Yes, I do agree, that some eukaryotic cells survive only on the resources provided by other eukaryotic cells and that prokaryotic cells are not involved in this type of \"supply for life\". Symbiotic root colonization by Eukaryotic cells by Mycorrhizal mycelia: Mycorrhizal mycelia can only survive in a symbiotic relationship with other plant root \"cells (eukaryotic)\" by supplying nitrogen materials to the plants followed by obtaining its nutrients for survival. Mycorrhizal mycelia cannot survive outside the environment as prokaryotes do The traits that allowed them to maintain symbiotic relationships are as explained in case of fungi, in which hydrolytic enzymes have capability to assimilate \"nitrogenous material and supply\" them to plants. The relative number of competitors, the relative availability of symbiotic partners such as Mycorrhizal mycelia are living on the roots surface of the host plant as mutualistic symbionts (supply of life) and enabling the host root colonization of land plants with increased absorption of nutrients such as phosphates, nitrates, water etc. by providing the surface area for absorption. Fungi and plant symbiosis represents one of the most important interspecific eukaryotic partnerships to have occurred on the planet. Fungal mycelia and ancient archaic prokaryotes are living on the roots surface of the host land plants as mutualistic symbionts in 500 millions of years ago and enabling the host root colonization with increased abruption of nutrients such as phosphates, nitrates, water etc. by providing the surface area for absorption. This process produced a vital photosynthesis rate by increasing total gross primary productivity finally enhancing the release of exclusive amounts of oxygen in the atmosphere result in higher oxygen concentration together to form ozone layer to protect against harmful UV radiation. The oxygen gas is conductive to air-breathing animals on the land whereas dissolved oxygen is conductive to all aquatic animals. These land plants with differential reproductive ability to produce gametophytes enabled their sexual reproduction (embryophytes, all vascular plants including angiosperms and gymnosperms) to produce more progeny to generate higher rate of photosynthesis associated with increased rate of colonization to produce oxygen gas to air- breathing animals. The traits that allowed them to maintain symbiotic relationships are as explained in case of fungi, in which hydrolytic enzymes have capability to assimilate \"nitrogenous material and supply\" them to plants. The altitudinal increase of root-to-shoot (C/N) ratio is meticulously due to low nutrient availability. This is because of “low Michorrizha availability for symbiotic relationship” to supply nutrient as elevated altitudes lowered temperatures. Therefore, low temperature and low soil microbial decomposition with organic matter with water logging & low nitrogen availability make the plants to increase their C/N ratio as an ev.