Architectural and genetic characterization of Hydrangea aspera subsp. aspera Kawakami group, H. aspera subsp. sargentiana and their hybrids

Hydrangea macrophylla (Thunb.) Ser. and H. paniculata Sieb. are the two most economically important species within the genus Hydrangea, and have been used as ornamental garden plants for a long time. However, other species such as H. aspera D. Don are of horticultural interest, particularly for the color of their inflorescences and plant shape. This species is composed of four sub-species and has previously been characterized both genetically and morphologically. The previous morphological characterization was qualitative, but was based mainly on leaf and inflorescence parameters outlined by UPOV, and provided little information about plant shape. To better characterize the shape of H. aspera, an architectural analysis was applied to the two most distantly related sub-species at the cytogenetic level: subsp. sargentiana (Redher) E.M. McClint. (clone 188) and subsp. aspera Kawakami group (clone 352). This method made it possible to reveal significant differences between these clones, both at the axis and the growth unit (GU) scale, in agreement with the high level of genetic differentiation (Jaccard dissimilarity index equal to 0.97) revealed between the two clones by Inter simple sequence repeats markers. Because this method is difficult to apply to a large population of individuals, a qualitative architectural characterization was tested on ten progenies derived from hybridization of the two clones, on the basis of their most discriminating architectural components. The hybrid nature of the progeny was confirmed by the architectural analysis. The architectural components of the hybrids are therefore a combination of those of the parents, with a predominance of clone 352, the female parent. Architectural differences between hybrids were clearly revealed by the length of the first vegetative GU (VGU1), the presence or the absence of VGU2 and the length of the floral GU of the A2 axis, and GU branching, allowing us to define five architectural profiles. These differences are supported by the average Jaccard dissimilarity index (0.33). This method, based on a qualitative description of the main architectural components of the plant, proved to be useful for characterizing the shape of H. aspera subsp. sargentiana, and subsp. aspera Kawakami group, and their hybrids. It could be extended to other sub-species of H. aspera and to their respective hybrids, providing an efficient tool for better characterizing genetic resources of H. aspera

Morphogenetic analysis of the phenotypic variability of the architectural unit of Hydrangea macrophylla

Hydrangea macrophylla is a ligneous plant that has attracted the attention of many plant breeders and agronomists for the purpose of enhancing its phenotypic plasticity. However, this plasticity was always exploited empirically.Can this plasticity be assessed by a more scientific approach? In this work, the phenotypic variation is analysed via a description of the different development sequences of the plant and by exposing the plant to different contrasted environments. The architectural unit consists of two morphogenetic units: the Vegetative Unit (VU) and the Vegetative and Floral Unit (VFU). They result in four successive development sequences: an organogenetic phase accompanied by continuous growth (sequence A), floral transformation (sequence B), dormancy (sequence C) and flower bloom (sequence D). Under the effect of environmental factors, the formation of the mixed terminal bud (sequence B) provides a considerable source of spatial variability, whereas the absence or presence of dormancy (sequence C) is responsible for a source of temporal variation. The in-depth description of the architectural unit with its morphological components and the characterisation of the four development sequences provide a necessary scientific basis to identify environmental effects on plant development and for the integrated use of its plasticity

Mass vegetative propagation of Ostrya carpinifolia by continual removal of axillary branches from juvenile donor plants

The propagation of ornamental standard trees by seedlings or traditional cutting methods does not allow to obtain a juvenile plants with a high degree of homogeneity. Vegetative propagation by microcutting may be a solution to attain this object. This technique is based on the construction of juvenile donor plants through frequent and regular pruning of young plants. Our experiment involved one arborescent species, Ostrya carpinifolia, using one unpruned control and two types of pruning treatments, in relation with the number of internodes of axis bearing the cuttings. The treatment with axis constituted of four internodes gave the best results, with 147 cuttings after 143 days of growing of donor plants and 83% of rooting, after 21 days of cutting. For this species, vegetative propagation using juvenile donor plants with pruning to two internodes is highly satisfactory. Therefore, this vegetative propagation by juvenile donor plant can be proposed to produce homogeneous standard tree

Engineering spin-orbit coupling for photons and polaritons in microstructures

One of the most fundamental properties of electromagnetism and special relativity is the coupling between the spin of an electron and its orbital motion. This is at the origin of the fine structure in atoms, the spin Hall effect in semiconductors, and underlies many intriguing properties of topological insulators, in particular their chiral edge states. Configurations where neutral particles experience an effective spin-orbit coupling have been recently proposed and realized using ultracold atoms and photons. Here we use coupled micropillars etched out of a semiconductor microcavity to engineer a spin-orbit Hamiltonian for photons and polaritons in a microstructure. The coupling between the spin and orbital momentum arises from the polarisation dependent confinement and tunnelling of photons between micropillars arranged in the form of a hexagonal photonic molecule. Dramatic consequences of the spin-orbit coupling are experimentally observed in these structures in the wavefunction of polariton condensates, whose helical shape is directly visible in the spatially resolved polarisation patterns of the emitted light. The strong optical nonlinearity of polariton systems suggests exciting perspectives for using quantum fluids of polaritons11 for quantum simulation of the interplay between interactions and spin-orbit coupling.Comment: main text: pages 1-11 (4 figures); supplementary material: pages 12-28 (9 figures

Assessing the visual aspect of rotating virtual rose bushes by a labeled sorting task

Aesthetics is one of the major parameters for consumers when buying a rose bush. Therefore, managing this quality is important for agronomists. Tools are needed to assess visual characteristics and to find links with architectural plant parameters. Sensory analyses were developed using real plants and photographs as stimuli. With technology and modeling improvements, using virtual plants could presents numerous advantages. This study demonstrated the feasibility of using rotating virtual rose bush videos as stimuli for a labeled sorting task. The virtual rose bush reflected a natural within-crop variability of one cultivar based on bud breaks location and axes length. Two panels of subjects closely linked to the horticulture sector sorted and described 40 rotating virtual rose bush videos. Non-metric Multidimensional Scaling (MDS) results for both panels were similar and allowed us to highlight five groups of virtual rose bushes with their specific sensory characteristics and their own most representative products using a combination of the paragons and the most typical products. This approach revealed that subjects detected high visual differences between products, and that by using rotation, they were able to integrate 3D properties about variations around plant facets. Finally, a labeled sorting task is a powerful method for preliminary exploration of the visual aspect of virtual plants

Analysis of the Impact of Climatic Conditions on Floral Transformation in Hydrangea macrophylla ‘Leuchtfeuer’

Hydrangea macrophylla is a horticultural plant of considerable commercial interest that has been widely studied with the aim to more effectively control the different stages of its development during production. However, although floral transformation is a key factor underlying the commercial quality of the product, it remains difficult to control despite these efforts. The floral transformation sequence consists of three successive phases: floral induction (B1), floral evocation (B2), and floral organogenesis (B3). The first is a phase of vegetative organogenesis without elongation leading to the formation of a bud composed of eight phytomer primordia under inductive climatic conditions. This work shows that climatic conditions favorable to floral transformation must be continuously applied without interruption throughout phase B1 to ensure the formation of the floral bud in Hydrangea macrophylla ‘Leuchtfeuer’. In the opposite case, floral transformation is stopped and vegetative growth begins once again

The Influence of Pruning on Morphological and Architectural Characteristics of Camellia japonica L. in a Tropical Climate

The ornamental qualities of Camellia japonica have long been of interest to horticulturists. The European garden plant market has traditionally been characterized by erect, branched and flowered plants. More recently, a new market linked to increasing urbanization has developed for compact, highly branched and flowered plants to decorate balconies and patios. Two flushes are formed per year in temperate climates, and three years are required to obtain a garden plant. In the humid, tropical climate of Reunion Island, at an altitude of 700 m, three to four flushes are formed in a single growing season. Under these conditions and with no pruning, it is possible to produce an upright plant with a height of 48.5 cm and 7.5 branchings, adapted to the traditional garden market. With two prunings and the same growing period, a compact plant with a height of 25.4 and 17.0 branchings can be produced, adapted to the new balcony-patio market. In both cases, floral induction occurs in November when the nighttime temperature is above 15 degrees C. This research shows that it is possible to generate diversified and innovative forms of Camellia japonica with considerable marketing potential using adapted pruning and under appropriate climatic conditions