Natural germinals

The final steps in a total synthesis of (+ )-gloeosporone (3, a natural germination inhibitor of a fungus) required oxidation of the acetylene group of 1 to a diketone group. The oxidation was carried out in 74% yield by the catalytic Ru02 procedure of Sharpless. On liberation (pyridine-HF) of the C7-hydroxyl group, the hydroxy... 

The identification of natural germination inhibitors enables us to study their effect as allelochemicals in detail. Because most of these compounds are natural products not previously known, they have to be synthesized at first in order to obtain sufficient material for such investigations. This work is in progress. 

Naturally occurring phenolic compounds such as catechol, resorcinol, pyro-gallol, salicylic, gallic, ferulic, caffeic, and coumaric acids all serve as germination inhibitors. Indeed, some of the selective herbicides such as the substituted phenols and cresols also serve as germination inhibitors. Because of the widespread occurrence of coumarin in plants and its demonstrated inhibitory effects at levels found in fruits and some seeds, it is considered to be a natural germination inhibitor (Lerner et al. 1959). In time, of course, coumarin is metabolized in resting seeds to a level below inhibition. 

B. In the Germination of Soybean and Japanese Radish Seeds. Chitinase and chitosanase activities increase in the course of the natural germination of the uncoated soybean seeds (Figure 4). The maximum activities... 

Veralrum alkamines. These may occur naturally as such, or in the form of the esters, or glucosides of types (1) and (2). Cevine, germine jervine, protoverine, rubijervine, isorubijervine, veratramine. They are all, so far, Cj, compoimds. 

Thiourea and allylthiourea (20), D-xylulose (22), sodium diethyldithiocarbamate, L-methionine, and -propyl-di- -propylthiol-carbamate (163), 12 6-(substituted) purines (166), and two coumarin derivatives (164) have been found to promote Striga seed germination. None of these materials, however, appear to be constituents of the natural stimulant preparations. 

In nature, spores canrevertto the vegetative form by a process called either germination or germination and outgrowth. The process of germination may be triggered by specific... 

Agrochemicals from Natural Products, edited by C. R. A. Godfrey Seed Development and Germination, edited by Jaime Kigel and Gad Galili Nitrogen Fertilization in the Environment, edited by Peter Edward Bacon Phytohormones in Soils Microbial Production and Function, William T. 

Possible Mechanism of Allelopathlc Action of Water-Insoluble Plant Lipids. Many non-polar natural products with germination and growth regulation activities In laboratory tests are In pure form not sufficiently water soluble to account for their allelopathlc activities observed In the field. For this reason the notion exists that sterols and other non-polar plant constituents are not likely to play a role In allelopathlc actions, and It Is generally concluded that the bioactivity data observed In the laboratory are therefore coincidental. 

Strigol is a natural product with unusually strong properties as a germination stimulant for parasitic weeds of the genera Striga (witchweed) and Orobanche (broomrape). 

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. 

None of these compounds has been reported in natural stimulant preparations. Similarly, Riopel 2) in a more recent review noted that many compounds promote or inhibit seed germination. Ethylene is an effective germinator, but its use in under developed countries is minimal. 

Much remains to be accomplished in the separation, isolation, and identification of both naturally occurring and synthetic bioactive materials effective in the germination of parasitic weed seeds. Structure-activity studies suffer from the lack of separation of isomers in most synthetic samples. Strigol is an important tool in basic studies on the effect of chemicals on seed germination, but it is highly unlikely that the compound will meet practical field... 

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