Morpho-physiological responses of four chamomile species to rainfed conditions and drought stress under greenhouse conditions

Drought stress is one of the most important factors limiting the survival and growth of plant in different parts of Iran. In this study, the morphological characteristics of four perennial chamomiles species, Anthemis tinctoria, Matricaria recutita, Tripleurospermum sevanense and Tanacetum parthenium, were evaluated in rainfed and greenhouse conditions in Alborz research field, Research Institute of Forests and Rangelands, Iran. The results showed that M. recutita had the highest plant crown surface, height, flower number,plant dry weight; and early flowering date in rainfed conditions compared to the other three species. In the greenhouse experiment in order to study the physiological mechanisms of response to water deficit, the four species were subjected to four drought treatments including well-watered (control), mild drought stress (75% of field capacity (FC)), moderate drought stress (55% of FC), and severe drought stress (35% of FC). Changes in compatible solutes (proline and soluble sugars), relative water content (RWC), antioxidant enzymes (peroxidase and polyphenol oxidase) and pigments of stress plants were investigated. The result of the physiological response of the chamomile species in greenhouse condition showed that M. recutita was the most tolerant species to severe drought stress conditions due to its the higher osmotic regulation capacity, while the other three species A. tinctoria, T. servanes and Tanacetum parthenium showed good tolerant to moderate stress conditions.