The effect of temperature on
coleoptile elongation of three groups of wheat varieties
R. E. ALLAN, O. A. VOGEL, and J. R. BURLEIGH
Crops Research. Division, ARS, USDA, Pullman, Washington.
Poor stands often result from early seeding (late August,
early September) of winter wheat in eastern Washington even
when moisture is adequate. Late-sown (October) wheat
generally produces suitable stands. Work at Pullman,
Washington, has shown that selections which possess long
coleoptiles generally emerge more rapidly than selections
with short coleoptiles. Furthermore, selections which emerge
rapidly generally produce better stands than selections that
emerge slowly and erratically. High soil temperatures often
occur during August and September in eastern Washington;
readings as high as 90F have been recorded at soil depths of
3 inches during August at Pullman.
This study was initiated to determine the effect of high
temperature on coleoptile elongation of wheat selections in
3 groups. Fourteen standard height, 25 common-type semidwarf
and 16 club-type semidwarf selections were grown at
temperatures of 50 and 90F in a totally darkened plant
growth chamber. The selections were sown in shallow sand
flats with each selection replicated 4 times.
Analysis of variance indicated that the high temperature
(90F) significantly reduced the coleoptile lengths of wheat
selections in all 3 groups as compared with measurements
taken at low temperature (50F). Furthermore, highly
significant variety by temperature interactions occurred
within the standard-height and club-type semidwarf group
which showed that within these 2 groups selections differed
in their sensitivity to high temperature. No significant
difference in sensitivity occurred among the 25 common
Table 1 shows the average
coleoptile measurements obtained at both temperatures and
the percentage reduction in length caused by high
temperature. The rankings of the various selections for all
measurements are also shown.
Among the standard-height selections Spinkcota, a rapid
emerging variety, was reduced the least; whereas Brevor, a
poor emerging variety, was reduced the most. The semidwarf
clubs showed the greatest varietal variability in reduction
due to high temperature. Selection 216, which has a short
coleoptile even at low temperatures, showed the least
reduction (25%); whereas selection 229 was reduced 54%.
Although reduction varied from 38% to 55% in the common-type
semidwarf group, no significant differences among selections
Results of the present study showed that high temperature
(90F) inhibited coleoptile elongation. This observation may
partially explain why early seedings during the warm months
of August and September generally emerge poorer than late
seedings in October, when cool weather prevails.
Further tests are underway with selections of diverse origin
in a search for germ plasm stocks that are less sensitive to
reduction in coleoptile lenght at high temperatures than our
own indigenous lines. Field trials are being made to measure
more accurately the association that appears to exist
between amount of coleoptile reduction at high temperature
and rate of seedling emergence.