Table 2.

Porosity of sediment and aquatic roots of Cotula coronopifolia and Meionectes brownii

		Porosity (% gas volume per unit root volume)
Treatment	Root type	C. coronopifolia	M. brownii
Initial harvest	Sediment	12·5 ± 3·0a	15·3 ± 0·8a
Aerated	Sediment	13·0 ± 1·1a	15·8 ± 1·3a
Stagnant	Sediment	38·2 ± 1·7b	30·5 ± 1·3b
Partial submergence	Sediment	n.d.	n.d.
Complete submergence	Sediment	n.d.	35·5 ± 1·4b
Partial submergence	Aquatic	42·5 ± 2·0b	20·9 ± 0·2c
Complete submergence	Aquatic	38·2 ± 1·2b	20·8 ± 1·9c

Porosity was measured on approx. 0·5 g of fresh root segments taken 4–9 cm from the root/shoot junction. Data presented are means ± s.e., n = 3. Diffrent letters indicate significant differences at P < 0·05 (comparisons within species, i.e. down columns).

n.d.: not determined as these roots were too flaccid or partially decayed.