(Table 1). The increased antioxidant activity positively correlated with host biomass and root length but negatively with secondary root counts (Kumar et al. 2009; Table 1) compared to endophyte free (E-) plants. Similarly, Waller et al. (2005) found E + wheat produced significantly more antioxidants and biomass when

exposed to salt stress compared to E- wheat (Table 1). NVP-BGJ398 Though not measuring antioxidant nor reactive oxygen species directly, Mandyam et al. (2010) documented production of polyphenol oxidases, which are known to scavenge reactive oxygen species, in E + but not E- hosts. For example, Grünig et al. (2003) reported enzymatic differentiation within Phialocephala spp. suggesting these root endophytes are able to produce various enzymatic metabolites which may positively impact host physiology. Bartholdy et al. (2001) quantified the production LY2874455 ic50 of hydroxamate siderophores by Phialocephala fortinii at different pH values. Siderophores chelate iron thereby increasing iron uptake in iron-poor habitats. Production of siderophores suggests a potential currency for endophyte-plant mutualism. However research is needed to determine if siderophore production by the fungus occurs in situ and Geneticin concentration if it positively correlates with plant performance. Comparisons between E + and E- plant hosts in terms of physiological phenotypes

and stress have been investigated from the cell to whole plant level (Table 1). Cell cultures from wine cultivars colonized

by Trichoderma viride had significantly reduced cell volumes after 48 h of exposure but significantly increased cell conductivity (Calderón et al. 1993). We hypothesize conductivity could conceivably increase the transmission of molecules across cell membrane surfaces, thereby enhancing signaling and associated response mechanisms. However, we acknowledge this is highly speculative and research on whole plants is necessary. Additional support for altered physiological phenotype of E + plants comes from a specific strain of Trichoderma harzianum, T22, which is well documented to enhance host performance in a variety of contexts (Harman 2000 and 2006; Harman et al. 2004). Matsouri et al. (2010) looked for causal mechanisms PDK4 and concluded that increased E + host tolerance to salt and temperature stress resulted from changes in lipid peroxidation as well as ratios of reduced to oxidized forms of both glutathione and ascorbate. In addition, Bae et al. (2009) reported a significant increase in some amino acids and sugars in E + hosts exposed to drought. Interestingly, in this case root symbiotum did not produce significantly higher osmoprotectants, while drought exposed E- plants did. This suggests a complicated symbiotic outcome because increased amino acid and sugar production (both are indicators of increased osmolytic activity) are typical of plants possessing a drought tolerant phenotype (Shinozaki and Yamaguchi-Shinozaki 2007).