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Aromatic plant species for phytoremediation

Aromatic plants are those which produce essential oils having aromatic compounds and are widely used in cosmetics, toiletries, agarbattis, tooth paste, food products like confectionary, chocolate, ice cream, medicine, pharmaceuticals, etc. India is having unique advantage of growing majority of aromatic plant species due to diversity in its climate, soil, rainfall and geographical conditions. The growth rate of demand is 9% in domestic and 25% for export market. At present, India produces about 16,000-18,000 tons of essential oil out of 80,000 tons of world’s production which is about 20-25% of total world’s production. Most of the oil that have a good demand in the present market are: mints, lemongrass, rose oil, citronella oil, basil, geranium, palmarosa, eucalyptus, vetiver, jasmine, sandal wood, lavender, ginger oil, cinnamon, etc. (Figure 2).

Sources of essential oil: Essential oil or aromatic substances are present in one or more plant parts, such as flowers (rose, tuberose, violet, cananga, jasmine, narcissus, orange flower, ylang ylang), leaves (cimiaomon, cedar, patchouli, bitter orange, wintergreen, sweet worm wood, eucalyptus), wood (cedar, birch, rose, camphor, laurel, sandal), bark (birch, cascarilla, cassia, cedar, cinnamon, cypress), fruit peels (bergamot, citron, grapefruit, lemon, limes, mandarin, orange, tangerine), grass (citronella, ginger grass, lemongrass, palmarosa), seeds (ambrette, angelica, cardamom, carrot, croton, cumin, dill, mustard, parsley, bitter almond), diied leaves (cherry laurel, eucalyptus, nirouli, patchouli), dried fruits (coriander, anise, juniper, nutmeg), diied buds and berries (clove, cubeb, juniper, pimento), giuns (elemi, galbanum, mastic, myrrh, styrax), roots and rhizomes (angelic, costus, ginger, valerian, vetiver), and herbs (basil, chamomile, dill, fennel, geranium, lavender marjoram, parsley, peppermint, rosemary, sage, spearmint, thyme, verbena, womiseed, wormwood).

India is a veritable emporium of essential oil bearing plants. It is one of the few countries in the world where aromatic plants of all types can be cultivated in one or other areas of the country because of the vast areas and the climatic conditions. Cultivation of these crops will help in diversifying our agriculture for new cash crops. There is a need to provide genuine quality of raw material for the user

Some important aromatic plants m demand

Figure 2. Some important aromatic plants m demand: (a) Lemongrass (Cymbopogonflexuosus), (b) Palmarosa (Cymbopogon martini var. motia), (c) Citronella (Cymbopogon wintehamts), (d) Sweet wormwood (Artemisia annua), (e) Vetiver ( Vetiveria zizanioides), (f) Tulasi (Остит tenuiflorum), (g) Japanese mmt (Mentha atvensis), (h) Sweet Basil (Ocimum basilicttm), (i) Pathcouli (Pogostemon cablin), (j) Galangal (Alpinia galangal).

industries. Information regarding the ameliorative potential of aromatic crop species for improving salt affected soil is limited. Some of the aromatic grasses have the potential for hyper accumulation of salt, which helps in reclaiming the saline soil, e.g., palmarosa is a hyper salt accumulator. It has been reported that aromatic grasses such as palmarosa, and lemongrass (C. flexuosus) can be grown successfully on moderately alkaline soils having pH up to 9.0 and 9.5, respectively, while vetiver (Vetiveria zizanioides) withstands both high pH and salinity. These grasses not only produce essential oils used for industrial purpose but also ameliorate the degraded soil (Table 3). When palmarosa, lemongrass and vetiver were grown for two years on sodic soils having pH 10.6, 9.8 and 10.5, respectively, the reduction in pH was noticed as 9.4, 8.95 and 9.50 in each soil, respectively. The continuous growth of palmarosa may reduce the sodicity and improve the physico-chemical properties of sodic soils. Like other aromatic glasses, vetiver can reduce the sodicity and improve the physico-chemical properties of sodic soils (Patra et al. 1998, Xia and Shu 2003). Chand et al. (2014) conducted an experiment to assess the suitable and profitable medicinal and aromatic plants in different sodic soils. They obtained highest essential oil yield 154.25, 145.75, 145.00 and 144.10 kg ha-1 during different harvests under various sodic soils. Profitability of experiment indicated that palmarosa gave highest net returns of Rs. 71675, 62125, 61750 and 60160 ha-1 with more benefit: cost ratio of 1.97, 1.55, 1.54 and 1.47 followed by other plants under various sodic soils. On the basis of results, they showed that palmarosa was the most suitable and profitable crop under vaiious ranges of sodic soils. Therefore, they concluded that if managed judiciously, sodic soils can be successfully utilized for growing of palmarosa, lemongrass and klius without using amendments.

Sinlia et al. (2016) suggested that farmers/growers can raise palmarosa seedlings (varieties: PRC-1, Trishna and Tiipta) in the nursery under normal soil condition and transplant these seedlings in soil having KC1 salt concentration up to 50 mM except variety Trishna which can be grown only up to 100 mM KC1 concentration. It has also been reported that sweet wormwood (Artemisia amnia), which is commonly grown for both essential oil and medicinal properties, could withstand Exchangeable Sodium Percentage (ESP) as high as 55 (pH 9.6) (Kalaichelvi and Swaminathan 2009). Dagar et al. (2013) explored the possibilities of raising lemongrass on degraded calcareous soil using saline water up to EC 8.6 dSnr1 without build up of soil salinity if normal rainfall occurs once in 3-4 years.

An experiment was conducted in glazed pots with artificially prepared sodic soils having different ESP levels (16, 55, 65, 75 and 85 ESP) at CIMAP. Lucknow to evaluate the ameliorative potential of high value crop palmarosa for reclamation of sodic soil. The results revealed that growth attributes and herb yield decreased significantly with the increased ESP level. However, essential oil yield increased significantly at ESP-55 over ESP-16. The sodium (Na) concentration in plant tissue increased with increased soil ESP level, but decreased concentrations of calcium (Ca), magnesium (Mg) and potassium (K). This study indicated that cultivation of palmarosa in sodic soil would decrease the ESP level without the use of chemical amendments for reclamation of sodic soil (Kumar et al. 2004). The growth of selected cultivars of palmarosa, lemongrass and jamarosa on normal soil and sodic soil was evaluated to determine the tolerance and productivity of these three species in sodic environment (Patra et al. 1998). The effect of sodicity was less pronounced on essential oil yield and quality. Differences among cultivars of palmarosa and lemongrass in sensitivity to soil sodicity were noted. The growth and yield of jamarosa was the best among the three aromatic grasses evaluated. The effect of different amendments on sodic soil including normal soil on palmarosa was studied under field experiment (Singh et al. 2002). Palmarosa oil yield was increased when amendments were incorporated in the salt affected soil. It was concluded from the study that palmarosa is the best suitable aromatic crop in salt affected soil for good herb and oil yield as well to improve the salt affected soil. The herb yield of geranium was significantly increased with increasing soil ESP up to 16.0, and oil yield increased with increasing ESP up to 7.0. Further,

Table 3. Ameliorative potential of aromatic plants in degraded and marginal lands.

Aromatic plants

Soil category

Potential benefits

References

Palmarosa (Cymbopogon martini var. motia)

Sodic soil

Palmarosa crop has ameliorative potential and m the long term it may reclaim the sodic soil by reducing the pH and ESP and produce good amount of oil yield and income.

(Kumar et al. 2004)

Salt affected soil

Palmarosa improves the salt affected soil by decreasing the pH and SAR, Improves the physicochemical properties and fertility of salt affected soil.

(Smgh et al. 2002)

Saline soils

Yield of palmarosa was not affected adversely up to the EC of 12 mmhos cm-1, but it slightly decreased at EC of 16 mmhos cm-1 as compared to normal soil. Herbage yield and oil content were not affected by various salinity levels.

(Singh et al. 2004)

Saline water ungation

Palmarosa can tolerate irrigation water salinity up to 4.0 dSnr1 without adversely affecting herbage yield.

(Takankhar et al. 2018)

Sewage sludge

Cymbopogon martini acts as hyper-accumulator and thus could be used for phytoremediation of sewage sludge.

(Singh et al. 2019)

Vetiver grass (Vetiveria zizanioides)

Saline water ungation

Vetiver was well survived (93-95%) and remained unaffected by salme irrigation.

(Tomar and Minhas 2004)

Sodic soil

Vetiver withstands both high pH and stagnation of water, and can successfully be grown without significant yield reduction in highly alkaline soils. Soil pH, EC and ESP can be reduced by growing vetiver grass.

(Dagar et al. 2004)

Sodic soil

Vetiver could withstand soil alkalinity up to pH 9.5. Herb and oil yield of vetiver was not significantly affected up to pH 9.5.

(Anwar et al. 1996)

Sodic water ungation

Vetiver grass can withstand sodic irrigation water and increase the biomass yield and oil yield.

(Prasad et al. 1999)

Lemon grass (Cymbopogon flexuoits)

Calcareous soil and salme water ungation

Results indicated the possibilities of raising lemon grass on degraded calcareous soil using salme water up to EC 8.6 dSnr1.

(Dagar et al. 2013)

Salinity stress

Successfully grown with salinity upto 15 dSnr1

(Kumar and Chauhan 2017)

Sodic soil

Lemon grass could successfully be grown on moderately alkaline soils of pH up to 9.2. Soil pH and ESP decreased under influence of lemongrass.

(Dagar et al. 2004)

Citronella (Cymbopogon winterianus)

Saline soil

Citronella can tolerate salinity up to 5 dSm-1 and reduction in yield moderately up to 10 dSnr1.

(Chauhan and Kumar 2014)

Scented Geranium (Pelargonium graveolens)

Sodic soil

Geranium can tolerate the soil sodicity stress of ESP up to 20.0.

(Prasad et al. 2006)

Basil (Ocimttm Basilicum)

Sodicity stress

Basil is highly tolerant to soil sodicity stress of ESP up to 36.

(Prasad et al. 2007)

increase in soil ESP decreased the yield. When ESP level increased in the soil, sodium concentration was increased in plant roots and shoot tissue of the geranium. This study suggested that geranium is slightly or moderately tolerant of soil sodicity stress condition (Prasad et al. 2006).

The suitability to saline irrigation on the relative performance of aromatic grasses, viz. citronella (Citronella java), lemon grass (Cymbopogon citrates Stapf), palmarosa [Cymbopogon martini (Roxb.) Wats.], and vetiver [ Vetiveria zizanioides (L.) Nash] was evaluated by Tomar and Minlias (2004). On an average, vetiver produced the maximum bio-mass (90.9 tonnes ha-1 dry weight basis), followed by palmarosa (29.1 toime ha-1) and lemongrass (16.1 tonnes ha-1)- However, citronella could not survive. Reduction in yield with saline irrigation ranged from 24 to 29%, whereas it ranged from 3 to 21% with alternation in irrigation with canal and saline waters, vetiver being least affected. The effects of residual sodium carbonate (RSC) in irrigation water on soil sodication and yield and cation composition of palmarosa (Cymbopogon martinii Roxb. Wats) and lemongrass (Cymbopogon flexuosus Steud Wats) indicated that the increasing RSC in irrigation water significantly increased the pH, electrolyte conductivity (ECe) and SARe of the soil and, hence, considerably decreased the herb and oil yield of both the palmarosa and lemongrass. The concentration of Na increased significantly and К and Ca decreased with increase in RSC of irrigation water in vegetative tissues of both species. The lemongrass accumulates significantly greater amount of Na in shoot tissues as compared to palmarosa and it failed to survive at high RSC after 21 months of transplanting (Prasad et al. 2001).

 
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