Agriculture Reference
In-Depth Information
Fig. 4.9.
Illustrations of the negative association between seed viability and time to
germinate. (a) The relationship between the percentage germination (probability
scale) and the mean germination time at 20°C (log scale) for three seed-lots of
onion cv. 'White Lisbon' (solid symbols) and three of cv. 'Rijnsburger' (open
symbols) before and after different periods of storage at 45°C at 18% moisture (from
Ellis and Roberts, 1981. Courtesy of
Seed Science and Technology
). (b) The relation
between percentage germination at 19.1°C and the thermal time needed for 50%
germination at suboptimal temperatures for seed-lots of onion cv. 'Senshyu Semi-
globe Yellow' produced in three different years (from Ellis and Butcher, 1988.
Courtesy of
Journal of Experimental Botany
).
The equation that relates rate of germination to temperature at
suboptimal temperatures for each percentile of the seed population is:
1/t(G) = (T
3.5)/10
[(probit(G) + 9.134)0.1844]
(Eqn 4.8)
where
t(G) = time for the Gth percentile to germinate, days
T = temperature, °C
