R. Ferris et G. Taylor, INCREASED ROOT-GROWTH IN ELEVATED CO2 - A BIOPHYSICAL ANALYSIS OF ROOT CELL ELONGATION, Journal of Experimental Botany, 45(280), 1994, pp. 1603-1612
A biophysical analysis of root expansion was conducted in four chalk d
ownland herbs (Sanguisorba minor Scop., Lotus corniculatus L., Anthyll
is vulneraria L. and Plantago media L.) exposed to either ambient or e
levated CO, in controlled environment cabinets. Measurements of fine (
F) and extra-fine (EF) root extension rate (RER), water relations, and
cell wall tensiometric extensibility revealed differences in the diur
nal pattern of root growth between species. After 35 d of exposure to
elevated CO2, RER of both F and EF roots increased significantly in da
rkness and on illumination for S. minor, whilst for A. vulneraria (EF
roots only) and L. corniculatus a significant increase occurred at nig
ht whereas for P. media a significant increase occurred during the day
. Cells measured in the zone of elongation were longer in all species
exposed to elevated CO2. Water potential (Psi), solute potential (Psi(
s)), turgor pressure (P), yield turgor (Y) and effective turgor (Pe) w
ere measured by stress-relaxation of excised root tips placed in psych
rometers. Solute potentials decreased significantly for all species fo
llowing exposure to elevated CO2. In S. minor and L. corniculatus, P a
nd Pe, respectively, were higher in elevated CO2. No significant effec
ts of CO2 on Y were observed (not shown). Root cell wall tensiometric
extensibility, measured as % plasticity, increased in all species expo
sed to elevated CO2. These results suggest that root growth is enhance
d following increased cell expansion and that increased P and cell wal
l tensiometric extensibility are both important for root growth in ele
vated CO2.