Chlorophyllous and achlorophyllous specimens of Epipactis microphylla,(Neottieae, Orchidaceae) are associated with ectomycorrhizal septomycetes, including truffles.

Mycoheterotrophic species (i.e., achlorophyllous plants obtaining carbon from their mycorrhizal fungi) arose many times in evolution of the Neottieae, an orchid tribe growing in forests. Moreover, chlorophyllous Neottieae species show naturally occurring achlorophyllous individuals. We investigated the fungal associates of such a member of the Neottieae, Epipactis microphylla, to understand whether their mycorrhizal fungi predispose the Neottieae to mycoheterotrophy. Root symbionts were identified by sequencing the fungal ITS of 18 individuals from three orchid populations, including achlorophyllous and young, subterranean individuals. No rhizoctonias (the usual orchid symbionts) were recovered, but 78% of investigated root pieces were colonized by Tuber spp. Other Pezizales and some Basidiomycetes were also found. Using electron microscopy, we demonstrated for the first time that ascomycetes, especially truffles, form typical orchid mycorrhizae. All identified fungi (but one) belonged to taxa forming ectomycorrhizae on tree roots, and four of them were even shown to colonize surrounding trees. This is reminiscent of mycoheterotrophic orchid species that also associate with ectomycorrhizal fungi, although with higher specificity. Subterranean and achlorophyllous E. microphylla individuals thus likely rely on tree photosynthates, and a partial mycoheterotrophy in individuals plants can be predicted. We hypothesize that replacement of rhizoctonias by ectomycorrhizal symbionts in Neottieae entails a predisposition to achlorophylly.

Cancer of the large intestine and previous cholecystectomy: does a relationship really exist?

The possible relationship between cancer of the large intestine and previous cholecystectomy has been studied both experimentally and clinically but the results are contradictory. The present study, carried out in 250 patients undergoing intestinal resection for colorectal cancer and in 200 subjects who underwent cholecystectomy more than 10 years previously (with control groups) did not evidence any statistically significant relation (p = 0.2) between cholecystectomy and cancer of the large intestine. On the basis also of data from the literature, the etiopathogenetic hypotheses of the supporters of such relationship are reviewed and the different factors potentially able to explain the discrepancy between the concordant results of experimental studies and the contrasting ones of the clinical and epidemiologic experiences are examined. From the practical point of view, it is felt that a periodic (once a year) clinical and laboratory (guaiac test) control followed, when necessary, by x-ray/and or endoscopic examination should be carried out in all the patients over the age of 40, cholecystectomized since 10 years of longer, especially if females.