutrient solution were determined. Organic acids maintained less complexed Fe in the nutrient solution than EDTA, but the complexed Fe fraction was not associated with the efficiency of the Fe organic acids in supplying Fe to plants. Maize and soybean treated with Fe-MA and Fe-CA had reduced plant development. For maize, the TA treatment at both SRs increased Fe accumulation and promoted Fe translocation similar to EDTA. For soybean, Fe-OA at both SRs promoted biomass, Fe accumulation, and Fe translocation similar to EDTA. Therefore, Fe complexes were able to assure plant growth and nutrition and showed effectiveness depending on the plant species.

Phytotoxic Effects of 4-Chlorophenol and 2,4-Dichlorophenol in the Germination of Seeds of &amp;lt;i&amp;gt;Phaseolus vulgaris&amp;lt;/i&amp;gt; and &amp;lt;i&amp;gt;Zea mayz&amp;lt;/i&amp;gt;

Soil contaminated with pesticides may reduce plant development due to their toxicity. The aim of this study was to evaluate the influence on the germination of Zea mayz and Phaseolus vulgaris of the two main intermediates of the 2,4-D degradation, which are 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP). Maize and bean seeds were treated with distilled water (control treatment) and increased concentrations of 4-CP and 2,4-DCP (0.006, 0.1, 1.0, 1.5 g·L-1). It was assessed seed germination and calculated various parameters. The parameter most affected by chlorophenols was the index of germination rate, being the P. vulgaris seeds most affected. 2,4-DCP was the compound most toxic for both plants. The germination index was dependent doses for both plant models tested. The results indicate that 4-CP and 2,4-DCP affected the index of germination rate but not influenced in other parameters of germination of Zea mayz and Phaseolus vulgaris. Maize was most tolerance to both chlorophenols in the assessed concentrations. 2,4-DCP was the most toxic of chlorophenols tested.

Metabolomic, proteomic and physiological insights into the potential mode of action of thymol, a phytotoxic natural monoterpenoid phenol

Thymol is a natural phenolic monoterpene widely produced by different species belonging to the Labiateae family. Although the thymol phytotoxicity is well known, the knowledge of its potential toxic mechanism is still limited. In this regard, the model species Arabidopsis thaliana was treated for 16 days by sub-irrigation with 300 μM of thymol. The results confirmed the high phytotoxic potential of this phenolic compound, which caused a reduction in plant growth and development. Thymol induced a water status alteration accompanied by an increase in ABA content and stomatal closure. Furthermore, leaves appeared necrotic in the margins and their temperature rinsed. The increase in H2O2 content suggested an oxidative stress experienced by treated plants. Both metabolomic and proteomic analysis confirmed this hypothesis showing a strong increase in osmoprotectants content, such as galactinol and proline, and a significant up-accumulation of proteins involved in ROS detoxification. Furthermore, the down-accumulation of proteins and pigments involved in the photosynthetic machinery, the increase in light sensitivity and the lower PSII efficiency well indicated a reduction in photosynthetic activity. Overall, we can postulate that thymol-induced phytotoxicity could be related to a combined osmotic and oxidative stress that resulted in reduced plant development.

Commercial growth regulator has adverse effect over soybean seedlings under different cadmium levels

Aim of study: Soils contaminated by heavy metals, such as cadmium, may reduce plant development. Exogenous application of plant growth regulators (PGR), are used for optimizing the crops production in stressful environments. The aim of this study was to evaluate the effects of Cd concentrations on the development of soybean seedlings under exogenous application of a commercial PGR.Area of study: Presidente Prudente, São Paulo, Brazil.Material and methods: Soybean seeds were pre-treated in distilled water (control treatment) and in solution with plant growth regulator (PGR treatment) and then germinated with distillated water. The germinated seeds were transferred to different levels of Cd (0, 100, 500 and 900 mg of Cd).Main results: Cd exposure at increasing concentrations, decreased root development, (area, length and volume of roots) and activity of enzymatic antioxidants (SOD, CAT and APX) and enhanced MDA. These responses were accentuated by the PGR exposition. The root morphology and activity of antioxidant enzymes presented "hormesis" responses until 500 mg L-1 of Cd, and the proline content may have played a fundamental role in the maintenance of metabolic activities and biomass.Research highlights: The results indicate that the use of PGR intensified the toxicity responses caused by exposure to increased Cd level. In addition, stress indicators such as MDA content and antioxidant activity in different organs (root and shoot) of soybean seedlings, responded differently according with the use of PGR under exposure of Cd.

Overexpression of SlGRAS7 Affects Multiple Behaviors Leading to Confer Abiotic Stresses Tolerance and Impacts Gibberellin and Auxin Signaling in Tomato.

Abiotic stresses remain the key environmental issues that reduce plant development and therefore affect crop production. Transcription factors, such as the GRAS family, are involved in various functions of abiotic stresses and plant growth. The GRAS family of tomato (Solanum lycopersicum), SlGRAS7, is described in this study. We produced overexpressing SlGARS7 plants to learn more about the GRAS transcription factors. Plants overexpressing SlGARS7 (SlGRAS7-OE) showed multiple phenotypes related to many behaviors, including plant height, root and shoot length, and flowering time. We observed that many genes in the SlGRAS7-OE seedlings that are associated with auxin and gibberellin (GA) are downregulated and have altered sensitivity to GA3/IAA. SlGRAS7 was upregulated during abiotic stresses following treatment with sodium chloride (NaCl) and D-mannitol in the wild-type (WT) tomato. Tomato plants overexpressing SlGRAS7 showed more resistance to drought and salt stress comparison with WT. Our study of SlGRAS7 in tomato demonstrates how GRAS showed an integrative role, improving resistance to abiotic stresses and enhancing gibberellin/auxin signaling through reproductive as well as vegetative processes.