Refractometry of fungi.

Area of Science:

• Cell biology
• Biophysics
• Mycology

Background:

• Immersion refractometry relies on matching the refractive index of a surrounding medium to the cell's cytoplasm.
• This matching causes minimal contrast in phase contrast microscopy, making the cytoplasm nearly invisible at the match point.

Purpose of the Study:

• To detail the principles, preparation, and interpretation of immersion refractometry.
• To quantify the solid concentration within fungal hyphae and spores using this technique.

Main Methods:

• Utilized immersion refractometry to measure refractive indices of fungal cells.
• Correlated refractive indices to solid concentrations (g/100 ml) using the formula n-no = αC.
• Examined solid concentration variations in fungal hyphae and spores based on age and physiological state.

Main Results:

• Fungal hyphae exhibited solid concentrations ranging from 11% to 30%, highest at sites of active growth and reproduction.
• Mature, resting fungal spores showed high solid concentrations (45-54%), with powdery mildew spores at 30-32%.
• Spore germination was preceded by a decrease in solid concentration to 20-30%, followed by swelling and germ tube emergence.

Conclusions:

• Immersion refractometry provides a quantitative method to assess intracellular solid concentrations in fungi.
• Solid concentration dynamics are linked to fungal development, physiological activity, and germination processes.
• A significant drop in solid concentration precedes spore germination, indicating a requirement for metabolic activity.