Phosphorus deficiency reduced total root length (main plus
lateral roots) by more than one third (Fig. 3). The total lateral
root length (the product of the mean lateral root length and
the number of lateral roots) was significantly reduced by
phosphorus deficiency (Fig. 3). This was a result of the
reduction in lateral root number (Fig. 3), as mean lateral root
length was unaffected by phosphorus treatment (Table 1).
Lateral root density (the number of laterals per cm of main
root) was significantly reduced in phosphorus-deficient
roots compared with phosphorus-sufficient roots (Fig. 4).
Phosphorus deficiency reduced the DW of roots by
about one third (Table 2), but there was a proportionately
greater reduction in shoot DW, nearly doubling the root-toshoot
ratio (Fig. 4).
There was no difference between the sufficient and deficient
phosphorus treatments in ethylene concentrations in
the root zones. However, ethylene production per g DW
was significantly higher in phosphorus-deficient roots
compared with phosphorus-sufficient roots (Table 2).