فصلنامه زیست شناسی گیاهی ایران
سال پانزدهم شماره 4 (پیاپی 58، زمستان 1402)

Heavy metals pollution is increasing due to the excessive use of fertilizers and chemical pesticides in agricultural products. The application of nanoparticles can significantly reduce heavy metal pollution in soil. This research was conducted in the spring of 2022 to investigate the effect of nano-hydroxyapatite (n-HAP) on physiological indices and reduce oxidative stress caused by cadmium (Cd) stress (100 mg/kg of soil) in two grape cultivars (Bidaneh-Sefid and Perlette). The study was conducted factorially based on a completely randomized design in the research greenhouse of Malayer University. After 60 days of Cd stress and the application of n-HAP (1% by weight) in the pots, leaf samples were collected, and physiological indices and antioxidant activity were measured. The results showed that the application of n-HAP in both grape cultivars increased relative water content, chlorophyll, phosphorus contents, and the activity of catalase, guaiacol peroxidase, and ascorbate peroxidase enzymes in the leaves, while it reduced ion leakage. In plants under Cd stress, the highest chlorophyll content was observed in the Bidaneh-Sefid cultivar treated with n-HAP, which was 10.88% higher compared to the Cd-treated control vines. Under Cd stress, the highest relative water content was observed in the Bidaneh-Sefid cultivar treated with n-HAP, which was 4.09% higher compared to the control vines under Cd stress. The increase in ascorbate peroxidase enzyme activity was 15.71% in the Bidaneh-Sefid and 13.04% in the Perlette under Cd stress. Also, under Cd stress, the application of n-HAP led to an increase in leaf total phenol and total flavonoid content of the leaf in two grape cultivars. There was no difference in the content of these two secondary metabolites among the grape cultivars grown under Cd stress conditions. In the plants under Cd stress, the highest proline content was related to Perlette cultivar treated with n-HAP compound, which was 18.78% higher compared to control vines under Cd stress. According to the results of this research, the application of n-HAP in soil can be considered a useful strategy for controlling Cd in soils contaminated with this heavy metal.

The accumulation of heavy metals in the soil due to human activities is one of the most important ecological problems in the world. On the other hand, using plant growth regulators such as melatonin and serotonin is one of the strategies that help reduce the accumulation of heavy metals in plants and improve their tolerance. Based on this, a factorial pot experiment based on a completely random design at 3 levels of Pb heavy metal (0, 2000, and 4000 mg/l) and spraying melatonin and serotonin regulators in a concentration of 100 mM separately in 2 cultivars - RGS00s and Delgan of rapeseed plant was made with 4 replications. The results showed that heavy metal stress has a reducing effect on the shoot fresh and dry weight indices, photosynthetic pigments (chlorophyll a, chlorophyll b, carotenoid), gas exchange (net photosynthesis, transpiration, stomatal conductance, internal CO2). So, the highest traits were observed in the control and the lowest in severe lead stress. Also, with the increase in Pb concentration, the value of Fm, Fv/Fm, and Fv/F0 decreased and the value of F0 and F0/Fm increased in both rapeseed varieties. External application of serotonin and melatonin in moderate and severe stress most of the measured parameters. According to the results obtained from this research, it can be stated that the Delgan variety is more sensitive to lead stress compared to the RGS00s variety, and the use of melatonin and serotonin can improve the growth and photosynthesis parameters and create resistance in the rapeseed plant against heavy metal stress.

The developmental stages of the date palm (Phoenix dactylifera) fruit include Hababouk, Kimri, Khalal, Rutab, and Tamar. The physicochemical characteristics of fruit were investigated in Khenizi, Mordasang, and Halili cultivars at different developmental stages in four cultivation sites. All cultivars' highest levels of size, weight, and moisture were observed in Khalal, and then they decreased. In the Tamar stage, all cultivars had more than 30% moisture showing soft fruits. The highest and lowest levels of fruit weight were recorded in Rudan and Genow respectively. The interaction of developmental stage, cultivar, and site showed the highest fruit weight in the Khalal stage of Halili of Rudan and Minab, followed by the Khanizi cultivar of Bandar Abbas and Minab. The fruits of Halili and Khenizi cultivars showed a high pulp-seed ratio indicating their good quality. Soluble and reducing sugar levels of all cultivars increased during development till Rutab indicating their high energy at harvest time. The highest amount of reducing sugars was found in Halili and Mordaseng, and the lowest in Khanizi. The highest and lowest amounts of reducing sugars were observed in Minab and Genow, respectively. Khenizi is a medium ripening cultivar and can also be used in the Khalal stage. Halili cultivar is one of the slowest ripening cultivars of Iranian dates and is usually harvested in Autumn. The physicochemical characteristics of date palms vary according to maturity, genotype, and habitat. During development, fruit weight, size, and moisture content decreased, but sugar increased.

Purslane (Portulaca oleracea L.) is widespread in various regions around the world. The present study aimed to investigate the effects of different concentrations of salicylic acid, gibberellic acid, and naphthalene acetic acid, as well as the application of mechanical and salinity stresses, on morpho-physiological traits, phenolic compounds, flavonoids, and photosynthetic pigments. Salinity stress at 160 mM NaCl was applied four weeks after seed sowing (seedling stage). Plant growth regulators such as salicylic acid (50 and 100 mg L-1), gibberellic acid (50 and 100 mg L1), and naphthalene acetic acid (130 and 200 mg L-1) and control treatment (distilled water), were sprayed on the leaves during the vegetative stage with two intervals 14 days apart. Wounding treatment was applied eight weeks after sowing (beginning of the reproductive stage) and then all plants were harvested after 24 h. The highest dry weight of the aerial parts and roots was related to the external application of 100 mg L-1 salicylic acid and the control treatment, respectively. Salinity, wounding, and external application of growth regulators significantly increased cell membrane stability and the content of photosynthetic pigments. The highest total phenol and flavonoid content was associated with the 50 mg L-1 gibberellic acid and 160 mM salinity stress, respectively.  It seems that the increased activity of enzymes involved in anabolic processes, particularly phenylalanine ammonia-lyase, plays a key role in enhancing phenolic and flavonoid content.

This research aimed to investigate the nutrient uptake and morphophysiological characteristics of Stevia rebaudiana under biofertilizers and methyl jasmonate (MJ) application during drought stress. A factorial experiment, based on an randomized complete block design (RCBD) with three replications, was conducted in the research greenhouse of Yasouj University in 2021. The first factor included three irrigation levels after 20%, 40%, and 60% depletion of available soil water. The second factor comprised the application of Funneliformis mosseae, Bacillus subtilis, and the control, while the third factor evaluated foliar application (75 µM) and non-application of MJ. Drought stress at 40% and 60% water depletion significantly reduced nitrogen and phosphorus content, plant height, number of leaves, lateral branches, and root and shoot dry weight compared to 20% water depletion. However, root colonization (tripled), soluble sugar content (85.41%), catalase activity (12-fold), and leaf potassium content (73.67%) increased under drought. Biofertilizers enhanced most of these traits across all stress levels, except plant height and shoot dry weight. Methyl jasmonate significantly improved leaf nitrogen, phosphorus, potassium, soluble sugars, catalase activity, number of leaves, lateral branches, and root dry weight but did not significantly impact root colonization, plant height, or shoot dry weight. Overall, biofertilizers were effective in mitigating drought stress.

Plants employ various defensive strategies to cope with heavy metal stress in their growing environment. In this study, proline content, antioxidant enzyme activities, and phenolic compound levels were analyzed in saffron corms exposed to varying concentrations of cadmium stress. Saffron corms were cultivated under cadmium stress at concentrations of 0, 0.25, 0.5, 1, 2, 5, 10, and 20 mM, and samples were collected on days 0, 5, 10, 20, and 30 after cultivation. Antioxidant enzyme activities, proline levels, and phenolic content were measured. Statistical analysis was performed at a significance level of P < 0.05 using SPSS software. The results revealed significant increases in the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), polyphenol oxidase (PPO), guaiacol peroxidase (GPX), phenylalanine ammonia-lyase (PAL), as well as in proline content and phenolic compound accumulation, in response to cadmium treatments. The activity responses of PPO, CAT, APX, PAL, and GPX enzymes followed a biphasic pattern, while phenolic compound accumulation exhibited a linear regression trend. In contrast, the activities of SOD and proline accumulation conformed to a flattened exponential function. Maximum activities of PPO, CAT, APX, and PAL enzymes were observed at a cadmium concentration of 10 mM in corms harvested after 30 days of stress exposure. Similarly, the highest SOD activity and proline accumulation were recorded in 30-day-old corms, with phenolic compound accumulation significantly increasing with higher cadmium concentrations, albeit with varying rates depending on the duration of exposure. The observed changes in enzyme activities during growth suggest activating regulatory mechanisms in saffron to mitigate cadmium stress. The antioxidant roles of enzymes, proline, and phenolic compounds are critical in Safran’s response to cadmium-induced stress. Given that high cadmium levels induce the production of reactive oxygen species (ROS), the saffron plant enhances the synthesis of antioxidant enzymes to neutralize destructive radicals effectively.