Iranian Journal of Seed Research

Extended Abstract
Introduction: Sweet corn (Zea mays var. saccharata) is a corn variety that is distinguished from other varieties due to the presence of genes that affect starch production in the endosperm. Given that the most of plants including sweet corn face with problems such as non- uniform germination and poor seed emergence in the early stages of germination. Thus, the use of organic stimulants is one of the ways to reduce the harmful effects of non-biological stresses, increase seed germination, uniform appearance and increase their yield and quality. The present study was carried out to investigate the effect of different concentrations of chitosan on seed germination and some biochemical traits of sweet corn under osmotic potential conditions.
 Materials and Methods: To investigate the effect of chitosan and osmotic stress on germination and biochemical parameters of sweet corn, a factorial experiment was conducted in a completely randomized design with four replications at the Seed Technology Laboratory, Faculty of Agriculture, Yasouj University in 2017. The first factor was osmotic stress at 0, -3, -6, and -9 bar osmotic potentials and the second factor was pre-treatment at five levels of chitosan zero, 0.25%, 0.5%, 0.75% and 1% and one level of distilled water. The seeds were immersed in the desired solutions of chitosan for 3 hours at 25 °C and under dark conditions, and then the pre-treated seeds were germinated under standard germination condition. In each petri dish, 25 seeds were placed on a filter paper and osmotic potential was applied using polyethylene glycol 6000. Seed germination was carried out in the germinator at 25 ± 1 ° C for 7 days under dark conditions. The germination traits and biochemical traits were measured according to standard methods.
Results: Osmotic stress reduced germination percentage and germination rate, seedling vigour length index, germination uniformity coefficient, allometric coefficient, and soluble protein content and also increased the mean germination time, proline, soluble sugar content and hydrogen peroxide. Pre-treatment of seeds with a concentration of 0.5% chitosan increased protein, proline, and soluble sugars content at all osmotic stress levels. At the osmotic stress levels, the highest and lowest levels of hydrogen peroxide respectively were observed in 0.5% chitosan treatment and distilled water treatment. The results showed that pre-treatment with 0.5% chitosan increased germination percentage and rate and seedling vigour length index, and also reduced the mean germination time and malondialdehyde. Pre-treatment of seed with zero and 1% chitosan led to reduction in some of the germination and biochemical traits in comparison with 0.25, 0.5, and 0.75% chitosan.
Conclusions: The results showed that seed treatment with 0.5% chitosan could reduce the harmful effects of osmotic potential on some germination and biochemical traits in sweet corn seedlings and improve seedling growth.
 
Highlights:
1-Chitosan increases the germination percentage and germination rate.
2-Chitosan increases soluble sugars, proline, and soluble protein.
3-Chitosan reduces the amount of malondialdehyde and hydrogen peroxide.

Extended abstract
Introduction: Salinity is the most significant environmental stress that limits plant productivity by affecting morphology, physiology, and biochemistry of plants, especially in semi-arid and arid regions. Salinity disrupts and eventually delays seedling growth by delaying seed germination and reducing the germination rate. Seed priming stands out as a quick, easy, low-cost, and effective strategy for improving germination, seedling growth parameters, and overall plant defense against abiotic stresses in many crops. It is defined as the pre-sowing seed treatment during which seeds are immersed in water or chemical solutions and are dry until further use. The aim of this study was to assess the effect of priming with sodium nitroprusside on germination indices and biochemical traits in rice seedlings under salinity stress.
Materials and Methods: This experiment was conducted as a factorial based on a completely randomized design with three replications at the University of Mohaghegh Ardabili in 2023. Experimental treatments included four salinity levels (0, 50, 100, and 150 mM) and three levels of sodium nitroprusside (0, 40, and 80 µM).
Results: The results showed that salinity reduced germination and growth indicators including mean daily germination (MDG), germination coefficient (GC), allometric coefficient (AC), radicle length (RL), pedicel length (PL) and seedling length (SL), as well as radicle and pedicel fresh and dry weight (RFW, PFW, RDW and PDW), but seed pretreatment with different levels of sodium nitroprusside, especially the level of 80 µM, improved these traits. Salinity reduced the seedling moisture percentage (SMP), so that the highest SMP (70.13%) was observed in the control treatment. The highest daily germination rate (DGR) and malondialdehyde content (MDA) were observed at a salinity of 150 mM. Priming decreased DGS and MDA, so that the lowest DGS (0.08) and MDA (0.159 mM g^-1 FW) were obtained in priming with 80 μM sodium nitroprusside. Also, salinity decreased the activity of the α-amylase enzyme, so the lowest α-amylase activity (7.93 mg g^-1 FW seed) was obtained in the control (distilled water) and at a salinity of 150 mM.
Conclusions: The results showed that seed treatment with sodium nitroprusside at 80 µM is the most effective method to improve rice germination and biochemical traits under salinity stress. It can reduce the harmful effects of salinity on some traits in rice seedlings and improve seedling growth.

Highlights:

1. Seed priming using sodium nitroprusside improved the germination indices of rice seeds under salinity.
2. Priming with sodium nitroprusside decreased MDA content and increased α-amylase activity.
3. The concentration of 80 µM sodium nitroprusside showed a better effect on germination indices and biochemical characteristics.

Extended abstract
Introduction: Chemical compounds in plants include primary or secondary compounds. The allelopathic compounds are mainly of the secondary type, which are released by ways such as leaching, decomposition of plant residues, volatilization, and root exudation. Plants with allelopathic properties have a negative or even positive effect on the germination and growth of other plants by releasing substances in their surroundings. These effects depend on the type of organ, concentration, plant growth location, physiological maturity, etc.
Materials and Methods: An experiment was conducted to evaluate the allelopathic potential of wild barley (Hordeum spontaneum) weed on some germination, morphophysiological, and biochemical characteristics of a reference plant sensitive to allelochemicals, cress (Lepidium sativum), in 2021. This experiment was conducted in the form of a completely randomized design with three replications. The treatments included different concentrations of H. spontaneum aqueous extract at 11 levels (0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100%).
Results: The results showed that different concentrations of H. spontaneum aqueous extract had a significant decreasing effect on the percentage and rate of seed germination, radicle and shoot length, seedling length vigor index, radicle and shoot dry weight, as well as photosynthetic pigments (i.e., chlorophyll a, b, total, and carotenoids) of cress. Their effectiveness was dependent on the concentration threshold of the aqueous extract. In contrast, the content of proline amino acid , soluble sugars, ion leakage, catalase activity, guaiacol peroxidase enzymes, the concentration of malondialdehyde, and phenolic compounds showed an increasing trend compared with the control. In most cases, the highest increase in these compounds was obtained at the 100% aqueous extract concentration of H. spontaneum. This indicates the oxidative stress and high cytotoxicity caused by harmful compounds present in the aqueous extract of H. spontaneum.
Conclusions: According to the results of this experiment, it can be decucted that the aqueous extract of H. spontaneum, due to its allelopathic properties, prevented germination and seedling growth of L. sativum. Therefore, according to the proof of the harmful effect of H. spontaneum and its high biomass, it may be possible to introduce the bioactive compounds present in this plant for the production of environmentally friendly herbicides or even the potential to produce new formulations of synthetic herbicides in case its positive effect on other species is proven.

Highlights:

1. The difference in the effect of different concentrations of Hordeum spontaneum weed aqueous extract on germination and seedling growth of a reference plant sensitive to the allelochemicals, Lepidium sativum, is related to their concentration threshold.
2. The significant decrease in germination characteristics and photosynthetic pigments of L. sativum indicates the intensity of oxidative stress caused by the harmful compounds in the aqueous extract of H. spontaneum.
3. The allelopathic characteristics of H. spontaneum weed can be a suitable candidate for the production of biological herbicides.