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Salinity stress is a major factor affecting the nutritional and metabolic profiles of crops, thus hindering optimal yield and productivity. Recent advances in nanotechnology propose an avenue for the use of nano-fertilizers as a potential solution for better nutrient management and stress mitigation. This study aimed to evaluate the benefits of conventional and nano-fertilizers (nano-Zn/nano-Si) on maize and subcellular level changes in its ionomic and metabolic profiles under salt stress conditions. Zinc and silicon were applied both in conventional and nano-fertilizer-using farms under stress (100 mM NaCl) and normal conditions. Different ions, sugars, and organic acids (OAs) were determined using ion chromatography and inductively coupled plasma mass spectroscopy (ICP-MS). The results revealed significant improvements in different ions, sugars, OAs, and other metabolic profiles of maize. Nanoparticles boosted sugar metabolism, as evidenced by increased glucose, fructose, and sucrose concentrations, and improved nutrient uptake, indicated by higher nitrate, sulfate, and phosphate levels. Particularly, nano-fertilizers effectively limited Na accumulation under saline conditions and enhanced maize’s salt stress tolerance. Furthermore, nano-treatments optimized the potassium-to-sodium ratio, a critical factor in maintaining ionic homeostasis under stress conditions. With the growing threat of salinity stress on global food security, these findings highlight the urgent need for further development and implementation of effective solutions like the application of nano-fertilizers in mitigating the negative impact of salinity on plant growth and productivity. However, this controlled environment limits the direct applicability to field conditions and needs future research, particularly long-term field trials, to confirm such results of nano-fertilizers against salinity stress and their economic viability towards sustainable agriculture.

Using an original methodological and technical approach, we studied the real-time dynamics of radial water transfer in roots and transpiration rate in intact maize plants in response to water stress. It was shown that the response of maize plants to water stress, induced by 10% PEG 6000, was accompanied by changes in the intensity and redistribution of water transfer along different pathways of radial water transport in the roots. It was shown that during the first minutes of water stress impact, the intensity of transcellular and symplastic water transport in the roots decreased with a parallel short-term increase in the transpiration rate in leaves and, presumably, in apoplastic transport in roots. Further, after a decrease in transpiration rate, the intensity of transcellular and symplastic water transport was restored to approximately the initial values and was accompanied by parallel upregulation of some PIP aquaporin genes in roots and leaves, changes in aquaporin localization in root tissues, and changes in xylem sap pH. Under water stress conditions, cell-to-cell water transport in roots becomes dominant, and aquaporins contribute to the simultaneous regulation of water transport in roots and shoots under water stress.

Monocots and dicots differ in their boron (B) requirement, but also in their capacity to accumulate silicon (Si). Although an ameliorative effect of Si on B toxicity has been reported in various crops, differences among monocots and dicots are not clear, in particular in light of their ability to retain B in the leaf apoplast. In hydroponic experiments under controlled conditions, we studied the role of Si in the compartmentation of B within the leaves of wheat (Triticum vulgare L.) as a model of a high-Si monocot and sunflower (Helianthus annuus L.) as a model of a low-Si dicot, with the focus on the leaf apoplast. The stable isotopes 10B and 11B were used to investigate the dynamics of cell wall B binding capacity. In both crops, the application of Si did not affect B concentration in the root, but significantly decreased the B concentration in the leaves. However, the application of Si differently influenced the binding capacity of the leaf apoplast for excess B in wheat and sunflower. In wheat, whose capacity to retain B in the leaf cell walls is lower than in sunflower, the continuous supply of Si is crucial for an enhancement of high B tolerance in the shoot. On the other hand, the supply of Si did not contribute significantly in the extension of the B binding sites in sunflower leaves.

In recent years; the interaction of nanoparticles (NPs) with plants has been intensively studied. Therefore, more and more aspects related to both the positive and negative impact of NP on plants are well described. This article focuses on two aspects of NP interaction with plants. The first is a summary of the current knowledge on NP migration through the roots into the plant body, in particular, the role of the cell wall. The second aspect summarizes the current knowledge of the participation of the symplast, including the plasmodesmata (PD), in the movement of NP within the plant body. We highlight the gaps in our knowledge of the plant–NP interactions; paying attention to the need for future studies to explain the mechanisms that regulate the composition of the cell wall and the functioning of the PD under the influence of NP.

The response of apoplastic antioxidant systems in root and leaf tissues from two onion genotypes (‘Texas 502’, salt-sensitive and ‘Granex 429’, salt-resistant) in response to salinity was studied. Electrolyte leakage data indicated the membrane integrity impairing by the effect of salts, especially in ‘Texas 502’. We detected superoxide dismutase (SOD) and peroxidase (POX) activity in the root and leaf apoplastic fractions from onion plants. Salinity increased SOD activity in the root symplast of ‘Texas 502’ and in ‘Granex 429’ leaves. In contrast, salinity reduced SOD activity in the leaf and root apoplastic fractions from ‘Texas 502’. In ‘Granex 429’, salt-stress increased leaf apoplastic POX activity and symplastic catalase (CAT) activity of both organs, but a decline in root apoplastic POX from ‘Texas 502’ took place. Salt-stress increased monodehydroascorbate reductase (MDHAR) in root and leaf symplast and in root glutathione reductase GR, mainly in ‘Granex 429’, but only in this genotype, leaf dehydroascorbate reductase (DHAR) activity increased. In contrast, a decline in leaf GR was produced only in ‘Texas 502’. Salinity increased leaf ASC levels, and no accumulation of dehydroascorbate (DHA) was observed in roots in both cases. These responses increased the redox state of ascorbate, especially in roots. In contrast, salinity declined reduced glutathione (GSH), but oxidised glutathione (GSSG) was accumulated in leaves, decreasing the redox state of glutathione. Salinity slightly increased root GSH concentration in the salt-tolerant genotype and was unchanged in the salt-sensitive genotype, but no accumulation of GSSG was produced, favoring the rise and/or maintenance of the redox state of the glutathione. These results suggest that the lower sensitivity to salt in ‘Granex 429’ could be related to a better performance of the antioxidant machinery under salinity conditions.

The article describes the current knowledge about the impact of nanoparticles on plant development with a particular emphasis on crop plants. Nanotechnology is an intensively developing field of science. This is due to the enormous hopes that have been placed on the achievements of nanotechnology in various areas of life. Increasingly, it has been noted that apart from the future benefits of nanotechnology in our everyday life, nanoparticles (NPs) may also have adverse effects that have not been sufficiently explored and understood. Most analyses to date have been focused on the influence of nanomaterials on the physiological processes primarily in animals, humans and bacteria. Although our knowledge about the influence of NPs on the development of plants is considerably smaller, the current views are presented below. Such knowledge is extremely important since NPs can enter the food chain, which may have an influence on human health.

Foliar application of Mg is a measure for the correction of Mg deficiency in crop plants. Foliar applied nutrients need to access the symplastic side where majority of physiological processes take place. To achieve an adequate uptake of the Mg ions through the leaf surface, high concentrations of of 100-200 mM MgSO4 are usually supplied. This can cause antagonistic perturbations on the subcellular distribution of Caand K cations. To test for such unintended side effects, we used the infiltration-centrifugation method to extract ions from the apoplastic and symplastic side of Vicia faba leaves and quantified concentrations of Mg, Ca and K in dependency to the dose of the foliar fertilized Mg. Results show that a large fraction of Mg accesses the symplast whereas the apoplastic fraction shows a concomitant increase. Symplastic and apoplastic K and Ca relations were only affected under conditions of high exogenous leaf supply of Mg (200 mM) but did not change upon moderate Mg supply (50; 100 mM). Overall, results reveal the suitability of leaf fertilization to biofortify plant-based products with magnesium. With respect to human nutrition, care must be taken that K and Ca do not become impoverished based on antagonistic effects.

A toxidez de Mn pode ser um problema comum nas regiões tropicais com predominância de solos ácidos. Entretanto, variações das concentrações desse nutriente nas plantas têm sido atribuídas também a diferenças inter e intra-específicas. O presente estudo foi desenvolvido em casa de vegetação e teve como objetivo avaliar as causas de tolerância diferencial à toxidez de Mn. Os cultivares de soja [Glycine max (L.) Merrill] Santa Rosa, IAC-15 e IAC-Foscarin 31 foram cultivados em solução nutritiva (pH 5,0) com cinco doses de Mn (2, 100, 150, 200 e 250 µmol L-1). O delineamento experimental foi o de blocos completos ao acaso em esquema fatorial 5 x 3 (cinco doses de Mn e três cultivares), com três repetições. Os cultivares IAC-15 e Santa Rosa exibiram sintomas visuais de toxidez. As concentrações nas folhas associadas ao excesso foram de 1.000 mg kg-1. Entretanto, o IAC-15 apresentou maior produção de grãos e de matéria seca da parte aérea, acompanhado pelo IAC-Foscarin 31 (intermediário) e Santa Rosa (menor produção). O maior comprimento total de raízes, as maiores produções de matéria seca de raízes e o acúmulo de Mn neste tecido, bem como a maior compartimentalização deste nutriente no apoplasto, conferiram ao IAC-Foscarin 31 maior tolerância ao excesso de Mn na solução. Há, pois, indicações de diferenças genotípicas entre os cultivares e de que vários mecanismos atuam conjuntamente na tolerância ao excesso de Mn em solução.Manganese (Mn) toxicity may be a constraint for crop production in acid soils of tropical regions. However, variations of Mn concentrations in plant tissues are also related to the genotypic differences. A greenhouse experiment was carried out to evaluate Mn tolerance of three soybean cultivars [Glycine max (L.) Merrill]. Cultivars Santa Rosa, IAC-15 and IAC-Foscarin 31 were evaluated under five Mn rates (2, 100, 150, 200, and 250 µmol L-1) in nutrient solution (pH 5.0). The experiment in randomized blocks was a 5 x 3 factorial of five Mn doses and three cultivars, with three replications. IAC-15 and Santa Rosa leaves showed visual symptoms of Mn toxicity. At toxic Mn levels in solution, the average Mn concentration in the leaf blades was close to 1,000 mg kg-1. Nevertheless, grain and dry matter in the aerial parts was higher for IAC-15 than IAC-Foscarin 31 (intermediate yield) and Santa Rosa (lowest yield). The greatest total root length and root dry matter yield, as well as root Mn accumulation and compartmentalization in root apoplast of IAC-Foscarin 31 contributes to explain differences in tolerance to the excess. There are, therefore, indications of genotypic differences among the soybean cultivars and that several mechanisms are involved in the tolerance to high Mn levels.

Plasmodesmos são canais responsáveis pela conexão citoplasmática entre células vizinhas, possibilitando a troca de moléculas de informação, funcionais, estruturais ou ainda de xenobióticos entre as células pertencentes a um mesmo grupo. Células pertencentes ao mesmo conjunto (domínio) constituem-se numa unidade funcional, e substâncias podem se mover entre estas células com velocidade muito superior à observada no transporte através de membranas. Os plasmodesmos podem atuar ainda no transporte a longa distância, tanto pela associação com o floema como pelo intercâmbio entre domínios simplásticos. Quando a planta se encontra sob estresse e as taxas de transporte via xilema e floema são mais reduzidas, os plasmodesmos podem ser mais efetivos no transporte a longa distância, das moléculas de herbicidas sistêmicos. Falta ainda esclarecer se existe afinidade entre moléculas de determinados herbicidas com as proteínas da superfície interna dos plasmodesmos, o que poderia facilitar o transporte desses herbicidas pela manipulação do Tamanho Limite de Exclusão do plasmodesmo, independentemente do tamanho da molécula, bem como determinar se a semelhança com algum composto natural da planta promove maior taxa de transporte simplástico. Pouca importância tem sido dada à participação dos plasmodesmos no transporte de herbicidas sistêmicos. No entanto, o avanço dos trabalhos com produtos marcados e a intensificação das pesquisas em fisiologia vegetal para melhor entendimento dos processos referentes à absorção, translocação, conjugação e/ou degradação de herbicidas podem esclarecer muitos aspectos ainda não definidos do transporte de herbicidas via xilema e floema e sua associação com o apoplasto e domínios simplásticos.Plasmodesmata are plasma channels connecting neighboring cells and allowing the exchange of informational, functional and structural molecules and xenobiotics among cells of the same "group". Cells of the same domain behave as functional units, and substances are able to move between them at rates above the observed for trans-membrane movement. Plasmodesmata participate in long distance movement, both by association with phloem and interchange among neighboring domains. When the plant is under stress and xylem and phloem flux is slower, plasmodesmata could be more participative in long distance transport of systemic herbicide molecules. It remains to be fully understood whether there is a relationship among molecules of some herbicide groups and proteins embedded in the inner surface of plasmodesmata, to determine if some groups are able to manipulate the size of exclusion limit, independent of molecule size, as well as to verify if similarities between native compounds and herbicidal molecules result in higher rates of symplastic uptake. The deserving importance is not given to the role plasmodesmata plays in systemic herbicidal transport within the plant. However, the progress achieved with works related to marked products and plant physiology research intensification will eventually elucidate some not so clear aspects involving herbicide uptake by xylem and phloem, and their association with apoplast and symplastic domains.

The discovery of abundant plasmodesmata at the bundle sheath/phloem interface in Oleaceae (Gamalei, 1974) and Cucurbitaceae (Turgeon et al., 1975) opened the questions whether these plasmodesmata are functional in phloem loading and how widespread is symplasmic loading. Analysis of over 800 dicot species allowed the definition of ‘open’ and ‘closed’ types of the minor vein phloem depending on the abundance of plasmodesmata between companion cells and bundle sheath (Gamalei, 1989; 1990). These types corresponded to potential symplasmic and apoplasmic phloem loaders, respectively; however, this definition covered a spectrum of diverse structures of phloem endings. Here, a review of detailed cytological analyses of minor veins in 320 species from the subclass Asteridae is presented, including data on several cell types and their combinations which have not been reported previously. The percentage of Asteridae species with ‘open’ minor vein cytology which also contain sieve-element-companion cell complexes with ‘closed’ cytology, i.e. that show specialization for both symplasmic and apoplasmic phloem loading, was determined. Along with recent data confirming the dissimilar functional specialization of structurally different parts of minor vein phloem in the stachyose-translocating species Alonsoa meridionalis (Voitsekhovskaja et al., 2009), these findings suggest that apoplasmic loading is indispensable in a large group of species previously classified as putative symplasmic loaders. Altogether, this study provides formal classifications of companion cells and of minor veins, respectively, in 24 families of the Asteridae based on their structural features, opening the way to a close investigation of the relationship between structure and function in phloem loading.