Comparative Morphology of the Primary Vascular Systems in Some Species of Rosaceae and Leguminosae

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.

Section: Introductionmentioning

confidence: 99%

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

Chapman

Robson²

1992

“…Clonally growing T. repens is a system of branching stolons witb each stolon consisting of a string of nodes, all differentiated from tbe stolon apical meristern, w-bich alternate in orientation so that successive nodes produce leaves, axillary buds and roots on opposite sides of the stolon (Erith, 1924). Stolons bave four independent axial hundles, an upper and lower axial bundle on each side of the stolon, running along their length (Devadas & Beck, 1972;Thomas, 1987). When a hrancb de\-elops at a node its vascular supply arises from the two axial bundles in the parent stolon on that side, from the lower axial bundle at the node of branching and from the upper axial bundle at the first node proximal to the hrancb.…”

mentioning

confidence: 99%

“…Each leaf is supplied by three \'ascular traces (median, upper and lower) whicb arise from different axial bundles in the stolon (Erith, 1924;Devadas & Beck, 1972;Thomas, 1987). The median and upper traces arise two nodes proximal to the leaf from tbe nearside lower and the farside upper axial bundles of tbe parent stolon respectively, whereas the lower trace arises from the lower axial bundle on the far side, one node proximal to the leaf.…”

mentioning

confidence: 99%

Influence of xylem vascular architecture on the translocation of phosphorus from nodal roots in a genotype of Trifolium repens during undisturbed growth

Hay

Hamilton

1996

SUMMARYOur objective was to establish whether the xylem vascular connections (architecture) of a genotype of Trifolium repens L. had in^plications for the intraplant allocation of recently assimilated phosphorus (P). One nodal root of each plant was isolated and fed -'^P-labelled nutrient solution for 24 h. The fed root was either on the parent axis (11-12 nodes proximal to the apex) or on a branch at the third or fourth node along the branch when counting from the junction with the parent stolon. Allocation patterns were obtained by dissecting plants and assaying each dissected component for ''-P.Under conditions of undisturbed growth in a controlled environment xylem architecture was found to have an important influence on the intraplant distribution of ''^P from nodal roots. Allocation patterns of ''^P were consistent with those predicted from knowledge of the xylem vascular architecture of the genotype and a predominantly acropetal direction of the transpiration stream. For instance, very little ^^P (< 1 "o of exported ^^P from the fed root) was found in branches on the opposite side of the stolon to the fed root, and the strong acropetal direction of the transpiration stream resulted in little allocation of ''^P to leaves that had traces that arose from axial bundles at positions proximal to that of the fed root (the leaf subtending the fed root and the next distal leaf had low -'-P content), to all plant organs proximal to the fed root (< 6"(,) and to all other roots (< 4°(j).The high allocation of-'-P to the branch arising at the same node as the fed root (64"o) reflects the numerous links that the fed root has to vascular bundles in the branch (3 -6, of which two are axial bundles) against the single connection it has to the adjacent lower axial bundle in the parent stolon. Allocation of ^^P to the leaf and axillary bud at each node along the branch strongly favoured nodes on the adaxial side, a result consistent with the fact that the root connections are to the upper and lower axial bundles on the adaxial side of the branch. Allocation to a particular node along the branch was also influenced by its nodal position relative to the fed root and the sink strength of its tissues for the transpiration stream.

“…are regarded as modified stem apices with determinate growth. The primary vascular patterns in stems of R. occidentalis have been determined as consisting of an open system of five well-defined sympodia with leaves arranged helically in a 2/5 phyllotaxy (Devadas & Beck, 1972). The tracing of vascular supplies through several nodes in 10/tm serial sections to study the relatedness of species and examine evolutionary trends is difficult work, and NMR microscopy, as described in the present paper, should greatly facilitate such studies.…”

Section: Resultsmentioning

confidence: 93%

“…McCully & Mallett, 1993). For over a century, the histology of vascular architecture has provided useful taxonomic markers in evolutionary studies of diverse and closely related plants (see Devadas & Beck, 1972;Fahn, 1982). However, the conventional methods needed to produce serial stained sections from large specimens and then to reconstruct key features from them in three dimensions are extremely time-consuming and labour-intensive, even when modern image analysis systems are applied (see Hibbard et al, 1993).…”

Section: N T R O D L" C T I O Nmentioning

confidence: 99%

The vascular architecture of the fruit receptacle of red raspberry determined by 3D NMR microscopy and surface‐rendering techniques

Williamson¹,

Goodman²,

Chudek

et al. 1994

The three-dimensional structure of the vascular system in the fruit receptacle of red raspberry was determined using NMK microscopy in combination with computer techniques which highhght the surfaces of specific tissue types. The surface-rendering technique is particularly valuable in situations where there are large differences in image characteristics between the tissue of interest and the rest of the specimen, and thus ideal for the delineation of the vascular tissue in the raspberry receptacle. This was shown to consist of a conical network of bundles with a spiral pattern of gaps; the carpellary traces emerged from the proximal end of each gap. The inner xylem and outer phloem tissues each appeared as a pair of fused columns in the surface-rendered images, and each carpellary trace had a separate supply from the xyletn and phloem.