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Plant density defines vegetative architecture and the competition for light between individuals. Brassica napus (canola, rapeseed) presents a radically different plant architecture compared to traditional crops commonly cultivated at high density, and can act as a model system of indeterminate growth. Using a panel of 152 spring-type accessions and a double-haploid population of 99 lines from a cross between the cultivars Lynx and Monty, we performed genome-wide association studies (GWAS) and quantitative trait locus (QTL) mapping for 12 growth and yield traits at two contrasting plant densities of 15 and 60 plants m–2. The most significant associations were found for time to flowering, biomass at harvest, plant height, silique and seed numbers, and seed yield. These were generally independent of plant density, but some density-dependent associations were found in low-density populations. RNA-seq transcriptomic analysis revealed distinctive latent gene-regulatory responses to simulated shade between Lynx and Monty. Having identified candidate genes within the canola QTLs, we further examined their influence on density responses in Arabidopsis lines mutated in certain homologous genes. The results suggested that TCP1 might promote growth independently of plant density, while HY5 could increase biomass and seed yield specifically at high plant density. For flowering time, the results suggested that PIN genes might accelerate flowering in plant a density-dependent manner whilst FT, HY5, and TCP1 might accelerate it in a density-independent. This work highlights the advantages of using agronomic field experiments together with genetic and transcriptomic approaches to decipher quantitative complex traits that potentially mediate improved crop productivity.

Evolutionary theories relating to aging predict that patterns of actuarial and reproductive senescence should be aligned, with a common onset of senescence set at the age of first reproduction. However, a few empirical studies reported asynchrony between actuarial and reproductive senescence. This asynchrony is expected to be particularly pronounced in organisms with indeterminate growth. Yet, this process is still poorly documented due to the lack of long-term demographic data on known-aged individuals. We investigated the asynchrony of actuarial and reproductive senescence in the European whip snake, Hierophis viridiflavus, an oviparous colubrid with indeterminate growth. Using demographic data collected over a 29-year period, we showed that females did not experience any fecundity loss late in life. In contrast, they suffered from an early, severe actuarial senescence. Our findings thus revealed a pronounced asynchrony in actuarial and reproductive senescence processes, a phenomenon that could be widespread across the tree of life.

The SELF PRUNING (SP) gene is a key regulator of growth habit in tomato (Solanum lycopersicum). It is an ortholog of TERMINAL FLOWER1, a phosphatidylethanolamine-binding protein with antiflorigenic activity in Arabidopsis (Arabidopsis thaliana). A spontaneous loss-of-function mutation (sp) has been bred into several industrial tomato cultivars, as it produces a suite of pleiotropic effects that are favorable for mechanical harvesting, including determinate growth habit, short plant stature, and simultaneous fruit ripening. However, the physiological basis for these phenotypic differences has not been thoroughly explained. Here, we show that the sp mutation alters polar auxin transport as well as auxin responses, such as gravitropic curvature and elongation of excised hypocotyl segments. We also demonstrate that free auxin levels and auxin-regulated gene expression patterns are altered in sp mutants. Furthermore, diageotropica, a mutation in a gene encoding a cyclophilin A protein, appears to confer epistatic effects with sp. Our results indicate that SP affects the tomato growth habit at least in part by influencing auxin transport and responsiveness. These findings suggest potential novel targets that could be manipulated for controlling plant growth habit and improving productivity.

Males may use tactics before, during and after mating to increase their reproductive success. With finite energy resources available, theory predicts that there should be a trade-off between investment in pre-copulatory traits (e.g. body size, armaments) and post-copulatory traits (e.g. testes size, spermatogenic efficiency). Western grey kangaroos (Macropus fuliginosus) are found in large, labile mixed-sex groups, in which the males show a dominance hierarchy. Males show indeterminate growth, and will reach up to six times the body mass of females. While the largest males use their size as a reproductive advantage, forelimb musculature further aids male–male contest, female attraction and/or female coercion. Under a trade-off scenario, we therefore predicted that larger, more muscular males would show less investment in sperm competitive traits. Consistent with this prediction, more muscular males showed decreased spermatozoa velocity. However, muscularity was also positively correlated with mass of two pairs of bulbourethral accessory glands, as well as mass of the penis and its muscles of erection. Seasonal changes in muscularity and accessory gland masses were also evident. Male kangaroos therefore invest in multiple reproductive traits on which selection can work.

In temperate deciduous forests, vertical gradients in leaf mass per area (LMA) and area-based leaf nitrogen (Narea) are strongly controlled by gradients in light availability. While there is evidence that hydrostatic constraints on leaf development may diminish LMA and Narea responses to light, inherent differences among tree species may also influence leaf developmental and morphological response to light. We investigated vertical gradients in LMA, Narea and leaf carbon isotope composition (δ13C) for three temperate deciduous species (Carpinus caroliniana Walter, Fagus grandifolia Ehrh., Liriodendron tulipifera L.) that differed in growth strategy (e.g., indeterminate and determinate growth), shade tolerance and leaf area to sapwood ratio (Al:As). Leaves were sampled across a broad range of light conditions within three vertical layers of tree crowns to maximize variation in light availability at each height and to minimize collinearity between light and height. All species displayed similar responses to light with respect to Narea and δ13C, but not for LMA. Light was more important for gradients in LMA for the shade-tolerant (C. caroliniana) and -intolerant (L. tulipifera) species with indeterminate growth, and height (e.g., hydrostatic gradients) and light were equally important for the shade-tolerant (F. grandifolia) species with determinate growth. Fagus grandifolia had a higher morphological plasticity in response to light, which may offer a competitive advantage in occupying a broader range of light conditions throughout the canopy. Differences in responses to light and height for the taller tree species, L. tulipifera and F. grandifolia, may be attributed to differences in growth strategy or Al:As, which may alter morphological and functional responses to light availability. While height was important in F. grandifolia, height was no more robust in predicting LMA than light in any of the species, confirming the strong role of light availability in determining LMA for temperate deciduous species.

Ecomorphology studies focus on understanding how anatomical and behavioral diversity result in differences in performance, ecology, and fitness. In mammals, the determinate growth of the skeleton entails that bite performance should change throughout ontogeny until the feeding apparatus attains its adult size and morphology. Then, interspecific differences in adult phenotypes are expected to drive food resource partitioning and patterns of lineage diversification. However, Formal tests of these predictions are lacking for the majority of mammal groups, and thus our understanding of mammalian ecomorphology remains incomplete. By focusing on a fundamental measure of feeding performance, bite force, and capitalizing on the extraordinary morphological and dietary diversity of bats, we discuss how the intersection of ontogenetic and macroevolutionary changes in feeding performance may impact ecological diversity in these mammals. We integrate data on cranial morphology and bite force gathered through longitudinal studies of captive animals and comparative studies of free-ranging individuals. We demonstrate that ontogenetic trajectories and evolutionary changes in bite force are highly dependent on changes in body and head size, and that bats exhibit dramatic, allometric increases in bite force during ontogeny. Interspecific variation in bite force is highly dependent on differences in cranial morphology and function, highlighting selection for ecological specialization. While more research is needed to determine how ontogenetic changes in size and bite force specifically impact food resource use and fitness in bats, interspecific diversity in cranial morphology and bite performance seem to closely match functional differences in diet. Altogether, these results suggest direct ecomorphological relationships at ontogenetic and macroevolutionary scales in bats.

Phytochrome B (phyB) enables plants to modify shoot branching or tillering in response to varying light intensities and ratios of red and far-red light caused by shading and neighbor proximity. Tillering is inhibited in sorghum genotypes that lack phytochrome B (58M, phyB-1) until after floral initiation. The growth of tiller buds in the first leaf axil of wild-type (100M, PHYB) and phyB-1 sorghum genotypes is similar until 6 d after planting when buds of phyB-1 arrest growth, while wild-type buds continue growing and develop into tillers. Transcriptome analysis at this early stage of bud development identified numerous genes that were up to 50-fold differentially expressed in wild-type/phyB-1 buds. Up-regulation of terminal flower1, GA2oxidase, and TPPI could protect axillary meristems in phyB-1 from precocious floral induction and decrease bud sensitivity to sugar signals. After bud growth arrest in phyB-1, expression of dormancy-associated genes such as DRM1, GT1, AF1, and CKX1 increased and ENOD93, ACCoxidase, ARR3/6/9, CGA1, and SHY2 decreased. Continued bud outgrowth in wild-type was correlated with increased expression of genes encoding a SWEET transporter and cell wall invertases. The SWEET transporter may facilitate Suc unloading from the phloem to the apoplast where cell wall invertases generate monosaccharides for uptake and utilization to sustain bud outgrowth. Elevated expression of these genes was correlated with higher levels of cytokinin/sugar signaling in growing buds of wild-type plants.

Gene duplications within the TFL1-like clade of tetraploid cotton are specific to the cotton lineage, and paralogs functionally diverged to differentially impact plant architecture., Genes of the CENTRORADIALIS/TERMINAL FLOWER 1/SELF-PRUNING (CETS) family influence meristem identity by controlling the balance between indeterminate and determinate growth, thereby profoundly impacting plant architecture. Artificial selection during cotton (Gossypium hirsutum) domestication converted photoperiodic trees to the day-neutral shrubs widely cultivated today. To understand the regulation of cotton architecture and exploit these principles to enhance crop productivity, we characterized the CETS gene family from tetraploid cotton. We demonstrate that genes of the TERMINAL FLOWER 1 (TFL1)-like clade show different roles in regulating growth patterns. Cotton has five TFL1-like genes: SELF-PRUNING (GhSP) is a single gene whereas there are two TFL1-like and BROTHER OF FT (BFT)-like genes, and these duplications are specific to the cotton lineage. All genes of the cotton TFL1-like clade delay flowering when ectopically expressed in transgenic Arabidopsis, with the strongest phenotypes failing to produce functional flowers. GhSP, GhTFL1-L2, and GhBFT-L2 rescue the early flowering Attfl1-14 mutant phenotype, and the encoded polypeptides interact with a cotton FD protein. Heterologous promoter::GUS fusions illustrate differences in the regulation of these genes, suggesting that genes of the GhTFL1-like clade may not act redundantly. Characterizations of the GhCETS family provide strategies for nuanced control of plant growth.

The mitochondrial theory of ageing proposes that the cumulative effect of biochemical damage in mitochondria causes mitochondrial mutations and plays a key role in ageing. Numerous studies have applied comparative approaches to test one of the predictions of the theory: That the rate of mitochondrial mutations is negatively correlated with longevity. Comparative studies face three challenges in detecting correlates of mutation rate: Covariation of mutation rates between species due to ancestry, covariation between life-history traits, and difficulty obtaining accurate estimates of mutation rate. We address these challenges using a novel Poisson regression method to examine the link between mutation rate and lifespan in rockfish (Sebastes). This method has better performance than traditional sister-species comparisons when sister species are too recently diverged to give reliable estimates of mutation rate. Rockfish are an ideal model system: They have long life spans with indeterminate growth and little evidence of senescence, which minimizes the confounding tradeoffs between lifespan and fecundity. We show that lifespan in rockfish is negatively correlated to rate of mitochondrial mutation, but not the rate of nuclear mutation. The life history of rockfish allows us to conclude that this relationship is unlikely to be driven by the tradeoffs between longevity and fecundity, or by the frequency of DNA replications in the germline. Instead, the relationship is compatible with the hypothesis that mutation rates are reduced by selection in long-lived taxa to reduce the chance of mitochondrial damage over its lifespan, consistent with the mitochondrial theory of ageing.

Our aim was to determine if a limitation of reproduction by available brood chamber space could explain indeterminate growth in Daphnia, and what conditions might affect this. We evaluated the brood chamber volumes of the larger Daphnia longispina and smaller D. cucullata species during the first three clutches of eggs and compared this with the volume of eggs produced in low and high food conditions. We also examined whether these Daphnia retained significant levels of unused lipids in their bodies after reproduction, and if the volume of eggs deposited in brood chambers of different capacities corresponded to the maximal egg volume specified by a geometrical model. Our results revealed that, at least during the early clutches, both Daphnia species produced as manyeggs as permitted by the available brood chamber volume in both high and low food conditions, thus indicating that “brood space constraint” can explain the simultaneous investment in growth and reproduction. The detailed evaluation of this hypothesis required not only brood chamber volume assessment, but also consideration of the effect of egg size on packing efficiency, especially in low food conditions and for the smaller Daphnia species. The significant lipid reserves detected in the Daphnia body after reproduction also support the limitation of reproduction by brood chamber volume, particularly in larger species.

Multipotent stem cell populations, the meristems, are fundamental for the indeterminate growth of plant bodies. One of these meristems, the cambium, is responsible for extended root and stem thickening. Strikingly, although the pivotal role of the plant hormone auxin in promoting cambium activity has been known for decades, the molecular basis of auxin responsiveness on the level of cambium cells has so far been elusive. Here, we reveal that auxin-dependent cambium stimulation requires the homeobox transcription factor WOX4. In Arabidopsis thaliana inflorescence stems, 1-N-naphthylphthalamic acid–induced auxin accumulation stimulates cambium activity in the wild type but not in wox4 mutants, although basal cambium activity is not abolished. This conclusion is confirmed by the analysis of cellular markers and genome-wide transcriptional profiling, which revealed only a small overlap between WOX4-dependent and cambium-specific genes. Furthermore, the receptor-like kinase PXY is required for a stable auxin-dependent increase in WOX4 mRNA abundance and the stimulation of cambium activity, suggesting a concerted role of PXY and WOX4 in auxin-dependent cambium stimulation. Thus, in spite of large anatomical differences, our findings uncover parallels between the regulation of lateral and apical plant meristems by demonstrating the requirement for a WOX family member for auxin-dependent regulation of lateral plant growth.

We compared light acclimation potential among three evergreen broadleaved species with contrasting patterns of shoot elongation, leaf emergence and leaf maturation. Understory saplings were transferred to a high-light environment before bud break, grown for 13 months, and then transferred back to the understory to observe subsequent carry-over effects. Acclimation potential was highest and sapling mortality was lowest for Cinnamomum japonicum Sieb. ex Nakai. Indeterminate growth and successive leaf emergence allowed this species to acclimate to both high and low light by adjusting leaf production as well as leaf properties. Sapling mortality occurred after both transfers for Camellia japonica L., which also has indeterminate growth and successive leaf emergence. In this species, carry-over effects were observed at the individual level, but leaf-level acclimation potential was high. Acclimation potential was lowest and sapling mortality occurred soon after the transfer to high light for Quercus glauca Thunb. ex Murray. Determinate growth and flush-type leaf emergence resulted in significant carry-over effects in this species. Indeterminate growth and successive leaf emergence increase whole-plant acclimation potential by extending the period of growth and architectural development during the growing season. Similarly, we inferred that delayed leaf maturation, observed in many evergreen species, increases the acclimation potential of current-year leaves by extending the period of leaf development. In evergreen species, the acclimation potential of preexisting leaves determines the role that leaf turnover plays in whole-plant light acclimation, resulting in diverse strategies for light acclimation among species, as observed in this study.

ACL-11-06; International audience; Background and Aims: Mechanical perturbation is known to inhibit elongation of the inflorescence stem of Arabidopsis thaliana. The phenomenon has been reported widely for both herbaceous and woody plants, and has implications for how plants adjust their size and form to survive in mechanically perturbed environments. While this response is an important aspect of the plant's architecture, little is known about how mechanical properties of the inflorescence stem are modified or how its primary and secondary tissues respond to mechanical perturbation. Methods: Plants of the Columbia-0 ecotype were exposed to controlled brushing treatments and then submitted to three-point bending tests to determine stem rigidity and stiffness. Contributions of different tissues to the inflorescence stem geometry were analysed. Key Results: Perturbed plants showed little difference in stem diameter, were 50 % shorter, 75 % less rigid and 70 % less stiff than controls. Changes in mechanical properties were linked to significant changes in tissue geometry – size and position of the pith, lignified interfascicular tissue and cortex – as well as a reduction in density of lignified cells. Stem mechanical properties were modified by changes in primary tissues and thus differ from changes observed in most woody plants tested with indeterminate growth – even though a vascular cambium is present in the inflorescence axis. Conclusions: The study suggests that delayed development of key primary developmental features of the stem in this ecotype of Arabidopsis results in a ‘short and flexible' rather than a ‘short and rigid' strategy for maintaining upright axes in conditions of severe mechanical perturbation. The mechanism is comparable with more general phenomena in plants where changes in developmental rate can significantly affect the overall growth form of the plant in both ecological and evolutionary contexts

A major life-history challenge for fairy shrimps (Anostraca) is the unpredictable environment of the ephemeral pool. The duration and predictability of pool inundations affects their life history strategy. The growth and reproduction schedule of a thamnocephalid fairy shrimp, Branchinella (Branchinellites) kugenumaensis, in an unpredictable ephemeral pool in northern Taiwan was monitored from 2004 to 2008. A total of 15 inundation episodes, resulting from typhoons or, occasionally, frontal systems, was recorded over the five-year period. Thirteen episodes lasted no more than 2-3 weeks. Two exceptionally long inundation periods were caused by additional rain events before the pool dried out. We recorded the growth patterns, egg spawning time, and clutch size of each fairy shrimp cohort during each inundation episode. No significant differences were observed in either growth or reproductive pattern from hatching to first spawning between short and long inundation episodes. The fairy shrimps stopped...

We investigated the short day (SD)–induced transition to dormancy in wild-type hybrid poplar (Populus tremula × P. tremuloides) and its absence in transgenic poplar overexpressing heterologous PHYTOCHROME A (PHYA). CENTRORADIALIS-LIKE1 (CENL1), a poplar ortholog of Arabidopsis thaliana TERMINAL FLOWER1 (TFL1), was markedly downregulated in the wild-type apex coincident with SD-induced growth cessation. By contrast, poplar overexpressing a heterologous Avena sativa PHYA construct (P35S:AsPHYA), with PHYA accumulating in the rib meristem (RM) and adjacent tissues but not in the shoot apical meristem (SAM), upregulated CENL1 in the RM area coincident with an acceleration of stem elongation. In SD-exposed heterografts, both P35S:AsPHYA and wild-type scions ceased growth and formed buds, whereas only the wild type assumed dormancy and P35S:AsPHYA showed repetitive flushing. This shows that the transition is not dictated by leaf-produced signals but dependent on RM and SAM properties. In view of this, callose-enforced cell isolation in the SAM, associated with suspension of indeterminate growth during dormancy, may require downregulation of CENL1 in the RM. Accordingly, upregulation of CENL1/TFL1 might promote stem elongation in poplar as well as in Arabidopsis during bolting. Together, the results suggest that the RM is particularly sensitive to photoperiodic signals and that CENL1 in the RM influences transition to dormancy in hybrid poplar.

The difference between indeterminate and determinate growth in plants consists of the presence or absence of an active meristem in the fully developed organ. Determinate root growth implies that the root apical meristem (RAM) becomes exhausted. As a consequence, all cells in the root tip differentiate. This type of growth is widely found in roots of many angiosperm taxa and might have evolved as a developmental adaptation to water deficit (in desert Cactaceae), or low mineral content in the soil (proteoid roots in various taxa).This review considers the mechanisms of determinate root growth to better understand how the RAM is maintained, how it functions, and the cellular and genetic bases of these processes. The role of the quiescent centre in RAM maintenance and exhaustion will be analysed. During root ageing, the RAM becomes smaller and its organization changes; however, it remains unknown whether every root is truly determinate in the sense that its RAM becomes exhausted before senescence. We define two types of determinate growth: constitutive where determinacy is a natural part of root development; and non-constitutive where determinacy is induced usually by an environmental factor. Determinate root growth is proposed to include two phases: the indeterminate growth phase, when the RAM continuously produces new cells; and the termination growth phase, when cell production gradually decreases and eventually ceases. Finally, new concepts regarding stem cells and a stem cell niche are discussed to help comprehend how the meristem is maintained in a broad taxonomic context.

In iteroparous animals, investment in growth is compromised by investment in reproduction, especially in species with indeterminate growth. Life-history theory predicts that growth should be favoured over reproduction, assuming size-related fecundity or survival. Hence, increase body condition represents an increase in reproductive potential. Simultaneous hermaphrodites should adjust their resource allocation to each sex function in response to current conditions but, recently, it has been suggested that, in hermaphrodites, gender allocation should be considered as a three-way trade-off, including the investment in somatic growth. Due to the higher costs involved, the female function is affected to a greater extent by environmentally stressful conditions rather than the male function. To examine this, we induced stress in the hermaphroditic earthworm Eisenia fetida (Savigny, 1826) and looked for changes in resource allocation in nonreproductive and reproductive individuals. Experimental stress was induced by using tweezers to elicit contractile escape movements. We predicted that stressed earthworms would preferentially allocate resources to growth. In nonreproductive individuals, however, stress had a negative effect on growth, although weight recovery was rapid once manipulation ceased, indicating the importance of body condition, as well as the existence of mechanisms of compensatory growth for growth trajectories in this earthworm species. The response of reproductive individuals was consistent with our expectation: (1) stressed worms maintained their growth rate at the expense of current reproduction and (2) stressed earthworms laid 25% fewer cocoons, which were 30% lighter than cocoons laid by control earthworms. The present results suggest that E. fetida regulates its reproductive effort and that future reproduction has more impact on its fitness than current reproduction. The trade-off between current and future reproduction should be taken into consideration in models of sex allocation in simultaneous hermaphrodites. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 593–600.

Corgos, A., and Freire, J. 2006. Morphometric and gonad maturity in the spider crab Maja brachydactyla: a comparison of methods for estimating size at maturity in species with determinate growth. e ICES Journal of Marine Science, 63: 851e859. Ontogenetic changes in the relative growth of males and females of the spider crab Maja brachydactyla, a species with terminal moult and determinate growth, were analysed and related to their reproductive (maturity) status. Based on the allometry of cheliped size, two morphometric groups of males separated juvenile and adult phases. Juvenile males also showed two growth phases, immature (smaller ones, without spermatophores) and adolescent (with spermatophores). Size at gonad maturity in males (estimated as CL50) was 96.2 mm carapace length (CL). Histological analysis of males showed that >60% of morphometric juveniles and 100% of morphometric adults had spermatophores in the gonad. Females begin to develop gonads 2e3 months after the terminal moult. Size at morphometric maturity was estimated comparing two methodologies: the size at 50% maturity (CL50) and the median size of adult cohorts (CLM). In all cases the CLM size at maturity was greater than that resulting from the CL50 method, and, in contrast to the CL50 method, CLM was greater for females in all cases. Therefore, CLM reflects better the real size at maturity for M. brachydactyla. Owing to spatial segregation of adults and juveniles and the availability of morphological and morphometric methods to estimate maturity status, we suggest a combination of spatial closures and direct protection of juvenile habitat as management strategies alternative to minimum landing sizes.

SYNOPSIS. Body size and temperature are the two most important variables affecting nearly all biological rates and times, especially individual growth or production rates. By favoring an optimal maturation age and reproductive allocation, natural selection links individual growth to the mortality schedule. A recent model for evolution of life histories for species with indeterminate growth, which includes most fish, successfully predicts the numeric values of two key dimensionless numbers and the allometry of the average reproductive allocation versus maturation size across species. Here we use this new model to predict the relationships of age-at-maturity, adult mortality and reproductive effort to environmental temperature and maturation size across species. Age-at-maturity, adult mortality and the proportion of the body mass given to reproduction per year are predicted to show 60.25 power allometries with mass at maturity, and an exponential (Boltzmann) temperature dependence. Temperature is assumed to affect only body size growth, so the temperature linkages of maturation, mortality and reproductive effort are indirect via life history optimization; this is briefly contrasted with the idea that (for example) temperature directly affects mortality.

Leaves are specialized organs characterized by defined developmental destiny and determinate growth. The overexpression ofKnotted1-like homeobox genes in different species has been shown to alter leaf shape and development, but a definite role for this class of genes remains to be established. Transgenics that overexpress Knotted1-like genes present some traits that are characteristic of altered cytokinin physiology. Here we show that lettuce (Lactuca sativa) leaves that overexpressKNAT1, an Arabidopsis kn1-like gene, acquire characteristics of indeterminate growth typical of the shoot and that this cell fate change is associated with the accumulation of specific types of cytokinins. The possibility that the phenotypic effects of KNAT1 overexpression may arise primarily from the modulation of local ratios of different cytokinins is discussed.

A cDNA clone from tomato fruit encodes a protein with strong homology with the rab11/YPT3 class of small GTPases that is thought to be involved in the control of protein trafficking within cells. The gene, LeRab11a, showed a pattern consistent with a single copy in DNA gel blots. The corresponding mRNA was developmentally regulated during fruit ripening, and its expression was inhibited in several ripening mutants. Its reduced expression in the Never-ripe mutant indicates that it may be induced by ethylene in fruit. The ripening-induced expression in tissues that are undergoing cell wall loosening immediately suggests a possible role in trafficking of cell wall–modifying enzymes. The message also was produced in leaves and flowers but not in roots. Antisense transformation was used to generate a “mutant phenotype.” Antisense fruit changed color as expected but failed to soften normally. This was accompanied by reduced levels of two cell wall hydrolases, pectinesterase and polygalacturonase. There were other phenotypic effects in the plants, including determinate growth, reduced apical dominance, branched inflorescences, abnormal floral structure, and ectopic shoots on the leaves. In some plants, ethylene production was reduced. These data suggest an alternative or additional role in exocytosis or endocytosis of homeotic proteins, hormone carriers, or receptors.

Carbon partitioning is important for understanding root development but little is known about its regulation. Existing models suggest that partitioning is controlled by the potential sink strength. They cannot, however, simulate hierarchical uptake other than by using absolute priorities. Moreover, they cannot explain that the changes in photoassimilate partitioning result from changes in photosynthesis. In this paper we present a model of phloem sieve circulation, based on the model of Minchin et al. (Journal of Experimental Botany44: 947–955, 1993). The root system was represented by a network of segments to which meristems were connected. The properties of the segments were determined by the differentiation stage. Photoassimilate import from each organ was assumed to be limited by a metabolic process and driven by Michaelis–Menten kinetics. The axial growth was proportional to meristem respiration, which drives the flux of new cells required for root elongation. We used the model to look at trophic apical dominance, determinate and indeterminate root growth, the effect of the activity of a root on competition with its neighbours, and the effect of photoassimilate availability on changes in partitioning. The simulated phloem mass flow yielded results of the same order of magnitude as those generally reported in the literature. For the main well vascularized axis, the model predicted that one single apical meristem larger than its neighbouring laterals, was enough to generate a taprooted system. Conversely, when the meristem of laterals close to the collar had a volume similar to that of the taproot, the predicted network became fibrous. The model predicted a hierarchical priority for organ photoassimilate uptake, similar to that described in the literature, during the decline in photosynthetic activity. Our model suggests that determinate growth of the first laterals resulted from a local shortage of photoassimilate at their meristem, as a result of the limited transport properties of the developed roots.

Determinate growth of floral meristems in Arabidopsis requires the function of the floral regulatory gene AGAMOUS (AG). Expression of AG mRNA in the central region of floral meristems relies on the partially overlapping functions of the LEAFY (LFY) and APETALA1 (AP1) genes, which promote initial floral meristem identity. Here, we provide evidence that AG function is required for the final definition of floral meristem identity and that constitutive AG function can promote, independent of LFY and AP1 functions, the determinate floral state in the center of reproductive meristems. Loss-of-function analysis showed that the indeterminate central region of the ag mutant floral meristem undergoes conversion to an inflorescence meristem when long-day-dependent flowering stimulus is removed. Furthermore, gain-of-function analysis demonstrated that ectopic AG function results in precocious flowering and the formation of terminal flowers at apices of both the primary inflorescence and axillary branches of transgenic Arabidopsis plants in which AG expression is under the control of the 35S promoter from cauliflower mosaic virus. Similar phenotypes were also observed in lfy ap1 double mutants carrying a 35S-AG transgene. Together, these results indicate that AG is a principal developmental switch that controls the transition of meristem activity from indeterminate to determinate.

Germinating seeds and regenerating shoot apical meristems of tomato exposed to the polar auxin transport inhibitors NPA and HFCA converted normal indeterminate growth of the shoot to that of a determinate pattern. The inhibitors produced linear, tendril-like shoots which phenocopied several forms of the homozygous lanceolate mutant in tomato.

Many marine gastropods are characterized by determinate growth, as inferred from the presence of unique terminal elaborations of the shell's aperture. Although determinate growth has evolved repeatedly in most major gastropod clades, it is especially frequent among siphonate caenogastropods. Analyses of shallow-water assemblages show that the incidence of species with determinate growth is far higher in the tropics (especially the tropical Pacific and Indian Oceans) than at higher latitudes. Compilations of fossil assemblages from warm-water environments indicate that, although determinate growth occurred in some Palaeozoic gastropods, it became widespread only in the Neogene. In some groups, terminal apertural elaborations arose in lineages whose growth was more or less continuous and indeterminate, but in others it was derived either from or was ancestral to episodic growth. The hypothesis that periodic or terminal apertural elaborations evolved as a means to dispose of calcium carbonate once growth in the spiral direction ceased is rejected in favour of functional interpretations. Among the latter, the roles of modified apertures in defence and in mate recognition are explored, but no firm conclusion regarding the latter possibility can be drawn owing to our ignorance of mate recognition in gastropods.

The present work was undertaken to characterize frond senescence in Lemna gibba G3, and to investigate its control by light, ABA and kinetin, all of which are known to affect leaf senescence one way or the other in many systems (Thimann 1987)

Measurement of leaf length and stem diameter in three Upper Carboniferous l.epidodendron species shows an exponential relationship between these parameters. Larger axes bear longer leaves even in material which had apparently completed its primary' growth. It is suggested that this is a direct product of the determinate growth pattern of the ontogeny of arborescent lycopods. Measurements of Cyclostigma from the Irish Devonian are not explicable in these terms, and it is suggested that some specimens were immature at fossilization. It is recommended that the term leaf cushion be applied to the expanded leaf base in the Lepidodendrales at all growth stages, and not only after leaf abscission. Problems in the terminology of ‘young’ and ‘old’ growth stages in these determinate plants are discussed.

There are several formsof individual and colon) organization available to benthic marine invertebrates with indeterminate growth In particular anthozoan coelenterates exhibit three such forms of organization 1 solitary individuals without asexual reproduction 2 colonies or clonal groups with determinate polyp size and indeterminate colony size and 3 colonies or clonal groups with both indeterminate polyp size and indeterminatecolony or clone size The last group includes species where asexual reproduction is continuous and those where it is limited to a single season of the year A model is presented which defines three optimal sizes for indeterminately growing organisms 1 optimal size for a solitary individual 2 optimal size of a polyp within a colony and 3 optimal size at asexual division The optima are derived by maximizing the difference between energy intake and energetic cost Simulations allow prey size and habitat quality to vary and derive predictions of optimal size and organization for each case Individual and clonal growth rates are modelled for the case where asexual reproduction is limited to a single season and poly p sizes within clones are compared The model predicts that the three torms of organization among anthozoan polyps are related primarily to the size distribution of prey

Flat, frond-like conifer shoots from the Upper Cretaceous of the eastern United States have been described in the past as three species of the genus Androvettia Hollick & Jeffrey. The characteristics of Androvettia are discussed and compared with descriptions of Moriconia Dehey & Ettingshausen. Specimens of all three species, including new material, have been studied by light and scanning electron microscopy. It is concluded that only one species, Androvettia statenensis Hollick & Jeffrey, is represented. The morphology and phyllotaxis of the shoots, which are phylloclades, are illustrated and discussed. Two forms of branches are present which it is suggested represent shoots of determinate and indeterminate growth. Membership of the family Cheirolepidiaceae is tentatively suggested.

The thallus of Penicillus is composed of two filament types: axial filaments of indeterminate growth and laterals of determinate growth. In vegetative reproduction new plants arise from horizontal rhizoids. Four stages can be distinguished in development. In the primordium stage the tip of a rhizoid swells and forms a primordium. In the germling stage ascending and descending axial filaments arise from the primordium, the former grow into a fascicle and give rise to lateral saccate branches, each of which forms an ascending and a descending arm and branches further into rhizoid-like branchlets. Together these structures constitute the foundation of the stipe. At the same time the descending axial filaments elongate and become main rhizoidal filaments with lateral rhizoidal branchlets. In the early juvenile stage the stipe is formed. The elongating ascending axial filaments form a medulla while their laterals produce a cortex. In the late juvenile stage the axial filaments form the capitulum. The Espera state of Penicillus lacks a stipe since the ascending axial filaments do not join in a fascicle. Espera has been grown in laboratory cultures from Penicillus plants collected in the Caribbean region and also been found uncommonly in nature in this area. This state may be a response to environmental stress. The flattening of thalli and their orientation perpendicular to the direction of waves are discussed. A comparison of Penicillus and Codium indicates that at least two types of development exist in multiaxial Eusiphoniidae.

SUMMARY In Nuphar and Nymphaea flowers are formed in leaf sites in the genetic spiral. The sequence of flowers and leaves is to some extent characteristic of the species; in Nymphaea alba there is alternation between stimulation and inhibition of flower formation. Vegetative buds occur occasionally in positions where flowers would be expected. In Victoria and Euryale flowers are formed in a separate spiral from the leaves; flowers occupy precise positions which may be described as to the anodic side of the axil of an older leaf. Flowering in these genera is not necessarily continuous after its inception, but even where there are gaps in the flower spiral subsequent flowers occupy normal positions; flower sites may therefore be more closely related to those of the leaves than to those of other flowers. Vegetative buds have never been observed. In all these genera, flower primordia are formed on the apical meristem, which itself continues indeterminate growth and gives rise to both flowers and leaves. Consequently physiological conditions in the rhizome apices must be exceedingly complex: in all these genera conditions favouring leaf and flower inception must alternate in specific ways, leaves and flowers being sometimes formed very close together in both time and space.

cucurbits in its indeterminate growth ; but it is different in the minor extent to which fruit size is influenced by environment and fruitfulness. In a regional variety study (3), 16 varieties of cotton planted during each of three years at eight locations showed locational variations in the varietal means of only 8% in fiber length, 6% in fiber weight-per-inch and 9% in fiber strength. In terms of use value, however, such differences have high significance. The tendency toward uniformity in the bolls of cotton is accounted for by the extent to which young bolls are shed as the plant becomes heavily fruited. Within varieties and environments, the number of developing bolls per unit of vegetative weight (11) has been found to be remarkably uniform. From California irrigation experiments, Adams et al. (1) record that reductions in water supply result generally in losses in staple length (usually within 1/32 inch), seed index (usually within 1.0 gram) and lint index (usually within 0.5 gram). Drought has been observed to decrease the length of cotton lint (2, 5, 18) ; with this effect, an increase in fiber strength was usually found. Berkley et al. (4), as well as others, have associated the increased strength of fibers with a narrowing of the angle of the cellulose crystallites (x-ray angles). Increased nitrogen supply has been found to result in some increase in length of fiber (7, 16, 19). On the other hand, little effect upon length was found by Sturkie (18), whereas, in the presence of inadequate supplies of some other elements, Brown (?) reported length reductions to result from nitrogenous fertilizers. As has been the general experience with other plants, Wadleigh (19) found increased nitrogen supply to result in lower carbohydrate accumulations. He associated as causal the plus and minus changes in carbohydrate or nitrogen with the changes in boll properties and in fiber length that corresponded in sign. Crowther (7) and Nelson (16) have shown phosphate to increase boll size but not to alter fiber properties. Nelson also found that potash additions which greatly increased yield also increased fiber length and weight per inch ; the x-ray angles were increased and the strength of fiber and yarn decreased. Younge (20) has shown sulphur deficiency that reduced boll production had little effect on fiber properties. 541