| Popis: |
Dipping leaves bearing 3-day-old infections into water at 50 °C for 25 sec caused the haustoria to shrink, the intercellular hyphae to stop growing, and some host cells to respond, but only at or near infection sites. Responses at all infection sites were synthesis of encasing material around many haustoria and death of a few of the cells which had been penetrated by haustoria or contacted by intercellular hyphae. Another response, seen around potentially incompatible infections only, was death of many cells surrounding fungal colonies; this occurred in a pattern characteristic of the necrosis that would have occurred naturally at a later stage of infection. Mixed inoculations with virulent and avirulent races affected the ways in which different types of infection sites developed, but only where these sites were close together. Necrosis was prevented on borders of avirulent colonies facing nearby virulent colonies, and the avirulent colonies grew more in these positions. The growth of virulent intercellular hyphae appeared to be less near the necrosis of incompatible infections. The results of these experiments are discussed in relation to hypotheses about underlying mechanisms regulating the development of incompatible and compatible interactions. |
