growth regulator

Thyme (Thymus vulgaris L.) is a perennial plant that belongs to Lamiaceae family, and native to the Mediterranean regions. Thyme is used in the medical, cosmetic and food industries due to its unique aroma and taste. The yield of thyme can be affected by environmental factors and agricultural management. Harvest cutting is one of the important factors determining the quantitative and qualitative characteristics of the thyme. It has also been reported that exogenous application of plant growth regulators at low concentrations has led to yield improvement. Cytokinins (CKs) are one of the five main types of plant growth regulators (PGRs) that affect plant growth and development. In addition to enhancing cell division and growth, CKs also prevent plant aging by inhibiting the breakdown of chlorophyll, nucleic acids, proteins, and other substances. CKs play a role in the transport and accumulation of photosynthesis products and affect the activity of enzymes. CKs also stimulate the growth of lateral branches, too. This study was conducted to investigate the effect of foliar spraying of cytokinin (benzylaminopurine) during harvest cuttings on the essential oil production and growth of thyme plant.

This experiment was carried out at the research farm of Razi University, Kermanshah, Iran (Longitude 47°, 9' east and latitude 34°, 21' north, 1319 m above sea level) during three consecutive years of 2017, 2018 and 2019. The research was conducted as a factorial experiment based on a randomized complete blocks design with three replications. The first factor was the harvest cutting (late June and late September) and the second factor was the concentrations of cytokinin (0, 100, 200 and 400 μM BAP). The measured traits included plant height, stem diameter, number of branches, leaf, stem and total dry weight, percentage and yield of essential oil. The analysis of variances (ANOVA) of data was performed using SAS ver.9 software and the means comparison was done using LSD test at 5% probability level.

The results of analysis of variance showed that the effect of harvest cutting on the traits of plant height, stem diameter, number of branches, leaf, stem and total dry weights and essential oil yield was significant, but its effect on the essential oil percentage was not significant. Also, the effect of foliar spraying of BAP was significant on all the mentioned traits. The interaction effect of harvest cutting × BAP spraying was significant on the number of branches, dry weight of leaves and stems, total dry weight and essential oil yield. A comparison of means showed that the highest plant height, number of sub-branches, leaf dry weight, stem dry weight and total dry weight (4355 kg ha-1) were obtained by foliar spraying of 400 µM BAP. The percentage of essential oil increased with the increase of BAP concentration. The highest essential oil (2.35%) was obtained by foliar spraying of 200 μM BAP. The highest and lowest essential oil percentage were obtained in 2020 and 2018 experiments, respectively. Also, the yields of essential oil were different in different cuttings under the influence of BAP foliar application. The increasing of the essential oil yield in the first harvest was higher compared to the second harvest. Foliar spraying of 400 μM BAP in the first harvest produced the highest essential oil yield (59.95 kg ha-1).

In general, the results of this study indicated that cytokinin spraying during the first harvest significantly influenced on the enhancement of traits such as plant height (16%), number of lateral branches (59%), leaf dry weight (200%), total dry weight (194%), and essential oil production (108-217%) in thyme. Additionally, as the plant aged (in the third year of the experiment), this enhancement in essential oil production was more. To enhance essential oil yield and vegetative growth of thyme, it is recommended to apply 400 µM cytokinin spraying during the first harvest.

Water deficiency is an effective method to optimize water consumption, particularly in arid and semi-arid regions, making it a highly desirable approach for reducing water use. Additionally, growth regulators can serve as a supplementary strategy for plants under water deficiency conditions. This research evaluated the effects of yeast extract and 24-epibrasinolide under various irrigation conditions. It was conducted as a factorial split-plot experiment based on a randomized complete block design with three replications. The treatments included different irrigation intervals (8, 12, and 16 days), spraying of yeast extract (0 and 12 g/L), 24-epibrassinolide (0, 5, and 10 μM). During the 12 and 16-day irrigation periods, seed yield decreased by 21.80% and 25.61%, respectively, compared to the 8-day irrigation period. However, foliar spraying with 10 μM 24-epibrassinolide and yeast extract increased seed yield by 10.14% and 20.28%, respectively. Additionally, total chlorophyll content decreased by 15.71% and 47.54% during the 12 and 16-day irrigation periods compared to the 8 days. The application of 10 μM 24-epibrassinolide along with yeast extract increased chlorophyll content by 57.69%. In the 16-day irrigation cycle, the activities of ascorbate peroxidase and catalase enzymes increased by 314.63% and 194.73%, respectively, using 10 μM brassinolide and yeast extract. Additionally, the levels of proline, flavonoid, and malondialdehyde increased by 52.85%, 109.89%, and 96.33%, respectively, compared to the 8-day irrigation period. This research demonstrated that applying 12 g per liter of yeast extract combined with 10 μM brassinolide effectively increases seed yield and mitigates the impact of low irrigation in cowpeas

Periwinkle herb, with the scientific name (Catharanthus roseus (L.) G.DON), is one of the most important medicinal plants globally. Besides having aesthetic features and ornamental applications, the plants’ leaves and root are rich in very important alkaloids. It is used in the chemotherapy of various cancers and the treatment of hypotension.

In order to investigate the effect of growth regulator and spraying by zinc and magnesium nanoparticles under the conditions of drought stresses on total alkaloids, anthocyanin, total chlorophyll, the weight of wet and dry branches contain alkaloids, and the number of lateral branches of the periwinkle herb, an experiment was arranged with a factorial layout based on a completely randomized design under greenhouse conditions during years 2020 and 2021 in Tehran, Iran. The first factor was the dryness factor using evaporation pans (at three levels of 40, 60 and 80 mm), the second factor comprised the growth regulators (Shahid, auxin, gibberellin, cytokinin each at a concentration of 50 ppm) and the third factor included the nanoparticles (control, Zn, and Magnesium, each at a concentration of 1 mg, and the combination of zinc and magnesium, each at a concentration of 0.5 mg) were applied.

The results showed that in study of the effects of drought stress and spraying of zinc and magnesium nanoparticles on all investigated traits (total alkaloid, anthocyanin, total chlorophyll, fresh and dry weight of alkaloid-containing branches, and the number of lateral branches), there was a statistically significant difference at the level of 1% (P≤0.01). Also, in the investigation of the effects of growth regulators on investigated traits other than total alkaloid, a statistically significant difference was established at the level of 1% (P≤0.01). In the investigation of the mutual effects of drought stress and growth regulators on the fresh weight of alkaloids-containing branches, a statistically significant difference was established at the level of 1% (P≤0.01). The highest dry weight of aerial parts was observed under optimal irrigation conditions and under the influence of the gibberellin hormone (34.96 gr). However, in other cases, no statistically significant effect was observed on the target traits.

Drought stress revealed defense mechanisms such as anthocyanin pigments and secondary compounds, and total alkaloids also increased with increasing drought stress. The highest percentage of total alkaloids was obtained under severe drought stress (1.57%). The use of micronutrient fertilizers in nano form increased the accumulation of dry matter and secondary compounds, and the effect of magnesium was greater than the effect of zinc. In the application of hormones, the use of gibberellin hormone had a greater effect on the fresh and dry weight of shoots under optimal irrigation conditions and drought stress.

Paclobutrazol is a growth regulator used to control growth and reduce the frequency of mowing in all types of turfgrass plants. This material also affects the height and quality of different types of turfgrass. Therefore, the purpose of this research is to compare the growth behavior of two types of turfgrass subjected to paclobutrazol treatment and also to evaluate the possibility of using paclobutrazol to reduce the growth of turfgrass in areas with the same climate of Tabriz.

To determine the effect of paclobutrazol on height, and visual properties of turfgrass such as density, clippings fresh weight, leaf chlorophyll index, length and width of leaf blade, two grass plants Poa pratensis and Festuca arundinacea were treated with paclobutrazol in different concentrations. Grass plants were tested with concentrations of zero (control), 15, 30 and 45 mg/L-1 paclotrazol as foliar spray in 4 replicates of each treatment. This research was carried out in as a split plot experiment in the form of a randomized complete block design, so that the type of grass as the main factor in 2 levels and paclobutrazol as a secondary factor were considered in all the evaluated traits in both plant species.

The results of this research showed that paclobutrazol significantly affects the height of P. pratensis and F. aranudinaceae turfgrass plants. This effect was in the form of a significant reduction in the height of plants and controlling their growth. By increasing the concentration of paclobutrazol from zero to 45 mg/L, the height of the plants decreased. In both mentioned types of turfgrass, the most effective concentration was 45 mg/L. By increasing the concentration of paclobutrazol, the density of P. pratensis and F. aranudinaceae turfgrass plants has increased. The increase in density after paclobutrazol treatment was more evident in F. aranudinaceae. In general, the fescue turfgrass plant has stronger foliage, deep and strong roots, and lower density. The only exception was the increase in the chlorophyll index of fescue leaves (10 days after treatment) and P. pratensis (20 days after treatment) and in both of them under the concentration of 30 mg/L of paclobutrazol. Following paclobutrazol treatment and increasing its concentration, the length and width of the leaf blade as well as the clippings fresh weight of turfgrass plants were decreased. The reduction in the length and width of the leaf blade was similar in both plants, and the most effective concentration of paclobutrazol was 30 mg/L. However, the optimal effect of paclobutrazol was observed up to 30 days after the treatment. In the fourth measurement (40 days after the treatment), the effect of paclobutrazol decreased and there was no significant difference in the length and width of the leaves of the treated plants and the control plants.

In general, with the treatment of different concentrations of paclobutrazol, the number of aerial branches produced in F. aranudinaceae was more than that of P. pratensis. Since paclobutrazol is a growth inhibitor and by preventing the synthesis of gibberellin hormone, it prevents plants from elongation, this substance can be used to control the growth of turfgrass plants. This growth control reduces the number of mowing times, reduces fertilizer consumption, increases the efficiency of water use, and ultimately saves the cost of maintaining turfgrass plants. Since paclobutrazol accumulates in the roots and eventually causes the formation of new branches, it can be concluded that the effect of paclobutrazol on the density of F. aranudinaceae is greater than that of P. pratensis.

Food security concerns have necessitated the increase in agricultural production due to the ever-increasing world population, projected to exceed 9.6 billion people by 2050. It has been reported that various physicochemical contents of plants are increased by the solution of plant smoke. The biologically active compounds of smoke are soluble in water and in very low concentrations, they cause significant physiological responses in plants. These compounds can be used in the form of aqueous extract under the name of water smoke, by designing a device based on previous research in this field. Through various studies, it has been reported that the smoke enhancing activity is due to the presence of karrikin compounds (KARs).

This research was carried out in a factorial experiment in base of randomized complete block design (RCBD) in three replications in the research farm of the Campus of Agriculture and Natural Resources, Razi University, in the crop years 2019-2020 and 2020-2021. The factors included irrigated wheat cultivars (Mihan and Sirvan) and foliar application with a concentration of one liter per hectare in the phenological growth stages of wheat at eleven levels including no application (control), application in the stages of double ridge, second node detectable, ear emergence, anthesis, double ridge + second node detectable, double ridge + ear emergence, double ridge + anthesis, second node detectable + ear emergence, second node detectable + anthesis, ear emergence + anthesis. The studied traits in this research include seed yield, biological yield, harvest index, seed per spike, 1000-seed weight, seed filling duration and seed filling speed.

The results of this study showed that the maximum seed filling speed in foliar application at the stage of second node detectable was average (1.38 mg. day-1) in both Mihan and Sirvan cultivars, and the maximum weight of 1000-seed weight (48.93 g) in Mihan cultivar in foliar application at the stage of ear emergence was obtained, also foliar application in the stage of double ridge + second node detectable had the highest harvest index with average (45.79%) and seed filling duration with average (48.51 days) All of which were in the Mihan cultivar. Foliar application in the stages of double ridge + second node detectable and anthesis caused the highest seed yield with average (6.02 t. ha-1). The maximum number of seeds per spike with average (55.83) and biological yield with average (15.61 t. ha-1) was related to foliar application at the stage of double ridge + ear emergence in Mihan cultivar.

Smoke water has the necessary potential to increase the quantity of wheat. If the results of this research are confirmed in other researches, it can be recommended to use water smoke as a practical and low-cost technology, especially for poor farmers in developing countries.

Durum wheat is known as the eighth agricultural product in the world and is used for spaghetti and pasta. In many studies, in vitro cultivation methods have been used a lot to shorten breeding periods. The use of different explants in the production of wheat embryo callus is known as the best explant in the production of callus. Plant regeneration from callus is also a complex morphogenetic phenomenon that can be affected by various internal and external factors.

An experiment was conducted to study callus induction and regeneration of immature embryos with 11 genotypes of durum wheat. In the callus induction stage, two characteristics, callus induction, and callus growth rate based on the completely randomized design with five replications were measured. Callus derived from an immature embryo was conducted in MS medium containing BAP (0.5, 1 and 1.5 g/l) using an 11*3 factorial experiment based on the completely randomized design with three replications.

Statistical analysis results in the callus induction stage showed a significant difference in the percentage of callus induction and callus growth rate among genotypes. Mean comparison results indicated that in the callus growth rate of genotypes, respectively Stj3//Bcr/lks4 and Quadalete//Erp/mol/3/unk/4/Mrb3/Mnal, had the fastest growth rate and at percentage callus induction genotype 25-25-1-5 showed the highest induction. In the regeneration phase with different concentrations of BAP growth regulator, genotypes 409 and Stj3//Bcr/lks4 showed the highest regeneration. Therefore, based on the results obtained in this study, Genotype Stj3//Bcr/lks4 was introduced as the best genotype among others due to giving the highest callus induction and regeneration.

Therefore, according to the availability of wheat embryos, it can be considered a suitable source in tissue culture through independent factors, which are located in the nucleus or cytoplasm. According to the results, it could be stated that the success in tissue culture is influenced by various factors such as genotype, type of micro sample, and concentration of growth regulators, which differs from one cultivar to another.

To evaluate the phenological stages and yield of wheat cultivars in response to the change of planting date and application of paclobutrazol, a field experiment was conducted in two years, 2020-2021 and 2021-2022, in Izeh city located in the northeast of Khuzestan, Southwest Iran. The experiment had three replications in a split factorial randomized complete block design. The main factor included planting date (November 16, December 11, and January 5) and the sub factors in the factorial form included cultivars (Karim, Mehrgan, and Chamran2) and the application of paclobutrazol (0, 60, 120 mg/L). In both years, the highest seeds/m2 (18847) belonged to Chmaran2 genotype when sown on 16 November and received 60 mg/L paclobutrazol. When the genotypes were sown in the delayed planting date of January 5, application of 60 and 120 mg/L paclobutrazol led to an increase in seed yield compared to the 0 paclobutrazol. With the application of 60 mg/L paclobutrazol, the seed yield of Chamran2 genotype was higher on the planting dates of November 16 (6941 kg/ha) and December 11 (6779 kg/ha), compared to other paclobutrazol levels. Chamran2 and Karim genotypes indicated the greatest and smallest number of days and growing degree days, respectively, in different stages of growth and development. However, these genotypes did not show significant difference in terms of biological yield, grain yield, and harvest index. When plants were sown on January 5, the length of the plant growth period from the planting to physiological maturity was reduced by 34 days compared to when sown on November 16. Overall, the effect of paclobutrazol on seed yield was positive, and the consumption of 120 mg/L paclobutrazol moderated the negative effects of the delayed planting of the examined wheat genotypes.

Considering the importance of water in agriculture as well as extending ​​autumn-sown sugar beet cultivation area, this study was conducted to evaluate the effect of growth restriction treatments, planting date and cultivar on bolting and other quantitative and qualitative traits of autumn-sown sugar beet in Karaj, Iran during two years (2018-19). The experiment was performed as a factorial split plot in a randomized complete block design with 3 replications. Studied factors included two planting date (22nd September and 22nd October) as the first factor, the growth restriction with four levels including control (without limit), paclobutrazol (300 pp M), Nitrogen fertilizer restriction (50% of the recommended amount), Paclobutrazole + Nitrogen fertilizer restriction as the second factor, and three cultivars including Giada, Eudoro, and one Iranian genotype resistant to bolting as the third factor. Planting date and growth restriction factors were included in main plots and genotype factor in subplots. The studied traits included bolting percentage, root yield, sugar content, molasses sugar, and white sugar yield. Results showed that the effect of the year on bolting percentage was significant. The lowest bolting percentage (50%) was obtained by Eudoro cultivar on the second year of study planted on 22nd October. The highest root yield (79.91 tha-1) was related to the Eudoro cultivar, planted on 22nd September and treated with paclobutrazol (300 ppm). Giada and Eudoro cultivars planted on the 22nd September had the highest white sugar yield of 8.15 and 8.62 t ha-1, respectively with no significant difference between.

Quinoa plant (Chenopodium quinoa Willd) is a grain- like crop with high nutritional values and resistant to abiotic stresses such as drought and salinity stress. Drought stress is one of major stresses, which had the undesirable effects on qualitative and quantitative yield of crops in arid and semi-arid regions of the world. On the other hand, Jasmonate (Jasmonic acid), are a new plant growth regulator that plays an important role in increase the resistance of plants to environmental stresses such as drought stress. That's why this experiment aims to investigate the impact of drought stress and foliar application Jasmonic acid on yield and some agronomic and physiologic characteristics of Quinoa cultivars.

This experiment was carried out in split factorial design based on randomized complete block design with three replications in Kerman agricultural research and education center (Joupar station) during 2018. The main factor was included non-stress (normal irrigation) and drought stress (based on 60% and 90% of usable soil moisture discharge) and foliar application of JA in three levels (0, 1 and 2 mg/l) and varieties (Giza1, Titicaca, Q29) as factorial arranged in sub factor. The measured traits were seed yield, inflorescence number in plant, seed 1000 weight, biological yield, plant height, harvest index, relative water content and chlorophyll index.

The results showed that drought stress reduced the seed yield and some agronomic and physiologic traits of Quinoa.  The application of JA, especially concentration of 2 mg/L improved these traits compared to the control treatments. The highest seed yield and biological yield were obtained from interaction of normal irrigation and 2 mg/l JA  and Titicaca cultivar by 3316 and 13265 kg/ha, respectively. The lowest seed yield and biological yield related to interaction of drought stress and non-application of JA and Giza1 cultivar by 1682 and 7733 kg/ha, respectively. The highest plant height was achieved from the interaction of Titicaca cultivar under non-stress conditions and application of 2 mg/l JA by 142.4 cm. The highest chlorophyll leaf index (SPAD index) was observed under non stress conditions and spraying of 1 mg/l JA in Giza1 by 58.8.

According to the result of this research, it can be suggested that JA as a growth regulator, can increase seed yield and productivity of quinoa cultivars, especially Titicaca cultivar through the reducing the negative effect of drought stress and improving plant growth.

Lead as a heavy metal and permanent chemical contaminant threat the health of environment and alive creatures through different artificial and natural sources. In order to investigate the effect of methyl jasmonate and lead stress on growth characteristics, the adsorption and accumulation of lead and hazardous index in basil, a pot factorial experiment was carried out based on completely randomized design in research greenhouse of Ferdowsi University of Mashhad. The treatments consisted of three levels of lead nitrate (0, 200 and 400 mg/kg soil), and methyl jasmonate spraying in three concentrations (0, 0.5 and 1 mM). The mean comparison of data represented the reduction in all the studied morphological traits and increasing the amount of lead in the leave and root of the plant and hazardous index with increasing lead stress levels and spraying with methyl jasmonate could partly improve some of these traits. So that spraying with 1 mM methyl jasmonate cause to increase 6.01% inflorescence length and cause to decrease lead amount of the eave 96.56, 79.31 and 99.20%, respectively and hazardous index, however, at o.5 mM methyl jasmonate cause to increase the number of branches and aerial fresh weight, 27.66 and 9.84%, respectively. Therefore, it seems that application of methyl jasmnate on stress conditions could improve partly the traits and so in some cases 1 mM methyl jasmonate concentration cause to decrease some morphological traits. Therefore, application of o.5 mM methyl jasmonate on lead stress is recommendable.