Allocation Pattern, Nutrient Partitioning, Sugar Metabolism, and Pigment Composition in Hydroponically Grown Loquat Seedlings Subjected to Increasing Boron Concentrations

Boron (B) is an essential micronutrient for plant growth and development, but in soil of arid and semiarid environments, B frequently exceeds the plant requirements. B toxicity hampers plant performances and productivity even though there is a lack of information about changes in leaf sugar metabolism and nutrient partitioning provoked by B excess, especially in tree sugar alcohol-producing species where B is highly mobile. In current experiment, hydroponically grown loquat seedlings were subjected to increasing B levels (25, 50, 100, 200, and 400 μΜ) in the nutrient solution for 69 days. B excess caused visible symptoms in the upper part of loquat shoots (leaves and stem), typical symptoms usually found in species where B is highly phloem mobile. Furthermore, Β excess caused significant (i) reduction of plant growth, leaf number, and stem diameter; and (ii) alterations in macro- and micronutrient allocation patterns in different plant organs, e.g., decrease of K, P, Mn, and Mg concentration in roots. Younger fully expanded leaves of B-treated seedlings showed a decline of sucrose paralleled by increments of glucose and fructose concentration in leaves, alteration of leaf pigment composition, and increased peroxidation of lipid bilayers (higher malondialdehyde by-products). Our observations suggest that loquat is very sensitive to B excess and B toxicity can affect dramatically the plant physiology and biochemistry, thus leading to changes in sugar patterns, a reduced growth and, eventually, a reduced productivity of this species

Allocation pattern, photosynthetic performance and sugar metabolism in hydroponically grown seedlings of loquat (Eriobotrya japonica Lindl.) subjected to salinity

n/

Metal nanoparticles: Phytotoxicity on tomato and effect on symbiosis with the Fusarium solani FsK strain

The effect of copper (Cu-NPs, CuO-NPs), silver (Ag-NPs) and zinc oxide (ZnO-NPs) nanoparticles (NPs) on plant growth, physiological properties of tomato plants and their symbiotic relationships with the endophytic Fusarium solani FsK strain was investigated. Fungitoxicity tests revealed that the FsK strain was significantly more sensitive to Cu-NPs and ZnO-NPs than CuO-NPs and Ag-NPs both in terms of mycelial growth and spore germination. All NPs were more toxic to FsK compared to their bulk counterparts except for AgNO3, which was 8 to 9-fold more toxic than Ag-NPs. Apart from AgNO3, NPs and bulk counterparts did not affect the number of germinated tomato seeds even in higher concentrations, while root length was significantly reduced in a dose dependent way in most cases. Dry weight of tomato plants was also significantly reduced upon treatment with NPs and counterparts with most pronounced effects in the cases of AgNO3, Cu-NPs, ZnO-NPs, and ZnSO4. Root and shoot length of grown tomato plants was also affected by treatments while differences between NPs and bulk counterparts varied. A marked oxidative stress response was recorded in all cases of NPs/bulk counterparts as indicated by increased MDA and H2O2 levels of treated plants. Treated plants had significantly reduced chlorophyl-a and carotenoid levels compared to the untreated control. NPs and counterparts did not affect FsK colonization of roots indicating a possible shielding effect of tomato plants once the endophyte was established inside the roots. Vice versa, a possible alleviation of CuO-NPs, ZnO-NPs, and ZnSO4 toxicity was observed in the presence of FsK inside tomato roots in terms of plant dry weight. The results suggest that phytotoxicity of NPs in tomato treated plants should be considered before application and while both FsK and tomato are sensitive to NPs, their reciprocal benefits may extent to resistance towards these toxic agents. © 2021 Elsevier B.V

Changes in sugar metabolism associated to stem bark thickening partially assist young tissues of Eriobotrya japonica seedlings under boron stress

Boron (B) toxicity frequently affects plant performances and productivity, especially in arid and semi-arid environments. In this experiment, loquat seedlings were subjected to 25 μM (control) or 400 μM B (B excess) to test the hypothesis that (i) B alters sugar/polyol metabolism in polyol-producing tree species as loquat and (ii) changes of leaf and stem anatomy assist young tissues against toxic effect of B. Gas exchange was monitored from the beginning of the experiment (FBE) till one week after the first visible symptoms of B toxicity appeared in the upper part of the stems (147 d FBE). At 147 FBE, plant biometric parameters and pattern of B accumulation, leaf and stem anatomy, chlorophyll a fluorescence kinetics as well as biochemical measurements were assessed in top (asymptomatic) leaves and upper stem bark. Boron accumulated principally (in the row) in top leaves > top bark > top wood in B-stressed plants, but no changes in allocation pattern were found between controls and B-stressed plants. Excess B promoted the increase in the spongy layer of top leaves and caused the development of cork and numerous collenchyma cells with increased cell wall thickness. This mechanism, which has never been described before, can be considered an attempt to store excessive B in tissues where B ions are less harmful. The accumulation of sorbitol (B-complexing polyol) in top leaves and stem bark can be considered as a further attempt to detoxify B excess. However, B toxicity drastically affects the photosynthetic rate of top leaves, mainly due to non-stomatal limitations, i.e., reduction of ambient CO2 use efficiency and of photosystem II (PSII) efficiency, modification of the partitioning excess energy dissipation in PSII, thus leading to an increased level of lipid peroxidation. Our results suggest that changes in sugar metabolism associated with leaf and stem bark thickening partially assist (but not totally preserve) young tissues of loquat plants under B stress

Allocation pattern, photosynthetic performance and sugar metabolism in hydroponically grown seedlings of loquat (Eriobotrya japonica lindl.) subjected to salinity

Hydroponically grown loquat seedlings were subjected to increasing NaCl concentrations (0, 12, 24, and 48 mM) for 42 d. At the whole plant level, Na+ and Cl– accumulated proportionally to the salt treatments; however, Na+ accumulated prevalently in leaves whilst Cl– accumulated prevalently in stems. Reduction of leaf biomass was only observed in seedlings grown with 48 mM NaCl, whereas net photosynthesis declined along with increasing NaCl concentration and salinity led to general accumulation of glucose, reduction of mannitol and sorbitol, and changes in pigment composition in loquat leaves. Increasing level of salinity induced accumulations of both proline and H2O2 but not of malondialdehyde byproducts. Dramatic alteration of sugar patterns in the leaves poses serious concerns about possible effects of salinity to fruit production. Further research is necessary to investigate the concentration at which NaCl significantly compromises the yield of this economically important fruit species

Morphological Diversity, Genetic Characterization, and Phytochemical Assessment of the Cypriot Tomato Germplasm

Tomato (Solanum lycopersicum L.) is considered one of the most valuable and versatile vegetable crops globally and also serves as a significant model species for fruit developmental biology. Despite its significance, a severe genetic bottleneck and intense selection of genotypes with specific qualitative traits have resulted in the prevalence of a restricted number of (geno)types, also causing a lack of diversity across widespread cultivated types. As a result, the re-emergence of landraces as well as traditional and heirloom varieties is largely acknowledged as a countermeasure to restore phenotypic, phytochemical and genetic diversity while enriching the aroma/taste tomato palette. On those grounds, the Cypriot tomato germplasm was assessed and characterized. Ten landrace accessions were evaluated under greenhouse conditions and data were collected for 24 IPGRI discrete phenotypic traits. Grouping of accessions largely reflected the fruit shape and size; four different fruit types were recorded across accessions (flattened, heart-shaped, rounded and highly rounded). Moreover, a single run panel consisting of ten SSRs was developed and applied in order to genetically characterize 190 Cypriot genotypes and foreign heirloom varieties. Based on genetic indexes it was established that tomato landraces have a rather low level of heterogeneity and genetic variation. Finally, mineral and phytochemical analyses were conducted in order to estimate biochemical attributes (total phenolics, ascorbic acid, lycopene, β-carotene, total soluble content, titratable acidity) across genotypes; thus, ascertaining that the Cypriot panel has a high nutritional value. Due to the thermo-drought adaptation and tolerance of these genotypes, the current study serves as a roadmap for future breeding efforts in order to incorporate desirable traits or develop novel tomato lines combining resilience and alimentary value