Growth Of Lateral Branches Research Articles

Physiological Characteristics and Transcriptomic Responses of Pinus yunnanensis Lateral Branching to Different Shading Environments.

Pinus yunnanensis is an important component of China's economic development and forest ecosystems. The growth of P. yunnanensis seedlings experienced a slow growth phase, which led to a long seedling cultivation period. However, asexual reproduction can ensure the stable inheritance of the superior traits of the mother tree and also shorten the breeding cycle. The quantity and quality of branching significantly impact the cutting reproduction of P. yunnanensis, and a shaded environment affects lateral branching growth, development, and photosynthesis. Nonetheless, the physiological characteristics and the level of the transcriptome that underlie the growth of lateral branches of P. yunnanensis under shade conditions are still unclear. In our experiment, we subjected annual P. yunnanensis seedlings to varying shade intensities (0%, 25%, 50%, 75%) and studied the effects of shading on growth, physiological and biochemical changes, and gene expression in branching. Results from this study show that shading reduces biomass production by inhibiting the branching ability of P. yunnanensis seedlings. Due to the regulatory and protective roles of osmotically active substances against environmental stress, the contents of soluble sugars, soluble proteins, photosynthetic pigments, and enzyme activities exhibit varying responses to different shading treatments. Under shading treatment, the contents of phytohormones were altered. Additionally, genes associated with phytohormone signaling and photosynthetic pathways exhibited differential expression. This study established a theoretical foundation for shading regulation of P. yunnanensis lateral branch growth and provides scientific evidence for the management of cutting orchards.

Regulatory Mechanisms of Strigolactones on the Development of Lateral Branches in Cucumber

Cucumber (Cucumis sativus L.) belongs to the cucumber genus of the Cucurbitaceae family, and the selection of cultivars with minimal or no lateral branches can enhance the cultivation management efficiency. The growth of lateral branches is inhibited by strigolactone. To investigate the regulatory mechanism of strigolactone on the lateral branch development in cucumber, the cultivar LZ1 exhibiting multiple lateral branches was selected as the experimental material. The axillae of the plants were infiltrated with 1, 5, and 10 μmol·L−1 germination releaser 24 (GR24) at the four- to five-leaf stage. It was identified that 1 μmol·L−1 GR24 exhibited the most potent inhibitory effect on cucumber lateral branches. Additionally, exogenous strigolactone decreased the auxin content in the apical bud and axillae and increased the auxin content in the stem. This inhibited polar auxin transport in the axillary bud and promoted polar auxin transport in the apical bud. The content of strigolactone in the axilla region of cucumbers was elevated, whereas the synthesis and expression of cytokinin in the same area were reduced. A low concentration of GR24 induced the expression of cucumber branched 1 (csbrc1), whereas a high concentration of GR24 downregulated the expression of cucumber lateral suppressor (cscls) and blind (csblind), which inhibited the growth of cucumber lateral branches.

Variations in growth and biochemical parameters in annual cherry plants under the infl uence of growth regulators

This study addresses the influence of the Applin drug on the growth and biochemical parameters of the leaves in three annual cultivars of cherries (Tyutchevka, Podarok Ryazani and Chermashnaya) grafted onto the Izmailovsky rootstock. The research was carried out in 2021-2022 both in field and laboratory conditions at the Federal Horticultural Centre for Breeding, Agrotechnology and Nursery. It was established that following treatment with Applin, the biometric indicators improved, with the yield of branched annual cherry seedlings increasing to 100 %. The treatment and removal of apical leaves stimulated the formation and growth of lateral branches in annual plants. The number of lateral shoots in experimental plants of the Chermashnaya cultivars increased by 6 times, while in the Tyutchevka and Podarok Ryazani cultivars, it increased by 3-4 times relative to the control. Growth regulators induced an increase in the average length of lateral shoots to 30-50 cm in all cultivars. The total length of the branches in the experimental Chermashnaya cultivar was 118.5 cm, which is 6.7 times higher than in the control. The other two cultivars exhibited a 4–4.5 times increase in total growth in treated plants compared with the control. Biochemical studies revealed an increase in photosynthetic pigment content in leaves following Applin treatment. The total content of phenolic compounds and antioxidant activity exhibited significant changes. A positive correlation (r = 0.709) was observed between the antioxidant activity of the aqueous extract and the amount of phenolic compounds. The content of chlorophylls (a+b) in the leaves of treated plants increased by 5-10%. Depending on the cultivar, the content of carotenoids varied from 1.1 to 1.8 mg/g, remaining practically constant following treatment. All cultivars showed an increase in the “chlorophyll (a+b)/carotenoids” ratio. Applin treatment also influenced the synthesis of primary and secondary metabolites, stimulating an increase in the content of carbohydrates (fructose, sucrose, turanose, and trehalose) and phenolic compounds (quinic and chlorogenic acids) in cherry plant leaves

CpCAF1 from Chimonanthus praecox Promotes Flowering and Low-Temperature Tolerance When Expressed in Arabidopsis thaliana.

CCR4-associated factor I (CAF1) is a deadenylase that plays a critical role in the initial step of mRNA degradation in most eukaryotic cells, and in plant growth and development. Knowledge of CAF1 proteins in woody plants remains limited. Wintersweet (Chimonanthus praecox) is a highly ornamental woody plant. In this study, CpCAF1 was isolated from wintersweet. CpCAF1 belongs to the DEDDh (Asp-Glu-Asp-Asp-His) subfamily of the DEDD (Asp-Glu-Asp-Asp) nuclease family. The amino acid sequence showed highest similarity to the homologous gene of Arabidopsis thaliana. In transgenic Arabidopsis overexpressing CpCAF1, the timing of bolting, formation of the first rosette, and other growth stages were earlier than those of the wild-type plants. Root, lateral branch, rosette leaf, and silique growth were positively correlated with CpCAF1 expression. FLOWERING LOCUS T (FT) and SUPPRESSOROF OVEREXPRESSION OF CO 1 (SOC1) gene expression was higher while EARLY FLOWERING3 (ELF3) and FLOWERING LOCUS C (FLC) gene expression of transgenic Arabidopsis was lower than the wild type grown for 4 weeks. Plant growth and flowering occurrences were earlier in transgenic Arabidopsis overexpressing CpCAF1 than in the wild-type plants. The abundance of the CpCAF1 transcript grew steadily, and significantly exceeded the initial level under 4 °C in wintersweet after initially decreasing. After low-temperature exposure, transgenic Arabidopsis had higher proline content and stronger superoxide dismutase activity than the wild type, and the malondialdehyde level in transgenic Arabidopsis was decreased significantly by 12 h and then increased in low temperature, whereas it was directly increased in the wild type. A higher potassium ion flux in the root was detected in transgenic plants than in the wild type with potassium deficiency. The CpCAF1 promoter was a constitutive promoter that contained multiple cis-acting regulatory elements. The DRE, LTR, and MYB elements, which play important roles in response to low temperature, were identified in the CpCAF1 promoter. These findings indicate that CpCAF1 is involved in flowering and low-temperature tolerance in wintersweet, and provide a basis for future genetic and breeding research on wintersweet.

Warming adversely affects density but not growth of balsam fir regeneration across a climatic gradient in the Acadian Forest Region of eastern Canada

Balsam fir ( Abies balsamea (L.) Mill.) is projected to decline in the Acadian Forest Region under climate change. We hypothesized that along a 700 km latitudinal gradient with increasing mean annual temperature from New Brunswick to Nova Scotia, Canada, balsam fir regeneration density and growth rates would (1) decline with warming and (2) decline more in immature than in mature stands due to greater exposure to adverse climate conditions. Regeneration density, height growth, and lateral branch growth were measured in 30 mature and 28 immature plots and related to climate and stand variables using generalized additive models. Balsam fir regeneration density was negatively affected by increased mean annual temperature and increased with summer precipitation, supporting our first hypothesis, but varied by height class. Canopy cover significantly affected seedling density, but its effect varied by substrate type (coniferous litter and dry moss litter), with seedling density being greatest under low canopy cover for large seedlings and greatest at intermediate canopy cover for small seedlings. Seedling growth rates were determined by height class, canopy cover, precipitation, and coniferous litter cover. Stand maturity did not significantly affect fir regeneration density or growth rates. Our results indicate that over time, increasing mean annual temperature may reduce balsam fir regeneration density within the Acadian Forest Region, while the marginal summer precipitation increases may lead to small gains in growth.

Identification of SHORT VEGETATIVE PHASE (SVP)-like genes and necessary responsibility of CmSVPc for the development of lateral branches in melon (Cucumis melo L.)

SVP acts as a central suppressor for floral transition and floral organ identity but also involves in the diverse functions among different species, such as abscission zones formation, plant height and dormancy. In this study, four SVP homologs were identified in melon and designated as CmSVPa, CmSVPb, CmSVPc and CmSVPd based on the similarity of their proteins to AtSVP. CmSVPc exhibited a clear difference in gene structure from the other CmSVP-like genes owing to its longer first and fifth introns. The results of exogenous gibberellin (GA3) and treatments with temperature and light suggested that CmSVPc and CmSVPd could be regulated by exogenous GA3 and all four CmSVPs involved in temperature and light responsive pathways. The results of RT-PCR indicated that transcripts of four CmSVPs were highly accumulated in shoot apices (MA and LA) and young leaves (YL) but they were present at relatively low levels in opening corolla (MF and BF). Compared with CmSVPa, CmSVPb and CmSVPd, the transcripts of CmSVPc were highest in all detected tissues except for LA in which CmSVPb accumulated to the highest level. Due to the specificity of gene structure and abundant transcripts of CmSVPc in melon, CmSVPc was chosen for further study. Subcellular localization revealed that CmSVPc was localized to the nucleus. Overexpression of CmSVPc in Arabidopsis led to increased numbers of lateral branches, delayed floral transition, and abnormal flower development compared with the wild type. However, CmSVPc-RNAi plants in melon inhibited the normal development of lateral branches, and the transgenic plants in which CmSVPc was downregulated also displayed shorter internodes, smaller petals and shorter fruits compared with the control. These results indicated that CmSVPc plays an important role in maintaining the growth of lateral branches in melon.

Evaluation of the U.S. Peanut Germplasm Mini-Core Collection in the Virginia-Carolina Region Using Traditional and New High-Throughput Methods

Peanut (Arachis hypogaea L.) is an important food crop for the U.S. and the world. The Virginia-Carolina (VC) region (Virginia, North Carolina, and South Carolina) is an important peanut-growing region of the U.S and is affected by numerous biotic and abiotic stresses. Identification of stress-resistant germplasm, along with improved phenotyping methods, are important steps toward developing improved cultivars. Our objective in 2017 and 2018 was to assess the U.S. mini-core collection for desirable traits, a valuable source for resistant germplasm under limited water conditions. Accessions were evaluated using traditional and high-throughput phenotyping (HTP) techniques, and the suitability of HTP methods as indirect selection tools was assessed. Traditional phenotyping methods included stand count, plant height, lateral branch growth, normalized difference vegetation index (NDVI), canopy temperature depression (CTD), leaf wilting, fungal and viral disease, thrips rating, post-digging in-shell sprouting, and pod yield. The HTP method included 48 aerial vegetation indices (VIs), which were derived using red, blue, green, and near-infrared reflectance; color space indices were collected using an octocopter drone at the same time, with traditional phenotyping. Both phenotypings were done 10 times between 4 and 16 weeks after planting. Accessions had yields comparable to high yielding checks. Correlation coefficients up to 0.8 were identified for several Vis, with yield indicating their suitability for indirect phenotyping. Broad-sense heritability (H2) was further calculated to assess the suitability of particular VIs to enable genetic gains. VIs could be used successfully as surrogates for the physiological and agronomic trait selection in peanuts. Further, this study indicates that UAV-based sensors have potential for measuring physiologic and agronomic characteristics measured for peanut breeding, variable rate input application, real time decision making, and precision agriculture applications.

The Carotenoid Cleavage Dioxygenase Gene CCD7-B, at Large, Is Associated with Tillering in Common Wheat

Wheat, an important cereal crop, is responsible for the livelihoods of many people, and a component of national food security. Tillering, which determines plant architecture and spike number, is a critical agronomic trait of wheat. The carotenoid cleavage dioxygenase 7 (CCD7) has an important effect on the growth of tillers or lateral branches and lateral roots of plants. In order to study the relationship between CCD7 and tillering in wheat, CCD7-B was isolated from 10 Chinese wheat varieties with different tiller numbers. Subsequently, bioinformatics, allelic variation analysis, and field experiments were performed. Wheat CCD7-B belongs to the retinal pigment epithelial membrane receptor (RPE65) superfamily; it displays the greatest homology with monocot CCD7 proteins. Phylogenetic analysis of wheat CCD7-B proteins indicated division into dicotyledonous and monocotyledonous clades. Allelic variation analysis of CCD7-B via SrgAI enzyme digestion (a marker of cleaved amplified polymorphic sequences) suggested that 262 Chinese wheat micro-core collections and 121 Chinese wheat major cultivars from the Yellow and Huai River Valley winter wheat region can be divided into two groups: CCD7-B1 (C/T/T) and CCD7-B2 (G/C/A). CCD7-B1 showed better allelic variation than did CCD7-B2 for increasing the number of effective tillers of wheat varieties in China. This study provides reference data for the application of CCD7-B alleles to wheat breeding and supports further research regarding the mechanism of tillering in common wheat.

Ammonium regulates the development of pine roots through hormonal crosstalk and differential expression of transcription factors in the apex.

Ammonium is a prominent source of inorganic nitrogen for plant nutrition, but excessive amounts can be toxic for many species. However, most conifers are tolerant to ammonium, a relevant physiological feature of this ancient evolutionary lineage. For a better understanding of the molecular basis of this trait, ammonium-induced changes in the transcriptome of maritime pine (Pinus pinaster Ait.) root apex have been determined by laser capture microdissection and RNA sequencing. Ammonium promoted changes in the transcriptional profiles of multiple transcription factors, such as SHORT-ROOT, and phytohormone-related transcripts, such as ACO, involved in the development of the root meristem. Nano-PALDI-MSI and transcriptomic analyses showed that the distributions of IAA and CKs were altered in the root apex in response to ammonium nutrition. Taken together, the data suggest that this early response is involved in the increased lateral root branching and principal root growth, which characterize the long-term response to ammonium supply in pine. All these results suggest that ammonium induces changes in the root system architecture through the IAA-CK-ET phytohormone crosstalk and transcriptional regulation.

Strigolactone regulates plant architecture by inhibiting lateral branch growth in Quercus mongolica seedlings

ABSTRACT Mongolian oak (Quercus mongolica) is an important timber species in northeast China, but overdeveloped lateral branches during the seedling stage often result in poor plant architecture and reduce the growth potential. Strigolactones (SLs) were proposed to play an important role in plant architecture by inhibiting the growth of lateral branches; however, there is no knowledge on the strigolactone effects in Mongolian oak. In this study, 0.3, 3, 10, and 30 mg/L of GR24 (analogue of SLs) and 1 mg/L Thidiazuron (TDZ) were applied to Mongolian oak seedlings by the lanolin method. All GR24 treatments significantly reduced the number and biomass of lateral branches; in addition, the length increment of lateral branches was decreased by 3, 10 and 30 mg/L GR24. In addition, the auxin content in lateral branches was significantly increased by the 10 mg/L GR24 treatment, which might be one of the main reasons for the inhibition of lateral branch growth. Increased sucrose content in apex, combined with a decrease of sucrose content in lateral branches, further demonstrated the important role of GR24 in inhibiting lateral branch growth.

Summer pruning improves the branch growth and tea quality of tea trees (Camellia sinensis)

At present, twice-a-year pruning is usually adopted for the tea garden, in which only spring tea is picked. Effects of different times and heights of summer pruning on tea trees are unknown. Here the effects of summer pruning on ‘Jin Guan Yin’ oolong mature tea trees were studied. The results showed that pruning at 30 cm (summer pruning at 30 cm above the cut surface of spring pruning) on Jul 25 could benefit to the growth of lateral branches, whereas two pruning treatments in August reduced their growth vigor. Pruning at 30 cm could also provide a benefit by decreasing the ratio of total tea polyphenols to free amino acids (TP/AA), an important factor in tea quality. Pruning at 30 cm and two pruning in August all significantly enhanced the contents of ester catechins [‘(−)-epigallocatechin gallate (EGCG) + (−)-epicatechin gallate (ECG)’] as compared to conventional summer pruning. Pruning on Aug 15 (summer pruning at 20 cm on Aug 15) had the lowest (EGCG + ECG)%. In addition, enhanced AA content induced by pruning at 30 cm was significantly associated with enhanced transcription of glutamine synthetase (CsGS) or glutamine:2-oxoglutarate aminotransferase (CsGOGAT). In a word, the summer pruning at 30 cm on Jul 25 was best to benefit the growth of lateral branches and spring tea yield and quality, whereas pruning on Aug 15 had the worst comprehensive effects.

Estimation of the Survival Rate of Pinus Sylvestris Urban Landscaping Facilities in the City of Krasnoyarsk

Scotch pine takes an increasing place in urban greening. Its high decorative qualities, especially in winter, undemanding to soil conditions, rapidity of growth, winter hardiness, high sanitary and hygienic and environmental protection properties contribute to the greatest distribution. It has been established that when creating green spaces at city greening objects, it is necessary to take into account the dynamics of plant survival. The study of the survival rate of Scots pine according to the reaction of the growth of lateral branches showed that the main decrease in growth after transplantation occurs in the second year, the restoration of growth occurs after 7-8 years. The survival rate of plants largely depends on the state of the urban environment and the technology after planting care for plantings, especially in the first and second years after transplanting. At the same time, when creating green spaces, it is also necessary to comply with the recommendations of the “Building codes and regulations" in relation to the minimum distances to buildings, structures, footpaths and driveways, as well as the schedule of work to create a landscaping facility.

Heterogeneity of the Dendrite Array Created in the Root of Cored SX Turbine Blades during Initial Stage of Crystallization.

The roots of cored single-crystalline turbine blades made of a nickel-based CMSX-4 superalloy were studied. The casts were solidified by the vertical Bridgman method in an industrial ALD furnace using the spiral selector and selector continuer situated asymmetrically in the blade root transverse section. Scanning electron microscopy, the Laue diffraction and X-ray diffraction topography were used to visualize the dendrite array and the local crystal misorientation of the roots. It has been stated that heterogeneity of the dendrite array and creation of low-angle boundaries (LABs) are mostly related to the lateral dendrite branching and rapid growth of the secondary and tertiary dendrites near the surface of the continuer–root connection. These processes have an unsteady character. Additionally, the influence of the mould walls on the dendrite array heterogeneity was studied. The processes of the lateral growth of the secondary dendrites and competitive longitudinal growth of the tertiary dendrites are discussed and a method of reducing the heterogeneity of the root dendrite array is proposed.

Study on cultivation of pistachio (Pistacia vera L.) seedlings in containers

This article highlights the results from the effect of changing the volume of containers on the growth and development of pistachio seedlings, as well as the effect of hydrogel, moisture-accumulating substances on the preservation of pistachio seedlings planted on plantations. According to the research, seedlings of pistachio, planted on containers 20x40 cm in size, reached an average height of 18.2 cm, an average diameter at the root collar of 4 mm and an average root length of 30.4 cm. Pistachio seedlings (planted in a permanent place) grown by this method reached safety 95%, which is 122% compared to control group. It is possible to maintain a high field moisture capacity for 2-3 years by adding moisture-accumulating substances - hydrogel to the soil. This allows retaining moisture sufficient for the preservation and growth of pistachios in dry conditions. The preservation of moisture is necessary for pistachio seedlings for good growth and development, branching, budding, to shorten the period of entry into fruiting and increase the yield. Studies, conducted on the effect of hydrogel on transplanted annual shows that the most effective rate is 100 grams/plant. At this application rate, the average plant growth was 20.5 cm, which is 113% compared to control group, the average growth of lateral branches is 6.5 cm, which is 118.0% compared to control group.

Shoot branching regulation and signaling

Plant development and structure are constantly adjusted throughout their life cycle to adapt environmental changes in nature. The amount of branches mainly depends on whether axillary buds form, release and growth of axillary buds. The plants branching is regulated by many factors including gene transcription, hormone homeostasis, and environmental factors such as light, water, and nutrition. People control shoot branching according to their demands to facilitate agricultural production. The activation and growth of lateral branches depend on a variety of internal and external environmental signals. Here we reviewed the recent progresses on genes, hormones, signaling materials, and external environmental conditions on the development of lateral branches in plant. Understanding these key nodes or regulatory networks is necessary and worthy challenges. The discussion of the factors affecting the formation of lateral branches provides a basis for the rational method of crop breeding and the cultivation of ideal plant type crops.

Self-healing properties of lateral-root branches of three shrub species after fracture force injure in semi-arid mining area

To clarify the sustainable soil reinforcement capacity of the lateral root branches of shrubs after injury by fracture force in a semi-arid coal mining subsidence region of Shendong, we analyzed the ultimate anti-fracture mechanical characteristics of three shrub species, Caragana microphylla, Salix cheilophila, and Hippophae rhamnoides, as well as the self-healing ability of their growth indices and mechanical characteristics after injury by fracture force. The results showed that the anti-fracture force and its strength had significant difference among the three shrub species in their late-ral root branches in the early stage of growing season, with the order of C. microphylla > S. cheilophila > H. rhamnoides. The anti-fracture strengths of C. microphylla and S. cheilophila were positively correlated with the contents of cellulose, lignin and holocellulose, while that of H. rhamnoides was significantly negatively correlated with cellulose and lignin contents, but significantly positively correlated with holocellulose content. The fracture force damage caused by activity in the subsidence area significantly reduced the normal growth and mechanical properties of lateral root branches, which could not return to control levels even after three months of self-healing. For the shrubs, stronger self-healing ability of growth indicators resulted in a higher degree of self-healing of anti-fracture forces. Self-healing ability of growth indicators was in the order of H. rhamnoides (91.2%) > S. cheilophila (82.0%) > C. microphylla (73.9%), and self-healing degree of anti-fracture forces was in the order of H. rhamnoides (41.4%) > S. cheilophila (37.1%) > C. microphylla (30.0%). Sustainable soil reinforcement indices of the shrubs' lateral root branches were in the order of C. microphylla (2.2084) > S. cheilophila (0.2009) > H. rhamnoides (-2.4093). Our results indicated that C. microphylla was the best, S. cheilophila was intermediate, and H. rhamnoides was the least in soil reinforcement in semi-arid coal mining subsidence areas.

Effect of shoot parameters on cracking in vegetated soil

The relationship of shoot parameters, which play a major role in transpiration, with the cracking of soil has rarely been investigated. Such relation helps to analyse water use efficiency accurately. This study investigated the effect of vegetation (cowpea) age on crack formation and explored any correlation between age and cracking. The age of vegetation was expressed in the form of shoot parameters (shoot length (SL) and leaf area index (LAI)). Crack formation was expressed in the form of crack intensity factor (CIF). Ten experimental test pots were used to observe crack formation on vegetated and bare soil in a greenhouse. Image analysis in the experimental pots revealed that under drying–wetting cycles, the CIF of vegetated soil increased compared with that of bare soil. There was an evident increase in CIF with SL growth, up to a threshold length (400 mm), where lateral branch growth starts forming. There was no observable increase in CIF, with further SL growth (with negligible lateral branch formation). CIF increased with LAI up to a certain threshold value (0·56), after which the CIF was relatively the same. Two correlations have been identified for shoot parameters (SL, LAI) with the CIF for the selected species.

Drought inhibition of tillering in Festuca arundinacea associated with axillary bud development and strigolactone signaling

Drought stress inhibits tiller formation and growth, but the underlying mechanism is not well understood. Tiller development and lateral branch growth in monocot and dicot species respectively involve two stages: axillary bud initiation and subsequent outgrowth. The objective of this study was to investigate whether drought-inhibition of tiller growth is mainly due to the suppression of axillary bud initiation or subsequent outgrowth in perennial grass species and to determine whether drought-inhibition of tiller development and growth in grass species are associated with strigolactone (SL) accumulation and signaling. Seedlings with one fully-expanded leaf without axillary buds and those with three-fully expanded leaves and two axillary buds were grown in 20% polyethylene glycol (PEG) solution to induce drought stress. Plant height, number of leaves, axillary buds, tillers and length of axillary buds were monitored during 21 d of stress. Both axillary bud initiation and outgrowth were inhibited by drought stress, with outgrowth being more sensitive to drought stress. qRT-PCR analysis showed that expression level of genes involved in axillary bud activity was down-regulated at 14 d of drought stress while genes involved in axillary bud dormancy was up-regulated. Strigolactone (SL) content was elevated under drought stress in crowns. qRT-PCR analysis showed that expression level of genes involved in SL biosynthesis and signaling transduction were up-regulated during drought stress. Axillary bud outgrowth was sensitive to drought stress and could be associated with SL signaling, contributing to drought-inhibition of tillering in perennial grass species.

Investigations of fluid flow effects on dendritic solidification: Consequences on fragmentation, macrosegregation and the influence of electromagnetic stirring

Solidification experiments and numerical simulations have been performed to improve the understanding of the complex interrelation between melt flow and the formation of dendritic structures during solidification of Al-Cu and Ga-In alloys. Melt flow induces various effects on grain morphology primarily caused by convective transport of solute, such as a facilitation of the growth of primary trunks or lateral branches, dendrite remelting, fragmentation or freckle formation depending on the dendrite orientation, the flow direction and intensity. Within this project special interest was focused on fragmentation and segregation phenomena. Natural convection is caused by density variations within the solidifying alloys. Forced convection was produced by electromagnetic stirring. X-ray radioscopy was applied as a powerful tool for the visualization of dendritic growth and coarsening.

A New Approach for Olive (Arbequina cv.) Micropropagation: Effect of Dikegulac, Light and Carbon Source

Micro-propagation of olive provides the possibility of producing clones of native plants with appropriate attributes and mass reproduction in short period of time, compared to conventional methods. Apical dominance in olive explants limits the growth of lateral branches in vitro. The effect of Woody Plant Medium (WPM), Olive Medium (OM) and Murashig and Skoog (MS) with carbohydrate source (mannitol and sucrose), was investigated for in vitro shoot proliferation of olive. Different concentrations of sodium dikegulac (0.0, 2.5, 5.0, 7.5 and 10 mg L-1) along with 3 mg L-1 zeatin and 0.5 mg L-1 BAP and two light qualities (red and white) were used to overcome apical dominance. Effects of different IBA concentrations on the in vitro root induction were also investigated. More than 74% of explants rooted when IBA was used at 2 mg L-1. OM was the most effective medium, resulting in better and morphologically superior microshoots. Mannitol showed a positive effect on shoot proliferation. Using sodium dikegulac at 5 mg L-1 under white light significantly stimulated axillary bud growth. In the corresponding concentrations of sodium dikegulac, red light had a significant effect on longitudinal growth compared to the white light.