Temperature responses and nuclear DNA amounts of seven white clover populations which differ in early spring growth rates

Abstract

The growth of seven white clover populations differing in morphology, geographic origin, and seasonality of growth was measured at constant temperatures ranging from 5°C to 25°C in controlled environment chambers. All populations showed increased growth up to a maximum of 20-25°C, but there were significant shifts in the relative performance of the populations at different temperatures. Leaf appearance rates, leaf sizes, and stolon extension rates were all differentially affected by temperature. Growth potential in the late winter to early spring period in the warm-temperate New Zealand climate appeared to be strongly related to the ability of plants to grow at 5°C. The most rapid growing populations at 5°C ('Daeno', ML-48-65) originated from continental climates. Differences of up to 21% in 2C nuclear DNA amounts were measured between the white clover populations by microdensitometry. The results were generally consistent with the prediction that large genome size is associated with capacity for growth at low temperatures, whereas small genome size is associated with superior growth at higher temperatures. The two closely-related Pitau and G49 populations were an exception to this trend.

The Large Genome Constraint Hypothesis: Evolution, Ecology and Phenotype

“…Those that grew early in the spring had larger GS (here recorded as a negative correlation with temperature, Table 2.). Campbell et al (1999) found the same correlation for populations of white clover. However, Bretagnolle and Thompson (1996) found the opposite relationship for sympatric Dactylis glomerata populations.…”

Leaf Area, Competition with Grass, and Clover Cultivar: Key Factors to Successful Overwintering and Fast Regrowth of White Clover (Trifolium repens L.) in Spring

“…Restoration of photosynthetic capacity and metabolic activity is an important factor in low temperature acclimation of white clover and herbaceous winter annuals (Woledge and Dennis, 1982;Woledge et al, 1989;Hurry et al, 1995). Although leaf emergence is strongly temperature dependent (Haycock, 1981;Eagles and Othman, 1988;Campbell et al, 1999;Corbel et al, 1999), the present results suggest that cultivars that produce leaves at low temperatures are at a considerable advantage compared with cultivars with a higher temperature threshold for leaf emergence.…”

“…The number of leaves that emerged during winter, and the increase in the rate of leaf emergence per temperature increment, were clearly higher for AberHerald than for Grasslands Huia, although the temperature threshold (2.9 C) for leaf emergence was the same for both cultivars and was similar to that reported by Haycock (1981). Similarly, the experiments of Corbel et al (1999) showed a significantly smaller decrease in the rate of leaf emergence of AberHerald compared with Grasslands Huia after chilling at 5 C. A comparative study with seven white clover cultivars showed that temperature had a stronger effect on plant growth during winter and spring than during the growing season, and that the capacity for growth at 5 C was important for the success of several white clover populations in the late winter and early spring (Campbell et al, 1999). In the experiment conducted by Campbell et al (1999), Grasslands Huia had the highest rate of leaf emergence at 5 C of the seven cultivars tested.…”

“…In the field, the functioning of leaves is expected to be adversely affected by (1) low temperature, (2) low irradiance, (3) short photoperiod and (4) shading by the companion grass. Campbell et al (1999) showed that leaf emergence rate, leaf size and stolon extension rate are each affected differently by temperature, and that the growth potential from late winter to early spring appears to be strongly related to the ability to grow at 5 C. The main aim of the European multisite research programme (Wachendorf et al, 2001a, b) was to investigate the importance of leaf area and stolons, as well as the physiological characteristics of different clover cultivars, for the winter hardiness and regrowth of clover in spring under widely varying environmental conditions. In the three experiments presented here, more detailed measurements, especially on leaf emergence and leaf death, and additional treatments (defoliation, grass competition) to vary the amount and light interception of leaf area, were included to provide information which is complementary to that of the European multisite experiment.…”

Phylogeny and Biogeography of Endemic Festuca (Poaceae) from New Zealand Based on Nuclear (ITS) and Chloroplast (trnL–trnF) Nucleotide Sequences

“…Trifolium repens L. var. 'Grasslands Huia' was used as the standard as it was known to have a 2C-value of 2.38 picograms (pg) (Campbell et al 1999). For each sample, a leaf segment of this reference tissue was co-chopped with the test sample, and the ratio of the test sample to the standard peak channel was used to compute the 2C-values for each test sample.…”