Studies on factor(s) in sweet potato which specifically inhibits germ tube growth of incompatible isolates of Ceratocystis fimbriata

Sweet potato root contained a factor or factors which differentiallyinhibited the growth of various isolates of Ceratocystis fimbriata.The factor scarcely inhibited germ tube growth of sweet potatoisolate, compatible to sweet potato. On the other hand, thegrowth of prune, oak, taro and almond isolates, all incompatibleto sweet potato, was strongly inhibited. The germ tube growthof coffee and cacao isolates, incompatible to sweet potato,were less inhibited. Inhibitory factor was distributed throughvarious fractions when centrifuged on a sucrose density gradient.The germ tube growth of pre-germinated oak isolate became lesssensitive to the inhibitory factor after being treated withpronase, suggesting the interaction of the factor with someprotein-containing surface structure of the fungal cell. Treatmentof the factor by phospholipase c, lipase and pronase causedno changes in its inhibitory activity, whereas periodate treatmentpartially inactivated the factor. These results suggest thatthis inhibitory factor constitutes one of the factors determiningthe specificity in sweet potato-C. fimbriata interactions. (Received July 18, 1977; )     

Herbivores and the evolution of the semelparous perennial life-history of plants

The relationship between a plant and its potential enemies changes drastically after reproduction has started. Using a dynamic modelling approach we study the effects of herbivores and pathogens, that are attracted by reproducing plants, on optimal allocation of resources, and life-history strategies. We assume that the level of attack increases with the investment in reproduction, which may lead to a reduction of current years reproductive success, a reduction of storage efficiency or an increase of plant mortality. If herbivores or pathogens attracted by flowering plants mainly reduce current years reproductive success, the optimal life-history is annual or iteroparous perennial if the attack is an all or nothing event. If the level of consumption increases with the number of herbivores attracted, the optimal life-history is most likely iteroparity with or without mast years. Only under very restricted conditions this may lead to semelparity. If herbivores mainly reduce the efficiency of the resources stored for next year, the optimal life-history is iteroparity. If herbivores mainly reduce survival, the optimal solution is likely to be mast years or semelparity. For parameter values that are realistic for Cynoglossum officinale, a semelparous perennial from calcereous soils, the model predicts that reproduction should start in the third year and that 99% of the available resources at the end of season should be invested in reproduction and only 1% saved for growth next year. With such an investment only c. 1% of the plants would survive after reproduction, so the optimal life-history is close to semelparity. For the small fraction of plants that reproduce more than once, years of vegetative growth only and years with reproduction should alternate. Multiple reproduction is rare in C. officinale. However, such a life history is very common for plants known as semelparous perennial. Although the available empirical evidence is, as yet, circumstantial rather than conclus ive we propose that reproduction related mortality mediated through herbivores or pathogens may play a role in the evolution of the semelparous perennial life-history.     

Multicorrelation analyses of toxic and antigenic components of DPT and DP vaccines produced in Japan

The combined diphtheria-pertussis-tetanus and combined diphtheria-pertussis vaccines, of which the contents of endotoxin, LPF and HSF were reported in the previous paper, have been tested for the respective potencies of pertussis, diphtheria and tetanus components. In order to obtain some information concerning possible adjuvanticities of the toxic components of pertussis cells, relationship between respective toxic activities and the potencies of the respective antigenic components were tested by applying the multiple regression analyses. The results showed that the effects of the toxic components were fairly complicated. Within the ranges of contents of the respective toxic components of the vaccines used in the present experiment, LPF appeared to enhance all the three potencies as the content increased, while the effects of endotoxin and HSF were either enhancing or suppressive depending on the antigenic components.