Shoot Initiation Research Articles

Micropropagation of Selected Hybrid Tomato (Solanum lycopersicum L.) Varieties Using Shoot Tip Culture

Tomato (Solanum lycopersicum L.) is one of the most important vegetable crops in the world. The use of hybrid varieties is a great option to increase its production but using F2 seed leads to lack of uniformity as a result of segregation. Therefore mass propagation using tissue culture could help to solve these problems. The objective of this study was to develop an optimum micropropagation protocol for Valouro, Uwezo and Shelter hybrid tomato varieties using shoot tip culture. Three successive experiments: shoot initiation; shoot multiplication and root inductions were conducted. Different concentrations of BAP (0.0, 0.25, 0.5, 0.75, 1.0 and 1.25 mg/l) and (0.0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3 mg/l) were used for shoot initiation and shoot multiplication, respectively. While different concentrations of IBA (0.0, 0.25, 0.5, 0.75, 1.0, 1.25 and 1.5 mg/l) were used for root induction. The three separate experiments were laid out as factorial arranged in completely randomized design. The result of shoot initiation showed that the interaction of BAP*Varieties highly significant (P<0.01) effect. In the multiplication experiment, all parameters showed highly significant difference (P<0.01). In rooting experiment the interaction effect of IBA*Variety showed highly significant difference for the studied parameters. In conclusion MS medium without growth regulators was the optimum for shoot initiation. For shoot multiplication experiment 2mg/l, 0.5mg/l and 1.5mg/l of BAP was the optimum concentration for number of shoots per explant, shoot length, and leaf number respectively. For in vitro rooting MS medium containing 0.5 mg/l IBA was optimum for all varieties.

ELONGATED HYPOCOTYL5-mediated light signaling promotes shoot regeneration in Arabidopsis thaliana.

Injured plant somatic tissues regenerate themselves by establishing shoot or root meristems. In Arabidopsis (Arabidopsis thaliana), a two-step culture system ensures regeneration by first promoting the acquisition of pluripotency and subsequently specifying the fate of new meristems. Although previous studies have reported the importance of phytohormones auxin and cytokinin in determining the fate of new meristems, whether and how environmental factors influence this process remains elusive. In this study, we investigated the impact of light signals on shoot regeneration using Arabidopsis hypocotyls as explants. We found that light signals promote shoot regeneration while inhibiting root formation. ELONGATED HYPOCOTYL 5 (HY5), the pivotal transcriptional factor in light signaling, plays a central role in this process by mediating the expression of key genes controlling the fate of new meristems. Specifically, HY5 directly represses root development genes and activates shoot meristem genes, leading to the establishment of shoot progenitor from pluripotent callus. We further demonstrated that the early activation of photosynthesis is critical for shoot initiation, and this is transcriptionally regulated downstream of HY5-dependent pathways. In conclusion, we uncovered the intricate molecular mechanisms by which light signals control the establishment of new meristems through the regulatory network governed by HY5, thus highlighting the influence of light signals on plant developmental plasticity.

In vitro micropropagation and mass multiplication of Stevia rebaudiana Bertoni

Stevia rebaudiana Bertoni, an ancient perennial herb produces steviol glycosides including stevioside and rebaudioside-A that are valuable as low calorie sweeteners, about 300-400 times sweeter than saccharose. Conventional propagation methods are not produce adequate planting material. Micro propagation is an imperative technology that could be extensively exploited to meet the growing demands of elite planting material for commercially cultivated. The prime objective of this study was to established standard protocol for in vitro regeneration and mass multiplication in Stevia. In present investigation, different concentrations of Auxin and Cytokinin were tried for optimization of shoot initiation, shoot multiplication, root initiation and callus induction of Stevia from different explant. BAP and IBA (1.0+0.5) mg/l, IBA (2.0) mg/l shows promising results of shoot multiplication and root initiation respectively.

Propagasi In Vitro Kaliandra Merah (Calliandra calothyrsus Meisn.) II: Induksi Perakaran Tunas dan Aklimatisasi Planlet

Red calliandra is one of woody plants that has been extensively developed as biofuel. Tissue culture techniques are employed to produce a large and uniform quantity of seedlings in a relatively short period. Previous stages of in vitro initiation and multiplication of shoot from calliandra explants have shown promising results. The shoots that were multiplied by in vitro technique need to be induced for rooting process to produce plantlets. These plantlets are then prepared for the subsequent acclimatization process. This research was conducted in two stages; root induction of shoots using a modification of MS half-strength media (MS ½) supplemented with 1-4 mg/L 1-naphthaleneacetic acid (NAA), and acclimatization of the plantlets into soil media. The results shown that MS ½ medium and media supplemented with 1 mg/L NAA were suitable for root induction, particularly to induce the root length. Furthermore, MS ½ media supplemented with 1-2 mg/L NAA stimulates the increment of plantlet height and leaves numbers. Plantlets which were transferred into soil exhibit robust growth during 3-weeks of acclimatization process, up to 100% plantlets survived during this stage. These results underscore the potential of tissue culture techniques in providing large scale calliandra seedlings production for future biofuel development.

Effect of Plant Growth Regulators on Mass Propagation of Strawberry (Fragaria sp.)

Efficient in vitro regeneration protocols for strawberries are crucial for accelerating the propagation of superior cultivars and improving overall productivity through controlled manipulation of plant growth regulators. This study investigated the influence of different concentrations and combinations of plant growth regulators on in vitro regeneration process of strawberries. BARI Strawberry-1 runner tips were sterilized and placed on Murashige and Skoog medium (MS) supplemented with various combinations of cytokinins, including 6-benzylaminopurine (BAP) and kinetin (KIN), to initiate shoot growth. Notably, the combination of 1.5 mg/L BAP + 1.0 mg/L KIN led to the shortest duration for shoot initiation (9 days), resulting in the highest number of shoots per explants (6.33), longest shoot length (2.87 cm), and maximum number of leaves per shoot (4.00). Additionally, this combination also exhibited the highest rate of shoot regeneration (70.33%). Subsequently, the proliferated shoots were transferred to MS medium supplemented with various concentrations and combinations of auxins, specifically 3-indolebutyric acid (IBA) and 1-naphthaleneacetic acid (NAA), for root induction. The in vitro regenerated shoots cultured in MS medium supplemented with 1.5 mg/L IBA + 1.0 mg/L NAA showed the shortest duration for root formation (8 days), the highest number of roots per explants (4.00), and the longest root length (2.77 cm). Furthermore, this combination also resulted in the highest rate of root regeneration (40%). These findings contribute valuable insights for the mass production of healthy strawberry plantlets using in vitro culture techniques. J Bangladesh Agril Univ 22(2):178-184, 2024

Somatic epigenetic drift during shoot branching: a cell lineage-based model.

Plant architecture is shaped by the production of new organs, most of which emerge postembryonically. This process includes the formation of new lateral branches along existing shoots. Current evidence supports a detached-meristem model as the cellular basis of lateral shoot initiation. In this model, a small number of undifferentiated cells are sampled from the periphery of the shoot apical meristem (SAM) to act as precursors for axillary buds, which eventually develop into new shoots. Repeated branching thus creates cellular bottlenecks (i.e. somatic drift) that affect how de novo (epi)genetic mutations propagate through the plant body during development. Somatic drift could be particularly relevant for stochastic DNA methylation gains and losses (i.e. spontaneous epimutations), as they have been shown to arise rapidly with each cell division. Here, we formalize a special case of the detached-meristem model, where precursor cells are randomly sampled from the SAM periphery in a way that maximizes cell lineage independence. We show that somatic drift during repeated branching gives rise to a mixture of cellular phylogenies within the SAM over time. This process is dependent on the number of branch points, the strength of drift as well as the epimutation rate. Our model predicts that cell-to-cell DNA methylation heterogeneity in the SAM converges to nonzero states during development, suggesting that epigenetic variation is an inherent property of the SAM cell population. Our insights have direct implications for empirical studies of somatic (epi)genomic diversity in long-lived perennial and clonal species using bulk or single-cell sequencing approaches.

In vitro mass propagation of Dendrocalamus asper (Giant bamboo) through direct organogenesis

Dendrocalamus asper (giant bamboo) is a clumping type of bamboo belonging to the Poaceae family. Due to its economic and environmental value, demand for this species has increased tremendously. Conventional propagation methods have limitations due to low seed viability and the lack of healthy clumps. Therefore, an in vitro mass propagation protocol was developed to provide healthy plants for large-scale plantations. Seeds were used as the explant and they were surface sterilized and cultured on MS medium free of growth regulators. Nodal segments taken from in vitro germinated seedlings were used for shoot initiation. The best medium for shoot induction (MS medium supplemented with 0.0–2.5 mg/L BAP), best medium for multiple shoot induction (MS medium supplemented with 0.0–5.0 mg/L BAP), effect of shoot cluster size (shoot clusters containing 1–4 shoots) and effect of physical state of the medium (semisolid and liquid media) on multiple shoot induction were determined using shoots per node, mean shoot length and mean number of leaves per shoot after 6 weeks of incubation. Elongated shoots were transferred into a rooting medium and the best medium for root induction (MS medium supplemented with 0.0–5.0 mg/L IBA and IAA) and effect of cluster size (shoot clusters containing 1–4 shoots) on rooting were determined using the number of roots and root length after 6 weeks of incubation. All the cultures were maintained under a 16-hour photoperiod. Well-developed plantlets were transferred to coir pellets and after four weeks transferred into different potting mixtures containing different combinations of sand, compost and coir dust. Unless otherwise mentioned there were at least twenty replicates in all treatments. The highest mean number of shoots per node (16.87±0.52), mean shoot length (4.12±0.27 cm) and mean number of leaves per shoot (4.80±0.33) were observed in the MS medium supplemented with 1.0 mg/L BAP. The MS medium supplemented with 2.0 mg/L BAP was the best for multiple shoot induction, shoot cluster with 3 shoots was the best cluster size and the liquid medium had a better effect on shoot multiplication. The half-strength MS medium supplemented with 2.0 mg/L IBA was the best for in vitro root induction with the highest mean number of roots (7.15±0.77) and a mean root length of 10.79±1.11 cm. Shoot clusters with 3 shoots was the best cluster size for root induction. A sand: compost: coir dust (1:1:1) mixture was the best potting mixture giving 100% survival. These findings provide a reliable micropropagation protocol for D. asper, which holds great promise for meeting the growing demand for bamboo resources and promoting sustainable bamboo cultivation.

In vitro Propagation of Singgalang Cabbage (Brassica oleracea var. capitata L.) on Murashige and Skoog Modification Media for Preservation Purpose

Singgalang Cabbage is one of the local cabbage cultivated on the foothills of Mount Singgalang, West Sumatra. Recently, the existence of this cabbage has decreased, so conservation and preservation efforts need to be carried out. This research was conducted to develop method for in vitro propagation and preservation of singgalang cabbage. The Murashige and Skoog (MS) were used as basal media with two experimental stages, i.e., shoot initiation with 6-Benzylaminopurine (BAP), and root induction and plantlet preservation with modification of MS media. The nodal and shoots were used as explants. The results showed that increment of BAP concentrations gave a significant effect on shoot initiation after 60 days of treatment. MS media-enriched with BAP 2 mg/L gave significant increment of shoots (4 shoots/nodus) and leaves (11.67) numbers when compared to other treatments. For root induction and plantlet preservation, it was found that the earlier of root formation was observed in modification of MS media at ½ and ¼ strength. Meanwhile, MS media at ⅛ strength was observed to be better media for plant height increment (4.75 cm) when compared to other treatments. It was found that the plantlets survived and grew well after 120 days under in vitro condition.

Advancements in Mutation Breeding in Phalsa (Grewia asiatica L.) Crop Improvement: A Comprehensive Review of Radiation and Chemical Induced Mutagenesis Studies

Phalsa (Grewia asiatica L.), a member of the Tiliaceae family, is a remarkable fruit-bearing shrub with significant medicinal and nutritional value. Originating in South Asia, it has gained popularity worldwide, particularly in subtropical and tropical regions. This review comprehensively examines the botanical characteristics, medicinal properties, nutritional composition, cultivation practices, and challenges faced by Phalsa growers, with a focus on its potential for crop improvement through mutagenesis and polyploidization techniques. With around 150 species, Grewia is the sole genus in the Tiliaceae family that produces edible fruit. Phalsa bushes, known for their rapid growth, yield orbicular fruits with moderately acidic yet nutritious pulp. The fruit is esteemed for its medicinal benefits, ranging from anti-inflammatory and anti-diabetic properties to its use in treating various respiratory and cardiovascular ailments. Despite its nutritional and medicinal significance, Phalsa cultivation faces challenges such as poor post-harvest management, limited germplasm diversity, and abiotic stress susceptibility. To address these challenges and enhance Phalsa's agricultural potential, mutagenesis and polyploidization techniques have been explored. Induced mutagenesis offers a promising avenue for creating genetic diversity and improving traits such as stress tolerance and disease resistance. However, culture contamination remains a significant obstacle in achieving optimal shoot initiation and propagation efficiency. Overall, this review underscores the importance of Phalsa as a valuable crop with immense medicinal and nutritional benefits. By leveraging mutagenesis, polyploidization, and tissue culture techniques, Phalsa growers can overcome existing challenges and unlock its full agricultural potential, contributing to food security and public health.

Effect of Different Concentrations of Auxin as Well as Cytokinin on Shoot Initiation, Formation and Multiplication of Pepino (Solanum muricatum Ait.) cv. Valentia with MS Semi-solid Medium

The pepino (Solanum muricatum Aiton) is conventionally propagated through vegetative means. But, this approach of propagation is not feasible for commercial production of plants and has at more time the chances of reduction yield. Therefore, the availability of quality planting material is of urgent need. Recently, there has been a promising approach for pepino multiplication at large scales through tissue culture because it generates a large number of contamination free plantlets in a minimum space and time. The combination of different growth regulators may be tried to maximize the initiation, growth and development of shoot in commercial propagation of pepino plants. The Minimum days taken for shoot initiation (5.21 days) was noted under BAP 3.00 mgl-1 + IBA 0.50 ppm, and minimum days taken for shoot development (40.82 days) was noted under of BAP 3.00 ppm + IBA 1.00 ppm. The highest length of shoot (9.52 cm) was produced in media supplemented with BAP 3.00 ppm + IBA 1.00 ppm. Maximum percent of developed shoots obtained from the established culture (67.79) was noted under the treatment of BAP 3.00 ppm + IBA 1.00 ppm; While maximum shoots per explants/ innoculums from the established culture (4.06) was noted under the treatment of BAP 3.00 ppm + IBA 1.00 ppm. Maximum number of leaves / plantlet from the established culture (10.85) was noted under the treatment of BAP 3.00 ppm + IBA 1.00 ppm and maximum fresh weight (mg) of shoot / plantlet obtained from the established culture (26.05 mg) was noted under the treatment of BAP 3.00 ppm + IBA 1.00 ppm.

Maximizing Zygopetalum maculatum orchid yield through calcium nutrition: Unveiling calcium content and dynamics across different plant parts at different growth stages of the orchid

This study explores the pivotal yet often overlooked role of calcium (Ca) in Zygopetalum maculatum orchid cultivation. Six different treatments, featuring graded doses of Ca (ranging from 0 to 100 mg Ca L−1 nutrient solution), were used to assess the impact of Ca on growth, development, and physiological responses of the orchids. Notably, the Ca untreated control treatment (Ca0) exhibited a rapid decline in potting media pH (became acidic in reaction with time), whereas under Ca100 treatment potting media pH declined slowly and remained near neutral. Dehydrogenase activity in the potting media significantly increased under Ca100 treatment. Significant improvements in vegetative growth parameters, like, bulb length, bulb width, and leaf characteristics, were evident under Ca100 treatment compared to the Ca0 treatment. The economic yield, measured by the number of flower spikes and various floral attributes (i.e. number of florets per spike, spike length, florets size), displayed a remarkable enhancement under Ca100 treatment. The Ca100 treatment produced 100 % more number of flower spikes as compared to Ca0 treatment. The number of new shoot initiation, and overall flower biomass also substantially increased under Ca100 treatment. Ca content analysis in different plant parts revealed presence of elevated Ca concentrations in leaves, back bulbs, new bulbs, and roots under Ca100 treatment. The Ca content in back bulbs and roots decreased after flowering phase of the orchid, but the Ca levels in leaves and new bulbs remained statistically similar during both pre and post-flowering phases.These findings underscore the positive influence of Ca application on Zygopetalum maculatum orchids for enhancing its vegetative growth and economic yield. The study contributes valuable insights into Ca dynamics in different plant parts of the orchid, and recommends a 100 mg L−1 Ca application at 7-day intervals for improving Zygopetalum maculatum cultivation practices.

Rapid multiplication of Zingiber cassumunar using axillary bud explant

An in vitro regeneration system was standardized on a traditional medicinal plant of Zingiber cassumunar. The rhizome axillary buds upon transfer to MS basal medium with benzyl adenine (3mg/l) found optimum exhibiting maximum percent of shoot initiation as 92.5 ± 0.6, thereby maximum number of shoots as 6.8 ± 0.3 and maximum number of roots as 22.0 ± 0.4 were found in benzyl adenine (3mg/l) and indole acetic acid (0.5mg/l) combination. The micropropagated plants were transferred to field for successful establishment as 90% respectively. Furthermore, the morphological characteristic analysis was done between the conventional and micropropagated plants which showed very less significant variation. The present protocol reports the propagation of Z. cassumunar plantlets which could be used for commercial exploitation in future.

In vitro regeneration of exotic fruit dragon (Hylocereus undatus) from stem fraction

Hylocereus undatus, commonly known as dragon fruit, is one of the most popular exotic fruits due to its high quality and market value. This fruit is facing different constraints, such as loss of seed viability and various diseases that affect production because the seed and cutting methods are followed to create a new generation. In vitro plant regeneration is a promising technique to overcome these barriers with explants. An efficiency of this protocol was established in dragon fruit using MS + 2.0 mg/L BA + 2.0 mg/L Kin. with explants, stem fraction. Eighty percent explants were responded for shoot initiation treated with 2.0 mg/L BAP in combination with 2 mg/L Kin. The highest number of shoots and the maximum shoot lengths were observed in this medium inoculation after 90 days. Shoots were transferred to media containing ½ strength of MS with root induced PGRs. Ninety percent of the in vitro raised shoots were responded for rooting treated with 2.5 mg/L IBA inoculation after 30 days. The highest number of roots and the maximum root lengths were recorded at 2.5 mg/L IBA. The response of inoculated explants or in vitro raised shoots were positively correlated with the number of shoots and roots respectively. The average shoot and root lengths were negatively correlated with each other resulting in root lengths increasing by decrease of shoot lengths. The healthy shoots with well rooted plantlets were transferred to natural condition where about 80% plantlets were found to be acclimatized.

Rapid In Vitro Regeneration and Genetic Fidelity Assessment of Regenerated Plants in Ayapana Triplinervis (Vahl) R.M. King & H. Robinson: An Ethnomedicinal and Ornamental Herb

Background: Ayapana triplinervis is a popular ethnomedicinal and ornamental plant species. Due to its high medicinal importance, A. triplinervis was recently documented in the French Pharmacopeia. Objective: Rapid and efficient tissue culture protocol development is crucial for the high production and biotechnological applications of this plant. Methods: In this study, an efficient tissue culture protocol was developed for plant regeneration using nodal explants of A. triplinervis. The nodal explants were treated in Murashige and Skoog’s (MS) medium supplemented with various individual concentrations of cytokinins (BAP and KIN) and auxins (IAA and IBA). The nodal explant was regenerated in three different steps: (1) initial shoot induction, (2) shoot multiplication and elongation, and (3) rooting. Results: The results revealed that all individual concentrations (10, 20, 30, or 40 mg/L) of BAP or KIN responded to induce shoot initiation. The highest shoot multiplication and elongation were achieved in the MS medium with 20 mg/L BAP and 20 mg/L KIN. The regenerated plantlets produced better roots on MS medium containing 1.0 mg/L of each IAA or IBA. The well-established rooted plantlets were maintained in the culture room and greenhouse for better acclimatization and achieved a 100% survival rate. We analyzed the genetic fidelity of in vitro regenerated plants using random amplified polymorphic DNA (RAPD) markers. No genetic polymorphisms were observed in vitro plants compared to the mother plants. Conclusion: This efficient protocol could benefit future biotechnological applications like mass multiplication, genetic transformation and gene editing for improving the bioactive molecules in A. triplinervis.

Effect of different plant growth regulators on shoot initiation of banana varieties

Effect of different plant growth regulators on shoot initiation of banana varieties

Callus Induction Followed by Regeneration and Hairy Root Induction in Common Buckwheat.

This section describes a set of methods for callus induction followed by the successful regeneration of whole plants and obtaining a culture of transgenic hairy roots from buckwheat plants (Fagopyrum esculentum Moench.). Callus induction and regeneration are key steps for many biotechnological, genetic, and breeding approaches, such as genetic modification, production of biologically active compounds, and propagation of valuable germplasm. Induction of hairy roots using Agrobacterium rhizogenes is also an important tool for functional gene research and plant genome modification. While many efforts were invested into the development of the corresponding protocols, they are not equally efficient for different cultivars. Here, we have tested and optimized the protocols of callus induction, regeneration, and transformation using A. rhizogenes for a set of cultivars of F. esculentum, including wild ancestor of cultivated buckwheat F. esculentum ssp. ancestrale and a self-pollinated accession KK8. The optimal medium for callus induction is Murashige-Skoog basal medium with 3% sucrose which includes hormones 2,4-dichlorophenoxyacetic acid 2mg/L and kinetin 2mg/L; for shoot initiation 6-benzylaminopurine 2mg/L, kinetin 0.2mg/L, and indole-3-acetic acid 0.2mg/L; for shoot multiplication 6-benzylaminopurine 3mg/L and indole-3-acetic acid 0.2mg/L; and for root initiation half-strength Murashige-Skoog medium with 1.5% sucrose and indole-3-butyric acid 1mg/L. A. rhizogenes R1000 strain proved to be the most efficient in inducing hairy roots in buckwheat and T-DNA transfer from binary vectors. Seedling explants cut at the root area and immersed in agrobacterium suspension, as well as prickling the cotyledonary area with agrobacteria dipped syringe needle, are the most labor-effective methods of infection, allowing to initiate hairy root growth in 100% of explants.

In Vitro Seed Germination and Seedling Development of Mimusops laurifolia (Forssk.) Friis.: An Endangered Plant Species

Mimusops laurifolia (Forssk.) Friis is an endangered medicinal plant and natural propagation of this plant through seeds is found to be very difficult due to its hard seed coat. To conquer this problem, an efficient in vitro seed germination as well as subsequent in vitro regeneration technique has been developed in conserving this endangered plant species. Seed germination was achieved on half strength of MS (HMS), full strength MS (FMS) and MS medium supplemented with different concentration and combination of Plant Growth Regulators (PGR) like BA, Kn and GA. The highest seed germination rate (18%) was obtained from water soaking de-coated seeds inoculated on full strength of MS (FMS), on the other hand, 12% germination of seeds was recorded on HMS medium, but both the conditions required more than 90 days to germinate. A similar rate of germination was also found on MS with PGRs, but it required 55-60 days. Best responses towards seed germination with elongated shoots (2.8 cm and 3.0 cm) were obtained when seeds were inoculated on MS with 3.0 mg/l BA, 0.5 mg/l Kn and 0.2 mg/l GA. After a long period of period of 8 months following germination, seedlings produced elongated tap roots only. Rooted seedlings were successfully transferred to soil for their further growth and development. Apart from this, for in vitro regeneration of shoots, explants of nodal segments and shoot tips from the natural plant were cultured on woody plant medium (WPM) supplemented with various combination and concentration of BAP, Kn and TDZ. In these cases, there was no positive response recorded towards the initiation of shoots from nodal segment and shoot tips. Plant Tissue Cult. & Biotech. 33(2): 143-153, 2023 (December)

A low carbon balance triggers Microvine inflorescence abscission at high temperatures

IntroductionGlobal warming is a major threat to yield sustainability in most crops, including grapevine. Whether or not grapevine fruitfulness is impaired by an imbalance between carbon supply and demand caused by high temperatures was investigated in the present study.MethodsFive experiments were conducted on Microvine, a natural mutant of grapevine that is insensitive to gibberellins, presents with a dwarf stature, and has continuous flowering along the vegetative axes. The last property was used to infer temporal patterns of inflorescence development from their spatial distribution at harvest. Two sets of plants, characterized by low or high levels of initial shoot vigor, were grown under contrasting day and night temperatures: 22°C/12°C and 30°C/20°C.Results and discussionThe rate of leaf development of the main shoot was stable, regardless of the initial vigor and temperature treatment. In contrast, the warm temperatures delayed the timing of flowering for low-vigor plants or the onset of ripening for high-vigor plants. Fruitfulness was impaired by high temperatures as a result of the abscission of young inflorescences (before the flowering stage). From a careful spatiotemporal analysis of cluster abscission, we concluded that inflorescence drop under elevated temperatures was triggered by the increase in plant carbon demand due to the oldest clusters starting to unload sugars. Elevated temperatures may have also lowered the carbohydrate supply in the zone of inflorescence abscission due to the higher leaf respiration while all organ growth demand was maintained. Interestingly, inflorescence abscission occurred earlier when whole-plant vigor was low and was followed by a recovery period, in spite of a lower non-structural sugar status than in high-vigor plants. Taken together, our results suggest that inflorescence abscission is linked to the variations of the carbon pool induced by changes in temperature and not to its absolute value. Our study, therefore, provides new hypotheses about the impacts of warm temperatures on the regulation of temperature-induced reproductive failure in grapevine.

Effect of Growth Regulators on the Quality of Apple Tree Whorls

High-quality nursery stock ensures the dynamic development of orchard crops. The most desirable by orchardists is a tree with a strongly developed crown, which makes it possible to shorten the investment period of newly planted orchards. The quality of the perianth and the degree of its branching depend on the growth strength of the rootstock, the ability of a given variety to form lateral shoots, the type and effectiveness of the treatments used to stimulate branching, soil and climatic conditions related to the location of the nursery and the course of the weather during the period of initiation and growth of young shoots. The study was conducted in 2017–2019 at a private nursery farm near Lublin. The aim of the experiment was to study the effect of mixtures based on the compounds benzyladenine (BA) and gibberellins (GA3) and (GA4+7) for chemical stimulation of lateral shoot outgrowth in apple cv. ‘Alwa’ and ‘Najdared’. In the course of the research, significant effects of the type of growth regulations used and the variety on the height of the perianths, the number and length of lateral shoots and the degree of branching were demonstrated.

Establishment of An in Vitro Mass Propagation System for Dendrocalamus asper.

Dendrocalamus asper is a species of bamboo that has high commercial value and is the bamboo of choice for large scale agro-forestry plantations in the tropical regions of the world. Micropropagation using tissue culture is essential to generate uniform clones that are amenable to establishment in industrial agro-forestry projects for bamboo biomass, habitat restoration or in carbon sequestration. This paper reports on the establishment of D. asper invitro using commercially available seeds. The seeds were surface sterilized using three different chemical agents which were Sodium Hypochlorite (20%), Mercuric Chloride (0.1%) and Ethanol (70%) followed by shoot initiation on Murashige and Skoog (MS) medium supplemented with 6-Benzylaminopurine (BAP) with a concentration ranging from 1.0 - 5.0 mg/L. Propagules were multiplied on MS media supplemented with different concentration of IBA Indole-3-Butyric Acid (IBA) and Naphthalene Acetic Acid (NAA), and finally rooted and hardened in peat moss. The findings of our study indicate that the sterilization protocol eliminated all the plant pathogens, resulting in an axenic culture. Full strength MS medium supplemented with 5 mg/L BAP yielded the highest number of shoots (11.46 per explant) after four weeks of inoculation. The highest multiplication rate (3.95 shoots per explant) was obtained on MS medium supplemented with 3 mg/L BAP. The time required from initiation to hardening was 70 to 90 days, following which the plantlets were ready for field trials. The findings of this study will facilitate the establishment of plant tissue culture programmes dedicated to the production of D. asper locally, thus eliminating the need for imports and the possible entry of plant pathogens that can be detrimental to the local agro-forestry industry.