provided to the endophyte. Endophytes may benefit host plants by preventing other pathogenic or parasitic organisms from colonizing them. Endophytes can extensively colonize plant tissues and competitively exclude other potential pathogens. Some fungal and bacterial endophytes have proven to increase plant growth and improve overall plant hardiness. Studies have shown that endophytic fungi grow in a very intimate interaction with their host plant cells. Fungal hyphae have been seen growing either flattened or wedged against plant cells. This growth pattern indicates that fungal hyphae are substantially attached to the plant host's cell wall, but do not invade plant cells. Endophytic fungal hyphae appear to grow at the same rate as their host leaves, within the intercellular spaces of the plant tissue. The presence of certain fungal endophytes in host meristems, leaves and reproductive structures has been shown to dramatically enhance the survival of their hosts. This enhanced survivability is largely attributed to endophytic production of secondary metabolites which protect against herbivory as well as increased uptake of nutrients. Studies have also shown that during experimental circumstances endophytes contribute significantly to plant growth and fitness under light-limited conditions, and plants appear to have increased reliance on their endophytic symbiont under these conditions. There is evidence that plants and endophytes engage in communication with each other that can aid symbiosis. For example, plant chemical signals have been shown to activate gene expression in endophytes. One example of this plant-endosymbiont interaction occurs between dicotyledonous plants in the Convolvulaceae and clavicipitaceous fungi. When the fungus is in the plant it synthesizes ergoline alkaloids at a higher rate, compared to when it is grown apart from the plant. This supports the hypothesis that plant signaling is required in order to induce expression of endophytic secondary metabolites. Effects on plant behavior There are various behaviors that have been studied that resulted from endophyte symbiosis with plants. Through association with fungal endophytes, the root and shoot structures of Pseudotsuga menziesii (Douglas-fir) saplings in low-nutrient conditions have been shown to be elongated, as well as undergo overall biomass increases. The proposed mechanisms behind this include high inorganic phosphate solubilization ability by the fungi as well as organic phosphate mineralization, increased mycorrhizal associations through root colonization, and enhanced nitrogen and phosphorus uptake. Specific endophyte species can also stimulate root growth by increasing the flux of auxin to where the endophyte is. Additionally, various reports on endophyte interactions have shown