en Application of Plant Biostimulants as New Approach to Improve the Biological Responses of Medicinal Plants- A Critical Review كشاورزی و اتنوبوتانی Agriculture & Ethnobotany مروری Review <div dir="ltr" style="text-align: justify;">The aim of this review was to represent a category of applied plant biostimulants and to highlight the effect of their application on morphological and phytochemical properties of medicinal plants in <em>in vivo </em>and<em> in vitro</em> conditions and their mechanism of action. Plant biostimulants, safe for both human beings and the environment, are substances or materials, except for nutrients and pesticides, which have the ability to beneficially modify plant growth and have been accepted over the past decade. Plant biostimulants have natural and synthetic origin. The natural biostimulants contain amino acids, bacteria, seaweed, yeast, chitosan, phytohormones, and also plant growth regulators (synthetic hormones), phenolic compounds, inorganic salts, essential elements, and other different substances are some examples of synthetic biostimulants. The plant biostimulants through different mechanisms of action (such as nitrogen assimilation) are sustainable management practice for production of medicinal plants, increasing biomass production, and enhancing secondary metabolites synthesis and it is investigated and shown in many studies in recent years. Furthermore, there are many reports on positive effects of biostimulants and elicitors application on medicinal plants in <em>in vitro</em> culture condition. Some products of companies active in the formulation of biostimulants in Iran are mentioned in this review. In conclusion, yield response in medicinal plants to biostimulants application showed that each medicinal plant responds in a different way based on the chemical composition and components of biostimulants, the timing and rate of application.</div> <div dir="ltr" style="text-align: justify;">The aim of this review was to represent a category of applied plant biostimulants and to highlight the effect of their application on morphological and phytochemical properties of medicinal plants in <em>in vivo </em>and<em> in vitro</em> conditions and their mechanism of action. Plant biostimulants, safe for both human beings and the environment, are substances or materials, except for nutrients and pesticides, which have the ability to beneficially modify plant growth and have been accepted over the past decade. Plant biostimulants have natural and synthetic origin. The natural biostimulants contain amino acids, bacteria, seaweed, yeast, chitosan, phytohormones, and also plant growth regulators (synthetic hormones), phenolic compounds, inorganic salts, essential elements, and other different substances are some examples of synthetic biostimulants. The plant biostimulants through different mechanisms of action (such as nitrogen assimilation) are sustainable management practice for production of medicinal plants, increasing biomass production, and enhancing secondary metabolites synthesis and it is investigated and shown in many studies in recent years. Furthermore, there are many reports on positive effects of biostimulants and elicitors application on medicinal plants in <em>in vitro</em> culture condition. Some products of companies active in the formulation of biostimulants in Iran are mentioned in this review. In conclusion, yield response in medicinal plants to biostimulants application showed that each medicinal plant responds in a different way based on the chemical composition and components of biostimulants, the timing and rate of application.</div> Biostimulants, Elicitors, Medicinal Plants, Plant growth regulators, Secondary metabolites Biostimulants, Elicitors, Medicinal Plants, Plant growth regulators, Secondary metabolites 6 39 http://jmp.ir/browse.php?a_code=A-10-59-15&slc_lang=en&sid=1 H Rafiee هانیه رفیعی hanieh_r20032003@yahoo.com 100319475328460040515 100319475328460040515 No Department of Horticulture Science, Islamic Azad University (IAU), Science and Research Branch, Tehran, Iran Department of Horticulture Science, Islamic Azad University (IAU), Science and Research Branch, Tehran, Iran HA Naghdi Badi حسنعلی نقدی‌بادی Naghdibadi@yahoo.com 100319475328460040516 100319475328460040516 No Medicinal Plants Research Center, Institute of Medicinal Plants, ACECR, Karaj, Iran Medicinal Plants Research Center, Institute of Medicinal Plants, ACECR, Karaj, Iran A Mehrafarin علی مهرآفرین A.Mehrafarin@gmail.com 100319475328460040517 100319475328460040517 Yes Medicinal Plants Research Center, Institute of Medicinal Plants, ACECR, Karaj, Iran Medicinal Plants Research Center, Institute of Medicinal Plants, ACECR, Karaj, Iran A Qaderi اردشیر قادری Ardeshir582008@gmail.com 100319475328460040518 100319475328460040518 No Medicinal Plants Research Center, Institute of Medicinal Plants, ACECR, Karaj, Iran Medicinal Plants Research Center, Institute of Medicinal Plants, ACECR, Karaj, Iran N Zarinpanjeh نسیم زرین پنجه Nassimzp@yahoo.com 100319475328460040519 100319475328460040519 No Medicinal Plants Research Center, Institute of Medicinal Plants, ACECR, Karaj, Iran Medicinal Plants Research Center, Institute of Medicinal Plants, ACECR, Karaj, Iran A Sękara آگنیسزکا سکارا A.Sekara@ur.krakow.pl 100319475328460040520 100319475328460040520 No Department of Vegetable and Medicinal Plants, University of Agriculture in Krakow, Krakow, Poland Department of Vegetable and Medicinal Plants, University of Agriculture in Krakow, Krakow, Poland E Zand اسکندر زند eszand@yahoo.com 100319475328460040521 100319475328460040521 No Weed Research Department, Iranian Plant Protection Research Institute, Tehran, Iran Weed Research Department, Iranian Plant Protection Research Institute, Tehran, Iran