Secondary Xylem Development Research Articles

Canopy dynamics and the morphological development of Abies balsamea: effects of foliage age on specific leaf area and secondary vascular development.

Data were collected from two branches from each whorl of nine open-grown Abies balsamea (L.) Miller trees to test the hypothesis that specific leaf area (SLA, m(2) projected fresh leaf area kg(-1) oven-dry foliage) is constant among five foliage age classes (current-year, 1-year-old, 2-year-old, 3-year-old and 4-year-old-plus). Between-tree variation in SLA was greater than within-tree variation. Differences in SLA among the foliage age classes were small, but statistically significant, showing a trend of decreasing SLA with increasing foliage age. Using data from two previous biomass studies, we found that three different methods of calculating SLA of individual trees produced the same projected leaf area estimates. To test the hypothesis that foliage mass increases with foliage age as a result of secondary xylem or phloem development, we examined the secondary vascular development of foliage collected from five age classes and three crown sections in an open-grown A. balsamea. The number of rows of xylem cells was not constant among foliage age classes, but the differences were small and showed no consistent pattern of change with foliage age. Total number of rows of phloem cells increased, number of living rows of phloem cells decreased, and the number of rows of nonliving crushed phloem cells increased with foliage age.

Changes in leaf, stem, and root anatomy of Chrysanthemum cv. Lillian Hoek following paclobutrazol application

Plants ofChrysanthemum cv. Lillian Hoek were treated with a paclobutrazol (PBZ) soil drench and histologically examined after 3 months. PBZ application resulted in thicker leaves, reduced stem diameter, and roots with an increased diameter and an unusual segmented appearance. Increased leaf thickness was partly due to an additional layer of palisade mesophyll, although individual palisade cells were shorter, of smaller diameter, and more tightly packed. Spongy mesophyll depth was also greater and the individual cells were more rounded and the volume of intercellular space was reduced. The narrower stems had an increased development of secondary xylem, but had a marked reduction in the number of sclerenchyma bundle caps. Increased root diameter was due to an increase in the number of rows and diameter of cortical cells. In PBZ-treated plants, root cortical cell length was 50–70% less than in untreated plants, and this reduction appeared to be associated with the segmentation of the roots. PBZ inhibited secondary vascular development in the roots. This study is similar to other relevant studies in recording thicker leaves and roots with PBZ application; however, many of the underlying anatomical changes described above have not been previously reported.

Effects of water deficit on flower opening in coffee (Coffea arabica L.).

The response of coffee (Coffea arabica L.) floral buds to different water deficits followed by re-irrigation was investigated. Flower opening was stimulated by irrigation after one period of water deficit if predawn leaf water potential declined below -0.8 MPa. Similar stimulation of flowering was observed when less severe but more prolonged water deficits (ca. -0.3 to -0.5 MPa for two weeks) were imposed, even if water deficit was relieved by re-irrigation several times during this period. Consistent results were obtained in the field and in two greenhouse locations. Stimulation of flower opening by water deficit followed by re-irrigation was restricted to buds at the "open white cluster" stage of development (Stage 4). Only buds at this stage exhibited development of secondary xylem. Split-root experiments indicated that a root signal stimulated flower opening, independently of predawn or midday leaf water status. Frequent irrigation to prevent flowering, followed by a controlled water deficit and re-irrigation to stimulate flowering, may represent a practical method to synchronize flowering and shorten the harvest period in leeward coffee production areas in Hawaii.

Histological evidence of resistance to Endocronartium harknessii in Pinus contorta var. latifolia

Resistance to the western gall rust fungus, Endocronartium harknessii, was observed in 3-, 10-, 20-, and 33-month-old greenhouse-grown seedlings of lodgepole pine (Pinus contorta var. latifolia). Three sites of resistance were identified: epidermal, cortical, and cambial. In cases of epidermal resistance, penetration of the epidermis occurred, but infection was prevented by an apparent hypersensitive response. Cortical resistance occurred where infected cells in the cortex were successfully isolated by necrophylactic periderm and the infected tissue was exfoliated with the rhytidome. In cambial resistance, infections progressed to the vascular cambium where infected cells and cambial initials were inactivated. This resulted in abnormal secondary xylem development, characterized by a zone of pathological tissue extending from the pith to the epidermis. In a number of infected seedlings, cambial function was restored and infected lesions were overgrown. Live mycelium was often maintained in cortical lesions and in some cases reinvaded healthy cortical cells. These latent-type infections resulted in the initiation of gall formation up to 1 year after initial resistance to infection occurred. Key words: tree improvement, western gall rust, pine stem rust.

Water Flow Through Cotton Roots in Relation to Xylem Anatomy

Oosterhuis, D. M. and Wullschleger, S. D. 1987. Water flow through cotton roots in relation to xylem anatomy.—J. exp. Bot. 38: 1866-1874. The effect of root anatomy on water flow was studied in 7-d-old cotton (Gossypium hirsutum L.) seedlings grown in solution culture. The total water flux of the intact root system was measured using a pressure chamber. Then successive terminal root sections were removed at 2,6,10 and 12 cm behind the root tip and the flux was remeasured after each successive cut was made. Xylem development at different distances behind the root apex was studied with a microscope using sections cut free-hand and stained with toluidine blue. Water flux increased with the removal of successive terminal root sections and this coincided with the degree of basipetal primary xylem development. The large increase in water flux at 10 to 12 cm was associated with secondary xylem development and increased xylem vessel number. A comparison of water flow and xylem anatomy between roots with tetrarch (Stoneville 506 and Deltapine 41) and pentarch (T25 strain) vascular bundle arrangements showed no significant differences in the measured values of water flux for the primary root. Water flux, estimated using Poiseuille's equation and measured xylem dimensions, was greater for the tetrarch roots, primarily because of the larger diameter of individual vessel elements. The increased number of vessel elements in the pentarch primary root of T25 did not result in any apparent decrease in axial resistance to water flow.

Polar Gradients of Tracheid Number and Diameter During Primary and Secondary Xylem Development in Young Seedlings of Pin us pinea L.

Polar Gradients of Tracheid Number and Diameter During Primary and Secondary Xylem Development in Young Seedlings of Pin us pinea L.

Developmental Changes in the Fusiform Cambial Cells of some Tropical Trees

Divisional activity, intrusive growth and loss of fusiform cambial cells have been studied in three tropical trees: Tectona grandis L.f. (Verbenaceae) , Gmelina arborea R oxb . (Verbenaceae) and Mangifera indica L. (Anacardiaceae) . Periclinal divisions of fusiform initials lead to the development of secondary xylem and phloem elements while anticlinal divisions enhance the number of cells to increase the circumference of cambial cylinder. In Tectona and Gmelina periclinal divisions occur seasonally, whereas in Mangifera the divisions are continuous. Anticlinal divisions are oblique and lateral with a great variation in the length of partition wall. Radial anticlinal divisions do occur sporadically in the fusiform initials of Tectona and Gmelina . The radial walls are relatively thick during dormant period. The cells elongate by intrusive growth at the vertical ends. Forking of cell tips and intrusion into the adjacent cells are commonly observed. Splitting of rays occurs by the intrusion of elongating cell tip into ray initials. Fusiform cambial cells undergo various structural changes during the periodic growth adjustments in the cambium. The rate of fusiform cambial cell loss is apparently high when the cambium is active.

Correlations between net auxin and secondary xylem development in young Populus deltoides

Stems of cottonwood (Populs deltoides Bartr. ex Marsh.) plants grown under different conditions were examined to determine the relation between net endogenous auxin yields and the acropetal advance of the primary‐secondary vascular transition zone (TZ). In all treatments, the internode yielding maximum net auxin activity, as determined by the Avena curvature bioassay, closely corresponded with the internode in which the TZ occurred. Under short‐day (SD) dormancy‐inducing conditions, auxin yield declined steadily while the maximum auxin peak and the TZ shifted toward younger internodes. Auxin yields from these plants were extremely low after 5 weeks of SD compared with those from long‐day (LD) plants. The only consistent auxin yield was obtained from internodes subtending young leaves beneath the apical bud. Plants placed in SD for 3 weeks and then returned to LD conditions showed an immediate increase in auxin yield in the stem, and the progressive acropetal advance of the TZ under SD was reversed. Therefore, within 7 LD the positions of the TZ and peak auxin yield corresponded to those observed before the imposition of SD Fully dormant plants placed in LD showed a dramatic rise in auxin yields during the first 2 weeks of renewed growth. Although low levels of auxin were found in the newly developing shoots after 6 LD, yields increased rapidly after 9 and 14 LD. The position of the TZ corresponded with the peak of net auxin activity after 9 and 14 LD.

The Initiation and Development of Secondary Xylem in Axillary Branches of Populus deltoides

The initiation of secondary xylem in elongating axillary branches of Populus deltoides Bartr. ex Marsh. is independent of that in the main stem. Although secondary xylem differentiates acropetally in the main stem, it does not differentiate from the stem into the axillary branch. Secondary xylem is usually initiated in internode 4 (occasionally 3) of the axillary branch, and from this site it develops both acropetally in the elongating branch and basipetally toward the main stem. Secondary vessel differentiation always precedes fibre differentiation. Although secondary xylem differentiates in internodes that have ceased elongation, it differentiates first in traces of the vascular cylinder serving rapidly expanding and maturing foliage leaves. As younger leaves on the branch expand and mature, secondary xylem differentiates in their traces eventually producing a complete secondary vascular cylinder. Scale leaves do not initiate secondary xylem independently in their traces; they are activated by adjacent traces in the vascular cylinder serving foliage leaves. Once established, the primary-secondary vascular transition zone advances acropetally in a branch just as it does in the main stem.

EFFECTS OF SHADE ON XYLEM DEVELOPMENT IN SEEDLINGS OF EUCALYPTUS GRANDIS HILL EX. MAIDEN

SummarySeedlings of Eucalyptus grandis were grown under light regimes of 12·6 and 2·8 E m−2 day−1 for 7 weeks, during which time secondary xylem development was studied. The rate of cambial cell division was approximately 50% greater in the high light than in the low light treatment. Rates and durations of fibre expansion were similar, but the rate of wall thickening was almost three times as great in the high as in the low light treatment. Also, the duration of fibre wall thickening was estimated to be 7 days in high light as compared with 21 days in low light. Secondary vessel lumen area and the cross sectional area of vessels per unit area of leaf surface were greater in high than in low light plants, although the proportion of xylem cross sectional area occupied by vessels did not differ significantly between treatments.

Histological and Morphological Effects of Auxin Transport Inhibitors on Honey Mesquite

Both DPX 1840 (3,3a-dihydro-2-[p-methoxyphenyl]-8H-pyrazolo-[5,1-a] isoindol-8-one) and REGIM-8 (dimethylamine salt of 2,3,5-triiodobenzoic acid) modified secondary xylem development in Prosopis glandulosa (Torr.) var. glandulosa (honey mesquite) seedlings so that a large number of axial elements that would have differentiated as fibers become parenchyma cells instead. In seedlings treated with DPX 1840 or REGIM-8, 88% and 67% of the axial elements, respectively, differentiated as parenchyma cells versus only 52% in controls. The effect of DPX 1840 was systemic in the hypocotyl and all along the woody stem. Radial growth, height growth, and internode formation were significantly reduced in DPX 1840-treated seedlings. Thus DPX 1840 may be potentially useful in woody brush control, since it is the only auxin transport inhibitor that significantly promoted the outgrowth of axillary stem buds.

Tracheid length in relation to seedling height in conifers

Changes in tracheid length during the development of primary and secondary xylem are analysed in relation to the division and elongation of cambial initials, in first year seedlings ofPinus sylvestris andPicea sitchensis. During primary and early secondary growth tracheid length varies with leaf internode length, but this relationship soon becomes obscured during later secondary growth. Correlations between seedling height and tracheid length thus depend on variation in tracheid length with radial xylem increment before and after terminal bud production. Since the relation between shoot and tracheid length is a complex one, the clonseness of the correlation varies with environmental treatment, but overall, a doubling of shoot length increased tracheid length by about 10%.

Seasonal development of secondary xylem in Pinus Strobus L.

Secondary xylem, or wood, is the tissue that conducts water and minerals in the tree; thus it performs physiologically one of the most important functions for the tree. In addition secondary xylem is the tissue that primarily determines the suitability of a tree for various economic uses.

Some Histological Effects of 2,4,5-Trichlorophenoxyacetic Acid Applied to Mature Apricot Leaves

Apricot trees were sprayed with 2,4,5-trichlorophenoxyacetic acid at concentrations of 50, 100, and 200 ppm on May 22, 1965, when spur leaves were fully expanded. Some effects of 2, 4,5-T were studied in leaves collected up to October 2. Increase in petiole diameter resulted from enlargement of cells of the ground tissue and from greatly stimulated development of secondary xylem and phloem. Increase in leaf blade thickness was caused primarily by increased depth of palisade tissue and bundle sheaths and their extensions, but evidence of limited induced cell division in both mesophyll tissues contributed in some leaves; in a few leaves from the 50-ppm treatment, much cell division without cell enlargement in mesophyll tissues accounted for all the increase in leaf thickness between vascular bundles. In the mesophyll of leaves treated with the higher concentrations, many cells and nuclei were larger than in controls. Distributions of frequencies of cell widths and of nuclear diameters in palisade cell populations indicated that the general degree of endopolyploidy increased following 2,4,5-T treatment and that some of the comparable cells in controls were also polyploid. The number of stomata per unit length of the lower epidermis was almost one-half less in leaves given the highest 2,4,5-T concentration than in the controls. The immediate causes were (a) a great increase in treated plants in the cell size in bundle sheath extensions and correspondingly of some epidermal cells, and (b) stretching, or (c) a few cell divisions of other epidermal cells. Tyloses in control petioles and midveins were not numerous until October, but in petioles of treated leaves many developed early. It is suggested that the actions of 2,4,5-T in stretching cell walls and in stimulating endopolyploidy combined to cause tylosis formation, the stretched pit membranes of the vessels not having been able to withstand the pressure of enlarging polyploid xylem parenchyma. Aside from exceptional instances of limited cell proliferation in phloem ray cells, no abnormalities were induced. The general effects of 2,4,5-T as applied here were concluded to have been acceleration or stimulation of processes occurring normally in untreated leaves.

Some Observations on the Root Development as Related to the Growth of the Aerial Part of Rice Plant Treated with Shading and Nitrogen Application into Lower Part of Furrow Slice.

Root developmental phase was investigated in connection to the growth of the aerial parts of rice plants cultured under two treatments, shading and deep placement of Nitrogen fertilizer. 1. It has been reported that crown root emerges on the (n-3) -th node at the time of emergence of the N-th leaf (the node number on which the N-th leaf emerged is expressed as n). Root emergence was delayed by shading, and the interval was prolonged to 3.5 nodes. But, when shading was stopped, this delay of emergence was restored to 3 nodes. 2. The total area of the cross section of secondary xylem per single root was measured related with the node-locus at which the root emerged. The development of secondary xylem of the root which emerged under shading treatment was inferior to that without shading treatment. But the development of secondary xylem of the root which emerged after the end of shading treatment was superior to that without shading treatment. 3. When nitrogen was applied into lower-layer, the growth af rice was inferior to that without treatment at the early growing period, but it became superior at the late growing period. Similarly, the development of secondary xylem of the root which emerged at the early growing period was inferior, while that of root which emerged at the late growing period was superior.

Anatomy of Seed Plants

INTRODUCTION. Internal Organization of the Plant Body. Summary of Types of Cells and Tissues. General References. DEVELOPMENT OF THE SEED PLANT. The Embryo. From embryo to the Adult Plant. Apical Meristems and Their Derivatives. Differentiation, Specialization, and Morphogenesis. References. THE CELL. Cytoplasm. Nucleus. Plastids. Mitochondria. Microbodies. Vacuoles. Paramural Bodies. Ribosomes. Dictyosomes. Endoplasmic Reticulum. Lipid Globules. Microtubules. Ergastic Substances. References. CELL WALL. Macromolecular Components and Their Organization in the Wall. Cell Wall Layers. Intercellular Spaces. Pits, Primary Pit--Fields, and Plasmodesmata. Origin of Cell Wall During Cell Division. Growth of Cell Wall. References. PARENCHYMA AND COLLENCHYMA. Parenchyma. Collenchyma. References. SCLERENCHYMA. Sclereids. Fibers. Development of Sclereids and Fibers. References. EPIDERMIS. Composition. Developmental Aspects. Cell Wall. Stomata. Trichomes. References. XYLEM: GENERAL STRUCTURE AND CELL TYPES. Gross Structure of Secondary Xylem. Cell Types in the Secondary Xylem. Primary Xylem. Differentiation of Tracheary Elements. References. XYLEM: VARIATION IN WOOD STRUCTURE. Conifer Wood. Dicotyledon Wood. Some Factors in Development of Secondary Xylem. Identification of Wood. References. VASCULAR CAMBIUM. Organization of Cambium. Developmental Changes in the Initial Layer. Patterns and Causal Relations in Cambial Activity. References. PHLOEM. Cell Types. Primary Phloem. Secondary Phloem. References. PERIDERM. Structure of Periderm and Related Tissues. Development of Periderm. Outer Aspect of Bark in Relation to Structure. Lenticels. References. SECRETORY STRUCTURES. External Secretory Structures. Internal Secretory Structures. References. THE ROOT: PRIMARY STATE OF GROWTH. Types of Roots. Primary Structure. Development. References. THE ROOT: SECONDARY STATE OF GROWTH AND ADVENTITIOUS ROOTS. Common Types of Secondary Growth. Variations in Secondary Growths. Physiologic Aspects of Secondary Growth in Roots. Adventitious Roots. References. THE STEM: PRIMARY STATE OF GROWTH. External Morphology. Primary Structure. Development. References. THE STEM: SECONDARY GROWTH AND STRUCTURAL TYPES. Secondary Growth. Types of Stems. References. THE LEAF: BASIC STRUCTURE AND DEVELOPMENT. Morphology. Histology of Angiosperm Leaf. Development. Abscission. References. THE LEAF: VARIATIONS IN STRUCTURE. Leaf Structure and Environment. Dicotyledon Leaves. Monocotyledon Leaves. Gymnosperm Leaves. References. THE FLOWER: STRUCTURE AND DEVELOPMENT. Concept. Structure. Development. References. THE FLOWER: REPRODUCTIVE CYCLE. Microsporogenesis. Pollen. Male Gametophyte. Megasporogenesis. Female Gametophyte. Fertilization. References. THE FRUIT. Concept and Classification. The Fruit Wall. Fruit Types. Fruit Growths. Fruit Abscission. References. THE SEED. Concept and Morphology. Seed Development. Seed Coat. Nutrient Storage Tissues. References. EMBRYO AND SEEDLING. Mature Embryo. Development of Embryo. Classification of Embryos. Seedling. References. Glossary. Index.

Effects of Inhibitory Concentrations of 3-Indolylacetic Acid and 3-Indolylacetonitrile on Cell Division and Tissue 2

Inhibitory concentrations of 3-indolylacetonitrile (IAN) cause, in cultured excised tomato roots, a marked decrease in the rate of cell division at the apical meristem but only a slight reduction in the lengths of mature exodermal and cortical cells. The reduced rate of cell division is associated with a decrease in the number of meristematic cells at the root apex. By contrast, 3-indolylacetic acid (IAA) causes marked reduction in the lengths of mature cortical cells but does not markedly reduce cell-division rate at the apical meristem. Various lines of evidence indicate that both IAA and IAN cause a relative increase in the number of longitudinal and a decrease in the number of transverse division walls in the meristematic zone of the root apex. Partial inhibition of the linear growth of excised tomato roots by IAA and IAN is accompanied by increases in root and stelar diameters. These increases result from radial enlargement of the cortical cells and increase in the number of stelar cells in the transverse section. The enlarged steles contain an increased number of lignified xylem elements, but only with the most inhibitory concentra tion of IAN (10 4g./ml.) is there evidence of the development of secondary xylem. Both auxins increase significantly the xylem vessel unit length.

Responses of Sunflower Stems to Growth-Promoting Substances

1. Sunflower plants were treated upon a decapitated surface in the third inter-node with one of five growth-promoting substances in lanolin. 2. Certain responses are common to treatment with all of the acids. Among these responses are: the formation of parenchymatous or meristematic callus tissue at the exposed surface of the pith, of the parenchyma of the xylem and phloem, and of the cortex, especially the endodermis; and increased secondary thickening near the apex of the stump. The conducting elements of the xylem and phloem, the pericycle, and the epidermis do not react to any of the acids. 3. A horizontal cambium-like tissue is formed soon after treatment, which connects with the true cambium at the cut edges of the latter and forms a platelike meristem across and within the callus. Cells which it forms to the lower side develop into tracheids. 4. Some of the acids bring about characteristic and specific responses, as follows: a. Indoleacetic acid causes the partial inhibition of bud development at the third node and the formation of adventitious roots. b. Indolebutyric acid causes partial inhibition of bud development, but it does not cause general formation of root tips, extreme secondary thickening, marked cell enlargement, nor marked activity of the interfascicular cambium. c. Indolepropionic acid inhibits bud development slightly if at all, and its application results in a characteristic stump which tapers from apex to base, owing to a gradient of cell enlargement, chiefly in the cortex and pith, and near the uppermost portion of the tumor to cell divisions. d. Naphthaleneacetic acid causes marked epinasty, completely inhibits bud development, causes extreme development and differentiation of secondary xylem, and marked development and activity of the horizontal "cambium." e. Phenylacetic acid induces in the third internode disproportionate activity of the interfascicular cambium, the cambium becoming outwardly distended between the vascular bundles.

XIX.—Notes on the Kidston Collection of Fossil Plant Slides. No. I. The Anatomy of the Axis of Lepidodendron Brownii Unger sp., with special reference to the Relationship between this Stem and Lepidostrobus Brownii Unger sp.

The Kidston Collection of fossil plant slides in the Botany Department of the University of Glasgow contains a number of sections of a very notable stem labelled “Lepidodendron textum, Kidston, n.sp.” No mention is made of this species in any of Dr Kidston's publications, but the correspondence relevant to the Collection indicates the history of the slides. This may be briefly summarised.As early as 1883, Dr Kidston had received from Mr J. Coutts two sections (Nos. 51 and 52) of this stem, which had been collected by the latter at East Kilbride, Lanarkshire, Scotland, from the Carboniferous Limestone Series of the Calderwood Beds (Hosie Limestone) in the Lower Limestone Group. Dr Kidston postponed description of this stem till he had better sections at his disposal; the specimen, however, was lost, and it was not till many years later that he rediscovered it in Dr John Young's collection in the Glasgow Municipal Museum, and had more sections cut from it (Nos. 1144–1153). No manuscript notes of Dr Kidston's descriptive of these slides have been found, with the exception of a pencilled reference in his manuscript slide catalogue, opposite Nos. 51 and 52, to the “foliar bundles—there is an appearance as if there was a development of secondary xylem, whereas the axial bundle has no secondary wood.”