The physiological role of old stolon material in white clover (Trifolium repens L.)

Abstract

SUMMARYClonal plants of white clover {Trifolium repens L,), consisting of a single stolon plus roots and either three fully unfolded leaves or one fully unfolded leaf at the stolon apex, were grown in a controlled environment and sampled three times (after 7, 49 and 85 d growth) to examine the effects of increasing respiratory demand imposed by an increasing mass of old stolon material upon carbon allocation patterns and plant morphology.Where the total pool of available carbohydrate remained more-or-less constant over time, greater C allocation to stolon tissue was associated with reduced allocation to new leaf growth between d 7 and d 49. Rapid death of old stolon material began about d 70, perhaps as the result of withdrawal of C previously supplied to stolon tissue by leaves at the apex. Current assimilate no longer needed to maintain this old stolon material was, in part, reallocated to the apex region.Stolon death was greater when stolons were covered rather than fully illuminated, reflecting the elimination of direct CO.^ assimilation by stolon tissue (estimated to be 12-22% as efficient as leaves in assimilating COj, on a surface area basis) and accentuation of the carbohydrate deficit. Respiration accounted for an estimated 32 °o of C fixed by leaves on d 85 when stolons were covered, compared to 25 % when stolons were fully illuminated. The relevance of these results to the seasonal changes in plant morphology in pastures, and the effects of stolon burial, are discussed.

On the ecological and evolutionary significance of storage in clonal plants

“…Up to now, only few studies have specifically investigated storage and re‐mobilization of resources in stolon internodes of clonal plants in an ecologic context. Tracer studies have shown that in Trifolium repens, a considerable part of the assimilated carbon is stored in stolon internodes (Chapman & Robson 1992 and references therein). Other authors have shown that storage of resources in stolon internodes of T. repens is also related to winter survival (Collins & Rhodes 1995; Turner & Pollock 1998), and that selection can act on the degree of stolon storage in this species (Collins et al 1997).…”

“…In T. repens, stolon internodes usually contain a large percentage of biomass (Chapman & Robson 1992), and they are well protected against damage from grazers by their position close to the soil surface. The stolon system of T. repens seems thus functionally comparable to the extensive and long‐lived, belowground stem system of rhizomatous species.…”

Role of proline and leaf expansion rate in the recovery of stressed white clover leaves with increased phosphorus concentration

“…Restriction in forage supply during dry periods can also result in frequent grazing by livestock. Frequent defoliation has been reported to affect root growth (Jarvis & Macduff, 1989 ;Chapman & Robson, 1992 ;Singh & Sale, 1998). Restricted root growth in turn would probably affect water uptake from drying soil, and plant water status in terms of Ψ leaf and\or relative leaf water content, playing an important role in osmotic concentration, turgor pressure and cellwall extensibility.…”

Genetic variation in clonal traits of Trifolium repens and species interactions

“…Second, the large‐leaved type exhibits greater plasticity, by which it can persist under heavily grazed conditions for a lengthening period. Third, the large‐leaved type produces a larger amount of stolon, which also functions as a storage organ (Chapman & Robson 1992; Turner & Pollock 1998), promoting persistence under heavily grazed conditions for a period.…”