Pattern Of Elongation Research Articles

Influence of Day and Night Temperature Differentials on Root Elongation Rate, Root Hydraulic Properties, and Shoot Water Relations in Chrysanthemum

The difference between night and day temperature (DIF = day - night temperature) has been shown to affect plant height. A positive DIF (+DIF), cooler night than day temperature, increases stem elongation while a negative DIF (- DIF), warmer night than day temperature, decreases stem elongation. The physiological mechanism underlying the growth response to DIF is not understood, however, and the effects of day/night temperature differentials on root permeability to water and root elongation rate have not been studied. The objective of this study was to describe how +DIF and -DIF temperature regimes affect leaf water relations, root water flux (Jv), root hydraulic conductivity (Lp), and root elongation rates of `Boaldi' chrysanthemum [Dendranthema ×grandiflora Kitam. `Boaldi' (syn. Chrysanthemum ×morifolium Ramat.)] plants over time. Leaf turgor pressure (ψp) was 0.1 to 0.2 MPa higher in plants grown in a +6 °C DIF environment throughout both the light and dark periods, relative to those in a -6 °C DIF environment. Jv differed markedly in roots of plants grown in +DIF vs. -DIF environments. Rhythmic diurnal patterns of Jv were observed in all DIF treatments, but the relative timing of flux minima and maxima differed among treatments. Plants grown in positive DIF regimes exhibited maximum root flux at the beginning of the light period, while those in negative DIF environments had maximum root flux during the first few hours of the dark period. Plants grown in +DIF had significantly higher Lp than -DIF plants. Plants grown in +DIF and -DIF environments showed differences in the diurnal rhythm of root elongation. During the dark period, +DIF plants exhibited minimal root elongation rates, while -DIF plants exhibited maximal rates. During the light period, the converse was observed. In -DIF temperature regimes, periods of rapid root elongation coincided with periods of high Jv. Results of this study suggest that negative DIF environments lead to leaf turgor reductions and markedly alter diurnal patterns of root elongation. These changes may, in turn, act to reduce stem elongation.

Plasma membrane recycling and flow in growing neurites

Axonal growth requires insertion of newly synthesized membrane components into the plasmalemma. Imbalance between exocytotic membrane addition and endocytic retrieval at specific axonal sites may lead to the bulk plasma membrane flow along the axon and, thus, contribute to the renewal of plasma membrane components. By using fluorescent lipid analogs incorporated into the plasma membrane, we determined the sites of membrane internalization in growing Xenopus embryo neurons. Vectorial traffic of endocytic membranes from the distal axon to the cell body was observed, suggesting bulk retrieval of plasma membrane at the growth cone. No long-range axonal transport of membrane material internalized at the cell body or along the axon was detected. In addition, we measured the rate of plasma membrane flow in Xenopus neurites. Axonal plasma membrane was found to flow anterogradely with the rate equal to approximately 30% of the rate of neurite elongation. Our results suggest that the “growth from the tip” pattern of neurite elongation may coexist with transport of new membrane components along plasmalemma by anterograde membrane flow.

High metabolism and subsequent elongation of 3-hydroxyeicosanoyl-CoA in very-long- chain fatty acid deficient PNS of Trembler mice

The developmental patterns of the overall fatty acid elongation and of the last two partial activities of microsomal elongase (dehydration and reduction of 3-hydroxyacyl-CoA) were investigated in the PNS of normal and Trembler mice. Unexpectedly, Trembler microsomes synthesized normal C22-CoA amounts from 3-hydroxyeicosanoyl-CoA (3-OHC20-CoA), a C18-CoA elongation intermediate. Hydroxy- acyl-CoA dehydrase and enoyl-CoA reductase activities were found to be higher in the mutant than in the control, whatever the stage of development. Moreover, C20-CoA elongation led to normal C22-CoA and C24-CoA formation in the mutant whereas C20-CoA formation from C18-CoA was always far lower in Trembler than in control. C18-CoA condensing enzyme emerges as the only elongation step involved in the VLCFA deficit evidenced in Trembler PNS.

Intraocular lenses in children: changes in axial length, corneal curvature, and refraction

AIMTo assess changes in axial length, corneal curvature, and refraction in paediatric pseudophakia.METHODS35 eyes of 24 patients with congenital or developmental lens opacities underwent extracapsular cataract extraction and posterior chamber...

Circadian dysfunction causes aberrant hypocotyl elongation patterns in Arabidopsis.

Many endogenous and environmental signals control seedling growth, including several phototransduction pathways. We demonstrate that the circadian clock controls the elongation of the Arabidopsis hypocotyl immediately upon germination. The pattern of hypocotyl elongation in constant light includes a daily growth arrest spanning subjective dawn and an interval of rapid growth at subjective dusk. Maximal hypocotyl growth coincides with the phase during which the cotyledons are raised, in the previously described rhythm of cotyledon movement. The rhythm of hypocotyl elongation was entrained by light-dark cycles applied to the imbibed seed and its period was shortened in the toc1-1 mutant, indicating that it is controlled by a similar circadian system to other rhythmic markers. The daily groth arrest is abolished by the early flowering 3 (elf3) mutation, suggesting that this defect may cause its long-hypocotyl phenotype. Mutations that affect the circadian system can therefore cause gross morphological phenotypes, not because the wild-type gene functions pleiotropically in several signalling pathways, but rather because the circadian clock exerts wide-spread control over plant physiology.

HORMONE-INDUCED SIGNALING DURING MOSS DEVELOPMENT.

Understanding how a cell responds to hormonal signals with a new program of cellular differentiation and organization is an important focus of research in developmental biology. In Funaria hygrometrica and Physcomitrella patens, two related species of moss, cytokinin induces the development of a bud during the transition from filamentous to meristematic growth. Within hours of cytokinin perception, a single-celled initial responds with changes in patterns of cell expansion, elongation, and division to begin the process of bud assembly. Bud assembly in moss provides an excellent model for the study of hormone-induced organogenesis because it is a relatively simple, well-defined process. Since buds form in a nonrandom pattern on cells that are not embedded in other tissues, it is possible to predict which cells will respond and where the ensuing changes will take place. In addition, bud assembly is amenable to biochemical, cellular, and molecular biological analyses. This review examines our current understanding of cytokinin-induced bud assembly and the potential underlying mechanisms, reviews the state of genetic analyses in moss, and sets goals for future research with this organism.

Quantifying Stem Elongation in Oriental and Asi-florum Lilies

Our objective was to quantify the stem-elongation patterns of several Oriental and Asi-florum lily cultivars to develop graphical tracking charts where actual crop height can be compared visually against a target growth curve. Oriental lilies (`Mona Lisa' and `Stargazer') were grown in research greenhouses at Michigan State Univ. (MSU) during 1994 and 1995. Asi-florum lily cultivars (`Centurion', `LA-87', `Non-stop', `Salmon Queen', and `Salzburg') were grown at MSU in 1995. Plants received constant 20 °C from emergence to flower in 1995, and constant 15, 18, 21, 24, or 27 °C in 1994. Elongation of Oriental lily plants followed a sigmoid pattern. Oriental lily cultivars elongated rapidly after emergence until 60% of the relative time between dates of emergence and first open flower, at which time plants had achieved ≈82% (`Stargazer') or 85% (`Mona Lisa') of their final height; elongation then exhibited a plateau phase. In contrast to the Oriental lilies, Asi-florum cultivars consistently exhibited a more constant elongation rate throughout the growing period. Simplified graphical tracking curves were developed based on the patterns of elongation and were programmed into a computer decision—support system (`UNH FloraTrack'). The graphical tracking curves were tested by growing `Stargazer', `Mona Lisa', and four Asiflorum cultivars (`Donau', `Dream', `Moneymaker', `Spirit') at the Univ. of New Hampshire and MSU during 1997 to height specifications of 51 to 56 cm (including a pot height of 15 cm). Sumagic growth retardants were applied as a prebulb dip at 5 ppm and as a foliar spray at 3 ppm when plant height was above the target curve. Final height targets were achieved using this method. E-mail prf@hopper.unh.edu; phone, (603) 862-4525.

Exsertion, elongation, and senescence of leaves of Eriophorum vaginatum and Carex bigelowii in Northern Alaska

The seasonal patterns of leaf exsertion, elongation, and senescence were described and compared for two of the most abundant graminoid species of Alaskan moist tussock tundra, Eriophorum vaginatum and Carex bigelowii. In addition the responses of both species to NPK fertilizer and to variation in site fertility (water track vs. non‐track areas) were also assayed and compared. The research was done over two full growing seasons at two sites near Toolik Lake, Alaska, where other aspects of the ecology of both species have been the subject of intensive and ongoing research.Both species showed the typical graminoid pattern of sequential leaf growth, in which the exsertion and elongation of new leaves is coincident with the senescence of old leaves. However, the rates of these processes were much slower and steadier in Eriophorum than in Carex, with much greater overlap in the life histories of individual leaf cohorts. The total and green leaf lengths of whole tillers in Eriophorum were also less variable over the entire year than in Carex. The conclusion is that leaf growth in Carex should depend more on external storage of carbon and nutrients than Eriophorum, with a much greater seasonal variation in demands on storage and retranslocation to and from leaves.The effects of fertilizer and the water track on leaf growth dynamics and turnover rates were largely nonsignificant, despite major effects on total tiller size and productivity. This is in contrast to previous research on evergreen leaf dynamics, but similar to results of previous research on overall production and biomass regulation in Eriophorum. It is concluded that the graminoid response to increased nutrient availability in the Arctic is to dilute the greater amounts of nutrient uptake by greater growth, so that nearly the same metabolic homeostasis is achieved as under low nutrient availability, but at a higher biomass.

Induction of branch roots by cutting method in Hyoscyamus niger root culture

Root tips of Hyoscyamus niger were cultivated on agar or in liquid medium, and patterns of elongation and branching were investigated. The elongation of roots compared to branching, particularly tertiary root branching, was more effective in liquid medium than on agar medium. The number (0.06 per cm) of tertiary roots which branched out from secondary roots was far less than that (4.2 per cm) of secondary roots from primary root particularly in liquid medium. When the secondary roots were cut from the primary root in liquid medium, branching of tertiary roots was markedly enhanced, from 8.4 to 17.5. Scopolamine content in the cut roots increased by 46.3% compared to that in normal roots.

Spermatogenesis and sperm structure of the hydrothermal vent prosobranch gastropod Lepetodrilus fucensis (Lepetodrilidae, Mollusca)

Summary Sperm and spermatogenic ultrastructure in a member of the gastropod superfamily Lepetodriloidea (Lepetodrilus fucensis, Lepetodrilidae), is described for the first time and the results compared with available information on other major prosobranch taxa. The head of the sperm of L. fucensis is comprised of an elongate nucleus (about 9 μm×0.4 μm mid-diameter) capped by a conical acrosome (2.3 μm) which sits on a centrally perforated basal plate. The acrosome is invaginated posteriorly, the invagination housing an axial rod. Posterior to the nucleus, the mid-piece consists of a complex centriolar apparatus and laterally positioned mitochondrion. The axoneme, which emerges from the centriolar complex, is surrounded anteriorly by a long (2.5 μm) cytoplasmic sheath which contains regularly spaced (periodicity 62 nm) electron-dense microtubules and filaments. Spermatozoa of L. fucensis resembles most closely those of the lepetelloidean Addisonia sp. and to a lesser degree those of some skeneimorph vetigastropods. The electron-dense structures associated with the cytoplasmic sheath (seen in Lepetodrilus and Addisonia) are strongly reminiscent of a similar, possibly homologous, feature observed in euspermatozoa of the Neritimorpha. Neritimorphs nevertheless show several sperm differences from L. fucensis and Addisonia sp. Spermatogenesis in L. fucensis follows a similar pattern to that described for many shallow water gastropods. Acrosome formation begins in spermatocytes with the production of small electron-dense vesicles, which, probably via fusion form the larger definitive acrosomal vesicle of spermatids. The pattern of chromatin condensation and nuclear elongation is typical of that of molluscs, but, as observed in other vetigastropods and the Neritimorpha, elongation of the nucleus occurs without the participation of a microtubular manchette.

Rhythmic Growth and Optimization of Micropropagation: The Effect of Excision Time and Position of Axillary Buds on in vitroCulture of Citrus aurantiumL.

We wanted to ask whether the rhythmic pattern of shoot elongation should be taken into account for the micropropagation of Citrus aurantiumL. and whether in vitroculture altered the rhythmic properties. It has been established in the present work that (1) where and when the axillary buds are excised with respect to the elongation cycle are of importance to optimize micropropagation and (2) the infradian rhythmic growth pattern of micropropagated plants is maintained with a period of 45.8d not significantly different from that of plants derived from seeds (42.4d).

The role of apical development around the time of leaf initiation in determining leaf width at maturity in wheat seedlings (Triticum aestivumL.) with impeded roots

High soil resistance to root penetration (measured as penetrometer resistance, R s ) slows down leaf growth and reduces mature leaf size in wheat seedlings (Triticum aestivum L.). Underlying changes in the kinetics of cell partitioning and expansion and in the size and organization of mature cells were reported in companion papers (Beemster and Masle, 1996 ; Beemster et al., 1996). In the present study, the relationships between apex growth, primordium initiation and expansion were analysed for plants grown at contrasting R s , focusing on a leaf whose whole development proceeded after the onset of root impedance (leaf 5). High R s reduced the rates of apex and leaf development, but did not appear to have immediate effects on the pattern of development of the newly initiated phytomers. During an initial short period, the rate of development of a leaf primordium and associated node were related to plastochronic age, according to similar relationships (slopes) at the two R s . Effects on developmental patterns were first detected on phytomer radial expansion during plastochron 2. The ontogenetic pattern of leaf elongation was affected later, during the next few plastochrons preceding leaf emergence ('post-primordial stage'). It is concluded that a reduction in the number of formative divisions and in the number of proliferative cells along the intercalary meristem reported earlier (Beemster and Masle, 1996 ; Beemster et al., 1996) is not related to the size of the apical dome at leaf initiation nor to the size and number of meristematic cells initially recruited to the leaf primordium, which were all unaffected by R s . Rather they are generated at the primordial and post-primordial stages.

Surgical treatment for equinus feet deformity in pre-school children with infantile cerebral paralysis

The treatment results of 184 children under school age with infantile cerebral paralysis and equinus deformity were analysed. There were 268 feet with equinus deformity. Out of 312 operations 137 (44%) Str operations, 63 (20,3%) aponeurotic elongation of gastrocnemical muscle, 56 (18,1%) Z-shape elongation of gastrocnemical muscle and 14 (4,5%) achilloplasty by Hoke-method were performed. The indications to apply the surgical management depending on the orthopedic and neurologic status as well as the methods of aponeurotic elongation of gastrocnemical muscle are presented. Excellent and good results were achieved in 86% of cases, recurrence of deformity was observed in 8% of cases. Minimum trauma, high efficiency, organ-sparing pattern of aponeurotic elongation of gastrocnemical muscle makes this procedure the method of choice in children under school age.

Kinematics of axial plant root growth

Axial growth of plant roots can be modeled as the deformation of a one-dimensional continuum. In this study we present a theory of root elongation that incorporates different roles of cell division in the meristem and axial growth in the elongation region in overall root extension. The meristem is idealized as being located at the root tip, from which material points are produced continuously by cell division. Elongation takes place after material points leave the meristem. Each material point along the root axis is associated with a unique time at which it was produced. The total rate of root growth is the sum of the rate of elongation of all cells present plus the contribution from the meristem. Under steady-state conditions, the rate of elongation of a particular segment of the root is a function of its age only. The theory enables us to compare spatial patterns of steady-state root elongation with distribution of cell sizes along the root axis. The theory is also used to characterize the effects of soil water stress and temperature on root growth. Soil water stress reduces both the rate of meristem production and the subsequent cell elongation, resulting in a shorter elongation region. The effect of temperature is characterized by a temperature-time equivalence effect, leading to an elongation region with its length independent of temperature.

Inhibition of hypocotyl elongation by ultraviolet‐B radiation in de‐etiolating tomato seedlings. II. Time‐course, comparison with flavonoid responses and adaptive significance

UV‐B radiation inhibits hypocotyl elongation in etiolated tomato (Lycopersicon esculentum Mill. cv. Alisa Craig) seedlings acting through a photoreceptor system with peak apparent effectiveness around 300 nm. In order lo further characterize the response and gain insight into its potential ecological significance, the time‐course of inhibition was measured and compared with the time‐course of flavonoid accumulation in the same seedlings. When a background of strong (> 620 μmol m−2 s−1) white light (WL) was supplemented with low irradiance UV‐B (∼ 3 μmol m−2 s−1). substantial (∼ 50%) inhibition of elongation occurred within 3 h of the light treatment. The magnitude of UV‐B‐induced elongation inhibition was similar in wild type (WT) and au‐mutant seedlings, in spite of the large differences between genotypes in rate and temporal pattern of elongation. In comparison to the effect of UV‐B on elongation, induction of flavonoid accumulation in WT and au seedlings undergoing de‐etiolation was a much slower response. Several UV‐absorbing compounds appeared to be specifically induced by light, and some of them accumulated faster under the WL + UV‐B treatment than under WL alone. However, there was little or no delectable effect of WL on flavonoid levels until up to 3 h of treatment, and the specific UV‐B effect was measurable only after 6 h of continuous treatment. Indeed. UV‐B‐screening properties of crude alcoholic extracts were not different between WL and WL + UV‐B treatments until after 9 or 24 h. When the light treatments were applied to seedlings that were just breaking through the soil surface. UV‐B was found to consistently retard seedling emergence. These results suggest that the rapid inhibition of elongation in de‐etiolating seedlings is an evolved response lo UV‐B, which may serve to minimize seedling exposure to sunlight until protective pigmentation responses (triggered by WL and UV‐B) have taken place in the seedlings epidermis.

Structural aspects of in vitro pollen tube growth and micropylar penetration inGasteria verrucosa (Mill.) H. Duval andLilium longiflorum Thunb.

In vitro penetration of the micropyle of freshly isolatedGasteria verrucosa ovules by pollen tube was monitored on agar medium. 40–60% of the micropyles were penetrated, comparable with in vivo penetration percentages. When germinated on agar,Gasteria pollen tube elongation lasts for up to 8 h while plasma streaming continues for about 20–24 h. The generative cell divides between 7 and 20 h after germination, and after 20 h the pollen tube arrives at one of the synergids. The sperm cells arrive after 22 h. The whole process takes more time in vitro than in vivo. In fast growing pollen tubes, a pulsed telescope-like growth pattern of tube elongation is observed. The formation of pollen tube wall material precedes tube elongation and probably prevents regular enlargement of the pollen tube tip-zone. Rapid stretching of the new pollen tube wall material follows, probably due to gradually increased osmotic pressure and the use of lateral wall material below the tip. The stretching ceases when the supplies of plasma membrane and excretable wall material are exhausted. Multiple pollen tube penetration of the micropyle occurs in vitro as it does in vivo. Most pollen tube growth ceases within the micropyle but, if it continues, the pollen tubes curl. Inside the micropyle the pollen tube shows haustorial growth. At the ultrastructural level, the wall thickening of in vitro pollen tubes is quite similar to that in vivo. Before transfer of pollen tube cytoplasm a small tube penetrates one of the synergids. Sperm nuclei with condensed chromatin are observed in the pollen tube and the synergid. In vivo prometaphase nuclei are found in the most chalazal part of a synergid, against the egg cell nucleus and nucleus of the central cell at a later stage. Using media forLilium ovule culture,Gasteria ovules were kept alive for at least 6 weeks. Swelling of the ovule depends on pollen tube penetration. The conditions for fertilization to occur after in vitro ovular pollination seem to be present.

Auxin‐dependent microtubule responses and seedling development are affected in a rice mutant resistant to EPC

SummaryMutants in rice (Oryza sativa L. cv. japonica) were used to study the role of the cytoskeleton in signal‐dependent morphogenesis. Mutants obtained by gamma ray irradiation were selected that failed to show inhibition of coleoptile elongation by the antimicrotubular drug ethyl‐N‐phenylcarbamate (EPC). The mutation EPC‐Resistant 31 (ER31), isolated from such a screen, caused lethality in putatively homozygous embryos. Heterozygotes exhibited drug resistance, impaired development of crown roots, and characteristic changes in the pattern of cell elongation: cell elongation was enhanced in mesocotyls and leaf sheaths, but inhibited in coleoptiles. The orientation of cortical microtubules changed correspondingly: for etiolated seedlings, compared with the wild‐type, they were more transverse with respect to the long cell axis in mesocotyls and leaf sheaths, but more longitudinal in coleoptiles. In mutant coleoptiles, in contrast to wild‐type, microtubules did not reorient in response to auxin, and their response to microtubule‐eliminating and microtubule‐stabilizing drugs was conspicuously reduced. In contrast, they responded normally to other stimuli such as gibberellins or red light. Auxin sensitivity as assayed by the dose‐response for callus induction did not show any significant differences between wild‐type and mutant. The mutant phenotype is interpreted in terms of an interrupted link between auxin‐triggered signal transduction and microtubule reorientation.

An in vivo comparison between intraoperative isometric measurement and local elongation of the graft after reconstruction of the anterior cruciate ligament.

This study was designed to determine if isometric measurement can be used to predict the pattern of elongation (the change in length) of a bone-patellar ligament-bone graft during passive flexion-extension of the knee at the time of reconstruction of the anterior cruciate ligament in vivo. A standard operative reconstruction technique was performed on nine patients. The tunnel sites for the grafts were selected, and the change in the distance between these sites was measured, with use of a CA-5000 drill-guide isometer as the knee was subjected to passive flexion-extension. After the reconstruction was completed, a Hall-effect transducer was implanted in the graft to measure the local displacement in the mid-substance of the graft that was produced by passive flexion-extension of the knee. For comparison, the isometric measurements and the values for local displacement of the graft were normalized by calculation of the percentage change in the length. With the knee in 10 to 30 degrees of flexion, the average isometric measurements and the measurements of local displacement demonstrated a decrease in length; however, the two techniques of measurement deviated at angles of flexion of 40 degrees and more. On the average, the isometric measurement of elongation between the trial insertion sites predicted that the graft would increase in length in flexion relative to extension, in contrast to the response of the graft after fixation. There was no significant correlation between the isometric measurements and the local elongation of the graft (r2 = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The role of nodal regions in growth of Xanthium (Compositae) stem

Vegetative Xanthium plants grown under noninductive conditions were marked with India ink along the stem and photographed at three consecutive time intervals. Relative elemental rates (d[dX/dt]/dX) of stem elongation were estimated from displacement of marks during stem elongation. Young internodes elongated with constant relative elemental rates of 0.2 day‐1. Older internodes displayed an acropetal pattern of elongation in which the basal segments of an internode stopped elongating first and the apical portion last. Nodal regions elongated with very small relative elemental rates of 0.05 day‐1. Rates decreased as the age of the internodes and nodes increased and stopped shortly after Leaf Plastochron Index 9.

Vegetation control and site preparation affect patterns of shoot elongation for 3-year-old loblolly pine

Effects of vegetation control and site preparation on the magnitude, morphology, and phenology of loblolly pine (Pinustaeda L.) height growth were investigated duing the third growing season following planting in the Piedmont of North Carolina. Biweekly measurements were made of shoot elongation (by flush) throughout the growing season on a subsample of trees within three replicated plots receiving a factorial combination of site preparation (chop versus shear, pile, disk) and weed control (none, partial control with herbicide, and complete control by hand weeding) treatments. Cumulative height growth on the most intensively treated plots was twice that found on the chopped-only plots, with weed control having a more pronounced positive effect than intensive site preparation. Superior height growth resulted principally from greater length per flush but also from an increased number of flushes. Trees on plots where vegetation was controlled averaged between four and five flushes compared with trees on chopped-only plots, which averaged three flushes. As growth rate of one flush slowed, growth rate of the subsequent flush accelerated, resulting in a rather uniform elongation rate for the shoot apex throughout most of the growing season. Treatment effects on the seasonal distribution of growth and on growing season length were minimal. Thus, intensive culture influenced shoot growth rates and morphology, but not phenology. Apparently the effect of intensive culture was to improve the availability of limited environmental resources and, consequently, to increase growth rate throughout the growing season.