Bd. Campbell et al., Temperature responses and nuclear DNA amounts of seven white clover populations which differ in early spring growth rates, NZ J AGR RE, 42(1), 1999, pp. 9-17
The growth of seven white clover populations differing in morphology, geogr
aphic origin, and seasonality of growth was measured at constant temperatur
es ranging from 5 degrees C to 25 degrees C in controlled environment chamb
ers. All populations showed increased growth up to a maximum of 20-25 degre
es C, but there were significant shifts in the relative performance of the
populations at different temperatures. Leaf appearance rates, leaf sizes, a
nd stolen extension rates were all differentially affected by temperature.
Growth potential in the late winter to early spring period in the warm-temp
erate New Zealand climate appeared to be strongly related to the ability of
plants to grow at 5 degrees C. The most rapid growing populations at 5 deg
rees C ('Daeno', ML-48-65) originated from continental climates. Difference
s of up to 21% in 2C nuclear DNA amounts were measured between the white cl
over populations by microdensitometry. The results were generally consisten
t with the prediction that large genome size is associated with capacity fo
r growth at low temperatures, whereas small genome size is associated with
superior growth at higher temperatures. The two closely-related Pitau and G
49 populations were an exception to this trend.