Mohammad Mahmoodi Sourestani
Abstract
Introduction: Spearmint (Mentha spicata L.) is an aromatic plant belonging to the Lamiaceae family. The ground fresh biomass and dried leaves of the plant are used as spice and herbal tea, and cultivated commercially in the entire world. Spearmint oil also has economic importance and is used in perfumery, ...
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Introduction: Spearmint (Mentha spicata L.) is an aromatic plant belonging to the Lamiaceae family. The ground fresh biomass and dried leaves of the plant are used as spice and herbal tea, and cultivated commercially in the entire world. Spearmint oil also has economic importance and is used in perfumery, confectionary and pharmaceutical preparations. Major components in cultivated spearmint oil are carvone, limonene, and 1,8-cineole. Essential oil compositions of aromatic plants depend on their genetic structure, the climatic factors and the agronomical practices as well as harvest and post-harvest managements. A climate with adequate and regular rainfall and good sunshine during its growing period ensures a good yield. Climatic condition is one of the most important factors influencing the growth and accumulation of active ingredients that its effect is concealed at the harvesting time of plants. In addition, harvest time (cut) and phonological stages can affect herbage yield and oil content and composition of perennial medicinal plants.
Materials and Methods: Plant materials were harvested from a farm in Safiabad city, Khuzestan province, Iran. Five samples from each ecotype of spearmint (Kashan and Shushtar) were collected during growth season at the beginning of flowering stage, from May to the end of November. Plants were hand-harvested by cutting the herbage at 5 cm above the soil. Then the plants were dried at room temperatures (approximately 40 °C). Spearmint essential oil was extracted via steam distillation using a Clevenger apparatus. The distillations were carried out on a sample size of 50 g of dry aerial parts with a distillation time of 180 min. The oil was dried over anhydrous sodium sulfate and was kept in a refrigerator until further analysis. The essential oil’s chemical composition was analyzed by GC and GC/MS.
Results and Discussion: The results showed that temperature and humidity conditions prevailing in the area at the time of harvest had significant effect on plant growth and ultimately leaf dry weight, oil content and composition. The highest leaf dry weight of the Kashan (250.67 g.m-2) and the Shushtar (290.23 g.m-2) were observed at the third and fifth harvest time, respectively. There was no significant difference between the first to fourth harvest times of the Kashan and the first, third, fourth and fifth harvest time of the Shushtar. The highest (3.33%) and the lowest (1.72%) amounts of essential oil of the Kashan ecotype were obtained from the third and the first cuts, respectively. The Shushtar ecotype had lower oil than the Kashan ecotype. The second harvest time of the Shushtar ecotype had the highest (2.53%) amount of essential oil and the lowest (1.36%) amount was observed at the first harvest time that had no significant difference with the third and fifth harvest times. The highest amount of oil yield of the Kashan (8.34 g.m-2) and the Shushtar (4.89 g.m-2) ecotypes was recorded at the third and the fourth cuts, respectively. It seems that plants during the second to the fourth harvests encouraged with hot stress and they produced more essential oil in response to high temperature. Limonene, cis-dihydrocarvone, carvone and caryophyllene were the main oil components at five harvest times. Both ecotypes were similar in regards of main oil components but the Shushtar had more oil composition than the Kashan. In the Kashan ecotype, limonene was at the lowest amount (12.22%) and reached to the maximum amount (20.55%) at the second harvest time. In contrast, cis-dihydrocarvone decreased from 4.95% to 2.34% at the second harvest time and finally the maximum amount (11.14%) was recorded at the fifth harvest time. Carvone content was 68.94% at the first harvest and after that increased to the highest level (74.21%) and finally decreased to the minimum level (65.15%) at the fifth harvest time. In the Shushtar, limonene increased from the first until the fourth harvest and ultimately declined in the last cut. The maximum amount of carvone (72/67%) was observed in the first harvest and then was relatively constant during the second to fourth harvests, and reached to the lowest level (56/58% ) at fifth harvest. The Kashan ecotype had more carvone than the Shushtar ecotype. The fluctuation of carvone and cis dihydrocarvone were in opposite of each other and it seems that lower temperatures in the fifth harvest caused to carvone convert to cis-dihydrocarvone. However, the amount of carvone was more than 50 % at all harvest times.
Conclusion: Although harvest times had a significant effect on the traits, both ecotypes showed a good oil content and yield at five cuts. Oil composition was also changed during different harvest times. Nevertheless, Carvone content was up to 50% at all harvest times and it seems that we can recommend harvesting of plants from May to the end of November.
Mohammad Mahmoodi Sourestani
Abstract
Introduction: Mediterranean climate conditions induce several stresses that plants have to cope with, especially during summer months when high temperature and radiation levels along with low water availability in the soil prevail for long periods. Variation in physiological traits such as photosynthesis ...
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Introduction: Mediterranean climate conditions induce several stresses that plants have to cope with, especially during summer months when high temperature and radiation levels along with low water availability in the soil prevail for long periods. Variation in physiological traits such as photosynthesis and plant water status and their association with morphological characters can play an important role in the adaptability of the species to environmental constraints. The previous studies show that scorching weather not only affects the rate of gas exchange, but also results in diurnal changes in activity. Thus, the impact of environmental stresses on plants growing in these conditions should be assessed by examining the evolution of their diurnal variations on leaf gas exchange. Aromatic plants represent a renewable source of valuable compounds that can be used in food, perfumery, and pharmaceutical industry. Among these plants, sweet basil (Ocimumbasilicum), holy basil (Ocimum sanctum), lemon balm (Melissa officinalisL.) and catnip (Nepetacataria) are very important for different industries. Studies on environmental physiology of medicinal plants are relatively scarce and very few information is available concerning the physiological basis of medicinal plant response to heat stress that is one of the most important factors limiting production of medicinal plants in Khuzestan province.
Material and methods: In order to evaluate the diurnal fluctuation of gas exchange of mentioned plants, an experiment was carried out in 2013 at research farm of Horticultural Science, Shahid Chamran University (31°20'N latitude and 48°40'E longitude and 22.5m mean sea level), Ahvaz (Iran), a site characterized by a semidry and scorching weather during late spring and summer. The experiment was arranged based on randomized complete block design (RCBD) with three replications and 4×8 factorial scheme (Four plants including lemon balm, catnip, holy basil and basil; and eight times of evaluation 7:00,9:00, 10:00, 11:00, 12:00, 13:00, 17:00 and 20:00 h). Land preparation consisted of disking and the formation of raised beds (15cm high and 45cm wide across the top) using a press-pan-type bed shaper. The plants were arranged on two rows on each bed, with 20 cm in-row and 40 cm between-row spacing. The plants were irrigated weekly as needed. Gas exchange parameters were investigated from June 9-11at end of vegetative phase under natural environmental conditions. The parameters of gas exchange were measured on the 5th and 6th nearly full expanded leaves between the hours of 07:00 and 20:00 during bright sunlight on clear and cloudless days. Determination of leaf net photosynthesis rate (Pn), stomatal conductance (gs) and transpiration (E) was made with Infra-red gas analyzer (LCA4, ADC Co. Ltd., Hoddesdon, UK).Instantaneous water use efficiency (WUEinst) and apparent quantum yield(AQY) were calculated as Pn/E andPn/PPFD ratios, respectively.
Result and discussion: The result showed that plant type had significant effect on all measured traits as well as record time. Interaction between plant type and record time were significant for PPFD, leaf temperature and net photosynthesis. The highest Pnof Lemon balm (8.97 µmol CO2 m-2 s-1), catnip (11.2 µmol CO2 m-2 s-1) and sweet basil (13.75 µmol CO2 m-2 s-1) were recorded at 9:00 when the photosynthetic photon flux density (PPFD) was 1488, 1598 and 1645 µmol photon m-2 s-1, respectively. Holy basil showed highest Pn (15.47 µmol CO2 m-2 s-1) at 10:00 when PPFD was 1821 µmol photon m-2 s-1.High irradiances caused photoinhibition of the four plants and it seems the four plants reach to light saturation point about 1500 µmol photon m-2 s-1.The midday depression of photosynthesis likely resulted primarily from long periods of high PPFD, limitation in stomatal conductance and high temperature. Catnip was more sensitive to high irradiance. The Pn had positive and significant correlation with gs in four plants. The stomatal conductance was also positively correlated with E in four plants. The plants represented double peak curve for WUE. The first and second peaks appeared at 9:00 and 17:00, respectively. The four plants also showed highest AQY at 7:00. There were significant difference between four plants for leaf temperature, gs, Pn, WUE and AQY. Lemon balm showed lower leaf temperature than other plants due to its high gs. The highest amounts of Pn, WUE and AQY were observed in holy basil.
Conclusion: In regard to Pn, WUE and AQY, it seems holy basil and sweet basil can tolerate weather condition of Ahvaz.
Zohreh Moghimi pour; Mohammad Mahmoodi Sourestani; Naser Alemzadeh Ansari
Abstract
Introduction: Holy basil is a perennial plant belongs to Lamiaceae family. The plant is a perennial and thrives well in the hot and humid climate. Its aerial parts have been in use for food, pharmaceuticals, cosmetics and perfumery industries. Leaves contain 0.5-1.5% essential oil and main oil components ...
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Introduction: Holy basil is a perennial plant belongs to Lamiaceae family. The plant is a perennial and thrives well in the hot and humid climate. Its aerial parts have been in use for food, pharmaceuticals, cosmetics and perfumery industries. Leaves contain 0.5-1.5% essential oil and main oil components are eugenol, methyl eugenol, carvacrol, methyl chavicol and1,8-cineole. A balanced fertilization program with macro and micronutrients is very important in producing high quality yield. Zinc is involved in IAA production, chlorophyll biosynthesis, carbon assimilation, saccharids accumulation, reactive oxygen radicals scavenging and finally carbon utilization in volatile oil biosynthesis.
Material and methods: In order to evaluate the effect on zinc foliar application on zinc content of leaves, photosynthetic indices and pigments of holy basil, an experiment was carried out in 2013 at a research farm of Horticultural Science, Shahid Chamran University (31°20'N latitude and 48°40'E longitude and 22.5 m mean sea level), Ahvaz (Iran), a region characterized by semi-dry climate. The experiment was arranged based on Randomized Complete Block Design (RCBD) with six treatments and three replications. The treatments were nano zinc chelate (0, 0.5, 1 and 1.5 g.l-1) and zinc sulfate (1 and 1.5 g.l-1) fertilizers. Land preparation includes disking and the formation of raising beds (15cm high and 45cm wide across the top) using a press-pan-type bed shaper. Holy basil seeds were sown on two rows on each bed, with 15 cm in-row and 40 cm between-row spacing. The plants were irrigated weekly as needed. Foliar application of zinc fertilizers was done at six-eight leaf stage and were repeated with interval 15 days until full bloom stage. Zinc content, stomata conductance (gs), CO2 under stomata (Ci), transpiration rate (E), net photosynthesis (Pn), light use efficiency (LUE), water use efficiency (WUE) and also chlorophyll a, chlorophyll b, chlorophyll a+b and carotenoid contents were measured at beginning of flowering stage. Photosynthetic parameters were measured by Infra-red gas analyzer (LCA4, ADC Co. Ltd., Hoddesdon, UK). Instantaneous water use efficiency (WUEinst) was calculated as Pn/E ratio. Light use efficiency was calculated as Pn/PPFD ratio.
Result and discussion: The results showed that the effect of foliar application of zinc fertilizers on all measured traits except Ci and WUE was significant (p≥0.01). The highest values of zinc content (110.53 mg.kg-1), chlorophyll a (0.99 mg.kg-1 fresh weight), chlorophyll b (0.30 mg.kg-1 fresh weight), chlorophyll a+b (1.29 mg.kg-1 fresh weight) and carotenoid (0.18 mg.kg-1 fresh weight) traits were obtained in plants sprayed with 1.5 g.l-1 nano zinc chelate. The lowest amount of zinc content (21.37 mg.kg-1), chlorophyll a (0.58 mg.kg-1 fresh weight), chlorophyll b (0.14 mg.kg-1 fresh weight), chlorophyll a+b (0.72 mg.kg-1 fresh weight) and carotenoid (0.13 mg.kg-1 fresh weight) traits were obtained in control plants. Foliar application of holy basil with 1.5 g.l-1 nano zinc chelate led to increase in stomata conductance (322.22 mm H2O.m-2.s-1), transpiration rate (2.86 mm H2O.m-2.s-1), net photosynthesis (11.75 μm CO2.m-2.s-1) and light use efficiency (6.10 μm CO2. μm photon-1). The minimum amount of stomata conductance (172.00 mm H2O.m-2.s-1), transpiration rate (2.16 mm H2O.m-2.s-1), net photosynthesis (8.23 μm CO2.m-2.s-1) and light use efficiency (4.46 μm CO2. μm photon-1) were observed in control plants. There were positive correlation (p≥0.01) between zinc content and chlorophyll a, chlorophyll b, chlorophyll a+b and carotenoid. Zinc content also had positive and significant correlation (p≥0.01) with stomata conductance, CO2 under stomata, transpiration rate, net photosynthesis and light use efficiency. So, providing zinc by foliar application with 1 and 1.5 g.l-1 nano zinc chelate and 1.5 g.l-1 zinc sulfate can lead to increase in chlorophyll and carotenoid contents. Increase in net photosynthesis may be due to higher photosynthesis pigments and also stomata conductance and CO2 under stomata. In the other hand, zinc is an essential micronutrient that acts either as a metal component of various enzymes or as a functional, structural, or regulatory cofactor such as carbonic anhydrase, ribulose 1, 5-bisphosphate carboxylase/oxygenase and fructose-1, 6-bisphosphate, and is thus associated with saccharide metabolism and photosynthesis.
Conclusion: Although the highest amount of most measured traits was obtained in plants that treated with 1.5 g.l-1 nano zinc chelate, there were no significant difference between 1 and 1.5 g.l-1 nano zinc chelate and 1.5 g.l-1 zinc sulfate treatments for zinc content, stomata conductance, CO2 under stomata, transpiration rate, net photosynthesis, water use efficiency and light use efficiency. Therefore, in order to increase zinc content and photosynthetic traits of holy basil, foliar application of with 1.5 g.l-1 zinc sulfate is recommended.
