Table 1.

Vessel density (number of vessels per mm²) and vessel connections in deep and shallow roots of S. lanuginosum and Q. fusiformis assessed using HRCT images (mean ± s.d.)

Species/depth	Vessel density	No. of vessel connections	Total no. of vessels observed	Fraction of vessels with connections
S. lanuginosum shallow	14·7 ± 9·3	409	1211	0·34
S. lanuginosum deep	20·9 ± 5·0	576	1295	0·44
Q. fusiformis shallow	11·4 ± 4·3	4	548	0·01
Q. fusiformis deep	16·9 ± 6·7	14	224	0·06