Shoot Architecture Research Articles

LED lighting affects the composition and biological activity of Cannabis sativa secondary metabolites

Growth conditions are expected to alter the relative and absolute content of the hundreds of phytochemicals produced by Cannabis sativa L.; some of these possess biological activity on the human body. However, relatively little information exists regarding the effects of different light regimes on the composition of C. sativa secondary metabolites and thus on their biological activity. In this study, we investigated how light quality influences the production and final content of secondary metabolites, as well as their bioactive properties. Toward these, plant growth and blooming were carried out at different illumination conditions, utilizing light-emitting diode (LED) fixtures vs. conventional fluorescent and high-pressure sodium (HPS) lamps as controls. Inflorescences were sampled at different time points along the blooming; extract compositions were analyzed by HPLC and GC/MS, and the biological activity of the extracted material was assessed using cell viability assays. We found that growth and blooming under LED illumination considerably changed shoot architecture and inflorescence mass. Moreover, the content of cannabinoids, terpenes, and alkanes were altered in the inflorescences of LED-grown plants during the flowering period as well as in the harvested flowers. In particular, significantly higher quantities of cannabigerolic acid accumulated in the inflorescences that flowered under LED fixtures, with a cannabigerolic acid to Δ9-tetrahydrocannabinolic acid (CBGA:THCA) ratio of 1:2 as opposed to 1:16 when grown under HPS. Notably, the cytotoxic activities of extracts derived from plants grown under the different illumination regimes were different, with extracts from LED-grown plants possessing higher cytotoxicity along the flowering stage. Our results thus indicate that the transition to indoor growth of C. sativa under LED lighting, which can have significant impacts on cannabinoid and terpene content, and also on the bioactive properties of the plant extracts, should proceed with thorough consideration.

Genetics of barley tiller and leaf development.

In cereals, tillering and leaf development are key factors in the concept of crop ideotype, introduced in the 1960s to enhance crop yield, via manipulation of plant architecture. In the present review, we discuss advances in genetic analysis of barley shoot architecture, focusing on tillering, leaf size and angle. We also discuss novel phenotyping techniques, such as 2D and 3D imaging, that have been introduced in the era of phenomics, facilitating reliable trait measurement. We discuss the identification of genes and pathways that are involved in barley tillering and leaf development, highlighting key hormones involved in the control of plant architecture in barley and rice. Knowledge on genetic control of traits related to plant architecture provides useful resources for designing ideotypes for enhanced barley yield and performance.

Root growth and development do not directly relate to shoot morphogenetic strategies in temperate forage legumes

Little is yet known about the component traits that control the deployment of root architecture in most grassland species. The aim of this study was to compare patterns of root growth in contrasting forage legumes and to analyse their dependency to shoot development. The parameters of a dynamic simulation model were identified for seven contrasting species in a series of greenhouse experiments in order to characterize root elongation, root branching and taproot growth. The model allowed us to explore the interactions between root development and whole plant growth. Most of the root morphogenetic parameters studied displayed significant inter-specific variability. Several traits appeared to be correlated, indicating a close association between extreme root tip diameters, the branching ability of roots and their maximal elongation rate. The species differed along two PCA axes which accounted respectively for the branching ability of fine roots and taproot development. Quite remarkably, the group of species identified for root development did not coincide with those previously identified for shoots, suggesting a degree of independence between the morphogenetic traits that control shoot and root architecture. However, both plant parts remained tightly linked through the trophic relationship represented by root biomass allocation. Our results suggest that the concomitant analysis of root and shoot development is necessary to properly decipher rooting strategies in forage legumes.

The effects of cultivar and training system on vegetative growth of mango (Mangifera indica) orchards in Far North Queensland

Understanding how and why canopy structural growth imposes productivity limitations is critical to managing high yielding, regular bearing mango (Mangifera indica) orchards. This study aimed to see how vegetative and reproductive growth responds to canopy management including bending. To investigate the relationship between shoot architecture, flowering and fruiting we measured structural, functional and temporal patterns of branching and flowering at the tree, scaffold and growth unit levels. Mango architectural analysis found strong varietal effects on vegetative growth, while increasing tree density led to increasing flowering across the orchard area. Single leader medium density trees had a significantly higher mean flower count (m-3 canopy volume tree-1) compared to the conventional training systems, and there was no significant difference between the densities within the conventional system. Limb bending of a parent in the single leader training systems led to an increase in the length of children growth units (bent = 16.07 cm, unbent = 12.05 cm). This paper outlines briefly the techniques used to collect architecture data and summarises the first year of vegetative and reproductive growth in each of the management scenarios.

Simulation of tree growth for three almond cultivars with contrasting architecture with the L-ALMOND model

The L-PEACH and L-ALMOND models use L-systems to simulate the architectural development and carbohydrate dynamics (assimilation, transport, distribution, storage and remobilization) of growing peach and almond trees, respectively. The models were able to successfully simulate tree growth and development and produce realistic estimates of tree size, structure and productivity over several years after planting, but always only for a specific cultivar. We here show how L-ALMOND can be adapted to simulate the architectural growth of three cultivars (‘Nonpareil’, ‘Aldrich’, and ‘Winters’) differing in tree architecture after three steps for each cultivar: i) inclusion of specific shoot architectures for six types of shoots (watersprouts, long, medium-long, medium, medium-short, and small shoots). Branching patterns and flowering occurrence for each type of shoot were previously assessed by developing hidden semi-Markov statistical models based on field research. Spur morphology was the same. Very different patterns emerged of sylleptic shoot production from lateral meristems on watersprouts, long, and medium-long shoots. ‘Aldrich’ and ‘Winters’ produced many more sylleptic shoots than ‘Nonpareil’. No sylleptic shoot growth appeared from medium, medium-short, and small shoots in any cultivar; ii) definition of the type of shoot derived from a sylleptic shoot. In ‘Aldrich’ and ‘Winters’ most sylleptic shoots were spurs and short shoots, respectively, while in ‘Nonpareil’ their length varied widely (spurs, small, medium-short, and medium shoots); and iii) adjustment of a parameter to modify shoot bending to simulate differences in growth habit observed in the field. ‘Aldrich’ was more erect than ‘Winters’ and ‘Nonpareil’. After modifications, L-ALMOND 3-dimensional tree simulations were similar to actual pictures of field trees, demonstrating how different shoot architectures result in different tree architectures over time, and especially the role that sylleptic shoot production plays in determining final tree architecture in almond.

A SOC1-like gene MtSOC1a promotes flowering and primary stem elongation in Medicago.

Medicago flowering, like that of Arabidopsis, is promoted by vernalization and long days, but alternative mechanisms are predicted because Medicago lacks the key regulators CO and FLC. Three Medicago SOC1-like genes, including MtSOC1a, were previously implicated in flowering control, but no legume soc1 mutants with altered flowering were reported. Here, reverse transciption-quantitative PCR (RT-qPCR) indicated that the timing and magnitude of MtSOC1a expression was regulated by the flowering promoter FTa1, while in situ hybridization indicated that MtSOC1a expression increased in the shoot apical meristem during the floral transition. A Mtsoc1a mutant showed delayed flowering and short primary stems. Overexpression of MtSOC1a partially rescued the flowering of Mtsoc1a, but caused a dramatic increase in primary stem height, well before the transition to flowering. Internode cell length correlated with stem height, indicating that MtSOC1a promotes cell elongation in the primary stem. However, application of gibberellin (GA3) caused stem elongation in both the wild type and Mtsoc1a, indicating that the mutant was not defective in gibberellin responsiveness. These results indicate that MtSOC1a may function as a floral integrator gene and promotes primary stem elongation. Overall, this study suggests that apart from some conservation with the Arabidopsis flowering network, MtSOC1a has a novel role in regulating aspects of shoot architecture.

Abscisic acid influences tillering by modulation of strigolactones in barley

Strigolactones (SLs) represent a class of plant hormones that are involved in inhibiting shoot branching and in promoting abiotic stress responses. There is evidence that the biosynthetic pathways of SLs and abscisic acid (ABA) are functionally connected. However, little is known about the mechanisms underlying the interaction of SLs and ABA, and the relevance of this interaction for shoot architecture. Based on sequence homology, four genes (HvD27, HvMAX1, HvCCD7, and HvCCD8) involved in SL biosynthesis were identified in barley and functionally verified by complementation of Arabidopsis mutants or by virus-induced gene silencing. To investigate the influence of ABA on SLs, two transgenic lines accumulating ABA as a result of RNAi-mediated down-regulation of HvABA 8'-hydroxylase 1 and 3 were employed. LC-MS/MS analysis confirmed higher ABA levels in root and stem base tissues in these transgenic lines. Both lines showed enhanced tiller formation and lower concentrations of 5-deoxystrigol in root exudates, which was detected for the first time as a naturally occurring SL in barley. Lower expression levels of HvD27, HvMAX1, HvCCD7, and HvCCD8 indicated that ABA suppresses SL biosynthesis, leading to enhanced tiller formation in barley.

A Core Regulatory Pathway Controlling Rice Tiller Angle Mediated by the LAZY1-Dependent Asymmetric Distribution of Auxin.

Tiller angle in cereals is a key shoot architecture trait that strongly influences grain yield. Studies in rice (Oryza sativa) have implicated shoot gravitropism in the regulation of tiller angle. However, the functional link between shoot gravitropism and tiller angle is unknown. Here, we conducted a large-scale transcriptome analysis of rice shoots in response to gravistimulation and identified two new nodes of a shoot gravitropism regulatory gene network that also controls rice tiller angle. We demonstrate that HEAT STRESS TRANSCRIPTION FACTOR 2D (HSFA2D) is an upstream positive regulator of the LAZY1-mediated asymmetric auxin distribution pathway. We also show that two functionally redundant transcription factor genes, WUSCHEL RELATED HOMEOBOX6 (WOX6) and WOX11, are expressed asymmetrically in response to auxin to connect gravitropism responses with the control of rice tiller angle. These findings define upstream and downstream genetic components that link shoot gravitropism, asymmetric auxin distribution, and rice tiller angle. The results highlight the power of the high-temporal-resolution RNA-seq data set and its use to explore further genetic components controlling tiller angle. Collectively, these approaches will identify genes to improve grain yields by facilitating the optimization of plant architecture.

Deregulation of MADS-box transcription factor genes in a mutant defective in the WUSCHEL-LIKE HOMEOBOX gene EVERGREEN of Petunia hybrida

ABSTRACTAngiosperm inflorescences develop in two fundamentally different ways. In monopodial plants, for example in Arabidopsis thaliana, the flowers are initiated as lateral appendages of a central indeterminate inflorescence meristem. In sympodial plants, flowers arise by terminal differentiation of the inflorescence meristem, while further inflorescence development proceeds from new sympodial meristems that are generated at the flank of the terminal flower. We have used the sympodial model species Petunia hybrida to investigate inflorescence development. Here, we describe a mutant, bonsai (bns), which is defective in flower formation, inflorescence branching, and control of meristem size. Detailed microscopic analysis revealed that bns meristems retain vegetative charateristics including spiral phyllotaxis. Consistent with a block in flower formation, bns mutants exhibit a deregulated expression of various MADS-box genes. Molecular analysis revealed that the bns mutant carries a transposon insertion in the previously described EVERGREEN (EVG) gene, which belongs to the WUSCHEL-LIKE HOMEOBOX (WOX) transcription factor gene family. EVG falls in the WOX9 subfamily, which has diverse developmental functions in angiosperms. The comparison of WOX9 orthologues in five model species for flowering shows that these genes play functionally divergent roles in monopodial and sympodial plants, indicating that the WOX9 regulatory node may have played an important role in the evolution of shoot architecture.

Genetic improvement of the shoot architecture and yield in soya bean plants via the manipulation of GmmiR156b.

SummaryThe optimization of plant architecture in order to breed high‐yielding soya bean cultivars is a goal of researchers. Tall plants bearing many long branches are desired, but only modest success in reaching these goals has been achieved. MicroRNA156 (miR156)‐SQUAMOSA PROMOTER BINDING PROTEIN‐LIKE (SPL) gene modules play pivotal roles in controlling shoot architecture and other traits in crops like rice and wheat. However, the effects of miR156‐SPL modules on soya bean architecture and yield, and the molecular mechanisms underlying these effects, remain largely unknown. In this study, we achieved substantial improvements in soya bean architecture and yield by overexpressing GmmiR156b. Transgenic plants produced significantly increased numbers of long branches, nodes and pods, and they exhibited an increased 100‐seed weight, resulting in a 46%–63% increase in yield per plant. Intriguingly, GmmiR156b overexpression had no significant impact on plant height in a growth room or under field conditions; however, it increased stem thickness significantly. Our data indicate that GmmiR156b modulates these traits mainly via the direct cleavage of SPL transcripts. Moreover, we found that GmSPL9d is expressed in the shoot apical meristem and axillary meristems (AMs) of soya bean, and that GmSPL9d may regulate axillary bud formation and branching by physically interacting with the homeobox gene WUSCHEL (WUS), a central regulator of AM formation. Together, our results identify GmmiR156b as a promising target for the improvement of soya bean plant architecture and yields, and they reveal a new and conserved regulatory cascade involving miR156‐SPL‐WUS that will help researchers decipher the genetic basis of plant architecture.

Towards molecular design of rice plant architecture and grain quality

Rice is one of the world’s most important crops, playing an important role in national food security. Considering the decrease of arable cultivated land, the development of social economy, and the environmental restrictions by climate change, it is important to cultivate high-yield and good quality elite varieties in rice. Plant architecture is one of the main factors that determine rice grain yield, which mainly includes tiller number, tiller angle, plant height, and panicle morphology. Over past decades, breeding practices have greatly increased rice grain yield with plant architecture improvement, and two significant achievements have been made due to dwarfism breeding through the application of “green revolution” gene sd1 and utilization of hybrid vigor with the development of hybrid rice. Thus, it is of great significance to reveal the molecular basis of rice plant architecture. Besides the grain yield, rice grain quality is another important goal for rice breeding, which is mainly influenced by nutritional value, cooking and eating properties, storage ability, and grain appearance. With the development of rice functional genomic research and modern biological technology, significant progresses have been made in understanding rice shoot architecture and grain quality, which in turn promotes the molecular design of rice elite varieties. In this review, we discuss the molecular basis of rice plant architecture, especially the key regulator IPA1 that encodes rice SQUAMOSA Promoter Binding Protein Like-14 (OsSPL14) and determines the ideal plant architecture traits including decrease tiller number, increase plant height and panicle branches. We then discuss the molecular basis of grain quality, especially the cooking and eating quality of rice, one major index of grain quality, which is determined by amylose content, gel consistency and gelatinization temperature. These three traits are regulated by a complex genetic network, and the elucidation of major regulatory genes provides important strategy for improving rice quality by molecular selection. At mean time, the development of new technologies has greatly accelerated the scientific researches on relate areas. Genome-wide association studies (GWAS) had been applied for the efficient utilization of the genetic information in various rice varieties in the dissection of complex traits and provided a fundamental resource of rice breeding. Meanwhile, the revolutionary CRISPR technology has greatly increased the efficiency in generating new genetic resources and benefitting molecular breeding by design. In the future, the application of important agronomical genes in molecular breeding by design and the broad popularization of new varieties will bring a new leap for agriculture production.

Circadian rhythms are associated with shoot architecture in natural settings

Circadian rhythms are key regulators of diverse biological processes under controlled settings. Yet, the phenotypic and fitness consequences of quantitative variation in circadian rhythms remain largely unexplored in the field. As with other pathways, phenotypic characterization of circadian outputs in the field may reveal novel clock functions. Across consecutive growing seasons, we test for associations between clock variation and flowering phenology, plant size, shoot architecture, and fruit set in clock mutants and segregating progenies of Arabidopsis thaliana expressing quantitative variation in circadian rhythms. Using structural equationmodeling, we find that genotypic variation in circadian rhythms within a growing season is associated directly with branching, which in turn affects fruit production. Consistent with direct associations between the clock and branching in segregating progenies, cauline branch number is lower and rosette branch number higher in a short-period mutant relative to wild-type and long-period genotypes, independent of flowering time. Differences in branching arise from variation in meristem fate as well as leaf production rate before flowering and attendant increases in meristem number. Our results suggest that clock variation directly affects shoot architecture in the field, suggesting a novel clock function and means by which the clock affects performance.

Genetic Regulation of Shoot Architecture

Shoot architecture is determined by the organization and activities of apical, axillary, intercalary, secondary, and inflorescence meristems and by the subsequent development of stems, leaves, shoot branches, and inflorescences. In this review, we discuss the unifying principles of hormonal and genetic control of shoot architecture including advances in our understanding of lateral branch outgrowth; control of stem elongation, thickness, and angle; and regulation of inflorescence development. We focus on recent progress made mainly in Arabidopsis thaliana, rice, pea, maize, and tomato, including the identification of new genes and mechanisms controlling shoot architecture. Key advances include elucidation of mechanisms by which strigolactones, auxins, and genes such as IDEAL PLANT ARCHITECTURE1 and TEOSINTE BRANCHED1 control shoot architecture. Knowledge now available provides a foundation for rational approaches to crop breeding and the generation of ideotypes with defined architectural features to improve performance and productivity.

Strigolactones affect the translocation of nitrogen in rice

Strigolactones (SLs) are involved in the nutrient-dependent control of plant root and shoot architecture. The total sufficient uptake of nitrogen (N), and also its appropriate distribution, is essential for the normal growth and development of plants; however, the effect of SLs on N translocation in plants remains unknown. Here, the SL-signaling mutant dwarf 3 (d3), the biosynthesis mutant dwarf 10 (d10), and wild-type (WT) rice (Oryza sativa ssp. Japonica cv. Nipponbare) were used to investigate the relationship between N nutrition and the regulatory role of SLs. Relative to WT, the d10 mutant had a higher N concentration in older leaves but a lower N concentration in younger leaves, while the d3 mutant showed a considerably lower N concentration, especially in its younger leaves under normal N levels. By contrast, both d3 and d10 mutants contained higher N in their leaves under N-deficient conditions. The 15N uptake and distribution analysis revealed that the significantly different N concentrations among the d3, d10, and WT plants only occurred in their leaves, not in their roots. Moreover, when provided with an external supply of GR24, the synthetic SLs altered the leaf N distribution of the d10 mutant but not those of the d3 mutant and WT. Together, these results suggested that the effect of SLs on plant growth and development may be linked to N translocation to different shoot tissues.

GRF-interacting factor1 Regulates Shoot Architecture and Meristem Determinacy in Maize.

Plant architecture results from a balance of indeterminate and determinate cell fates. Cells with indeterminate fates are located in meristems, comprising groups of pluripotent cells that produce lateral organs. Meristematic cells are also found in intercalary stem tissue, which provides cells for internodes, and at leaf margins to contribute to leaf width. We identified a maize (Zea mays) mutant that has a defect in balancing determinacy and indeterminacy. The mutant has narrow leaves and short internodes, suggesting a reduction in indeterminate cells in the leaf and stem. In contrast, the mutants fail to control indeterminacy in shoot meristems. Inflorescence meristems are fasciated, and determinate axillary meristems become indeterminate. Positional cloning identified growth regulating factor-interacting factor1 (gif1) as the responsible gene. gif1 mRNA accumulates in distinct domains of shoot meristems, consistent with tissues affected by the mutation. We determined which GROWTH REGULATING FACTORs interact with GIF1 and performed RNA-seq analysis. Many genes known to play roles in inflorescence architecture were differentially expressed in gif1 Chromatin immunoprecipitation identified some differentially expressed genes as direct targets of GIF1. The interactions with these diverse direct and indirect targets help explain the paradoxical phenotypes of maize GIF1. These results provide insights into the biological functions of gif1.

Comparative Genome-Wide-Association Mapping Identifies Common Loci Controlling Root System Architecture and Resistance to Aphanomyces euteiches in Pea.

Combining plant genetic resistance with architectural traits that are unfavorable to disease development is a promising strategy for reducing epidemics. However, few studies have identified root system architecture (RSA) traits with the potential to limit root disease development. Pea is a major cultivated legume worldwide and has a wide level of natural genetic variability for plant architecture. The root pathogen Aphanomyces euteiches is a major limiting factor of pea crop yield. This study aimed to increase the knowledge on the diversity of loci and candidate genes controlling RSA traits in pea and identify RSA genetic loci associated with resistance to A. euteiches which could be combined with resistance QTL in breeding. A comparative genome wide association (GWA) study of plant architecture and resistance to A. euteiches was conducted at the young plant stage in a collection of 266 pea lines contrasted for both traits. The collection was genotyped using 14,157 SNP markers from recent pea genomic resources. It was phenotyped for ten root, shoot and overall plant architecture traits, as well as three disease resistance traits in controlled conditions, using image analysis. We identified a total of 75 short-size genomic intervals significantly associated with plant architecture and overlapping with 46 previously detected QTL. The major consistent intervals included plant shoot architecture or flowering genes (PsLE, PsTFL1) with putative pleiotropic effects on root architecture. A total of 11 genomic intervals were significantly associated with resistance to A. euteiches confirming several consistent previously identified major QTL. One significant SNP, mapped to the major QTL Ae-Ps7.6, was associated with both resistance and RSA traits. At this marker, the resistance-enhancing allele was associated with an increased total root projected area, in accordance with the correlation observed between resistance and larger root systems in the collection. Seven additional intervals associated with plant architecture overlapped with GWA intervals previously identified for resistance to A. euteiches. This study provides innovative results about genetic interdependency of root disease resistance and RSA inheritance. It identifies pea lines, QTL, closely-linked markers and candidate genes for marker-assisted-selection of RSA loci to reduce Aphanomyces root rot severity in future pea varieties.

Morphological adaptations of signal grass in response to liming and cutting severities

Changes in morphological composition and in the plant population were evaluated during late spring, summer and autumn, in swards of Brachiaria decumbens cv. Basilisk in response to liming (C0.0, without liming; C0.7, limestone amount equivalent to 0.7 ton ha-1; and C1.0, limestone amount equivalent to 1.0 ton ha-1), which were subjected to severe or lenient cutting (40 or 60% of the pre-cutting height, respectively). Increased limestone doses did not result in higher herbage mass (HM), leaf area index (LAI) or proportion of leaves (%L) in the pre-harvest. However, lower proportion of dead material was registered in C0.7 treatment. The treatments C0.0 e C0.7 had higher %L during late spring and summer when associated to severe cutting regimes (R40%), although they reached the pre-harvest condition with lower HM and longer regrowth periods compared to lenient cuttings. The Brachiaria decumbens cv. Basilisk modifies its shoot architecture during the growth season, indicating that lower pre-harvest heights are required during autumn. The absence of liming led to a sharp decreasing of base saturation and levels of K, Ca and Mg in the soil. The minimum annual amount of limestone required for B. decumbens correspond to 0.7 ton ha-1.

A generic individual-based model to simulate morphogenesis, C-N acquisition and population dynamics in contrasting forage legumes.

Individual-based models (IBMs) are promising tools to disentangle plant interactions in multi-species grasslands and foster innovative species mixtures. This study describes an IBM dealing with the morphogenesis, growth and C-N acquisition of forage legumes that integrates plastic responses from functional-structural plant models. A generic model was developed to account for herbaceous legume species with contrasting above- and below-ground morphogenetic syndromes and to integrate the responses of plants to light, water and N. Through coupling with a radiative transfer model and a three-dimensional virtual soil, the model allows dynamic resolution of competition for multiple resources at individual plant level within a plant community. The behaviour of the model was assessed on a range of monospecific stands grown along gradients of light, water and N availability. The model proved able to capture the diversity of morphologies encountered among the forage legumes. The main density-dependent features known about even-age plant populations were correctly anticipated. The model predicted (1) the 'reciprocal yield' law relating average plant mass to density, (2) a self-thinning pattern close to that measured for herbaceous species and (3) consistent changes in the size structure of plant populations with time and pedo-climatic conditions. In addition, plastic changes in the partitioning of dry matter, the N acquisition mode and in the architecture of shoots and roots emerged from the integration of plant responses to their local environment. This resulted in taller plants and thinner roots when competition was dominated by light, and shorter plants with relatively more developed root systems when competition was dominated by soil resources. A population dynamic model considering growth and morphogenesis responses to multiple resources heterogeneously distributed in the environment was presented. It should allow scaling plant-plant interactions from individual to community levels without the inconvenience of average plant models.

Evidence for species-dependent biosynthetic pathways for converting carlactone to strigolactones in plants.

Strigolactones (SLs), comprising compounds with diverse but related chemical structures, are determinant signals in elicitation of germination in root parasitic Orobanchaceae and in mycorrhization in plants. Further, SLs are a novel class of plant hormones that regulate root and shoot architecture. Dissecting common and divergent biosynthetic pathways of SLs may provide avenues for modulating their production in planta. Biosynthesis of SLs in various SL-producing plant species was inhibited by fluridone, a phytoene desaturase inhibitor. The plausible biosynthetic precursors of SLs were exogenously applied to plants, and their conversion to canonical and non-canonical SLs was analysed using liquid chromatography-tandem mass spectrometry. The conversion of carlactone (CL) to carlactonoic acid (CLA) was a common reaction in all investigated plants. Sorghum converted CLA to 5-deoxystrigol (5-DS) and sorgomol, and 5-DS to sorgomol. One sorgomol-producing cotton cultivar had the same SL profile as sorghum in the feeding experiments. Another cotton cultivar converted CLA to 5-DS, strigol, and strigyl acetate. Further, 5-DS was converted to strigol and strigyl acetate. Moonseed converted CLA to strigol, but not to 5-DS. The plant did not convert 5-DS to strigol, suggesting that 5-DS is not a precursor of strigol in moonseed. Similarly, 4-deoxyorobanchol was not a precursor of orobanchol in cowpea. Further, sunflower converted CLA to methyl carlactonoate and heliolactone. These results indicated that the biosynthetic pathways of hydroxy SLs do not necessarily involve their respective deoxy SL precursors.

The origin and early evolution of vascular plant shoots and leaves.

The morphology of plant fossils from the Rhynie chert has generated longstanding questions about vascular plant shoot and leaf evolution, for instance, which morphologies were ancestral within land plants, when did vascular plants first arise and did leaves have multiple evolutionary origins? Recent advances combining insights from molecular phylogeny, palaeobotany and evo–devo research address these questions and suggest the sequence of morphological innovation during vascular plant shoot and leaf evolution. The evidence pinpoints testable developmental and genetic hypotheses relating to the origin of branching and indeterminate shoot architectures prior to the evolution of leaves, and demonstrates underestimation of polyphyly in the evolution of leaves from branching forms in ‘telome theory’ hypotheses of leaf evolution. This review discusses fossil, developmental and genetic evidence relating to the evolution of vascular plant shoots and leaves in a phylogenetic framework.This article is part of a discussion meeting issue ‘The Rhynie cherts: our earliest terrestrial ecosystem revisited’.