Iranian Journal of Seed Research

Extended Abstract
Introduction: Plants release much of bioactive chemicals from different parts such as leaves, stems and roots through different mechanisms to their surrounding environement. These biologically active chemicals are often referred to as "allelochemicals". Allelopathic compounds play a major role in reducing germination and the growth of crops.
Materials and methods: In this study, the effect of leaching on the reduction of phytotoxicity effect of soybean, black cumin, dragonhead and dill was investigated on the emergence and early growth of canola (Brassica napus L.). The experiment was conducted as factorial based on a completely randomized design with four replications in 2016. Treatments included four previous crop residue (soybean, black cumin, dragonhead, and dill), and three levels of leaching (without leaching, one-time leaching, and two-times leaching). The leaching-free treatment (control) was sub-irrigated to maintain the uniformity of environment moisture. Five days after the first leaching, the two leaching treatment was irrigated again. Five days after the second leaching, when the soil moisture was suitable for seed planting, 10 seeds of canola were cultivated in each pot at a depth of 3 cm of soil. After three weeks seedlings of canola were removed from the pot and the traits were measured.
Results: The results showed that the growth characteristics of canola, except root length, were affected by the residues of the previous crop. In non-leaching conditions, the residue of the four plants reduced the rate and amount of canola emergence, and the greatest reduction in canola emergence was recorded for the application of black cumin residue (7.5%). In the leaching conditions, the length of canola leaves increased, which was higher in the twice leaching treatment. This trend shows that as the amount of leaching frequency increased, it is highly likely that more inhibitiing materials leave the soil and conditions become suitable for canola germination and growth.. The highest dry weight of canola root was observed in one-time leaching treatment. The dry weight of canola leaf grown in dill and soybean residues was increased as a result of one-time leaching, whereas the dry weight of canola grown in black cumin and dragonhead residues showed a higher increase in two-times leaching. Results show that four studied plants have canola growth inhibiting compounds and leaching can ameliorate this effect. The response of canola in the soil containing black cumin and dragonhead residues is higher in two-times leaching, and in the soil containing plant residues dill, one-time leaching is sufficient. In soils containing soybean residue, the response index was almost similar in case of one and two-times leaching.
Conclusion: Generally, the results showed that the application of leaching before planting canola reduced the inhibitory effects of plant residue on germination and growth of canola. Therefore, it is suggested that in the agricultural ecosystems in which canola is present in crop rotation, cultivation of canola must be avoided in presence of soybean, black cumin, dragonhead, and dill residue to eliminate their inhibitory effects on canola growth. In areas with water restriction, autumn rainfall can act as leaching and reduce the effect of allelopathic compounds. In case leaching is not possible, cultivation of canola inside the residue of these plants must be avoided.
 
 
Highlights:
1-Leaching can reduce the effect of allelopathic compounds.
2- Allelopathic compounds of some plants such as black cumin showed better response to two-times leaching.

Extended Abstract
Introduction: Iranian oak has the largest forest habitat in the country and has a high position in terms of economy and protection. Recent studies have confirmed the positive effects of carbon nanotubes on the germination and organ growth of herbaceous and woody species. Nanotechnology is an evolving field in all periods of human life and various research is done to use nanomaterials in different fields. Nanotechnology can provide a good medium for the production of plants with suitable characteristics or provide better growth conditions for plants. The aim of this study was to investigate the effect of carbon nanotube treatments, calcium chloride 1% and potassium nitrate 1% on the germination traits of Iranian oak seed (Quercus brantii Lindl).
Materials and Methods: Treatments included carbon nanotubes at five levels (concentrations of 10, 25, 50, 75, and 100 mg/l) for six hours, 1% calcium chloride for 48 hours, potassium nitrate for hours 24 hours and control treatment, which were primed without using any materials and germination traits were tested on them.
Results: According to the results, carbon nanotubes affected germination traits, so that Iranian oak seeds at a concentration of 75 mg/l had the highest germination percentage and rate, and primed seeds with a concentration of 100 mg/l had the highest mean germination time. The lowest germination percentage, speed and mean germination time were related to control seeds.
Conclusion: The results showed that carbon nanotubes with 75 mg/l had the most positive effect on germination traits. Therefore, from an economic point of view, the use of this concentration is recommended for priming oak seeds.

Highlights: