The effects of Al on Ca transport could influence Ca accumulation in p
lants. Low forage C2 concentrations may cause hypocalcemia, a Ca defic
iency syndrome of ruminants. Solution culture experiments were conduct
ed in a growth chamber to examine the effects of Al (5-50 muM) on upta
ke and translocation of Ca (Ca-45) in winter wheat (Triticum aestivum
L.) cultivars (Al-tolerant Atlas 66 and Al-sensitive Scout 66). Three-
day-old seedlings, grown either in a CaCl2 solution (0.1 or 1.0 mM) or
in a complete-nutrient solution, were used. For plants grown in CaCl2
solution, addition of 5 muM Al significantly decreased Ca uptake and
translocation in Scout 66, but not in Atlas 66. Higher levels of Al (2
0 and 50 muM) decreased Ca uptake and translocation much more in Scout
66 than in Atlas 66. For plants grown in complete-nutrient solution,
Al (5-50 muM) exposure for up to 6 h had little effect on Ca uptake an
d translocation in either cultivar. This may be due to the reduction i
n Al3+ activities in the external solution, as well as lowered Al3+ ac
tivities near the root-cell plasmalemma. When roots were exposed to Al
for 24 h, Ca uptake and translocation were decreased significantly in
Scout 66, but were little affected in Atlas 66. The percentage of Ca
translocated to the shoots was significantly decreased by Al in Scout
66, but not in Atlas 66. These results suggest that Al inhibits both C
a uptake and translocation in Scout 66, but inhibits primarily root Ca
uptake in Atlas 66 (and only at higher Al levels). It appears that th
e use of Al-tolerant cultivars of wheat forages on acid soils could be
important for maintaining proper Ca nutrition of grazing animals.