Silicon In the Growth of Rice Seedlings Pretreated with Dietholate and Subjected to Cold Stress

Silicon (Si) is an enzyme stimulator that can promote signaling for the production of antioxidant compounds, important in cellular detoxification of excess ROS accumulated during stress. The aim of the study was to evaluate the effects of Si on post-germination rice seeds in the mitigation of cold stress combined with stress induced by seed treatment with the dietholate protector. The experimental design was fully randomized with three replicates and a 3x2x2x4x2 factorial arrangement: three temperatures (5, 10 and 20 °C), two cultivars (IRGA 424 RI and Guri INTA CL), two seed pretreatments (with and without dietholate), four rates of Si (0; 4.0; 8.0 and 16 mg.L-1) and two sources of Si (sodium and potassium metasilicate). Seed pretreatment with dietholate reduced shoot and radicle length, especially at the lower temperatures of 5 and 10 °C. Sodium metasilicate as the source of Si was more efficient in boosting shoot and radicle length, both with and without pretreatment, regardless of temperature. Si was found to attenuate low-temperature stress and the impairment of shoot and radicle growth in rice seedlings grown from seeds pretreated with dietholate.

Accumulation and Effect of Heavy Metals on the Germination and Growth of Salsola vermiculata L. Seedlings

The influence of different concentrations of heavy metals (Cu, Mn, Ni, Zn) was analyzed in the Salsola vermiculata germination pattern, seedling development, and accumulation in seedlings. The responses to different metals were dissimilar. Germination was only significantly reduced at Cu and Zn 4000 μM but Zn induced radicle growth at lower concentrations. Without damage, the species acted as a good accumulator and tolerant for Mn, Ni, and Cu. In seedlings, accumulation increased following two patterns: Mn and Ni, induced an arithmetic increase in content in tissue, to the point where the content reached a maximum; with Cu and Ni, the pattern was linear, in which the accumulation in tissue was directly related to the metal concentration in the medium. Compared to other Chenopodiaceae halophyte species, S. vermiculata seems to be more tolerant of metals and is proposed for the phytoremediation of soils contaminated by heavy metals.

Influența factorilor abiotici asupra capacităților germinative a semințelor de fag (Fagus sylvatica L.)

The diversification of beech genotypes on the territory of the Republic of Moldova could be a so-lution to avoid the risks caused by climate change. The objective of this research was to determine the viability of beech seeds collected from four areas of the Ivano-Frankivsk region (Ukraine) and their modi-fication under the influence of various abiotic factors. The analyzed seeds possessed high viability (77.89 – 96.63%), which under the influence of supra optimal temperature +40°C decreased 1.3-1.4 times de-pending on the applied dose. Seeds exposed to heat treatment used reserve substances for radicle growth 1.4 – 1.6 times more than the control.

Comparative response of Malaysian weedy rice (Oryza sativa) initial growth towards the allelopathic potential of Leucaena leucocephala (Lam.) de Wit and Dicranopteris linearis (Burm. f.) Underw

The infestation of weedy rice has becoming a threat which leads to competition between weedy rice and commercial rice for nutrient uptake. Weedy rice management is more dependent on the herbicides application that can contribute to various environmental problems. Thus, this study was conducted to assess the allelopathic potential of two invasive plants namely L. leucocephala and D. linearis in controlling the growth of weedy rice. The allelopathic potential was evaluated through laboratory bioassay namely the dish pack method, sandwich method and plant box method to determine the allelopathic potential on the seedling growth of two weedy rice variants collected in Peninsular Malaysia (designated as WRE and WRN) and MR220 CL2 rice variety. Highest concentration of L. leucocephala leaf litter (50 mg) inhibited the radicle elongation of MR220 CL2, WRN and WRE by 49 %, 51 % and 83 % compared to control, respectively. Through the dish pack method, the volatile compound from D. linearis leaf were found to disrupt the radicle growth of MR220 CL2, WRN and WRE by 21 %, 29 % and 25 % of the control at the nearest distance (41 mm) of the bioassay plants with the D. linearis leaf. Compared with D. linearis, the root exudate from L. leucocephala exhibited higher inhibitory effect towards the bioassay species. Overall, the findings from this study showed that the allelopathic potential of L. leucocephala was more preferable to be investigated further for sustainable weedy rice management in the future by infusing the biological approach.

Determination of the Allelopathic Potential of Cambodia’s Medicinal Plants Using the Dish Pack Method

Plants produce several chemically diverse bioactive substances that may influence the growth and development of other organisms when released into the environment in a phenomenon called allelopathy. Several of these allelopathic species also have reported medicinal properties. In this study, the potential allelopathic effects of more than a hundred medicinal plants from Cambodia were tested using the dish pack method. The dish pack bioassay method specifically targets volatile allelochemicals. Twenty-five species were found to have significant inhibitory effects on lettuce radicle growth. Eleven different plant families, including Iridaceae (2), Apocynaceae (2), Poaceae (2), Sapindaceae, Araceae, Combretaceae, Orchidaceae, Clusiaceae, Zingiberaceae, Rutaceae and Asparagaceae had the plant species with high inhibitory effects. Allophyllus serrulatus had the highest growth inhibitory effect on lettuce radicles more than 60%, followed by Alocasia macrorrhiza, Iris pallida, Terminalia triptera, Wrightia tomentosa, Cymbidium aloifolium, Garcinia villersiana and Kaempferia parviflora. The candidate species were subjected to further studies to identify the volatile allelochemicals in the volatile constituents.

Germination of Phaseolus vulgaris L. Seeds after a Short Treatment with a Powerful RF Plasma

Seeds of common bean (Phaseolus vulgaris L.), of the Etna variety, were treated with low-pressure oxygen plasma sustained by an inductively coupled radiofrequency discharge in the H-mode for a few seconds. The high-intensity treatment improved seed health in regard to fungal contamination. Additionally, it increased the wettability of the bean seeds by altering surface chemistry, as established by X-ray photoelectron spectroscopy, and increasing surface roughness, as seen with a scanning electron microscope. The water contact angle at the seed surface dropped to immeasurably low values after a second of plasma treatment. Hydrophobic recovery within a month returned those values to no more than half of the original water contact angle, even for beans treated for the shortest time (0.5 s). Increased wettability resulted in accelerated water uptake. The treatment increased the bean radicle length, which is useful for seedling establishment in the field. These findings confirm that even a brief plasma treatment is a useful technique for the disinfection and stimulation of radicle growth. The technique is scalable to large systems due to the short treatment times.

Impact of Melatonin on Growth and Antioxidant Activity of Cicer arietinum L. Grown under Arsenic Stress

The ability of melatonin to regulate number of physiological and biochemical processes under different environmental stresses has been widely studied in plants. So, this investigation was done to study the protective roles of melatonin on Cicer arietinum L. grown under arsenic stress. Subjecting Cicer arietinum L. seeds to arsenic stress caused significant decreases in germination percentage, radicle growth, biomass accumulation, protein content and activities of antioxidant enzymes. On the other hand, melatonin treatment significantly increased growth parameters and protein quantity via improving antioxidant enzyme systems as compared with their corresponding untreated controls.

Allelopathic potential of Malaysian invasive weed species to control weedy rice (Oryza sativa f. spontanea Roshev)

In laboratory bioassay, we studied the effects of methanolic extracts of 30-Malaysian invasive weed species (9 families) on the seeds survival rate and seedlings growth of Weedy rice (Oryza sativa f. spontanea Roshev). Five concentrations [6.25, 12.5, 25, 50, 100 (g L-1)] of methanolic extracts were used and control was distilled water. The Weedy rice seeds survival rate and seedlings growth (radicle and hypocotyl length) of 7-day-old seedlings were reduced by the increasing concentrations of extracts than control. Probit analysis and the concentrations required for 50% inhibition (EC50) showed that radicle growth was more suppressed than seeds survival rate and hypocotyl growth. Among the tested weed species, Parthenium hysterophorus L., Cleome rutidosperma DC. and Borrreria alata (Aubl.) DC. proved strongly allelopathic and thus, could be used to develop eco-friendly herbicides.

Tryptophan derivatives regulate the seed germination and radicle growth of a root parasitic plant, Orobanche minor

Root parasitic plant germination is induced by the host-derived chemical, strigolactone (SL). We found that a major microbial culture broth component, tryptone, inhibits the SL-inducible germination of a root parasitic plant, Orobanche minor. l-tryptophan (1a, l-Trp) was isolated as the active compound from tryptone. We further found that l-Trp related compounds (1b-11), such as a major plant hormone auxin (8, indole-3-acetic acid; IAA), also inhibit the germination and post-radicle growth of O. minor. We designed a hybrid chemical (13), in which IAA is attached to a part of SL, and found that this synthetic analog induced the germination of O. minor, and also inhibited post-radicle growth. Moreover, we found that N-acetyl Trp (9) showed germination stimulating activity, and introduction of a substitution at C-5 position incresed its activity (12a-12f). Our data, in particular, the discovery of a structurally hybrid compound that has two activities that induce spontaneous germination and inhibit subsequent radical growth, would provide new types of germination regulators for root parasitic plants.