Indeterminate Growth Pattern Research Articles

Short communication: Differential expression of piwi1 and piwi2 genes in tissues of tambacu and zebrafish: A possible relationship with the indeterminate muscle growth

Fish skeletal muscle is a component of the human diet, and understanding the mechanisms that control muscle growth can contribute to improving production in this sector and benefits the human health. In this sense, fish such as tambacu can represent a valuable source for exploring muscle growth regulators due to the indeterminate muscle growth pattern. In this context, the genes responsible for the indeterminate and determinate muscle growth pattern of fish are little explored, with piwi genes being possible candidates involved with these growth patterns. Piwi genes are associated with the proliferation and self-renewal of germ cells, and there are descriptions of these same functions in somatic cells from different tissues. However, little is known about the function of these genes in fish somatic cells. Considering this, our objective was to analyze the expression pattern of piwi 1 and 2 genes in cardiac muscle, skeletal muscle, liver, and gonad of zebrafish (species with determinate growth) and tambacu (species with indeterminate growth). We observed a distinct expression of piwi1 and piwi2 between tambacu and zebrafish, with both genes more expressed in tambacu in all tissues evaluated. Piwi genes can represent potential candidates involved with indeterminate muscle growth control.

Moderate Water Stress Impact on Yield Components of Greenhouse Tomatoes in Relation to Plant Water Status.

The scarcity of water resources affects tomato production. Deficit irrigation may optimize water management with only a low reduction in yield. Deficit irrigation scheduling based on applied water presented no clear conclusions. Water stress management based on plant water status, such as water potential, could improve the scheduling. The aim of this work was to evaluate the physiological and yield responses of different tomato cultivars to deficit irrigation. Three experiments were carried out in 2020 and 2022 at the University of Seville (Spain). "Cherry" and "chocolate Marmande" cultivars with an indeterminate growth pattern were grown in a greenhouse. Treatments were: Control (full irrigated) and Deficit. Deficit plants were irrigated based on water potential measurements. Moderate water stress did not significantly reduce the yield, although it affected other processes. Fruit size and total soluble solids were the most sensitive parameters to water stress. The latter increased only when persistent water stress was applied. However, truss development and fruit number were not affected by the level of water stress imposed. Such results suggest that moderate water stress, even in sensitive phenological stages such as flowering, would not reduce yield. Deficit irrigation scheduling based on plant water status will allow accurate management of water stress.

Multi-model approach for growth analysis of Evibacus princeps Smith, 1869 (Decapoda, Scyllaridae) in the Gulf of California

Abstract In Mexico, the spiny lobster fishery is well established but this is not the case with the slipper lobster fishery. For a sustainable fishery, many biological traits must be known, one of which is growth. The objective of the present study was to probe the multi-model approach to identify the curve that best describes the growth of Evibacus princeps from the Gulf of California. Specimens were collected aboard commercial trawlers during the industrial shrimp fishing season (October 2021-March 2022) at depths ranging from 10 to 55 m. Five versions of the Schnute model (including the Von Bertalanffy model) were applied and the best model was selected using the Bayesian information criterion. The estimation of an average model was performed because no model obtained 90% of the evidence. E. princeps from the Gulf of California exhibit an indeterminate growth pattern.

The interplay of carbon and nitrogen distribution: Prospects for improved crop yields

AbstractGrowth and productivity of plants primarily depend on the balanced distribution of carbon (C) and nitrogen (N) among different organs. Previous studies on crop improvement have focussed on the C or N assimilation and distribution. However, recent findings reveal that C and N form a complex integrated network and are often dependent on each other to affect crop productivity. The underlying physiological and molecular mechanisms involved in the coordinated distribution of C and N among different plant organs are yet to be fully uncovered. Crucial roles in regulating C and N balance are played by transporters that mediate their movement across different organs. In Cotton, which has an indeterminate growth pattern, source–sink assimilate distribution could be a major bottleneck impeding fibre productivity. This review summarises our current understanding of C and N transport mechanisms, explores and compares different physiological and molecular approaches involved in the C–N distribution cascade, including cotton and other plant species. A comprehensive understanding of these integrated regulatory mechanisms is crucial for improving crop yields and fibre productivity.

Foliar application of mepiquat chloride and nitrogen improves yield and fiber quality traits of cotton (Gossypium hirsutum L.).

Cotton (Gossypium hirsutum L.) is one of the most important cash crops primarily grown for fiber. It is a perennial crop with indeterminate growth pattern. Nitrogen (N) is extremely important for vegetative growth as balanced N-nutrition improves photosynthesis, resulting in better vegetative growth. Excessive N-supply results in more vegetative growth, which increases the incidence of insect pest and diseases’ infestation, pollute surface and ground water, delays maturity and produces low crop yield with poor quality. The use of plant growth regulators (PGRs) is an emerging option to control excessive vegetative growth. The PGRs help in improving plant architecture, boll retention, boll opening, yield and quality by altering growth and physiological processes such as photosynthesis, assimilate partitioning and nutrients dynamic inside the plant body. Mepiquat chloride (1,1-dimethylpiperidinum chloride) is globally used PGR for canopy development and control of excessive vegetative growth in cotton. This study investigated the effect of mepiquat chloride (MC) and N application on yield and yield components of transgenic cotton variety ‘BT-FSH-326’. Two N rates (0, 198 kg ha-1) and five MC rates (0, 30,60, 90 and 120 g ha-1) were included in the study. Results revealed that MC and N application improved boll weight, number of bolls per plant, and seed cotton and lint yields. The highest seed cotton and lint yields (3595 kg ha-1 and 1701 kg ha-1, respectively) were observed under foliar application of 198 kg ha-1 N and 120 g ha-1 MC. Fiber length, fiber strength, micronaire and uniformity were significantly improved with foliar application of MC and N. In conclusion, foliar application of MC and N could be helpful in improving yield and fiber quality of cotton.

Cell-by-cell dissection of phloem development links a maturation gradient to cell specialization.

In the plant meristem, tissue-wide maturation gradients are coordinated with specialized cell networks to establish various developmental phases required for indeterminate growth. Here, we used single-cell transcriptomics to reconstruct the protophloem developmental trajectory from the birth of cell progenitors to terminal differentiation in the Arabidopsis thaliana root. PHLOEM EARLY DNA-BINDING-WITH-ONE-FINGER (PEAR) transcription factors mediate lineage bifurcation by activating guanosine triphosphatase signaling and prime a transcriptional differentiation program. This program is initially repressed by a meristem-wide gradient of PLETHORA transcription factors. Only the dissipation of PLETHORA gradient permits activation of the differentiation program that involves mutual inhibition of early versus late meristem regulators. Thus, for phloem development, broad maturation gradients interface with cell-type-specific transcriptional regulators to stage cellular differentiation.

Modelling leatherback biphasic indeterminate growth using a modified Gompertz equation

Leatherback turtles (Dermochelys coriacea) are the largest extant marine turtle, with some individuals measuring more than 1.80 m carapace length. Given the exceptional size of this species and that females only return to land every few years to nest, it is difficult to investigate its ontogeny from hatchling to adulthood. Distinct chondro-osseous (cartilage and bone) tissue morphology has led to some speculation that sexual maturity may be reached as early as 3 years, while other studies suggest this could take as long as 25 years. Using a combination of longitudinal measurements obtained from nesting females in French Guiana as well as a reanalysis of the growth trajectories of juveniles maintained in captivity and the age-size relationship of individuals in the wild, we demonstrated that leatherback turtles exhibit a biphasic indeterminate growth pattern and continue to grow as adults. Using the fitted model, we showed that some individuals can reach maturity at 7 years in natural conditions, while others require 28 years or more. This extreme plasticity in age at sexual maturity was already demonstrated in loggerheads in natural conditions and in green turtles in captivity. This could be a general feature of marine turtles.

Flux-Based Ozone Risk Assessment for a Plant Injury Index (PII) in Three European Cool-Temperate Deciduous Tree Species

This study investigated visible foliar ozone (O3) injury in three deciduous tree species with different growth patterns (indeterminate, Alnus glutinosa (L.) Gaertn.; intermediate, Sorbus aucuparia L.; and determinate, Vaccinium myrtillus L.) from May to August 2018. Ozone effects on the timing of injury onset and a plant injury index (PII) were investigated using two O3 indices, i.e., AOT40 (accumulative O3 exposure over 40 ppb during daylight hours) and PODY (phytotoxic O3 dose above a flux threshold of Y nmol m−2 s−1). A new parameterization for PODY estimation was developed for each species. Measurements were carried out in an O3 free-air controlled exposure (FACE) experiment with three levels of O3 treatment (ambient, AA; 1.5 × AA; and 2.0 × AA). Injury onset was found in May at 2.0 × AA in all three species and the timing of the onset was determined by the amount of stomatal O3 uptake. It required 4.0 mmol m−2 POD0 and 5.5 to 9.0 ppm·h AOT40. As a result, A. glutinosa with high stomatal conductance (gs) showed the earliest emergence of O3 visible injury among the three species. After the onset, O3 visible injury expanded to the plant level as confirmed by increased PII values. In A. glutinosa with indeterminate growth pattern, a new leaf formation alleviated the expansion of O3 visible injury at the plant level. V. myrtillus showed a dramatic increase of PII from June to July due to higher sensitivity to O3 in its flowering and fruiting stage. Ozone impacts on PII were better explained by the flux-based index, PODY, as compared with the exposure-based index, AOT40. The critical levels (CLs) corresponding to PII = 5 were 8.1 mmol m−2 POD7 in A. glutinosa, 22 mmol m−2 POD0 in S. aucuparia, and 5.8 mmol m−2 POD1 in V. myrtillus. The results highlight that the CLs for PII are species-specific. Establishing species-specific O3 flux-effect relationships should be key for a quantitative O3 risk assessment.

Patterns of growth, brooding and offspring size in the invasive mussel Sinanodonta woodiana (Lea, 1834) (Bivalvia: Unionidae) from an anthropogenic heat island

In freshwater temperate environments, waterbodies warmed by power plants can serve as a stepping stone in the spread of tropical and subtropical species. This offers a unique opportunity to acquire an insight into the life history of organisms undergoing range expansions beyond their native habitat. Here, we studied the patterns of offspring production and growth in the Asian mussel Sinanodonta woodiana inhabiting the thermal plume of the Odra River in Central Europe. Compared to the S. woodiana males, females had more convex shells and had a greater tendency to continue post-maturation growth and thus follow an indeterminate growth pattern. Gravid females were observed all-year round, and individuals with either large or more convex shells brooded more offspring. The proportion of incubating females, brood size and glochidia size were linked to gonadal activity and changed seasonally. Females with a higher amount of nutritive substances in the ovaries produced more and larger offspring. The smallest and the largest offspring occurred in the summer and in the winter, respectively. Sinanodonta woodiana incubated different offspring generations simultaneously, constantly releasing them into the environment. Using a life history evolution perspective, we discuss our results in view of allocation trade-offs between growth and offspring production.

Characterization and diversity of blackgram germplasm

The experiment was conducted with 61germplasm of blackgram (Vigna mungo (L.) Hepper) in a Randomized Complete Block Design with 3 replications at the Plant Genetic Resources Centre of BARI Gazipur during March to June 2012 to know the diversity of germplasm. Two to four classes were observed among the 14 qualitative characters. Green and purple colours were found in epicotyl, petiole and stem. Light green to dark green was found in case of leaf and immature pods. Erect, semi-erect and spreading growth habit along with indeterminate and determinate growth pattern were observed. Ovate, ovate-lanceolate and rhombic terminal leaflet shape were found. Erect to sub-erect pod attachment to peduncle with glabrous to densely pubescent pods were found. The accessions showed black and brown mature pods having hook and knob types of pod beak shape. Black, brown, grayed-orange and yellow-green seed colours were observed among the blackgram accessions. Low to high phenotypic diversity index (0.12 to 0.91) were found among the qualitative characters. All the accessions exhibited purple hypocotyl, none twining tendency, glabrous leaf pubescence, abundant leafiness, very light green calyx, yellow flower, drum-shaped seeds, absent seed luster and non-concave seed hilum. Number of seeds per pod ranged from 5 to 7 and hundred seed weight ranged from 1.83 to 4.49 g. The highest PCV was observed in branch length (32.65%) and the lowest PCV was found in pod length (6.99%). The accessions were grouped into five clusters. Accessions collected from the same districts felt into different clusters. The inter and intra cluster distances ranged from 3.37 to 11.38 and 0.30 to 1.17, respectively. The maximum number of pods per plant, pod length and 100-seed weight was found in cluster IV. Accessions BD-6853, BD-6857, BD-6863, BD-6865 and BD-6866 were identified as potential germplasm for varietal improvement programme.
 Bangladesh J. Agril. Res. 44(2): 239-251, June 2019

Out of step: The function of TALE homeodomain transcription factors that regulate shoot meristem maintenance and meristem identity

The indeterminate growth pattern displayed by shoots is mediated by the proper maintenance of the shoot meristem. Meristem maintenance is dependent upon the balance of stem cell perpetuation in the central zone (CZ) and organogenesis in the peripheral zone (PZ). Although the mechanisms that coordinate CZ and PZ function is not understood, meristem cell fate is likely achieved by the spatial interplay between gene regulatory networks and hormone signaling pathways. During shoot maturation, the identity of the shoot meristem as well as the lateral organs are transformed during the vegetative and reproductive transitions. Studies in model plant systems indicate that three amino acid extension (TALE) homeodomain proteins integrate signaling events that transform the identity of the shoot meristem and establish reproductive patterns of growth. This review will highlight the function of TALE homeodomain transcription factors that regulate shoot meristem cell fate and also function with phase specific regulators to maintain shoot meristem identity.

Bone Histology in Dysalotosaurus lettowvorbecki (Ornithischia: Iguanodontia) – Variation, Growth, and Implications

Background Dysalotosaurus lettowvorbecki is a small ornithopod dinosaur known from thousands of bones and several ontogenetic stages. It was found in a single locality within the Tendaguru Formation of southeastern Tanzania, possibly representing a single herd. Dysalotosaurus provides an excellent case study for examining variation in bone microstructure and life history and helps to unravel the still mysterious growth pattern of small ornithopods.Methodology/Principal FindingsFive different skeletal elements were sampled, revealing microstructural variation between individuals, skeletal elements, cross sectional units, and ontogenetic stages. The bone wall consists of fibrolamellar bone with strong variability in vascularization and development of growth cycles. Larger bones with a high degree of utilization have high relative growth rates and seldom annuli/LAGs, whereas small and less intensively used bones have lower growth rates and a higher number of these resting lines. Due to the scarcity of annuli/LAGs, the reconstruction of the life history of Dysalotosaurus was carried out using regularly developed and alternating slow and fast growing zones. Dysalotosaurus was a precocial dinosaur, which experienced sexual maturity at ten years, had an indeterminate growth pattern, and maximum growth rates comparable to a large kangaroo.Conclusions/SignificanceThe variation in the bone histology of Dysalotosaurus demonstrates the influence of size, utilization, and shape of bones on relative growth rates. Annuli/LAGs are not the only type of annual growth cycles that can be used to reconstruct the life history of fossil vertebrates, but the degree of development of these lines may be of importance for the reconstruction of paleobehavior. The regular development of annuli/LAGs in subadults and adults of large ornithopods therefore reflects higher seasonal stress due to higher food demands, migration, and altricial breeding behavior. Small ornithopods often lack regularly developed annuli/LAGs due to lower food demands, no need for migration, and precocial behavior.

Growth and the regulation of myotomal muscle mass in teleost fish

Teleost muscle first arises in early embryonic life and its development is driven by molecules present in the egg yolk and modulated by environmental stimuli including temperature and oxygen. Several populations of myogenic precursor cells reside in the embryonic somite and external cell layer and contribute to muscle fibres in embryo, larval, juvenile and adult stages. Many signalling proteins and transcription factors essential for these events are known. In all cases, myogenesis involves myoblast proliferation, migration, fusion and terminal differentiation. Maturation of the embryonic muscle is associated with motor innervation and the development of a scaffold of connective tissue and complex myotomal architecture needed to generate swimming behaviour. Adult muscle is a heterogeneous tissue composed of several cell types that interact to affect growth patterns. The development of capillary and lymphatic circulations and extramuscular organs--notably the gastrointestinal, endocrine, neuroendocrine and immune systems--serves to increase information exchange between tissues and with the external environment, adding to the complexity of growth regulation. Teleosts often exhibit an indeterminate growth pattern, with body size and muscle mass increasing until mortality or senescence occurs. The dramatic increase in myotomal muscle mass between embryo and adult requires the continuous production of muscle fibres until 40-50% of the maximum body length is reached. Sarcomeric proteins can be mobilised as a source of amino acids for energy metabolism by other tissues and for gonad generation, requiring the dynamic regulation of muscle mass throughout the life cycle. The metabolic and contractile phenotypes of muscle fibres also show significant plasticity with respect to environmental conditions, migration and spawning. Many genes regulating muscle growth are found as multiple copies as a result of paralogue retention following whole-genome duplication events in teleost lineages. The extent to which indeterminate growth, ectothermy and paralogue preservation have resulted in modifications of the genetic pathways regulating muscle growth in teleosts compared to mammals largely remains unknown. This review describes the use of compensatory growth models, transgenesis and tissue culture to explore the mechanisms of muscle growth in teleosts and provides some perspectives on future research directions.

Canopy temperature based system effectively schedules and controls center pivot irrigation of cotton

Cotton is a perennial plant with an indeterminate growth pattern that is typically produced like an annual, but requires proper management to effectively produce high yields and good fiber quality in a thermally limited environment like the northern Texas High Plains. In 2007 and 2008, we investigated the effect of irrigation scheduling/control method and amount on cotton (Gossypium hirsutum L.) yield and water use efficiency. Methods were automatic irrigation scheduling and control of a center pivot system, and manually scheduled irrigation to replenish soil–water to field capacity. Cotton was irrigated with LEPA (low energy, precision application) drag socks in furrow dikes; three blocks were irrigated manually and three were irrigated automatically. Six replicates of the manual and automatic irrigation treatments were included in the randomized block design. Manual irrigations were based on the weekly replenishment of soil–water to field capacity in the top 1.5 m of the soil profile and included a fully irrigated treatment (I100), and treatments receiving 67% (I67) and 33% (I33) of the I100 amount, plus a non-irrigated treatment (I0). Automatic irrigations were triggered using a time temperature threshold (TTT) algorithm, which was designated as the I100 treatment, and treatments receiving 67%, 33%, and 0% of that amount (I67, I33 and I0, respectively). In 2007, overall mean lint yields (102.3 and 101.6 g m−2, manual and automatic, respectively) were not significantly different. Similarly, yields were not significantly different across automatic and manual treatments in the same treatment level, with the exception of the I67 treatment where the manual treatment yields were 11% greater. In 2008, the mean yields were 70% less than those in 2007 for both methods of irrigation (30.3 and 30.9 g m−2, manual and automatic, respectively) due to harsh climatic conditions at emergence and heavy rainfall and cooler temperatures in the month of August. Yields from the automatically irrigated plots in the I100 and I67 treatments, however, were significantly greater than yields from the corresponding manually irrigated plots; though there was no significant difference between yields in the drier treatments (I33 and I0) plots. These results indicate that the TTT algorithm is a promising method for auto-irrigation scheduling of short season cotton in an arid region. However, further studies are essential to demonstrate consistent positive outcomes.

Indeterminate Growth of the Fairy Shrimp, Branchinella (Branchinellites) kugenumaensis (Branchiopoda: Anostraca) in an Unpredictable Ephemeral Pool

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 increasing in size during the first clutch production. Upon subsequent rainfall before the pool dried, the shrimp stopped reproducing and resumed growth, demonstrating a discontinuously indeterminate growth pattern, before resuming egg production. Body length was positively correlated with clutch size, and this can be expressed as|$clutch{\rm{ }}size{\rm{ = 0}}{\rm{.0059 }} \times {\rm{ }}body{\rm{ }}length{{\rm{ }}^{{\rm{3}}{\rm{.165}}}}{\rm{.}}$|⁠. The potential reproductive fitness of this indeterminate growth strategy demonstrates optimal resource allocation between growth and reproduction.

Histopathologic and Ultrastructural Features of Surgically Excised Subfoveal Choroidal Neovascular Lesions

To identify the histologic and ultrastructural features of surgically excised subfoveal choroidal neovascular lesions from patients enrolled in the Submacular Surgery Trials and to compare them with clinical data. Surgically excised subfoveal choroidal neovascular lesions from patients enrolled in the Submacular Surgery Trials group N trial (lesion predominantly choroidal neovascularization [CNV] with evidence of classic CNV from age-related macular degeneration), group B trial (lesion predominantly hemorrhagic from age-related macular degeneration), and group H trial (idiopathic subfoveal CNV or subfoveal CNV from ocular histoplasmosis syndrome) between October 1, 1999, and September 1, 2001, were submitted to the pathology center. The lesion growth pattern (subretinal pigment epithelial [sub-RPE], subretinal, combined, or indeterminate) and the cellular and extracellular constituents were classified independently. Demographic, clinical, and fluorescein angiographic characteristics of patients, eyes, and lesions, respectively, were compared with the pathologic features. Of 269 patients assigned to surgery during the 24 months that pathologic specimens were collected, surgical specimens from study eyes of 199 were submitted to the pathology center. Of the 199 routine histologic specimens processed, 144 (72%) were classified as CNV, 51 (26%) as fibrocellular tissue, and 4 (2%) as hemorrhage. The median specimen size was smaller in group H (932 x 208 mum) than in groups N (1980 x 325 mum) and B (1800 x 395 mum). The CNV growth pattern was determined in 91 (46%) of 199 specimens. Of 159 group N and group B lesions, 76 (48%) had an indeterminate growth pattern, 28 (18%) had a sub-RPE growth pattern, and 33 (21%) had sub-RPE and subretinal growth patterns. Of 40 group H lesions, 32 (80%) had an indeterminate growth pattern, 7 (18%) had a subretinal growth pattern, and 1 (2%) had a combined sub-RPE and subretinal pattern. Based on electron microscopy, the most common cellular lesion components were RPE, macrophages, erythrocytes, fibrocytes, and vascular endothelium; the most common extracellular components were 24-nm collagen and fibrin. Basal laminar and linear deposits were found in 80% (40/50) and 16% (8/49) of group N specimens, 66% (43/65) and 5% (3/65) of group B specimens, and 8% (2/26) and 0% (0/26) of group H specimens, respectively. Most surgically excised subfoveal specimens had evidence of CNV or tissue associated with CNV. The constituents in CNV were consistent with granulation tissue proliferation. The presence of basal deposits in surgically excised specimens suggested a clinical diagnosis of age-related macular degeneration, even when blood was the predominant component of the lesion. Correlation of growth patterns above or below the RPE with fluorescein angiographic patterns of classic or occult CNV was limited because most specimens had insufficient material to determine these patterns.

Sex‐related growth patterns in a caecilian amphibian (genus Ichthyophis): evidence from laboratory data

AbstractPost‐metamorphic growth patterns were analysed in the tropical caecilian amphibian Ichthyophis cf. kohtaoensis (Amphibia: Gymnophiona) experimentally in captivity over 6 years. Two questions were addressed. (1) Does this Ichthyophis display sexual dimorphism for size? (2) Do ichthyophiid caecilians express an indeterminate growth pattern? Total length did not differ between sexes in the first, second or third year after metamorphosis. In the fourth, fifth and sixth years, females were significantly larger than males. The index of sexual size dimorphism increased from zero in the first year after metamorphosis to 0.104 in the sixth year. Relative growth rates of total length were different for each sex. In the first two growth seasons males grew at higher rates, while from the third growth season females grew faster than males. In general, growth rates increased from the first to the second year after metamorphosis and decreased dramatically after both sexes became mature. As all Ichthyophis in this study grew constantly throughout the first 6 years after metamorphosis, indeterminate growth probably occurs in caecilians as reported for frogs and salamanders. Additionally, growth curves for both sexes of Ichthyophis cf. kohtaoensis were estimated based on the von Bertalanffy model.

Establishing a New Wild Population of Tuatara (Sphenodon guntheri)

Abstract: Translocations of reptiles and amphibians have been questioned as a conservation tool because they generally have not been successful. However, translocation is the only method by which many species can be restored to parts of their former range, which increases their conservation security. Tuatara ( Sphenodon spp.), sole surviving members of the reptilian Order Sphenodontia, are restricted to offshore islands of New Zealand. Dispersal into former habitat on the mainland or other islands, following removal of the causes of extinction, is unlikely. Captive rearing of reptile hatchlings from eggs collected in the wild to produce founders for new populations is also a conservation technique that has had mixed success. However, captive incubation and rearing are techniques that allow large numbers of tuatara to be produced to start new populations without detrimental effects on small source populations. We document the first contemporary translocation of S. guntheri, providing details on selection of release sites and founders. Release sites were chosen on a rodent‐free island that provided a variety of habitats for tuatara as well as abundant food and shelter. The release propagule comprised 18 wild‐caught adults and 50 captive‐reared juveniles. Four separate release sites were established to separate adults from juveniles during the establishment phase. Five years of monitoring indicate that at least 57% of tuatara survived translocation and that reproduction has occurred on the new island. All tuatara increased in weight and length, demonstrating that tuatara have an indeterminate growth pattern. The 56% of recaptured juveniles represented a cross section of the sizes released. We evaluated the use of head‐started juveniles as founders, based on survival and growth data. Because tuatara are long‐lived, late‐maturing reptiles with slow reproduction, establishment of a self‐sustaining population will take decades of monitoring to confirm.

Do Bertalanffy's growth curves result from optimal resource allocation?

Bertalanffy's equation is commonly used to model indeterminate growth. Bertalanffy claimed that this growth pattern results from growth potential decreasing with age. An alternative approach provided by life history theory predicts that indeterminate growth is optimal for organisms in a seasonal environment and results not from decreasing growth potential but from allocating increasingly less energy with age into growth, and more into reproduction. Bertalanffy's curves are the result of evolutionary optimization and should not be used in optimization models as an assumption, but they can be used as a tool to describe the indeterminate growth pattern phenomenologically.

Populus tremuloides photosynthesis and crown architecture in response to elevated CO2 and soil N availability.

We tested the hypothesis that elevated CO2 would stimulate proportionally higher photosynthesis in the lower crown of Populus trees due to less N retranslocation, compared to tree crowns in ambient CO2. Such a response could increase belowground C allocation, particularly in trees with an indeterminate growth pattern such as Populus tremuloides. Rooted cuttings of P. tremuloides were grown in ambient and twice ambient (elevated) CO2 and in low and high soil N availability (89 ± 7 and 333 ± 16 ng N g-1 day-1 net mineralization, respectively) for 95 days using open-top chambers and open-bottom root boxes. Elevated CO2 resulted in significantly higher maximum leaf photosynthesis (A max) at both soil N levels. A max was higher at high N than at low N soil in elevated, but not ambient CO2. Photosynthetic N use efficiency was higher at elevated than ambient CO2 in both soil types. Elevated CO2 resulted in proportionally higher whole leaf A in the lower three-quarters to one-half of the crown for both soil types. At elevated CO2 and high N availability, lower crown leaves had significantly lower ratios of carboxylation capacity to electron transport capacity (V cmax/J max) than at ambient CO2 and/or low N availability. From the top to the bottom of the tree crowns, V cmax/J max increased in ambient CO2, but it decreased in elevated CO2 indicating a greater relative investment of N into light harvesting for the lower crown. Only the mid-crown leaves at both N levels exhibited photosynthetic down regulation to elevated CO2. Stem biomass segments (consisting of three nodes and internodes) were compared to the total A leaf for each segment. This analysis indicated that increased A leaf at elevated CO2 did not result in a proportional increase in local stem segment mass, suggesting that C allocation to sinks other than the local stem segment increased disproportionally. Since C allocated to roots in young Populus trees is primarily assimilated by leaves in the lower crown, the results of this study suggest a mechanism by which C allocation to roots in young trees may increase in elevated CO2.