Synthetic germination stimulants

The product (4) is a synthetic germination stimulant for parasitic plants. Normally these plants germinate only when the host is growing. Premature germination induced by (4) increases yields of sorghum (an African food crop) planted later. 

Johnson, A. W., Roseberry, G., and Parker, C. 1976. A novel approach to Striga and Orobanche control using synthetic germination stimulants. Weed Res. 16, 223-227... 

Verkleif, J. A. C., and Zwanenburg, B. 1999. Dose-response of seeds of the parasitic weeds Striga and Orobanche toward the synthetic germination stimulants GR24 and Nijmegen 1. J. Agric. Food Chem. 47, 1705-1710... 

Johnson, A. W., G. Rosebery, and C. Parker A Novel Approach to Striga and Orobanche Control using Synthetic Germination Stimulants. Weed Research 16, 223 (1976). 

The germination stimulant or stimulants from host plants have not yet been identified, but research on isolation and identification of these allelopathic compounds continues. Other nonhost plants, such as cotton, also release chemicals which stimulate the germination of witchweed seed and these crops can replace the cereal crops in witchweed-infected fields. If no acceptable host is present, the witchweed plant is unable to mature and produce seed. The importance of cereal crops as a staple food in underdeveloped countries makes growth of nonhost crops only partially acceptable, and there are numerous wild hosts that allow the witchweed to germinate, mature, and produce more seed (several thousand seeds can be produced by a single plant). Nevertheless, application of either natural or synthetic stimulants in the absence of a host plant is an effective way of reducing and eventually eliminating the witchweed problem. 

Matsui, J., Bando, M., Kido, M., Takeuchi, Y., and Mori, K. 1999. Plant Bioregulators, 3. Synthetic disproof of the structure proposed for Alectrol, the germination stimulant from Vigna unguiculata. Eur. J. Org. Chem. 9, 2195-2199... 

A variety of strigol analogs have been synthesized and tested as germination stimulants with seeds of Striga and Orobanche (27-30). To provide a general overview, the structures and in vitro activity of some of the many compounds that have been evaluated are summarized in Scheme 3. The compounds 20-23 are early synthetic intermediates from the total synthesis of strigol and the hydroxy aldehyde 22 exhibits activity similar to strigol. 

Scheme 3. Some Synthetic Strlga Seed Germination Stimulants...

Mori K, Matsui J, Bando M, Kido M, Takeuchi Y (1998) Synthetic disproof against the structure proposed fw alectrol, the germination stimulant from Vigna unguiculata. Tetrahedron Lett 39 6023-6026... 

Coumarin reduced labeled glucose incorporation and carbohydrate and protein content of the cytoplasm of Pythium, but enzymes related to the metabolism of cell wall polysaccharides were not affected [296]. It has been reported that moulds are more sensitive to coumarin when they are cultured on the simple synthetic nutrient medium than on the yeast water [140]. This suggests that coumarin blocks the synthesis of an unknown metabolite of ndamental importance. Coumarin was found to affect the level of a variety of free amino acids present in a cell. In addition, some nucleic acid precursors partially reverse the coumarin-induced inhibition of maize mesocotyle [131]. The stimulation of germination and growth caused by coumarin in low concentrations may be assumed as a supercompensation mechanism. 

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