Apical control of branch growth and angle in woody plants

Apical control is the inhibition of a lateral branch growth by shoots above it (distal shoots). If the distal shoots are cut off to remove apical control, the lateral branch can grow larger and may bend upwards. Apical control starts when new lateral buds grow after passing through a period of dormancy. Buds initially break and produce leaves, then apical control is exerted and the lower (proximal) laterals stop growing. Apical control also inhibits growth of large, old branches. Gravimorphism and restricted water and nutrient transport can inhibit branch growth, but they are not primary mechanisms of apical control. Apical control may reduce branch photosynthesis. Under apical control allocation of branch-produced assimilate to the stem is relatively high, so low assimilates in the branch may limit branch growth even though hormone levels are adequate for growth. Hormones appear to be involved in apical control, but it is not known how. One role of hormones may be to maintain the strength of the stem sink for branch-produced assimilate. Upward bending of a woody branch after release from apical control requires both new wood production and production of wood cells that can generate an upward bending moment. Apical control inhibits radial growth of branches and, in some species, may regulate the production of wood with an upward bending moment.     

Effect of cycles of feed deprivation on growth and food consumption of immature three-spined sticklebacks and European minnows

Individual juvenile three-spined sticklebacks Gasterosteus aculeatus and European minnow Phoxinus phoxinus , from sympatric populations, were subjected to four cycles of 1 week of food deprivation and 2 weeks of ad libitum feeding. Mean specific growth rate during the weeks of deprivation was negative and did not differ between species. The three-spined stickleback showed sufficient growth compensation to recover to the growth trajectory shown by control fish daily fed ad libitum . The compensation was generated by hyperphagia during the re-feeding periods, and in the last two periods of re-feeding, the gross growth efficiencies of deprived three-spined sticklebacks were greater than in control fish. The expression of the compensatory changes in growth and food consumption became clearer over the successive periods of re-feeding. The European minnow developed only a weak compensatory growth response and the mass trajectory of the deprived fish deviated more and more from the control trajectory. During re-feeding periods, there were no significant differences in food consumption or gross growth efficiency between control and deprived European minnows. The differences between the two species are discussed in terms of the possible costs of compensatory growth, the control of growth and differences in feeding biology.     

生长激素分泌促进剂及构效关系研究进展

生长激素分泌促进剂是一类作用于垂体和下丘脑的具有专一性促生长激素释放作用的寡肽及其类似物.由于其分子质量小、活性高、可口服、作用专一而有可能成为新的生长激素治疗药物.目前已经发展了很多具有此类活性的多种结构的化合物,如肽、环肽、肽醇及非肽类似物等.尽管这类化合物的作用机制尚未完全明确,但已有证据表明存在新的调节生长激素分泌的途径和新的调节因子.     

Effect of recombinant growth hormone on expression of growth hormone receptor, insulin-like growth factor mRNA and serum level of leptin in growing pigs

Growth hormone (GH) plays an important role in regulation of animal growth, metabolism and lactation[1]. Numerous studies have shown that exogenous somatotropin (ST) can increase average daily weight gain, improve feed efficiency, stimulate protein deposition and muscle growth and decrease lipid accretion rate[1]. The original somatomedin hypothesis suggested that the effect of GH on postnatal growth was mediated by insulin-like growth hormone factor 1 (IGF-I) which was thought to be deriv…     

The EGF-like homeotic protein dlk affects cell growth and interacts with growth-modulating molecules in the yeast two-hybrid system

Levels of dlk, an EGF-like homeotic protein, are critical for several differentiation processes. Because growth and differentiation are, in general, exclusive of each other, and increasing evidence indicates that Dlk1 expression changes in tumorigenic processes, we studied whether dlk could also affect cell growth. We found that, in response to glucocorticoids, Balb/c 3T3 cells with diminished levels of dlk expression develop foci-like cells that have lost contact inhibition, display altered morphology, and grow faster than control cell lines. Balb/c 3T3 cells spontaneously growing more rapidly are also dlk-negative cells. Moreover, screening by the yeast two-hybrid system, using Dlk1 constructs as baits, resulted in the isolation of GAS1 and acrogranin cDNAs. Interestingly, these proteins are cysteine-rich molecules involved in the control of cell growth. Taken together, these observations suggest that dlk may participate in a network of interactions controlling how the cells respond to growth or differentiation signals.     

Effect of recombinant growth hormone on expression of growth hormone receptor,insulin-like growth factor mRNA and serum level of leptin in growing pigs

Sixteen Large White × Landrace castrated male pigs were allotted into treatment and control group. The treatment group was injected intramuscularly with recombinant porcine growth hormone (rpGH, 4 mg d⁻¹) and the control group with vehicle for 28 days. Animals were slaughtered 4 h after final injection for liver, longissimus dorsi (LD) muscle and blood sampling. Serum concentration of insulin-like growth factor 1 (IGF-I) and leptin were determined by RIA. The total RNA was extracted from tissues to measure the abundance of growth hormone receptor (GHR), IGF-I mRNA by RT-PCR with 18S rRNA internal standard. Results showed that rpGH enhanced the average daily weight gain by 26.1% (P < 0.05), the serum IGF-I concentration by 70.94% (P < 0.01), decreased serum leptin by 34.8% (P < 0.01). The relative abundance of GHR and IGF-I mRNA in liver were increased by 24.45% (P < 0.05) and 45.30% (P < 0.01), respectively, but no difference of GHR (P > 0.05) and IGF-I mRNA (P > 0.05) in LD between GH treated and control group was found. These results suggest that rpGH can up-regulate hepatic GHR and IGF-I gene expression and improve animal growth. However the effect of rpGH on GHR and IGF-I gene expression are tissue-specific.     

Failure to induce over-compensation of growth in maturing yellow perch

Unlike juvenile F1 male bluegill Lepomis macrochrus × female green sunfish L. cyanellus , maximized episodes of compensatory growth (CG) in 2 year yellow perch Perca flavescens did not surpass control masses because internal regulation caused abrupt appetite reduction upon catch-up. Together, the hybrid sunfish study and present work indicate that CG-maximizing feeding schedules and absence of an internal growth limiting mechanism are both required to produce substantial growth overcompensation (GOC). The less vigorous and less resilient CG responses of the yellow perch relative to those of the similarly fed hybrid sunfish appear indicative of the lack of GOC capacity in the former. This contrast, and results of previous studies are interpreted to suggest that GOC capacity may be limited to early life stages of fishes which have a substantial reproductive potential but are at high risk of mortality due to their small size. The possibility that GOC capacity is time-of-year-dependent and species-specific is considered also. Food deprivation periods that produced the strongest CG responses differed for male (2 days) and female (12 days) yellow perch. Among controls fed without restriction, growth rate and growth efficiency of female yellow perch exceeded those of males two-fold, however, males showed a greater capacity to catch-up to same-sex controls when undergoing CG. A feeding schedule using maintenance feeding v. food deprivation to elicit CG yielded the most rapid catch-up to control masses in the yellow perch. Such feeding schedules may produce even greater GOC than was achieved previously in hybrid sunfish, where feeding schedules involving food deprivation were employed.     

Inferential control of the specific growth rate in fed-batch cultivation processes

Inferential control algorithms and systems for set-point control of the specific growth rate in fed-batch cultivation processes are presented. Realization of the proposed control systems does not require mathematical model and a priori knowledge of the culture of microorganisms under control. Feed-back signal in PID control loops of the investigated systems is based on measurements of the O₂ concentration in exhaust gas and the air supply rate, however, measurements of the other technological parameters related to the culture growth dynamics can also be applied.     

Positional specification in the segmental growth pattern of an early arthropod

In many arthropods, there is a change in relative segment size during post-embryonic development, but how segment differential growth is produced is little known. A new dataset of the highest quality specimens of the 429 Myr old trilobite Aulacopleura koninckii provides an unparalleled opportunity to investigate segment growth dynamics and its control in an early arthropod. Morphometric analysis across nine post-embryonic stages revealed a growth gradient in the trunk of A. koninckii. We contrastively tested different growth models referable to two distinct hypotheses of growth control for the developing trunk: (i) a segment-specific control, with individual segments having differential autonomous growth progression, and (ii) a regional control, with segment growth depending on their relative position along the main axis. We show that the trunk growth pattern of A. koninckii was consistent with a regional growth control producing a continuous growth gradient that was stable across all developmental stages investigated. The specific posterior-to-anterior decaying shape of the growth gradient suggests it deriving from the linear transduction of a graded signal, similar to those commonly provided by morphogens. A growth control depending on a form of positional specification, possibly realized through the linear interpretation of a graded signal, may represent the primitive condition for arthropod differential growth along the main body axis, from which the diverse and generally more complex forms of growth control in subsequent arthropods have evolved.     

Plasma Membrane-Bound Mechanisms of Signal Transduction in the Control of Plant Dormancy and Resistance

Data on membrane-bound biochemical mechanisms of control of plant dormancy and resistance to phytopathogens are discussed. Phytohormones are involved in the control of plant dormancy by the modification of activity of membrane-bound enzymes and ion channels. Similar constituents of the plasma membrane are influenced by fungal extracellular metabolites. Proposed interconnections between plasmalemma-bound signaling mechanisms responsible for plant resistance to infection and dormancy regulation are illustrated by a scheme.     

Dynamics of leaf and root growth: endogenous control versus environmental impact

AIMS: Production of biomass and yield in natural and agronomic conditions depend on the endogenous growth capacity of plants and on the environmental conditions constraining it. Sink growth drives the competition for carbon, nutrients and water within the plant, and determines the structure of leaves and roots that supply resources to the plant later on. For their outstanding importance, analyses of internal growth mechanisms and of environmental impact on plant growth are long-standing topics in plant sciences. SCOPE: Recent technological developments have made it feasible to study the dynamics of plant growth in temporal and spatial scales that are relevant to link macroscopic growth with molecular control. These developments provided first insights into the truly dynamic interaction between environment and endogenous control of plant growth. CONCLUSIONS: Evidence is presented in this paper that the relative importance of endogenous control versus the impact of the dynamics of the environment depends on the frequency pattern of the environmental conditions to which the tissue is exposed. It can further be speculated that this is not only relevant within individual plants (hence leaves versus roots), but also crucial for the adaptation of plant species to the various dynamics of their environments. The following are discussed: mechanisms linking growth and concentrations of primary metabolites, and differences and homologies between spatial and temporal patterns of root and leaf growth with metabolite patterns.     

XET-related genes and growth kinematics in barley leaves

DV, displacement velocity
GA₃, gibberellic acid
REGR, relative elemental growth rate
XET, xyloglucan-endotransglycosylase

Recently Schünmann et al. (1997 ; Plant, Cell and Environment 20, 1439–1450) investigated the correlation of spatial patterns of xyloglucan-endotransglycosylase (XET) activity, XET-related mRNAs, and growth in elongating barley ( Hordeum vulgare L.) leaves. Here, methodological difficulties in the kinematic growth analysis are discussed, and it is concluded that the role that XET-related gene activity plays in the control of spatial growth patterns remains undetermined.     

How do plant growth substances work? II

Abstract. This article continues the discussion on sensitivity prompted by the publication of an earlier paper by the author in 1981. It is indicated that appropriate measurements of sensitivity can help uncover the function of growth substances in development. The experimental constraints which are necessary for unambiguous measurements of sensitivity are outlined and it is shown that a specific sensitivity measurement, termed control strength, would most readily clarify function and help obviate controversy. Methods for measuring control strength which deal with the problem of compartmentalization are considered and it is suggested that stochastic variation in single cell biochemistry might provide a constraint on the accuracy of control strength determinations.     

TGF-β1 和CTGF 在大鼠高动力性肺动脉高压模型中的表达及意义*

目的:研究大鼠高动力性肺动脉高压模型转化生长因子-β1(transforming growth factor-beta 1,TGF-β1)和结缔组织生长因子(connective tissue growing factor,CTGF)的表达变化及意义。方法:45只SD大鼠随机分成左肺全切组(A)、假手术组(B)和对照组(C),每组15只。手术后6周测各组大鼠肺动脉平均压(mPAP),右心室肥厚指数(RVH),光镜下检测肺肌型小动脉占肺小血管百分比(SMA%)。免疫组化观察TGF-β1和CTGF在肺组织中的表达,RT-PCR检测肺组织TGF-β1mRNA和CTGF mRNA的表达水平。结果:①左肺全切后复制了高动力性肺动脉高压模型,引起mPAP、RVH和SMA%明显增高(P<0.05)。②左肺全切组TGF-β1和CTGF蛋白及mRNA表达均较假手术组和对照组显著性增加(P<0.05)。而假手术组和对照组之间各指标没有显著性差异。结论:TGF-β1和CTGF的过度表达是高动力性肺动脉高压发生发展的重要因素,可能共同促进了肺血管重构。     

窝雏数处理对两种雀形目幼鸟生长的影响

基于 1 997～ 1 999年野外实验 ,对高寒草甸小云雀和黄嘴朱顶雀两种雀形目鸟的窝雏数进行增减处理。结果表明 ,对照组的幼鸟生长率和离巢体重都大于增加组 ,说明窝雏数增加后 ,幼鸟质量下降。随着窝雏数增加 ,这两种幼鸟生长率显著下降 (小云雀 :r =-0 965 ,P =0 0 3 5 <0 0 5 ;朱顶雀 :r =-0 82 8,P =0 0 2 2 <0 0 5 )。窝雏数改变对小云雀幼鸟出飞重影响不显著 (r =-0 41 8,P =0 5 2 8>0 0 5 ) ,而对黄嘴朱顶雀有显著的影响 (r=-0 90 1 ,P =0 0 1 4<0 0 5 )。     

Transforming growth factors and control of neoplastic cell growth

Transforming growth factors (TGFs) are peptides that affect the growth and phenotype of cultured cells and bring about in nonmalignant fibroblastic cells phenotypic properties that resemble those of malignant cells. Two types of TGFs have been well characterized. One of these, TGF alpha, is related to epidermal growth factor (EGF) and binds to the EGF receptor, whereas the other, TGF beta, is not structurally or functionally related to TGF alpha or EGF and mediates its effects via distinct receptors. TGF beta is produced by a variety of normal and malignant cells. Depending upon the assay system employed, TGF beta has both growth-inhibitory and growth-stimulating properties. Many of the mitogenic effects of TGF beta are probably an indirect result of the activation of certain growth factor genes in the target cell. The ubiquitous nature of the TGF beta receptor and the production of TGF beta in a latent form by most cultured cells suggests that the differing cellular responses to TGF beta are regulated either by events involved in the activation of the factor or by postreceptor mechanisms. The combined effects of TGF beta with other growth factors or inhibitors evidently play a central role in the control of normal and malignant cellular growth as well as in cell differentiation and morphogenesis. Since transforming growth factor as a concept has partially proven misleading and insufficient, there is a need to find a new nomenclature for these regulators of cellular growth and differentiation.     

Fast-growing transgenic common carp mounting compensatory growth

Compensatory growth is a phase of accelerated growth apparent when favourable conditions are restored after a period of growth depression. To investigate if F₂ common 'all-fish' growth hormone gene transgenic common carp ( Cyprinus carpio ) could mount compensatory growth, a 9 week study at 29° C was performed. The control group was fed to satiation twice a day throughout the experiment. The other two groups were deprived of feed for 1 or 2 weeks, respectively, and then fed to satiation during the re-feeding period. At the end of the experiment, the live masses of fish in the deprived groups were still significantly lower than those of the controls. During the re-feeding period, size-adjusted mean specific growth rates and mean feed intakes were significantly higher in the deprived fish than in the controls, indicating a partial compensatory growth response in these fish. No significant differences were found in food conversion efficiency between the deprived and control fish during re-feeding, suggesting that hyperphagia was the mechanism responsible for increased growth rates. The proximate composition of the deprived fish at the end of the experiment was similar to that of the control fish. This study is, to our knowledge, the first to report that fast-growing transgenic fish can achieve partial compensation of growth following starvation.     

STEADY STATE GROWTH OF PHYTOPLANKTON IN CONTINUOUS CULTURE: COMPARISON OF INTERNAL AND EXTERNAL NUTRIENT EQUATIONS1,2

Previously, there have been conflicts over whether external or internal nutrient concentrations control phytoplankton growth rates at steady state in continuous culture. To experimentally demonstrate that both equations equally describe steady state growth, continuous culture studies with phosphorus-limited growth of the chrysophyte Monochrysis lutheri Droop were carried out over the entire growth rate region up to biomass washout. Data were examined using both the Monod and Droop equations, and, even though there were significant variations in the yield coefficient with growth rate, the data fit both equations reasonably well. Because of their relative simplicity, the Droop equation and an equation combining both the Monod and Droop equations are better suited for expressing kinetic data than the Monod equation. It is crucial, though, that the criteria necessary to achieve steady state be fulfilled.     

Comparing growth phenology of co-occurring deciduous and evergreen conifers exposed to drought

Plant phenological events are influenced by climate factors such as temperature and rainfall. To evaluate phenological responses to water availability in a Spring Heath-Pine wood (Erico-Pinetum typicum), the focus of this study was to determine intra-annual dynamics of apical and lateral growth of co-occurring early successional Larix decidua and Pinus sylvestris and late successional Picea abies exposed to drought. The effect of reduced plant water availability on growth phenology was investigated by conducting a rainfall exclusion experiment. Timing of key phenological dates (onset, maximum rate, end, duration) of growth processes were compared among species at the rain-sheltered and control plot during 2011 and 2012. Shoot and needle elongation were monitored on lateral branches in the canopy at c. 16 m height and radial growth was recorded by automatic dendrometers at c. 1.3 m height of >120 yr old trees. Different sequences in aboveground growth phenology were detected among the three species under the same growing conditions. While onset of radial growth in April through early May was considerably preceded by onset of needle growth in Larix decidua (5–6 weeks) and shoot growth in Pinus sylvestris (c. 3 weeks), it occurred quite simultaneously with onset of shoot growth in Picea abies. Low water availability had a minor impact on onset of aboveground growth, which is related to utilization of stored water, but caused premature cessation of aboveground growth. At the control plot mean growing season length was 130 days in Pinus sylvestris, 95 days in Larix decidua and 73 days in Picea abies, supporting the hypothesis that early successional species are resource expenders, while late successional species are more efficient in utilizing resources and develop safer life strategies. High synchronicity found in culmination of radial growth in late spring (mid-May through early June) prior to occurrence of more favourable environmental conditions in summer might indicate sink competition for carbohydrates to belowground organs. This is supported by completion of apical growth in mid June in all species, except for needle growth of Pinus sylvestris which lasted until early August. Phenological observations of conifers exposed to drought revealed that tree water status early during the growing season determines total annual aboveground growth and, besides temperature, species-specific endogenous and/or environmental factors (most likely photoperiod and/or different threshold temperatures) are involved in controlling apical and lateral growth resumption after winter dormancy.