Table 4.

Soil organism motility and extension rates

Organism	Species	Environment	Motility or extension rate* (mm d−1)
Bacterial cells	Undefined general populations†	Aqueous media	1700–3400
Fungal hyphae	Pythium ultimum‡	Solid agar medium, 16 °C	17
		Solid agar medium, 8 °C	4
	Gaemannomyces graminis	Surface of wheat seminal roots,§	Towards root tip, 0·4
		19 °C	Away from root tip, 4·4
		Surface of wheat seminal roots,§	Towards and away from root tip, 1·6
		10 °C
		Surface of slides buried in soil¶	Moist soil (−8 kPa matrix potential), 2·4–9
			Wet soil (−2 kPa), 1
	Rhizoctonia solani	Sandy soil**	Within wet (−2 kPa), 0·5
			Within moist (−6 kPa), 2
			On the surface, wet, 3·5
			Across a gap, 5
		Surface of wheat seminal roots††	1·6 (0·45–2·3)
Insect larvae	Sitona lepidus	Intact soil towards clover nodule‡‡	43

^*Motilities for bacteria and insect larvae; extension rates for fungal hyphae.

^†From Sherwood et al. (2003).

^‡Leach (1947).

^§Gilligan (1980). Direct quantification of hyphal front on wheat roots using microscopy.

^¶Grose et al. (1996, from Blair 1943).

^**Otten et al. (1999, 2004).

^††Refshauge (unpubl. res.). Means of growth at different temperatures and tissue types. Direct quantification of hyphal front on wheat roots using microscopy.

^‡‡Johnson et al. (2004), from measurements in intact soil using X-ray microtomography.