page_title: Strigolactone
section_title: Germination of parasitic plant
hierarchical_section_title: Strigolactone / Discovery / Germination of parasitic plant
caption_attribution_description: Latina: Striga asiatica
context_page_description: Strigolactones are a group of chemical compounds produced by a plant's roots. Due to their mechanism of action, these molecules have been classified as plant hormones or phytohormones. So far, strigolactones have been identified to be responsible for three different physiological processes: First, they promote the germination of parasitic organisms that grow in the host plant's roots, such as Striga lutea and other plants of the genus Striga. Second, strigolactones are fundamental for the recognition of the plant by symbiotic fungi, especially arbuscular mycorrhizal fungi, because they establish a mutualistic association with these plants, and provide phosphate and other soil nutrients. Third, strigolactones have been identified as branching inhibition hormones in plants; when present, these compounds prevent excess bud growing in stem terminals, stopping the branching mechanism in plants.
  Strigolactones comprise a diverse group, but they all have core common chemical structure, as shown in the image to the right.
context_section_description: Strigolactones were first isolated in 1966 from cotton plants, specifically from the roots. However its role in germination of other organisms was not determined until later. Previous studies with Striga lutea had already shown that root extracts from the host plants were necessary for the parasitic seed to start germinating, which made obvious that a substance produced in the roots was stimulating this process. The isolation of strigolactones lead to a series of tests that proved that this compound was the necessary molecule to induce germination of Striga species. Later on, similar compounds were proven to produce the same effect: sorgolactone and alecrol, both of them presented the characteristic lactone group, so they were classified as strigolactones. To induce germination of parasitic plants, strigolactones only needed to be present in trace amounts, in the order of 5 parts per million.
caption: Striga asiatica (Striga lutea)
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