COMPARATIVE WATER RELATIONS AND PHOTOSYNTHESIS OF MYCORRHIZAL AND NON‐MYCORRHIZAL BOUTELOUA GRACILIS H.B.K. LAG EX STEUD.

Abstract

SUMMARYThe rangeland grass, Bouteloua gracilis was inoculated with its mycorrhizal symbiont, Glomus fasciculatus, to determine the influence of vesicular-arhuscular mycorrhizae on water status, stomatal behaviour and photosynthesis as well as gross plant morphology, biomass and phosphorus content. Mycorrhizal infection increased transpiration rates by over 100% with 50 to 70 °o lower leaf resistances to water vapour diffusion. Leaf xylem pressure was not different between mycorrhizal and non-mycorrhizal plants indicating that whole-plant resistance to water transport was reduced by more than 50 %. Photosynthetic rates under saturating light conditions increased 68% with infection as a consequence of a 33 % reduction in stomatal resistance and a 67 % reduction in mesophyll resistance to CO2 uptake. Mycorrhizal infection did not affect biomass or gross plant morphology after 30 weeks of growth, but increased chlorophyll and phosphate concentrations by 28 °o and 70 % respectively. These physiological changes indicate that mycorrhizae may substantially alter survival ability of Bouteloua gracilis.

Impact of different levels of superphosphate using arbuscular mycorrhizal fungi and Pseudomonasfluorescens on Chrysanthemum indicum L

“…The height increment registered could be as a result of enhanced inorganic nutrient absorption (Cooper, 1984) and greater rate of photosynthesis (Allen et al, 1981). P. fluorescens was found to be common effective bioinoculant which increased the height of the plant in recommended dose of superphosphate.…”

Arbuscular mycorrhizae and soil/plant water relations

“…AM soil hyphae might serve this same function, perhaps even more effectively than root hairs, because most hyphae can enter finer pores than can root hairs (Tisdall 1991). Better soil-root contact could translate into higher soil-to-root hydraulic conductance, and there is evidence that AM symbiosis can change soil-to-root hydraulic conductance (Allen et al 1981Bildusas et al 1986). …”

The Effect of Removal of Extraradical Hyphae on Water Uptake by Vesicular‐arbuscular Mycorrhizal Plants

“…This results primarily from improved uptake of soil phosphorus (P) through extraradical hyphae which increase the root absorptive-surface area (Hayman, 1983). VAM infection has also been shown to enhance transpiration flux of the host plant (Hardie & Leyton, 1981;Allen et a/., 1981;Nelson & Safir, 1982;Levy, Syvertsen & Nemec, 1983;Graham & Syvertsen, 1984), probably as a result of reduced stomatal resistance (Allen & Boosalis, 1983;Huang, Smith & Yost, 1984;Stahl & Smith, 1984) and increased root hydraulic conductivity (Safir, Boyer & Gerdemann, 1971;Hardie & Leyton, 1981;Nelson & Safir, 1982;Graham & Syvertsen, 1984). It was suggested by Safir et a/.…”