I am really surprised to know that Geoff, an EC of 600 corresponds to roughly 400 to 450 ppm (mg/L) of TDS which is actually very high for the culture of most orchids. The sap exudate is no more than 0.66% mineral and 1-2 percent sugar, so to get to the figure of 400 mg TDS roughly 40 ml of sap per litre of water will be needed which sounds astronomical to me, could you email me your papers at halloamey@hotmail.com . I can comment more after reading the paper, but don't you think your test subjects (root drippings of Orchids) are biased? Did you have controls like say drippings from other plants like ferns, mosses or directly from the barks of the trees etc?
Quote Originally Posted by Dorsetman View Post
Epiphytes grow on other plants , and the water they get is not straight from the sky , it is what has landed on other plants, and then trickled down onto the epiphytes. Most plants in active growth express sap from the leaves - the pressure applied to keep the plant erect and turgid results in some " leakage " - e.g. as "honeydew" ( Try looking at your plants at 2 am - there may be surprised how much ther is then ). This gets dissolved in the rainwater, and provides nutrients to the epiphytes.
So I discovered when I sat in the rain forest in Thailand, in the rainy season, and took samples of water from the open sky ( EC as low as 20) and then collected drips from the roots of e.g. dendrobiums - and found the EC was up to 600. I did this at several sites,at different times, from several different genera ( paphs, Coleogynes, etc ) and always found more or less the same thing.