Studies are carried out about the effect of the culture filtrate of Phytophthora cryptogea on different plant species and animal smooth muscle samples.
The results point out that in the 16 plant species, treated with the culture filtrate of P. cryptogea, different types of response are registered: systemic, expressed by yellowing of the veins, leading to a sudden wilting of the plants; necrotic (local), shown as quick chlorosis and necrosis of the plant cells; local-systemic types – a systemic infection in the veins next to the necrotic spots.
On the smooth muscles, the effect of the filtrate has a two-phase profile. In concentrations up to 1.5 %, the filtrate stimulates the muscle tonus. In a higher concentration (≥ 2 %) the filtrate has an inhibitory effect. This effect is shown in two cases: when calcium ions (Са2+) in an extracellular solution are reduced, and when the Са2+-influx through the membrane is blocked.
The biphasic effect supports the following propositions: (1) the low concentration of the culture filtrate depolarizes the membrane, increases the Са2+-influx and stimulates the smooth muscles; (2) the higherconcentration of the culture filtrate hyperpolarizes the membrane, decreases the Са2+-influx and induces therelaxation of the smooth muscles.
Keywords: Phytophthora, culture filtrate, defense response in plants, smooth muscles, isometric contraction