نشریه فیزیولوژی محیطی گیاهی
پیاپی 62 (تابستان 1400)

Citrus fruits contain numerous beneficial bioactive compounds including vitamin C, phenolic compounds, flavonoids, carotenoids, and sugars which have high nutritional and antioxidant value. Some factors such as the canopy position of the fruit and fruit size affect the quality and quantity of these compounds. The aim of this study was to investigate the effect of canopy position and fruit size on morphophysiological and biochemical properties of Thomson orange fruit. In the first experiment, fruits with medium and uniform size were harvested from inside and outside canopy positions of the tree. In the second experiment, after harvest the fruits were grouped into three sizes of small, medium, and large. Traits such as weight, volume, length, and width of fruit, skin color, skin thickness, extract content, dry matter percentage, TA, TSS, TSS/TA, total chlorophyll and total carotenoids, antioxidant capacity, phenolic acid content, vitamin C, total sugars, and reducing sugars were evaluated on the peel and pulp of fruit along with a panel test. Results revealed that fruit volume, peel thickness, TSS/TA, a* value, CCI value, peel antioxidant capacity, and peel total sugars were higher in the fruits from the external canopy position while TA, L*, C*, h°, and b* in the fruits from internal canopies were significantly higher. Fruit size had a significant effect on physical parameters of fruit, CCI, h°, juice, and dry matter while it did not affect the quality and chemical traits of fruit. The results of this study showed that orange fruit with a position outside the crown and a large size has a significant increase in extract content, actual volume, average fruit diameter, aroma, taste, and sweetness compared to the position inside the crown with a small size.

Iris germanica L. is one of the most majestic and popular perennials used in landscape. The aim of this study was comparison of salinity tolerance in three new hybrids genotypes of Iris germanica L. inoculated with mycorrhizal fungi. Treatments consisted of four levels of water salinity (1, 4, 8, and 12 ds/m), three levels of mycorrhizal fungi (0, 15, and 25 g/kg) and three promising genotypes of iris (OPRC-122, OPRC-125, and OPRC-S54). Experiment was conducted based on a factorial and completely randomized design (CRD) with three replications in 2018-2019 in Ardakan University. Some morphological and physiological traits were evaluated. Application of 25 g/kg mycorrhizal fungi at 12 dS/m salinity level increased root length in OPRC122 and OPRCS54 genotypes by 83.77% and 65.38%, respectively compared with control. In OPRCS54 genotype under 8 dS/m salinity, using 25 g/kg mycorrhizal fungi increased the ratio of shoot to root fresh weights by 52.83%. Application of 15 and 25 g/kg mycorrhizal fungi at 12 dS/m salinity in OPRC122 genotype increased P uptake by 341% and 480%, respectively. The use of 15 g/kg mycorrhizal fungi in OPRC125 genotype reduced Na uptake by 32% at 12 dS/m salinity. In OPRCS54 genotype under the same level of salinity, application of 15 and 25 g/kg mycorrhiza fungi decreased sodium uptake by 63.51% and 55.24%, respectively. In general, using mycorrhizal fungi in all three genotypes at salinity level of 8 dS/m reduced the effect of salinity and increased plant yield.

Seeds deteriorate and become aged during storage so that the rate of this process depends on the temperature and seed moisture content. This experiment was conducted to study changes in the activity of antioxidant system of cottonseeds during deterioration. An Accelerated aging test was used to create different levels of deterioration. Cottonseeds were incubated at 43 ℃ for 0, 48, 96, 144, and 192 hours and 100% relative humidity. Results showed that the membrane electrical conductivity, lipid peroxidation, and hydrogen peroxide increased with lengthening of deterioration periods. Increase in hydrogen peroxide was accompanied with decreased activity of catalase and the increased activity and content of peroxidase and ascorbic acid, respectively, which indicates declined activity of catalase due to aging as compared with peroxidase activity and ascorbic acid content. Also, with an increase in the period of deterioration, percent, rate, and uniformity of germination reduced. In general, the study indicated that the oxidative stress due to the accumulation of reactive oxygen species and the reduction of the antioxidant system is one of the main reasons for cottonseed viability loss during storage.

Having carcinogenic and toxic effects, aromatic hydrocarbons cause serious damage to the environment and living organisms. These compounds are mainly discharged into the soil. For the remediation of contaminated soils, biological methods utilizing the efficient microorganisms isolated from the oil-contaminated soils as well as resistant plants are preferred. The aim of this study was to assess the effect of Conocarpus erectus and Pseudomonas aeruginosa on the removal efficiency of polycyclic aromatic hydrocarbons (PAHs) from contaminated and saline soils of the salt separation pond of a desalination unit during 275 days under non-laboratory condition. The study was conducted in a factorial experiment with two factors based on completely randomized design with three replications. The factors used in this experiment included four treatment types (plant, bacteria, plant-bacteria cultivated in the soil, and soil with no plant and bacteria (control)) and the concentration of contaminant (Bangestan crude oil) with 5 levels (0, 0.5, 1, 2.5, and 5 wt%). As hydrocarbon concentrations increased at all five levels, the percentage of PAHs removal, the dry weight of roots and shoots, and chlorophyll contents decreased. At 0 and 1 % concentrations, the highest percentages of removal were obtained as 99.43, 59.89, and 57.01 for bacteria-plant treatment and separate bacterial and plant treatments, respectively (p≤0.05). The plant and the bacteria showed almost equal efficiency in the removal of oil hydrocarbons (p≤0.05). Bacterial treatments led to increased chlorophyll content as well as higher dry weight of roots and shoots compared with the treatments without bacteria (p≤0.05). Results indicated that individual treatments of plant and bacteria had a positive effect on the decomposition rate of PAHs. However, the rate was more positively influenced by the synergistic activity of the bacteria and plants (p≤0.05).

To study the effect of interval irrigation and growth regulators on morphophysiological traits of cotton cultivars, an experiment was conducted as a split factorial in randomized complete block design in 2017 and 2018 in Hashemabad Cotton Research Station in Gorgan, Iran. Treatments consisted of intervals of irrigation at two levels (two weeks and four weeks) as the main factor and six-level growth regulator treatments (control, benzyl adenine, abscisic acid, salicylic acid, brassinosteroid, and cycocel) and three cotton cultivars (Golestan, Kashmar, and Shayan) were also considered as sub-factors. The results of this study showed that proline content and relative water content of leaf decreased with water deficit stress. Maximum proline content (3.55 µg/g fresh weight) was obtained from Shayan cultivar with salicylic acid. Benzyl adenine and brassinosteroids increased relative leaf water content. The highest cell membrane stability (2.998%) was observed in Kashmar cotton cultivar and two-week interval irrigation, and Cycocel increased the membrane stability by 15%. Plant height, number of flowers, and number of bolls were affected by growth regulators, irrigation intervals, and cultivars. With increasing irrigation period, plant height, flower number, and boll number decreased in all cultivars, but under drought stress, Golestan cultivar had more flowers and boll number than other cultivars. Cycocel, salicylic acid, and brassinosteroids significantly increased flowering of cultivars at both years and both irrigation intervals. Benzyl adenine and brassinosteroids increased plant height more than 7% and abscisic acid, cycocel, and salicylic acid decreased plant height compared with control. Application of abscisic acid reduced the number of bolls by 22% compared with the control. Overall, growth regulators, especially cycocel and salicylic acid, increased the morphophysiological traits of cotton cultivars indicating their positive effect on drought tolerance and it could play a role in moderating stress effects under stress conditions.

In order to investigate the effect of mycorrhizal symbiosis and foliar application of salicylic acid on yield and photosynthetic pigments of corn, an experiment was conducted in the form of split plot in a randomized complete block design with three replications during two cropping years 2018-2019 in the research farm of Islamic Azad University, Chalous Branch. Experimental factors included mycorrhiza species (G. mosseae), (G. geosporum), and (G. intraradices) at two levels (no consumption and consumption of mycorrhiza) and salicylic acid at two levels (no consumption and consumption of 1 mM salicylic acid). Results showed that the dual effects of mycorrhiza × year and mycorrhiza × salicylic acid had a positive and significant effect on all studied traits. The highest plant height was obtained in the treatment with G. intraradices and salicylic acid. Also, 1000 grain weight, seed yield, phosphorus, potassium, and nitrogen contents of seeds, and chlorophyll a and b levels were higher in salicylic acid foliar treatment compared with the other treatments. In general, the results showed that mycorrhizal application with salicylic acid spray increased vegetative and reproductive growth. This enhancement is due to the increase in photosynthesis index and, consequently an increase in photosynthetic materials dedicated to the development of reproductive organs, which ultimately improves corn yield.

In order to investigate the effects of foliar and root application of selenium (0 and 20 µM) on some physiological and biochemical parameters of wheat (Triticum aestivum L.) var. Chamran under salt stress (0 and 100 mM NaCl), an experiment was conducted hydroponically based on  a completely randomized factorial design with three replications at Payame Noor university in 2017. Results showed the significant decreases in growth parameters, chlorophyll to carotenoids ratio, and chlorophylls and total protein contents while significant increases were recorded in malondialdehyde, proline, anthocyanin, and total phenol contents of plant shoots under salt stress. Under control condition, both forms of selenium application significantly decreased the root length while increasing the total phenol content. Moreover, significant increases in proline and carotenoids contents were found under foliar application of selenium in control plants. Under salinity stress, foliar application of selenium significantly increased the root length and shoot fresh weight and its application at both forms improved the other growth parameters of plants. Likewise, significant increases in protein and chlorophylls contents of plants by foliar application and soluble sugars and total phenols contents of plants by both forms of application of selenium were attained under salinity. Only foliar form of application of selenium could decrease the malondialdehyde content of plants under salinity stress. According to the findings, selenium application, especially through leaves, played a remarkable role in ameliorating the effects of salt stress in wheat.

Employing biosynthesized nanoparticles plays an important role in increasing efficiency of agricultural practices. In recent years, the use of nanoparticles in plants has been considered as pesticides, protective agents, and nutrients. Viola tricolor belongs to the Violaceae family, which has antibacterial, anticancer, and antiviral properties. In this study, silver nanoparticles were synthesized using silver nitrate and Viola tricolor extract to investigate the effect of different concentrations of silver nanoparticles on the physiologic and biochemical indexes of Viola tricolor. Results showed that different growth parameters including root and stem fresh weight, root and shoot length, and protein content significantly increased under AgNPs. The highest levels of these indices were observed at 0, 10, 50 and 100 ppm silver nanoparticles, respectively. Proline and carbohydrates also increased under different concentrations of AgNPs compared with the control and the highest values of these indices were observed under 100 ppm silver nanoparticles. The contents of secondary metabolites, including phenol and flavonoids, were affected under 100 ppm AgNP showing the highest increase. The maximum increase in the anthocyanin content was observed at 10 ppm AgNPs. Analysis of the antioxidant enzyme activities showed that they increased under all AgNPs concentrations of the study. Increases in the activities of antioxidant enzymes (catalase and glutathione reductase) under AgNPs treatments led to a decrease in MDA content. Based on the results of the current study, silver nanoparticles are suggested as proper stimulants for increased growth and production of antioxidant properties.

Medicinal plants, as important agricultural products, can be considered as the greatest national wealth for any country because of their vital role in promoting national goals for health and also as genetic treasures. Having a diversity of climates, Iran has a great variety of medicinal plants. Detecting the growth status of medicinal plants under drought stress conditions can lead to the cultivation of resistant plants in dry or semidry areas. In the present study, we investigated the morphological and physiological responses of ten ecotypes of the medicinal plant Teucrium polium L. native to southeastern Iran under drought stress. For this purpose, a factorial greenhouse experiment was conducted in a completely randomized design with three replications. In this experiment, moisture treatments of 100, 70, and 40% of field capacity were applied. Analysis of the data showed that the morphological traits under study including stem length and fresh and dry weight of shoots decreased by 5% with increasing drought stress. Drought stress also increased root length, proline content, and phenolic compounds while decreasing chlorophyll a, b, total chlorophyll, and protein contents. The highest resistance to stress was shown by ecotypes growing in Sarcheshmeh and Kuhpayeh regions and the lowest resistance was shown by plants in Shahdad and Anbarabad regions. The results of the study indicated the relative resistance of this plant to drought stress. Therefore, it is a very suitable medicinal plant for cultivation in dry and low water areas of Iran. Among the studied ecotypes, the plants of Sarcheshmeh and Kuhpayeh regions responded 40% better to drought stress conditions and cultivation of these ecotypes in stressed areas can be recommended with more confidence.

Salicylic acid is a plant growth regulator that is involved in regulating physiological processes and the plants’ response to adverse biological conditions such as salinity. In the present study, an experiment was carried out to investigate the effect of different concentrations of salicylic acid, salinity, and the interaction of salicylic acid and salinity on morphological and biochemical parameters in pistachio. Salinity concentrations of 0, 25, 50, 75, and 100 mM and salicylic acid concentrations of 0, 0.5, 1, and 1.5 mM were used in the form of foliar factorial application in a completely randomized design (CRD) under greenhouse condition in 2019. The results of this study showed that salinity reduced shoot and root growth and fresh and dry weights, as well as chlorophyll, carotenoid, and anthocyanin contents while in plants pre-treated with salicylic acid, the effects of salinity on these parameters were modified. Accordingly, it can be concluded that salicylic acid application protects the plant against salt stress.