Chemical composition and phytotoxicity of essential oils of Croton doctoris S. Moore (Euphorbiaceae)

Essential oils from the stems and leaves of Croton doctoris were analyzed by gas chromatography and mass spectrometry, resulting in 22 identified compounds. The effects of these essential oils on the germination, root and shoot growth, total chlorophyll content, potential root respiration, peroxidase activity, catalase, superoxide dismutase, and mitotic index in lettuce and onion were determined. Antioxidant, antimicrobial, and cytotoxic activity were also investigated. The results revealed that the stem oil consisted of 15 compounds, of which caryophyllene oxide (24.5%) and E-caryophyllene (13.3%) were the major constituents. The leaf oil contained E-caryophyllene (39.6%) and α-humulene (13.2%) as major compounds. The oils inhibited the germination and growth of lettuce and onion seedlings and reduced chlorophyll content, root respiration, and cell division. They also caused oxidative stress, indicated by the increased activity of the evaluated antioxidant enzymes. These abnormal physiological processes contributed to the inhibition of plant growth. The most pronounced phytotoxic effects were observed in the stem oil. The cytotoxicity tests indicated that leaf oil was more active than stem oil, resulting from the presence of biologically active sesquiterpenes that inhibit the growth of cancer cells.

Variability in Physiological Traits Reveals Boron Toxicity Tolerance in Aegilops Species

Boron (B) is an important micronutrient required for the normal growth and development of plants. However, its excess in the soil causes severe damage to plant tissues, which affects the final yield. Wheat, one of the main staple crops, has been reported to be largely affected by B toxicity stress in arid and semi-arid regions of the world. The prevalence of B toxicity stress can be addressed by utilizing wild wheat genotypes with a variant level of stress tolerance. Wild wheat relatives have been identified as a prominent source of several abiotic stress-tolerant genes. However, Aegilops species in the tertiary gene pool of wheat have not been well exploited as a source of B toxicity tolerance. This study explores the root and shoot growth, proline induction, and extent of lipid peroxidation in 19 Aegilops accessions comprising 6 different species and the B-tolerant check wheat cultivar Bolal 2973 grown under Control (3.1 μM B), toxic (1 mM B), and highly toxic (10 mM B) B stress treatment. B toxicity stress had a more decisive impact on growth parameters as compared to the malondialdehyde (MDA) and proline content. The obtained results suggested that even the genotypes with high shoot B (SB) accumulation can be tolerant to B toxicity stress, and the mechanism of B redistribution in leaves should be studied in detail. It has been proposed that the studied Aegilops accessions can be potentially used for genetically improving the B toxicity-tolerance trait due to a high level of variation in the response toward high B toxicity. Though a number of accessions showed suppression in the root and shoot growth, very few accessions with stress adaptive plasticity to B toxicity stress leading to an improvement of shoot growth parameters could be determined. The two accessions, Aegilops biuncialis accession TGB 026219 and Aegilops columnaris accession TGB 000107, were identified as the potential genotypes with B toxicity stress tolerance and can be utilized for developing a pre-breeding material in B tolerance-based breeding programs.

Timing of Drought Affected the Growth, Physiology, and Mortality of Mongolian Pine Saplings

Background and Objectives: More frequent and severe droughts are occurring due to climate change in northern China. In addition to intensity and duration, the timing of droughts may be decisive for its impacts on tree growth, mortality, and the whole forest ecosystem. The aim of this study was to compare the effect of drought occurring in the early- and mid-growing season on the growth and physiology of Mongolian pine (Pinus sylvestris var. mongolica Litv.) saplings. Materials and Methods: Four-year-old container saplings that were about to sprout were exposed to three treatments: (i) regular irrigation throughout the growing season (CTRL), (ii) no irrigation in the early growing season (weeks 1–5) followed by regular irrigation (EGD), (iii) no irrigation in the mid growing season (weeks 5–10), and regular irrigation in the early and late growing season (MGD). We measured the root and shoot growth, sapling mortality, and the physiological changes in the roots and needles periodically. Results: Drought in the mid growing season was more harmful than in the early growing season in terms of chlorophyll fluorescence, electrolyte leakage of needles, needle length, stem diameter increment, and sapling mortality. The high mortality in the mid growing season might be attributed to the joint effect of drought and high temperature. Drought in the early growing season decreased root growth, and the starch and soluble sugars in roots as much as the drought in the mid growing season. Abscisic acid concentration increased in fine roots, but decreased in old needles after drought. Conclusions: Special attention should be paid on forest sites susceptible to drought during afforestation in the face of ongoing climate change.

Root and shoot growth of spring wheat (Triticum aestivum L.) are differently affected by increasing subsoil biopore density when grown under different subsoil moisture

A column experiment with five different pore densities (0, 1, 2, 3, and 4 pores column−1) and two varying moisture regimes (comparatively dry and comparatively moist regime) in the subsoil part of the columns was established. In each pore, Lumbricus terrestris was introduced for 28 days before sowing wheat plants. After 40 days of plant growth, watering was stopped to induce progressive topsoil drying. Parameters describing the shoot hydration, mineral uptake, and aboveground biomass were quantified. Root biomass and root length densities (RLD) were measured separately for six soil layers. Under dry subsoil conditions, plants grown under increasing biopore density showed an increase of the RLD and an improved shoot hydration but the aboveground biomass was unaffected. Since RLD but not root biomass was enhanced, it is assumed that roots were able to explore a larger volume of soil with the same amount of root biomass. Thereby, subsoil water likely was used more efficiently leading to an improved hydration. Under moist subsoil conditions, plants grown with increasing biopore density revealed enhanced shoot biomasses and nutrient uptake while the belowground biomass was unaffected. The improved nutrient uptake can be ascribed to, first, the higher subsoil water availability favoring mass flow driven nutrient uptake, and second, to direct and indirect effects of earthworms on the availability of soil nutrients. It is concluded that high biopore abundancies have the potential to improve not only the belowground but also the aboveground biomass. This, however, largely depends on subsoil moisture.

Effects of Polydopamine Microspheres Loaded with Silver Nanoparticles on Lolium multiflorum: Bigger Size, Less Toxic

The rapid development of nanotechnology and its widespread use have given rise to serious concerns over the potential adverse impacts of nanomaterials on the Earth’s ecosystems. Among all the nanomaterials, silver nanoparticles (AgNPs) are one of the most extensively used nanomaterials due to their excellent antibacterial property. However, the toxic mechanism of AgNPs in nature is still unclear. One of the questions under debate is whether the toxicity is associated with the size of AgNPs or the silver ions released from AgNPs. In our previous study, a sub-micron hybrid sphere system with polydopamine-stabilized AgNPs (Ag@PDS) was synthesized through a facile and green method, exhibiting superior antibacterial properties. The current study aims to explore the unique toxicity profile of this hybrid sphere system by studying its effect on germination and early growth of Lolium multiflorum, with AgNO3 and 15 nm AgNPs as a comparison. The results showed the seed germination was insensitive/less sensitive to all three reagents; however, vegetative growth was more sensitive. Specifically, when the Ag concentration was lower than 40 mg/L, Ag@PDS almost had no adverse effects on the root and shoot growth of Lolium multiflorum seeds. By contrast, when treated with AgNO3 at a lower Ag concentration of 5 mg/L, the plant growth was inhibited significantly, and was reduced more in the case of AgNP treatment at the same Ag concentration. As the exposures of Ag@PDS, AgNO3, and AgNPs increased, so did the Ag content in the root and shoot. In general, Ag@PDS was proven to be a potential useful hybrid material that retains antibacterial property with light phytotoxicity.

Comparisons of the Effect of Different Metal Oxide Nanoparticles on the Root and Shoot Growth under Shaking and Non-Shaking Incubation, Different Plants and Binary Mixture Conditions

We evaluated the toxicity of five metal oxide nanoparticles (NPs) in single or binary mixtures based on root and shoot growth of two plant species under non-shaking and shaking conditions. The effects of NPs on root and shoot growth differed depending on the NP type, incubation condition, and plant type. The half maximal effective concentration (EC50) of NPs based on root growth were significantly lower, by 2.6–9.8 times, under shaking than non-shaking conditions (p = 0.0138). The magnitude of the effects of NPs followed the order CuO > ZnO > NiO >> Al2O3, TiO2. In addition, Lactuca sativa L. was more sensitive to the tested NPs than Raphanus sativus L., with an EC50 0.2–0.7 times lower (p = 0.0267). The observed effects of 12 combinations of binary NP mixtures were slightly, albeit non-significantly, lower than expected, indicative of an additive effect of the individual NPs in the mixtures. The results emphasize the importance of careful plant model selection, appropriate application of incubation conditions, and consideration of chemical mixtures rather than single compounds when evaluating the effects of metal oxide NPs.

Improving Plant-Based Genotoxicity Bioassay for Trace Metal-Contaminated Water: Insights from Myriophyllum Aquaticum (Vell.) Verdc. and Cd.

In this work, we evaluated whether the species Myriophyllum aquaticum (Vell.) Verdc. can be a promising material for devising reliable ecotoxicological tests for Cd contaminated waters. Plants of M. aquaticum were exposed to Cd, using different concentrations and exposure times, in order to address as many possible effects as possible of its presence. Plant growth and Cd accumulation were monitored along the treatment period and Cd genotoxicity was assessed by analyzing Cd-induced changes in the AFLP fingerprinting profiles. Root and shoot growth was reduced already at the lowest Cd concentration used (1 mg L-1). Shoots showed a higher Cd sensitivity and a lower accumulation, thus being chosen as the more suitable organ for the genotoxic analysis. DNA variation was observed starting from 2.5 mg L-1, indicating that the metal-induced depression of plant growth at the lower concentration did not necessarily imply a genotoxic effect. Similar results were obtained in the time-dependent experiment, since Cd effect on DNA fingerprinting profile was observed after three days of exposure and without a significant growth decrease growth. Therefore, our results showed that M. aquaticum proved to be a suitable model system for the investigation of Cd genotoxicity through AFLP fingerprinting profile, whereas the more classic eco-toxicological tests based only on biometric parameters could underestimate the risk associated to undetected Cd genotoxicity.

Early Development of Fig (Ficus carica L.) Root and Shoot Using Different Propagation Medium and Cutting Types

This study aimed at determining the effects of propagation medium and cutting types on the early growth performance of fig (Ficus carica L.) root and shoot. The experiment was conducted at the Glasshouse and Nursery Complex (GNC), International Islamic University Malaysia (IIUM). The split-plot design was employed with the main plot (propagation medium) and sub-plot (types of cutting). The propagation medium were sand and topsoil (1:3) (M1), topsoil, peat and sawdust (1:1:1) (M2) and peat and perlite (1:1) (M3). Two types of cutting were semi-hardwood (C1) and hardwood (C2). As a result, there were a significant effect of propagation medium on measured parameters. This study revealed that the most effective propagation medium and cutting types for the propagation of fig were a combination of peat and perlite at 1:1 ratio (M3) and hardwood cutting (C2), respectively as evidenced by significantly higher root and shoot growth quality as compared to other treatments.