INTRODUCTION:

Medicative plants are the ‘keystone’ of customary medication which implies in excess of 3.3 million individuals in the less created Nations use therapeutic plants all the time. The word ‘therapeutic plants’ involved different kind of plants that are used from long years ago for curing diseases and that is the part of herbalism (Singh 2015). In both industrialized and developing countries, acknowledgment and advancement of medicinal and economical advantages of plants are on the increment. The plant part that is used for its medicinal properties, aroma and enhancement is called herb. Items produced using botanicals that is utilized to enhance or to maintain the body systems are called phytomedicines or herbal supplements (Jain et.al. 2016). The medicinal plants play a very important role in our daily lifestyle to make this lifestyle natural and healthy.

Our interest has increased in the natural bioactive compounds that could be existing in our diet or it can be used as natural remedy, like for the cure of Diabetes mellitus (DM) Gymnema plant has been used for more than 2000 years in the India, Diabetes Mellitus is frequently known as Diabetes, it is a kind of metabolic disease in which blood sugar is high that affects the ability of body to use the energy found in food. It was projected that there were 171 million people in the world suffered in the year 2000 and this is expected that in the year 2030 the number become enlarged to 366 million. (WHO international Diabetes Federation, 2006).

Because of these reasons, various plant growth regulators are used to alleviate the biotic and abiotic stress. Different plant growth regulators like auxins, cytokinin, salicylic acid, jasmonic acid, methyl jasmonate, indole acetic acid, gibberellic acid, NAA, brassinosteroids, ethylene etc were used. These PGR improves the quality, quantity of secondary metabolites and essential oil content of plants by enhancing the biochemical and physiological parameters (Khan et.al. 2016). In this project, I studied about Salicylic acid that has many effects on secondary metabolites of various medicinal plants. Salicylic acid is the phenolic compound that has an aromatic ring bearing its functional derivative (Raskin 1992). It helps to ameliorate the effect of abiotic stresses. Its exogenous application or foliar spray helps the plant to combat the stress like drought stress (Khatiby et.al. 2017) and also regulate the secondary metabolites of plants like in leaves of Matricaria chamomilla (Ducaiova et.al. 2013) and increase the seed yield, number of seeds per plant in Coriander (Hesami et.al. 2013). Plants modifying their features according to the environmental changes and adjust itself in different stress condition by the mean of morphological, anatomical, physiological, molecular and biochemical adaptation. Both primary and secondary metabolites are involved in biochemical adaptation.

Strategies to enhance the secondary metabolites of Withania somnifera:

A lot of work was already done by the different researchers for increasing the secondary or bioactive compounds of the Withania somnifera that is discussed below.

Types of abiotic signals:

Many of the abiotic elicitors can be use for the production of secondary metabolites of the Withania somnifera like Plant growth hormones or regulators; Methyl jasmonate, Salicylic acid, Jasmonic acid, Calcium, Polyamines, Nitric oxide, Serotonin, Abscisic acid, Melatonin, Brassinosteroids, Metal ions, Nitrogen source, Carbon source; sucrose, glucose, maltose, fructose etc, Climatic changes; light, temperature, cold stress, drought stress, salinity stress, nutrient stress, chemical stress etc (Akula et.al. 2011).

Abiotic elicitation:

Bioactive secondary metabolites have been differently appeared to be controlled by various abiotic0 and biotic stresses because of their defensive impacts under unfavorable natural conditions. Withanolides are most important constituents of 1steroidal lactones, have too been appeared to be managed by numerous abiotic2 and biotic burdens.

Drought stress:

Dry elicitor is a very much portrayed abiotic signal in which water supply is a noteworthy constraint alongside high temperature, low stickiness and extreme light. Basically leaf water content is reported to be diminished or reduced because of stomatal closure, CO2 supply confinement, and photosynthetic rate to a degree of 60–80 % during dry season condition (Marchese et.al. 2010, Silva et.al. 2009, Singh et.al. 2014). Withanolide content in Withania somnifera become alter by drought stress. While finding the pattern of different withanolides aggregation under drought stress, it was found that withaferin-A substance was expanded by 42.7% with accompanying reduction of withanolide-A and 12-withastromonolides by 78 and 71% individually as thought about to control (Singh R. et.al. 2015).

Salt stress:

Stress of salt frequently makes both ionic and also osmotic stress in plants and decline particular bioactive or secondary metabolites in plants (Mahajan et.al. 2005). Anthocyanins of the plants were increased because of salt stress (Akula et.al. 2017). In contrast to this, salt stress decreased anthocyanin level in the salt-sensitive species (Daneshmand et.al. 2010). In micro propagated developed shoots and callus of Withania somnifera, were presented to different sorts of salts under in vitro culture conditions. Film penetrability, lipid peroxidation, and the cancer prevention agent framework expanded in shoots and also in disorganized callus tissues under all the three immersion of KCl, NaCl, KNO₃, NaNO₃, and CaCl₂. The development reactions of shoots and callus culture under different salt medications revealed that the tissue could develop better under NaCl and KNO_3. The impact of KNO₃ and KCl was almost same for the biosynthesis of withanolides (Sabir et.al. 2012).

Table 3. Shows the effect of abiotic stress (heat, moisture, drought, light and metal) that alter the physiological, biochemical, morphological and biological response of the Withania somnifera and some other plants.

S/N	Experiment	Methodology	Result	Reference
1	Response of physiological character, gene formulation and secondary metabolites of ashwagandha in drought stress	The Plantlets of Withania somnifera that are one week old kept in growth chamber and gradually provide the 14 h light and 10 h dark, temperature 28 and 33°C with light intensity variation, 50-70% humidity. For drought experiment 1½ month old plant covered with thick plastic sheet up to 7 days to prevent vaporization.	In response to drought experiment stomatal conductance, water content of leaves, photosynthesis rate, rate of transpiration, chlorophyll content, quantum yield of PSI and PSII decreased. Withanolides were also increased with enhanced detoxification and osmotic regulation under drought stress.	Singh. R et.al. 2015.
2	Modification of biochemical, physiological and phytochemical characteristics of ashwagandha during drought stress	Seeds were sown in pots that containing the soil. Pots were divided in four groups and each group had 10 pots. One month old plants were used for experiment, one group they give drought stress, second was control, third rewatered and in fourth one watering occur with time interval. After 30 days of experiment, growth parameters, pigment, photochemical activity, chloroplast and withanolide were determined.	In drought stress, length of root and shoot, area of leaf and photosynthetic pigment and its activity decreased. Protein showed variation up to 30-40 kDa in stress of drought but concentration of withaferin was increased 5 % under stress equivalence to content.	Kannan et.al. 2011
3	Changes in the production of withanolide of Withania somnifera under the stress of low light	Experiment was conducted for 30 days by giving the twenty five percent, fifty percent and seventy five percent shade to the pots under the conditions of pot culture. After 30 days, content of withanolide and morphological parameters were checked	Results showed that more withanolide increased under 75 percent shade as comparison to 25 and 50 percent	Jacob et.al. 2014
4	Changes in Withania somnifera due to the stress of moisture in soil	Experiment performed in three design by giving one severe and two mild stress and then measurements were taken	Leaf area reduced, chlorophyll reduced, photosynthesis re4duced, withanolide and 12-deoxywithastramonolide also reduced up to 65% and 78%	Shah et.al. 2011
5	Alternations in the physiolology and growth of Vigna radiata seedling due to Arsenic stress	Germinated seedlings were treated with 0, 25, 50 and 100 µM sodium arsenate and also with combination of curcumin . Then different parameters were checked	Arsenic reduced the chlorophyll, carotenoid, root and shoot length but curcumin at 25 µM helps to alleviate the stress	Upadhaya et.al. 2014
6	Effect of arsenic stress with foliar spray of SA on wheat seeds	Different concentration of arsenic with 1mM SA was used for experiment	Arsenic decreased the roots, its length , chlorophyll, germination rate but increased the MDA, proline content but exogeneous application of SA alleviate the arsenic stress and increased protein and chlorophyll and reduced poline and MDA and help the plant to tolerate arsenic stress	Zengin. 2012
7	Effect of Copper toxicity on growth and antioxidant enzymes of Withania somnifera in in vitro experiment	Nodes were taken and taken in media that contain different concentration of Copper (0, 25, 50, 100, 200 µM). After one month, physiological and biochemical parameters were measured	Chlorophyll, root and shoot length, carotenoid, fresh weight decreased. MDA increased, SOD, CAT, GR and GPx decreased	Khatun et.al. 2008
8	Carbon metabolism and photosynthesis enhancement in favor of tolerance of arsenic in Artemisia annua	Different concentration of arsenate was given to plants i.e. 50, 100, 150 µM	100µM concentration of arsenic was useful for plant, it increased the chl, ATP, NADPH in treated plants as comparison to control plants. Stress also increased the artemisinin and oil content of the plant	Rai et.al. 2014
9	Under Iron stress, alternation of morphological and protein content of Withania somnifera	Experiment was performed for 7 days under conditions of in vitro, four concentration of Iron 25, 50, 100, 200µM was given to plants	Growth parameters decreased even in 25µM concentration of Fe, Protein content first increased then decreased	Rout and Sahoo 2012

CONCLUSION:

Various abiotic elicitors like heat, cold, metals can be used effectively for increasing secondary metabolite contents of Withania which can help in managing huge demand of various medicinally important components.

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Received on 15.06.2018 Modified on 14.07.2018

Research J. Pharm. and Tech 2018; 11(11): 5139-5142.

DOI: 10.5958/0974-360X.2018.00938.1