Effects Of Pathogen Puccinia Elymi On Ecophysiological Characteristics Of Host Plant Leymus Chinensis

The interactions between pathogens and their host plants, which are very common in nature plant populations, have been studied as a focus by internal and external ecologists since 1980s. In general, the host plant isn't killed by the pathogen at once but physiological and biochemical characteristic is changed complicatedly. Accordingly morphology and metabolism are changed. Study on the relation of pathogen to host plant may give convenience to discovery the regulation of interaction between them and form the base of resistance mechanism to disease of host plant and inheritance breeding of disease free.The host Leymus chinensis is a perennial gramineous plant. It is the first discovered that this plant is infected by pathogen Puccinia elymi in nature. In the long run of co-evolution, they have set up a steady relation. This paper relates to changes of morphology and nutrition metabolism on L. chinensis in different infection stages and soil conditions. The results showed that:(1) When host plant L. chinensis infected by pathogen P. elymi, significant differences existed in the leave weight and leave morphology. The fresh weight, leaf length and leaf width of diseased leaves decreased with significant differences to the normal ones (P﹤0.05), but the percentage of dry matter increased. The fresh weight of gradeⅢinfected leaves (10.50g) decreased by 8.30% to the control (11.45g), however the dry weight of different disease severity leaves weren't obvious differences.(2) The soluble sugar, sucrose, fructose, crude protein and proline content of infected leaves increased with the increase of disease severity, while the photosynthetic pigment content decreased, which showed that the higher disease severity was the larger nutrition metabolism of L. chinensis leaves changed.(3) Whether infected by P. elymi or not, the nonstructural carbohydrates, crude protein and proline content of L. chinensis leaves in the urediospore stage were lower than that in the teliospore stage. The soluble sugar, sucrose and fructose content of gradeⅢdiseased leaves increased with significant differences to the normal ones (P﹤0.05). It was thus clear that nutritions were consumed because the pathogen would accomplish its life cycle that affected metabolism and photosynthesis characteristics of the host plant.(4) In natural habitat and under different soil conditions, the physiological and biochemical characteristic of host plant L. chinensis also showed some differences from normal ones when infected by P. elymi. The nonstructural carbohydrates, proline and photosynthetic pigment content of L. chinensis leaves increased with aggravating the extent of soil salt-alkalization, while the crude protein content decreased. L. chinensis populations could keep their physiological metabolism and photosynthesis characteristics better when they lived in the salt-alkaline and pathogenic environments. Therefore, it could be considered that the carbohydrates, proline and photosynthetic pigment were helpful to plant resistance mechanism. Additionally it showed that L. chinensis was a better resistant plant.The results suggested that P. elymi poisoned L. chinensis obviously. P. elymi not only affected leaves shape and growth but also influenced physiological metabolism characteristic of L. chinensis.