This paper is a literature survey and a stimulus for more research on the topic of leaf damage observed during carbon dioxide enrichment of greenhouse plants. The theories in this paper have consequences for the biodiversity and agriculture on our planet. Because some plants might show severe leaf damage above carbon dioxide concentrations of 700 ppm! A concentration to be exceeded in the atmosphere by our 'hydrocarbon society', which is using fossil fuels for energy production, in eighty years from now. This might seriously derail the flora and agriculture.
Beside the fact that elevated carbon dioxide might cause for instance chlorosis and necrosis, the exponents of leaf damage, in some plants. It certainly affects the opening or closure of the stomata, starch content of the leaves and photosynthesis rate of all plants. Because of this some plants will show growth acceleration and some growth retardation. The most favoured ones will overgrow the rest, thus affecting the biodiversity in the flora through the mechanisms of eutrophication and selective parasitic injuries. The last mechanism will occur because of the higher sugar and starch content of the leaves.
The agriculture might be affected because many of the carbon dioxide damage sensitive plants are nutritious crops, essential for the food production, especially in the third world. Since the industrialised world can afford to genetically engineer these plants and bring them to even higher yields. But will the poor third world be able to buy the expensive seeds?
The complex role of ethylene is discussed. A contaminant of the used carbon dioxide sources in experiments whereby leaf damage is observed. It is a plant hormone, which can also cause the main leaf damage symptoms chlorosis and necrosis. So questions remain: Is the factor causing leaf damage ethylene, carbon dioxide or perhaps both? Experiments to answer these questions are described in this paper. Hypothetically it is possible that ethylene is an exogenous and/or endogenous factor for leaf damage, whereby the biochemical production of it in plants is triggered by elevated carbon dioxide.