Artigos – LxCrop

Article 1

Referência:

Rosa AP, Barão L, Chambel L, Cruz c, Santana M. Early Identification of Plant Drought Stress Responses: Changes in Leaf Reflectance and Plant Growth Promoting Rhizobacteria Selection-The Case Study of Tomato Plants. Agronomy https://doi.org/10.3390/agronomy13010183

Drought is a worldwide problem, especially in arid and semi-arid regions. Detection of drought stress at the initial stages, before visible signs, to adequately manage irrigation and crop fertilization to avoid crop yield loss, is a desire of most farmers. Here, we evaluated the response of tomato plants to water scarcity, through changes in leaf reflectance due to modification in leaf pigments’ content, which translates into differences in spectral reflectance indices (SRI) values. Our methodology is innovative, as we were able to easily calculate and identify several SRIs for the early detection of drought stress “invisible” responses.

Article 2

Referência:

Martins-Loução MA, Dias T, Cruz C. Integrating Ecological Principles for Addressing Plant Production Security and Move beyond the Dichotomy ‘Good or Bad’ for Nitrogen Inputs Choice. Agronomy. 2022;12:1632. DOI:10.3390/agronomy12071632 (IF3.949).

Mankind’s strong dependence on nitrogen (N) began when we started farming and, ever since, we have depended on nitrogen in the soil for plant production. More than a century has passed since the discovery of N as an element until the advent of synthetic fertilizers. Today, after a century of Haber–Bosch innovation, many other endeavors and challenges can be launched to understand how the effects of N in the environment can be perceived as ‘good’ or ‘bad’. All this knowledge evolution was truly dependent on the scientific advances, both technological and methodological, and particularly on the approaches at the micro and macro level. As with nearly everything in our lives (e.g., events, people, food, decisions, world history), we tend to use the dichotomy ‘good or bad’ to categorize, and scientific advances are no exception. The integration of scientific and technological advances allows us to move beyond this simple dichotomy ‘good or bad’ and to make choices. Here, we review the main marks in understanding plant nutrition throughout time, with special emphasis on N, from the Greeks to the most recent trends in the 21st century.

Figure 1. Evolution of some historical marks on plant nutrition.

Article 3

Referência

asusi OA, Cruz C, Babalola OO. Agricultural Sustainability: Microbial Biofertilizers in Rhizosphere Management. Agriculture. 2021;11:163. DOI:10.3390/agriculture11020163 (IF 2.925)

The world’s human population continues to increase, posing a significant challenge in ensuring food security, as soil nutrients and fertility are limited and decreasing with time. Thus, there is a need to increase agricultural productivity to meet the food demands of the growing population. A high level of dependence on chemical fertilizers as a means of increasing food production has damaged the ecological balance and human health and is becoming too expensive for many farmers to afford. The exploitation of beneficial soil microorganisms as a substitute for chemical fertilizers in the production of food is one potential solution to this conundrum. Microorganisms, such as plant growth-promoting rhizobacteria and mycorrhizal fungi, have demonstrated their ability in the formulation of biofertilizers in the agricultural sector, providing plants with nutrients required to enhance their growth, increase yield, manage abiotic and biotic stress, and prevent phytopathogens attack. Recently, beneficial soil microbes have been reported to produce some volatile organic compounds, which are beneficial to plants, and the amendment of these microbes with locally available organic materials and nanoparticles is currently used to formulate biofertilizers to increase plant productivity. This review focuses on the important role performed by beneficial soil microorganisms as a cost-effective, nontoxic, and eco-friendly approach in the management of the rhizosphere to promote plant growth and yield.

Figure 1. Overview of rhizosphere as the bottleneck in controlling nutrients uptake by plants through the application of chemical and biofertilizer; Arbuscular mycorrhiza fungi (AMF), Plant growth-promoting rhizobacteria (PGPR).

Article 4

Referência

Hessini K, Jeddi K, Siddique KHM, Cruz C. Drought and salinity: A comparison of their effects on the ammonium‐preferring species Spartina alterniflora. Physiologia Plantarum. 2021;172:431-440.

Drought and salinity are the most serious environmental factors affecting crop productivity worldwide; hence, it is important to select and develop both salt- and drought-tolerant crops. The perennial smooth cordgrass Spartina alterniflora Loisel is unusual in that it is highly salt-tolerant and seems to prefer ammonium (NH₄⁺) over nitrate (NO₃⁻) as an inorganic N source. In this study, we determined whether Spartina’s unique preference for NH₄⁺ enhances performance under salt and drought stress. Greenhouse experiments were conducted to compare the interactive effects of N source, salinity, and low water availability on plant performance (growth and antioxidant metabolism). Drought significantly reduced growth and photosynthetic activity in S. alterniflora, more so with NH₄⁺ than NO₃⁻; in contrast, NH₄⁺ enhanced growth under high salinity. The increased tolerance of S. alterniflora to salt stress in the presence of NH₄⁺ was linked to a high level of antioxidant enzyme activity, combined with low MDA content, EL, and H₂O₂ production. In contrast, drought stress negated the growth advantages for S. alterniflora exposed to salt stress in the presence of NH₄⁺. The susceptibility of S. alterniflora to drought was partly due to reduced antioxidant enzyme activities, thereby reducing the defense against the oxidative damages induced by osmotic stress. In conclusion, in contrast to salt stress, drought stress negates the beneficial effects of ammonium as an N source in the C₄ plant Spartina alterniflora.

Figure 1. Interactive effects of nitrogen form (NO₃⁻and NH₄⁺) and osmotic stress (salinity or drought) on the activities of glutamate dehydrogenase (GDH, nmol NADH oxidized g⁻¹protein min⁻¹) in leaves of individualSpartina alternifloraplants. Each data point is the mean ± sdof three replicates per treatment. Values with different letters are significantly different atP = 0.05

Article 5

Referência

Carril P, da Silva A, Tenreiro R, Cruz C. An optimized in situ quantification method of leaf H2O2 unveils interaction dynamics of pathogenic and beneficial bacteria in wheat. Frontiers in Plant Science. 2020;11:889. DOI:10.3389/fpls.2020.00889 (IF 4.106).

Hydrogen peroxide (H₂O₂) functions as an important signaling molecule in plants during biotic interactions. However, the extent to which H₂O₂ accumulates during these interactions and its implications in the development of disease symptoms is unclear. In this work, we provide a step-by-step optimized protocol for in situ quantification of relative H₂O₂ concentrations in wheat leaves infected with the pathogenic bacterium Pseudomonas syringae pv. atrofaciens (Psa), either alone or in the presence of the beneficial bacterium Herbaspirillum seropedicae (RAM10). This protocol involved the use of 3-3′diaminobenzidine (DAB) staining method combined with image processing to conduct deconvolution and downstream analysis of the digitalized leaf image. The application of a linear regression model allowed to relate the intensity of the pixels resulting from DAB staining with a given concentration of H₂O₂. Decreasing H₂O₂ accumulation patterns were detected at increasing distances from the site of pathogen infection, and H₂O₂ concentrations were different depending on the bacterial combinations tested. Notably, Psa-challenged plants in presence of RAM10 accumulated less H₂O₂ in the leaf and showed reduced necrotic symptoms, pointing to a potential role of RAM10 in reducing pathogen-triggered H₂O₂ levels in young wheat plants.

Figure 2. (A) Steps for the generation of H₂O₂-DAB intensity calibration curve. Disks are put in microtubes, drenched at different H₂O₂ concentrations and 1 mg/mL DAB solution is added. After incubation, disks are digitalized and average DAB intensity in the deconvoluted image is determined. Finally, average DAB intensity values are related with those of the several H₂O₂ concentrations (μmol H₂O₂/cm²). (B) Leaf incubation in 1 mg/ml DAB solution and processing of the initial leaf RGB image resulting in the deconvoluted 8-bit DAB image. Leaf background average intensity (blank) was subtracted and ROIs were selected in leaf for quantification of the final DAB average pixel intensity of specific ROIs.

Article 6

Referência

Mokrani S, Nabti E-H, Cruz C. Current Advances in Plant Growth Promoting Bacteria Alleviating Salt Stress for Sustainable Agriculture. Applied Sciences. 2020;10:7025. DOI:10.3390/app10207025 (IF 2.679).

Humanity in the modern world is confronted with diverse problems at several levels. The environmental concern is probably the most important as it threatens different ecosystems, food, and farming as well as humans, animals, and plants. More specifically, salinization of agricultural soils is a global concern because of on one side, the permanent increase of the areas affected, and on the other side, the disastrous damage caused to various plants affecting hugely crop productivity and yields. Currently, great attention is directed towards the use of Plant Growth Promoting Bacteria (PGPB). This alternative method, which is healthy, safe, and ecological, seems to be very promising in terms of simultaneous salinity alleviation and improving crop productivity. This review attempts to deal with different aspects of the current advances concerning the use of PGPBs for saline stress alleviation. The objective is to explain, discuss, and present the current progress in this area of research. We firstly discuss the implication of PGPB on soil desalinization. We present the impacts of salinity on crops. We look for the different salinity origin and its impacts on plants. We discuss the impacts of salinity on soil. Then, we review various recent progress of hemophilic PGPB for sustainable agriculture. We categorize the mechanisms of PGPB toward salinity tolerance. We discuss the use of PGPB inoculants under salinity that can reduce chemical fertilization. Finally, we present some possible directions for future investigation. It seems that PGPBs use for saline stress alleviation gain more importance, investigations, and applications. Regarding the complexity of the mechanisms implicated in this domain, various aspects remain to be elucidated.

Figure 2. PGPB (Plant growth promoting bacteria) salinity resistance strategies and mechanisms of plant growth improvement under salt stress (SMPGSS: stimulation mechanisms of plant growth uFnigdueresa2l.tPsGtrePsBs;(MPlSaHntSg: rmoewcthanpirsomsostuinrvgivbiancgtehriag)hssalliiniitty,rPeGsisPtBa:npcelasnttragtreogwietsh-apnrdomoetcinhganbiascmtesrioaf, EpPlaSn:texgoropwoltyhsaicmchparorivdems)e.nt under salt s