مجله پژوهشهای گیاهی (زیست شناسی ایران)
سال سی و ششم شماره 4 (زمستان 1402)

Light-emitting diodes (LEDs) can be used as a useful alternative to in vitro culture of various plant species, which not only accelerates plantlet growth and development but also reduces illumination costs. Here, the effects of different light treatments (fluorescent (control), blue LED, red LED, 70% blue/30% red, 70% red/30% blue and SMD lights) on protocorm-like bodies (PLB) growth and development, photosynthetic pigments, antioxidant enzyme activity, and the content of protein and soluble sugars of Phalaenopsis pulcherrima obtained from protocorm explants on ½ MS (Murashige and Skoog) or VW (Vacin and Went) with or without growth regulators (IBA+BAP) were evaluated. The results showed that LED and SMD treatments improved the induction and growth of PLBs compared to fluorescent treatments, which had the highest numbers of PLBs and biomass under blue and red LED light, respectively. Under the same light treatments, the highest numbers of PLBs and biomass were obtained on ½ MS+IBA+BAP. Compared to fluorescent light, LED and SMD lights increased the content of photosynthetic pigments. Among the culture media used, the highest content of photosynthetic pigments was observed on ½MS+IBA+BAP. Compared with fluorescent treatment, a significant increase in the activity of antioxidant enzymes and the content of protein and soluble sugars was observed under LED and SMD treatments, with the largest increase recorded under blue LED. Therefore, our results proved that the use of LEDs can be a practical and effective way to increase the induction of PLBs and improve photosynthetic pigments in the in vitro culture of P. pulcherrima.

Source and sink allocation organs play an important role in the balance between sugar production and consumption. In this experiment, the metabolism of carbohydrates and the activities of enzymes related to them were investigated in young leaves (sink), old leaves (source) and stems of Melissa plant after several plants were treated with smoke. The results showed that with the increase ofsmoke time the fructose sugars in the source and sink decreased. The amount of sucrose decreased in the stem and the source and increased in the sink. The amount of verbascose, glucose, and fructose sugars increased in the source and decreased in the sink and stem. The amount of starch, raffinose, maltose increased in the sink and decreased in the source and stem. Comparing the change process of starch and sucrose, smoking increased the amount of sucrose in the destination and decreased the amount of starch. In fact, soot pollution has increased the amount of soluble sugar in the destination. The regression between SPS enzyme activity and sucrose synthesis in sink and source showed a correlation of R2=0.52 and R2=0.18, respectively. Therefore, the level of SPS enzyme activity in old leaves is higher than that of young leaves, or it is due to the lack of reduction of sucrose in the sink. The activity level of AI acid invertase enzyme, which is involved in breaking down sucrose, increased in the source,, which is involved in breaking down sucrose, increased in the source and destination.

Citrus sinensis cv Thomson Navel and Citrus limon cv Lisbon are known as relatively resistant and cold-sensitive garden products. Thus, in the present study attempts are made to investigate the vulnerability of Thomson oranges and Lisbon lemons to cold stress under controlled environmental conditions compared to treatment temperatures (4, -4 and -8 °C). This factorial experiment was conducted according to a completely randomized design. The ANOVA results showed that the temperature/cultivar interaction can significantly affect some traits such as lipid peroxidation, superoxide dismutase, ascorbate peroxidase, total flavonoids, ion leakage, chlorophyll a, carotenoids, total chlorophyll and LT50 (P> 0.001). However, the catalase/chlorophyll b interaction was found to be significant at p= 5%. The highest levels of ion leakage (59.65%), lipid peroxidation reaction (0.77 µg g−1 FW MDA) in lemon and catalase and superoxide dismutase (33.43 µmol•g−1 FW and 160.3.3 μmol g −1FW min respectively) in orange was recorded at -8 °C. In contrast, the highest levels of ascorbate peroxidase (39.7 µg g−1 FW) was recorded in lemon and total flavonoids (32.48 mg g−1 FW of catechin) was recorded in oranges at 4 °C. in the present study, different reactions were also observed at different temperatures. Oranges showed higher resistance to cold compared to lemons. As for the measured traits, however, oranges were mostly ranked higher than lemons. Exposure of genotypes to cold stress led to an increase in malondialdehyde.

The aim of this study was to investigate the effect of chitosan on ZmPIP gene expression, growth parameters and physiological characteristics of rapeseed under salinity stress which was performed in a factorial experiment based on a completely randomized design with 3 replications. For this purpose, rapeseed seedlings was treated with different concentrations of salinity (0, 50, 100, 150 mM) and chitosan (0, 5, 10 mg/L). ZmPIP gene expression was evaluated using Real Time PCR, germination percentage and speed, length, fresh and dry weight of root and shoot, relative leaf water content, electrolyte leakage and sodium and potassium contents. In salinity stress, treatment with chitosan increased the expression of ZmPIP gene so that the highest gene expression was at 50 and 100 mM salinity with 5 mg / l chitosan. In treared plants with salinity increased percentage and germination rate, fresh and dry length and weight of root and shoot, relative leaf water content and potassium content especially at concentrations of 100 and 150 mM with chitosan compared to salinity at the same concentration and electrolyte leakage and relative water content and sodium content reduced. It is likely that chitosan has increased plant tolerance under salinity stress by maintaining the relative leaf water content, increasing potassium and growth of shoot and root and reduce the negative effects of stress on rapeseed and increase plant resistance

Saintpaulia ionantha is one of the most important commercial plants with unique natures in color and shape, which has made it, the most popular indoor plant. Genetic engineering would be one of the most widely used technique for plant breeding. However, these methods are based on tissue culture techniques to create and produce novel cultivars. It also seems that successful direct regeneration constitutes the first step in developing strategies for genetic manipulation. This study aimed to determine the influence of MS medium supplemented with various amounts of growth regulators including IAA, BA, TDZ on direct organogenesis of two African violet cultivars (Little Maya and Grinia) from leaf and petiole explants, using the response surface methodology. Treatments applied on both cultivars resulted in the induction of regeneration in leaf and petiole explants. However, leaf explants showed more organogenic potential than petioles. The potential of direct organogenesis of both cultivars was not significantly different from each other in the same explants. Although, predicted model by historical data design which were investigated practically in 3 replications indicated that, the Little Maya cultivar had the highest percentage of direct organogenesis. In this regard, medium containing BA 0.05 mg/l + TDZ 0.01 mg/l + IAA 1 mg/l was more successful in inducing direct organogenesis in both cultivars. Therefore, according to the obtained model, it seems that the direct organogenesis potential was affected by the interaction of hormones and explants, which could also result from the genotypes.

Knowledge of medicinal plants and their biochemical properties provide basic steps for the optimal use of their compounds and medicinal properties. In this study, the content of phytochemical compounds and antioxidant activity of roots, leaves and fruits of Caper (Capparis spinosa L.) were investigated in two regions of Razo Jarglan and Esfarayen located in North Khorasan province. Anthocyanin content and phenolic and flavonoid compounds were determined by laboratory assays and antioxidant capacity of various plant organs was done by DPPH free radical scavenging test. The results showed that the phenol and flavonoid content of fruit extracts of Caper plants grown in Esfarayen region with 35.1 (mg GA/g D.W) and 8.1 (mg Q/g D.W) were the highest, Compared to other groups respectively. The highest anthocyanin content was obtained from the leaf extract of Caper plants in Esfarayen region. The results also showed that the highest antioxidant activity was observed in the fruit extract of Caper plants in Esfarayen district and the lowest amount was observed in the leaf extract of Caper plants in Razo Jarglan district. All extracts of different parts of the Caper plant show different levels of antioxidant activity and due to the appropriate antioxidant effects of this plant, it is expected that it can be used in food, medicine and health products.

Recently, melatonin was proved to be a candidate hormone that could increase the cold and heat stress of the plant. Cold stress is important abiotic stress for plants in nature. In this study, in order to investigate the effect of exogenous application of melatonin on some physiological traits related to cold stress on the strawberry cultivar ‘Paros’ a pot experiment with three replications was performed in a completely randomized design. Strawberry plants pre-treated with 100 μM melatonin were subjected to freezing stress treatment (-9◦C for 3 h without cold acclimation) after two weeks some physiological traits (proline, carbohydrate, total flavonoid, chlorophyll content, ion leakage, hydrogen peroxide, content of water, malondialdehyde, and total phenol) related to cold stress in plant leaves were measured. The results showed that melatonin treatment has a significant effect on some physiological traits (proline, carbohydrate, total flavonoid, chlorophyll content, ion leakage, and hydrogen peroxide) in the strawberry plant under freezing stress. Proline, carbohydrate, total flavonoid, and chlorophyll content were significantly enhanced, and a significant reduction was observed in ion leakage and hydrogen peroxide in melatonin-pre-treated plants. In this experiment, melatonin treatment had no significant effect on the relative water content, malondialdehyde, and total phenol. According to the results of our study, exogenous application of melatonin may be effective to improve freezing tolerance in strawberry plants after two weeks of application.