Ipomoea spp

An interesting feature of this list is that some of our most troublesome and difficult to control weeds are not suspected allelopathics. Many weeds, such as morningglory (Ipomoea spp.), cocklebur (Xanthium strumarium L.), and sicklepod (Cassia obtusifolia L.), which make almost all lists of serious weed species, are strong competitors with little or no evidence of allelopathic activity. In fact, cocklebur is probably the epitome of what a competitor can be, being even more devastating than... 

Friedman, M., Dao, L., Gumbmann, M. R. (1989). Ergot alkaloid and chlorogenic acid content in different varieties of morning-glory (Ipomoea spp.) seeds. J. Agric. Food Chem., 37, 708-712. 

However, as can be concluded from Table 3.2 tropane alkaloids are no suitable chemotaxonontic indicators as far as intergeneric relationships are concerned. Independent of this, tropanes in species from genera belonging to the advanced tribe Ipomoeeae (Argyreia, Ipomoea etc.) are rather rare with the exception of Old World (Australasian) Ipomoea spp. and the /MncsaAstripomoea. Furthermore,... 

In this connection the question arises whether swainsonine is a metabolite synthesized by such Ipomoea spp. themselves. This alkaloid was found as a L-lysine-derived metabohte in fungi, e.g., Metarhizium anisopliae (Sim and Perry 1997), Rhizoctonia leguminicola (Harris et al. 1988). Thus, it might be that the unusual occurrence of swainsonine in certain Ipomoea spp. is due to certain unknown symbiotic endophytes. Exactly this has already been proved in the case of ergoline alkaloids in a few species of this genus (see Sect. 4.2). 

Some members of section Mina represent popular ornamentals, e.g I. hederifolia, I. lobata, /. quamoclit, I. sloteri. Though of neotropical origin they have become popular pantropical and pansubtropical ornamentals. They are characterized by scarlet to red-yellow coloured (see Sect. 6.8.3), predominantly trumpet-shaped corollas both characters are rather unusual for Ipomoea spp. 

As already mentioned, at present only 23 Ipomoea spp. are to be considered as ergoline-positive without any doubt. Surprisingly, the alkaloid profiles of these species are apparently very similar. Seventeen species show a characteristic profile of... 

Table 4.3 summarizes 41 Ipomoea spp. for which only ergoline-negative reports have been published. Negative results are also important from the chemotaxonomic point of view. Tables 4.1. 3 altogether include 79 out of about 650 species of this largest convolvulaceous genus. Twenty-three species only were found to be ergohne-positive (-30%). 

From grasses it is well known that there are infected and non-infected populations, e.g., of Festuca armdinacea, which are defined scientifically in publications in abbreviated form as El (= endophyte-infected) or E+ (= endophyte is present) vs EE (= endophyte free) or E- (= endophyte is not present), respectively. To date it is an umesolved issue whether there are also infected as well as uninfected species or populations of species in the ergoline-positive Ipomoeeae. If this would be the case this could explain perhaps - at least in some cases - the existence of contradictory reports on the occurrence of ergoline alkaloids in certain Ipomoea spp. (Table 4.2). 

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