Effects of Pedicularis kansuensis parasitism on the photosynthetic characteristics of host grass-Epichloë symbionts

Abstract:

[Objective] Pedidcularis kansuensis forms parasitic relationship with Epichloë-infected host grasses through root haustoria connections. However, only few studies have paid attention to the effects of Epichloë endophyte on host grass photosynthetic characteristics while the host grasses were parasitized by root hemiparasitic plants. [Methods] Thus, in this study, we evaluated effects of endophyte infection on net photosynthesis rate (P_n), transpiration rate (T_r), stomatal conductance (G_s), concentration of CO₂ intercellular (C_i) and water use efficiency (WUE) of two host grasses (Stipa purpurea and Elymus tangutorum) in the presence (or absence) of P. kansuensis.[Results] Irrespective of endophyte status, P_n, T_r and G_s of host plants decreased in the presence of P. kansuensis; however, C_i and WUE of host plants increased in the presence of P. kansuensis. P_n, T_r and G_s of endophyte-infected (E+) S. purpurea were higher than endophyte-free (E-) counterpart, while C_i and WUE of E+ S. purpurea were lower than E- ones. By contrast, P_n, T_r and G_s of E+ E. tangutorum was lower than E- counterpart, while C_i and WUE of E+ E. tangutorum higher than E- ones. [Conclusion] Consequently, these results suggest that interactions between endophyte and host grasses are context-dependent, and the relationships between host grass and Epichloë endophyte range from mutualism to parasitism when grasses become common hosts to root hemiparasitic plant and Epichloë endophyte.