Seasonal Variation in Appearance and Growth of Grass Roots

Abstract

Data from two field experiments, and from a root observation trench, suggest an annual cycle of root growth by grass swards. The production of adventitious roots from the tillers of four grass species, and from perennial ryegrass in a grass/clover sward varied greatly during the year. They were produced in increasing numbers through late winter to early spring; this rate fell sharply in April or May, and was low in summer. The differences in this annual cycle between grass species were small. Examination of roots of perennial ryegrass in a glass-sided trench showed that root elongation was most rapid in summer and was largely confined to the lower soil horizons. Rather more roots were produced in early autumn than during summer, but the rate of elongation was slow from October until spring. Individual roots of grasses appeared to survive for limited periods. Their longevity depended upon the time of year in which they were first formed; those produced in autumn or winter lived longer than those produced in spring or summer.

Comparison between net and gross root production by winter wheat and by perennial ryegrass

“…The estimates of ryegrass root longevity were similar to those reported by Garwood (1967) in the United Kingdom, although the estimates made by Troughton (1981) were slightly larger than those reported here. Garwood (1967) showed that ryegrass root longevity (as determined by the period which elapsed before the root cortex became brown when observed in a field rhizotron) varied between 61 and 188 days.…”

“…Garwood (1967) showed that ryegrass root longevity (as determined by the period which elapsed before the root cortex became brown when observed in a field rhizotron) varied between 61 and 188 days. Root longevity was greatest when the roots were produced in the autumn and winter, and least when the roots were produced in spring or summer.…”

“…However, there is evidence that significant rates ofroot death during the growing season could render such estimates inaccurate. Root longevity may be quite short in some grasses (Garwood 1967;Troughton 1981). Furthermore, substantial amounts of root turnover have been reported for some woody dicotyledenous species (e.g., Caldwell & Camp 1974;Fogel 1985;Santantonio & Santantonio 1987), red clover (Trifolium pratense L.) (Steen 1989), some pasture grasses (Hansson & Andren 1986;Mathew et al 1986), grain sorghum (Sorghum bicolor Moench) (Cheng et al 1990), and barley (Hordeum disticum L.) (Hansson & Steen 1984).…”

Root production and turnover and carbon budgets of two contrasting grasslands under ambient and elevated atmospheric carbon dioxide concentrations

“…In this soil, virtually all 1994) or in below-ground production, because of the the soil C was derived from C4 photosynthesis and very short lifespan of many roots. That roots can be so had a very low S^^C signal ( 21 %"); they were short-lived has been known for many years able to detect recently added C because it had been (Garwood, 1967), but only with the advent of fixed by C3 photosynthesis (i^^^C t\'pically -28%o).…”

Do Phytomer Turnover Models of Plant Morphology Describe Perennial Ryegrass Root Data from Field Swards?

“…Historic studies of grass sward dynamics have tended to focus separately on behavior of leaves [1,2], tiller populations [3], or roots [4]. Compartmentalisation of sward dynamics studies in this way probably occurred, in part, as a pragmatic reaction to the fact that such studies are extremely time consuming, and focusing on one aspect of sward behavior helps ensure data quality.…”