UNGAR, IRWIN A.* AND M. AJMAL KHAN. Department of Environmental and Plant Biology, Ohio University, Athens, Ohio 45701. - Effect of bracteoles on the seeds of two species of Atriplex.
A comparison was made to determine the effects of bracteoles on the
germination response of a salt marsh annual Atriplex prostrata
and a salt desert perennial Atriplex griffithii. Attached
bractoles did not inhibit the germination of A. prostrata but
completely inhibited the germination of A. griffithii seeds.
The presence of detached bracteoles of A. griffithii in petri
dishes with seeds also inhibited germination. Water soluble extracts
from bracteoles of both species indicated that they contained up to
132 g/kg total salts in A. griffithii and 87 g/kg total salts
in A. prostrata. The water potential of dissolved substances
in bracteoles extracts was –15.2 ± 0.17 MPa for A. griffithii
and -12.1 ± 0.74 for A. prostrata. The ash content of
bracteoles on a dry weight basis was 28.7 ± 0.4% for A.
prostrata and 30.0 ± 0.3% for A. griffithii. Soluble
salts are inhibitory to the germination of both species and the
presence of relatively high concentrations of total salts in
bracteoles may explain the reduced germination in A.
griffithii. Germination of seeds of the perennial A.
griffithii may also be mechanically inhibited by the presence of
persistent bracteoles, whereas, the annual A. prostrata has
ephemeral bracteoles that may serve to limit germination in the fall
but they are not present during the normal spring germination period.
Bracteoles may play a significant role in the dispersal of seeds by
water since seeds enclosed in bracteoles remained floating longer than
seeds with the bracteoles removed.
Key words: Atriplex, bracteoles, dispersal, germination, salinity, seeds