Ammonium reduces leaf stomatal conductance of tobacco plants. The flow and partitioning of potassium in tobacco plants can be changed, depending on the nitrogen forms and nutrient levels.
The effect of the endophyte Neotyphodium lolii on susceptibility of perennial ryegrass (Lolium perenne) to ten fungal pathogens in detached leaves was studied. The pathogens were Alternaria alternata, Ascochyta leptospora, Bipolaris sorokiniana, Curvularia lunata, Fusarium acuminatum, F. avenaceum, F. chlamydosporum, F. solani, F. oxysporum, and Gliocladium roseum. In addition, the effect of the endophyte on four pathogens (A. alternata, B. sorokiniana, Curvularia lunata and F. avenaceum) in living plants was studied, and changes in host superoxide dismutase (SOD) or peroxidases (POD) activity were examined. The total lengths of lesions on detached leaves were greater (P<0.05) on Eplants than on E+ plants except for A. leptospora although differences between E+ and E-were not consistently significant at all sample times (days after inoculation).The numbers of lesions were greater (P< 0.05) and the lesions were larger (P<0.05) on intact E-plants than on intact E+ plants for all of the four pathogens. SOD enzyme activity was significantly greater (P<0.05) in E+ plants than in E-plants only for A. alternata, C. lunata, and F. avenaceum. POD enzyme activity was significantly greater (P<0.05) in E+ plants than in E-plants only for C. lunata, B. sorokiniana and the uninoculated control.
Achnatherum inebrians (drunken horse grass), a grass that is intoxicating to grazing animals and commonly found within native grasslands of China, is host to a symbiotic endophyte, Neotyphodium gansuense. In laboratory tests, N. gansuense infections of A. inebrians increased mortality rates and reduced the survival of an aphid Rhopalosiphum padi and a mite Tetranychus cinnabarinus. Both species demonstrated a quantitative preference for feeding on endophyte-free (E)) compared with endophyte-infected (E+) leaves. In the field, populations of the two species were lower on E+ compared with E) specimens for most of the growing season. Results of tests with a grasshopper species (Oedaleus decorus) gave similar results. A species of seed-harvesting ant (Messor aciculatus) showed a preference for collecting E) seeds. These results demonstrate that the antiherbivore activity of E+ A. inebrians is effective against a wide range of arthropod groups. Thus, the Neotyphodium endophyte may help this grass to improve its invasive ability and, therefore, broaden its range.
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