The response of white clover (Trifolium repens L.) seedlings to spring root temperatures: The relative roles of the plant and the Rhizobium bacteria

Abstract

Three experiments are reported which examine the relative roles of host and Rhizobium genotypes as ~ factors limiting clover (Trifolium repens L.) growth at low soil temperatures.In the first experiment un-nodulated clover and perennial ryegrass (Lolium perenne L.) were grown with non-limiting nitrate at root temperatures of 8, 10 and 12~ The ryegrass had substantially better relative growth rates (RGR) than the clover with the biggest difference occurring at 8~ Alterations in growth rate with temperature were more marked in clover than in ryegrass but the latter still produced several times more dry matter than clover at each temperature. In the subsequent experiments clover nodulated with different strains of rhizobia was grown with and without non-limiting additions of nitrate at root temperatures of 9, 12 and 15~ Plants receiving nitrate generally produced more dry matter than those dependent upon Rhizobium for nitrogen but differences in yield between these treatments did not alter with temperature. This suggests that limitations imposed by nitrogen fixation are similar at both high and low temperatures. Indeed, there was some evidence that nitrogen limitations were rather more pronounced at the highest temperature. The first experiment clearly demonstrated that the clover genotype makes particularly poor use of nitrate at low root temperatures when compared to its common companion perennial ryegrass.It can be concluded that improvements in spring growth of clover will rest largely with alterations to the plant genotype and its ability to use combined nitrogen for growth at lower temperatures rather than with changes in rhizobia or any symbiotic characters.

Effect of temperature on growth and morphology of two varieties of white clover (Trifolium repens L.) and their impact on soil microbial activity

“…The N concentration of the plants was significantly lower at the low temperature. This is in contrast with Glendining & Mytton (1989) who found higher N concentrations in plants grown at 9°C than at 12 or 15°C. N fixation may have been less efficient at the (Kessler, Boller & Nösberger, 1990;Hatch & Macduff, 1991;Nesheim & Boller, 1991;Svenning & Macduff, 1996).…”

Symbiotic growth of indigenous white clover (Trifolium repens) with local Rhizobium leguminosarum biovar trifolii

“…According to Kessler et al (1990), nitrogen fixation was not the limiting factor for growth at low temperatures. The differences in dry weight reflected more the differences in growth potential than the effectiveness of symbioses (Giendining and Mytton 1989). Wotedge and Suarez (1983) conclude that the reasons for slow growth at low temperature are a low photosynthetic rate and, particularly in nodulated plants, a large root shoot ratio and smali leaf area.…”

“…Macduff et al 1989 found a preference for nitrogen fixation over nitrate uptake in white clover with roots at 5°C. Growth of white clover, also when supplied with mineral nitrogen, was greatly reduced at temperatures between 6 and 12°C (Junttila et al 1990) and the ability for white clover to use combined nitrogen was primarily determined by the plant genotype (Glendining and Mytton 1989). Temperature could also affect the efficiency of the symbiosis by changing the frequency of different isolates of Rhizobium in nodules (Hardarsoti and Jones 1979).…”

Agronomical and physiological responses of white clover(Trifolium repens)and perennial ryegrass(Lolium perenne)to nitrogen fertiliser applied in autumn and winter

“…This reduction in N2 fixation reported at low temperatures (Hatch & Macduff 1991) may be a response to a decrease in C supply, reflecting a reduction in photosynthesis at low temperatures . The result is a decrease in leaf growth and area of leaves available to intercept radiation (Wilson 1988;Glendining & Mytton 1989;Ericsson 1995). This has been proposed as a key determinant of N demand because the photosynthetic function of leaves requires a large content of reduced N (Grindlay 1997).…”