Cytokinin Type Research Articles

Hyperhydricity-induced changes among in vitro regenerants of gerbera

Gerbera (Gerbera jamesonii Bolus) ranks amid the top five commercially preferred cut-flowers in global floriculture industry. Conventionally, gerbera is propagated by seed or by vegetative approaches. However, in vitro propagation cropped up as a better alternative with high commercial success since past two decades. Simultaneously, hyperhydricity of shoots has become a matter of serious concern during in vitro propagation. For the first time in gerbera, the present study highlights the morphometrical and physiological changes in hyperhydric shoots developed in high cytokinin-supplemented media. Four concentrations (2.5, 5, 7.5 and 10 mg L − 1) of kinetin and N6-benzylaminopurine (BAP) were tested individually in supplementation with Murashige and Skoog basal medium. It was found that occurrence of hyperhydricity was significantly influenced by the type and concentrations of cytokinins used. Nevertheless, gradually increasing hyperhydricity along with significantly poorer multiplication were observed with the increasing concentrations of BAP and kinetin compared to its lower levels. Majority of explants in the presence of high levels (> 5 mg L − 1) of kinetin or BAP became hyperhydric, losing their capability to regenerate. Hyperhydric plantlets exhibited lower chlorophyll and higher relative water content, resulting in glassy appearance of leaves and shoots with pale or yellowish green color accompanied with inward folding of the leaf blade towards the midrib. The roots of hyperhydric plantlets were thinner, shorter and fewer in number. Hyperhydricity further resulted in delayed development of plantlets as well as lower frequency and size of stomata.

The Effects of Different Cytokinin Types and Their Concentration on in Vitro Growth of Apricot (Prunus armeniaca L.) Shoots

The objective of this study was to assess the effects of different cytokinin types [(6-benzylaminopurine (BAP), thidiazuron (TDZ) and meta-topolin (mT)] and their concentration on in vitro growth of apricot shoots. Sufficiently developed shoots were transferred to different multiplication media, which differed regarding the presence of cytokinin and its concentration. The subcultivation period lasted nine weeks. Analysis of covariance (ANCOVA) was performed to investigate the influence of plant growth regulators and their concentration on the final shoot weight of obtained tissue per regenerating explant. The results showed that all three cytokinins had a positive effect on shoot growth. There was a significant difference between used concentrations in the case of TDZ and BAP, while in the case of mT, the concentration did not significantly affect shoots’ regeneration. In our study, the most significant increase in shoots weight was obtained on medium supplemented with 1.0 mg/L BAP.

Topolin cytokinins enhanced shoot proliferation, reduced hyperhydricity and altered cytokinin metabolism in Pistacia vera L. seedling explants

The effect of 10 µM meta-topolin (mT) and meta-topolin riboside (mTR) on in vitro proliferation and anomalies of Pistacia vera L. were evaluated and compared to that of 6-benzylaminopurine (BA). The highest proliferation rate (15.6) was recorded in the mT-medium, with a value 6 times higher than in BA-medium. Moreover, the lowest percentage of hyperhydric usable shoots (58,9%) and callus weight (46,9%) were found in mTR-treated shoots. Shoot tip as well as leaf necrosis were not influenced by cytokinin (CK) type. Image analysis was used to evaluate photosynthetic efficiency as well as anthocyanin index. Photosynthesis was more efficient with BA and mTR but the higher anthocyanin accumulation in BA-treated shoots suggests more stress. Endogenous CKs and their metabolites were determined in seedlings and, for the first time, the metabolism of exogenous BA, mT and mTR was studied in pistachio. The stimulating effect on cis-zeatin and its riboside and the appearance of BA and traces of ortho-topolin and para-topolin as natural CKs are discussed. The quantitative and qualitative CK metabolite analyses provides some initial clues as to why topolin would be superior to BA in terms of proliferation rate and avoiding hyperhydricity and allowed a better understanding of the effect of exogenous administration of CK.

Evaluation of the role of different types of cytokinins as zeatin replacement in in vitro proliferation of Vaccinium dunalianum

Evaluation of the role of different types of cytokinins as zeatin replacement in in vitro proliferation of Vaccinium dunalianum

Review of In Vitro Flowering Method for Tomato (Solanum Lycopersicum L.)

Tomatoes are one of the most popular vegetable plants globally because of the many benefts that can be obtained from tomatoes. However, its availability is still insuffcient for market demand. Therefore, researchers began to develop tissue culture methods to cope with market demand. Although there have been several studies on tomato flowering in vitro, information about this method is minimal and needs further development. In vitro flowering is a technique in tissue culture for flowering plants in vitro. One of the benefts is cultivating plants in a relatively short time under controlled conditions to prevent disease transmission between plants. Therefore, we conducted a literature study to compare the results of these studies to know an effective and efcient method of factors that increase the in vitro flowering plants of tomatoes. In vitro flowering methods generally focus on flowering media, especially cytokinin types such as 6-Benzylaminopurine (BAP) and kinetin, and the concentration of those hormones, also light intensity used to induce flowering of tomato plants. Factors that affect in vitro flowering of tomato plants are tomato plant varieties, hormones, and light intensity.

Antioxidative Defense System, Hormones, and Metabolite Accumulation in Different Plant Parts of Two Contrasting Rice Cultivars as Influenced by Plant Growth Regulators Under Heat Stress.

We examined the metabolic, hormonal, enzymatic, and non-enzymatic responses of various plant components (leaf, root, and xylem sap) to plant growth regulators [methyl jasmonate (MeJA), ascorbic acid (Vc), brassinosteroids (Br), triazoles (Tr), alpha-tocopherol (Ve), and control] under heat stress [ambient temperature (AT), heat stress at night time (HNT), and heat stress at day (HDT)] in heat-sensitive (IR-64) and heat-tolerant (Huanghuazhan) rice cultivars under greenhouse conditions. Our results showed that heat stress altered the antioxidant activities and hormonal balance and rigorously reduced total soluble sugars, proteins, and proline, whereas increases were observed in H2O2 and Malondialdehyde (MDA) content accumulation in the plant xylem sap and leaves of both tested cultivars; however, the impact was more pronounced in IR-64. The superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), Glutathione (GSH), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR) activities were higher in Huanghuazhan than in IR-64 in response to temperature stress, when compared to AT. Additionally, heat stress increased abscisic acid (ABA) levels in both rice cultivars, especially in IR-64. The highest concentrations of hormones were recorded in the roots, followed by the leaves and xylem sap, in both cultivars. HDT and HNT stresses severely reduced the concentrations of all of the cytokinin types (except for iP9G and tZ9G) and IAA in the different plant parts of rice cultivars. Moreover, HNT was more detrimental for hormone and metabolite synthesis in both cultivars. The growth regulators (especially Vc + Br + Ve + MeJA) were comparatively more effective in minimizing the hostile impact of heat stress on most of the studied traits and should be applied to obtain the optimum yield of rice in subtropical and tropical areas under changing climatic conditions.

Micropropagation of pokeweed (Phytolacca americana L.) and comparison of phenolic, flavonoid content, and antioxidant activity between pokeweed callus and other parts.

BackgroundPokeweed (Phytolacca americana L.) is regarded as an invasive plant in many parts of the world but possesses therapeutic characteristics used for antitumor and rheumatism treatment. This study investigated the effects of auxins and four explants on pokeweed callus induction. The effects of cytokinins and combinations between cytokinins and NAA on shoot and root induction were also studied. TPC, TFC and antioxidant activity of calli were screened and compared with other pokeweed plant parts.MethodsFour explants were used to induce callus using 2,4-D and IBA at 1, 2, 3 and 4 mg/l for each auxin. Direct shoot organogenesis from nodal explants was investigated using BAP, kinetin and TDZ (1, 2 and 4 mg/l for each cytokinin). Combined effects between cytokinins and NAA at 0.1, 0.2 and 0.3 mg/l were further simultaneously estimated with root induction. Calli derived from the leaves were compared with other plant parts for TPC, TFC and antioxidant activity using the Folin-Ciocalteu, AlCl3 colorimetric assay and DPPH assays, respectively.ResultsResults showed that MS medium containing 2 mg/l 2,4-D induced callus formation on leaf explants that provided highest fresh and dry weights. Three types of synthetic cytokinins as kinetin, TDZ and BAP were used for direct shoot organogenesis from pokeweed nodes. MS medium containing 2 mg/l kinetin was effective in stimulating normal shoots, with the largest number of shoots and leaves and the longest shoots. The combination between cytokinins and NAA showed no positive effect on shoot and root induction from pokeweed nodal explants. For TPC and TFC determination, pokeweed seeds and leaves possessed the highest phenolic and flavonoid contents, respectively. Highest phenolic content of pokeweed seeds led to lowest IC50 by DPPH assay. Phenolic content was higher than flavonoid content.ConclusionResults suggested promising conditions for callus induction. Leaf explants cultured on MS medium with 2 mg/l 2,4-D and nodal explants cultured on MS medium with 2 mg/l kinetin provided the largest number of normal shoots and leaves. NAA did not show positive effects on shoot and root induction when combined with cytokinins. Chemical constituent screening indicated that seeds and leaves provided highest TPC and TFC, respectively, while pokeweed calli contained higher phenolic than flavonoid content. This is the first report describing chemical constituent screening and antioxidant activity of calli and other parts of the pokeweed plant. Results provided significant information to further enhance bioactive compound contents of pokeweed calli using elicitation methods.

Root-specific Reduction of Cytokinin Perception Enhances Shoot Growth in Arabidopsis thaliana.

Previous studies suggest that root-derived cytokinins (CKs) contribute to shoot growth via long-distance transport; therefore, we hypothesized that an increase in root-derived CKs enhances shoot growth. To verify this, we grafted Arabidopsis Col-0 (wild type, WT) scion onto rootstock originated from WT or a double-knockout mutant of CK receptors Arabidopsis histidine kinase 2 (AHK2) and AHK3 (ahk2-5 ahk3-7; ahk23) because this mutant overaccumulates CKs in the body probably due to feedback homeostasis regulation. The grafted plants (scion/rootstock: WT/WT and WT/ahk23) were grown in vermiculite pots or solid media for vegetative growth and biochemical analysis. The root-specific deficiency of AHK2 and AHK3 increased root concentrations of trans-zeatin (tZ)-type and N6-(Δ2-isopentenyl) adenine (iP)-type CKs, induced CK biosynthesis genes and repressed CK degradation genes in the root. The WT/ahk23 plants had significantly larger shoot weight, rosette diameter and leaves area than did the WT/WT plants. Shoot concentrations of tZ-type CKs showed increasing trends in the WT/ahk23 plants. Moreover, the root-specific deficiency of AHK2 and AHK3 enhanced shoot growth in the WT scion more strongly than in the ahk23 scion, suggesting that shoot growth enhancement could occur through increased shoot perception of CKs. In the WT/ahk23 shoots compared with the WT/WT shoots, however, induction of most of CK-inducible response regulator genes was not statistically significant. Thus we suggest that the root-specific reduction of CK perception enhances shoot growth only partly by increasing the amount of root-derived tZ-type CKs and their perception by shoots. The unknown mechanism(s) distinct from CK signaling would also be involved in the shoot growth enhancement.

Cyclanilide Induces Lateral Bud Outgrowth by Modulating Cytokinin Biosynthesis and Signalling Pathways in Apple Identified via Transcriptome Analysis.

Cyclanilide (CYC), a plant growth regulator, is a potent shoot branching agent in apple. However, its mechanism remains unclear. The current study revealed that CYC treatment resulted in massive reprogramming of the axillary bud transcriptome, implicating several hormones in the response. We observed a marked increase (approximately 2-fold) in the level of zeatin riboside and a significant decrease (approximately 2-fold) in the level of abscisic acid (ABA). Zeatin metabolism gene cytokinin (CTK) oxidase 1 (CKX 1) was down-regulated at 168 h after CYC treatment compared with the control. Weighted gene co-expression network analysis of differentially expressed genes demonstrated the turquoise module clusters exhibited the highest positive correlation with zeatin riboside (r = 0.92) and the highest negative correlation with ABA (r = −0.8). A total of 37 genes were significantly enriched in the plant hormone signal transduction pathway in the turquoise module. Among them, the expressions of CTK receptor genes WOODEN LEG and the CTK type-A response regulators genes ARR3 and ARR9 were up-regulated. ABA signal response genes protein phosphatase 2C genes ABI2 and ABI5 were down-regulated in lateral buds after CYC treatment at 168 h. In addition, exogenous application of 6-benzylaminopurine (6-BA, a synthetic type of CTK) and CYC enhanced the inducing effect of CYC, whereas exogenous application of lovastatin (a synthetic type of inhibitor of CTK biosynthesis) or ABA and CYC weakened the promoting effect of CYC. These results collectively revealed that the stimulation of bud growth by CYC might involve CTK biosynthesis and signalling, including genes CKX1 and ARR3/9, which provided a direction for further study of the branching promoting mechanism of CYC.

Reduction of Early Fruit Abscission by Main-branch-girdling in Macadamia Is Related to the Favorable Status of Carbohydrates and Endogenous Hormones

Fruit abscission occurring severely in the early fruit development affects macadamia yield. Developing effective methods to improve fruit retention is a priority for macadamia cultivation and production. Girdling is an important horticultural practice that has been widely used to increase fruit yield. Previous studies have shown that girdling fails to increase macadamia yield despite enhancing the early fruit set, but few have examined the effect of girdling on its related physiological mechanism. The objective of this study was to investigate the effects of main-branch girdling (MBG) on early fruit retention and also on the levels of carbohydrates and endogenous hormones in the leaves, bearing shoots and fruit of macadamia. Herein, MBG was performed at fruit set using a single-blade knife on 9-year-old macadamia trees (Macadamia integrifolia). Results showed that MBG significantly reduced young fruit drop, concurrent with significant increases in the contents of starch in both the leaves and the bearing shoots and in glucose, fructose, and sucrose levels in the husk and seed. It was suggested that the availability of carbohydrate for fruit retention was improved by MBG. Additionally, MBG increased indole-3-acetic acid (IAA), gibberellin (GA3), and zeatin-riboside (ZR, a type of cytokinin) concentrations and decreased abscisic acid (ABA) contents in the husk and the seed, indicating that MBG reduced the early fruit drop by modifying the balance of endogenous hormones. Therefore, a positive interplay between carbohydrates and endogenous hormones induced by MBG was involved in the reduction of early fruit abscission in macadamia.

Meta-Topolin mediated improved micropropagation, foliar micro-morphological traits, biochemical profiling, and assessment of genetic fidelity in Santalum album L.

An improved in vitro propagation system has been developed for Santalum album L. using meta-Topolin for the first time. Direct organogenesis (100 %) was achieved by induction of axillary buds and a maximum of 8.2 shoots with 4.0 cm length was developed from nodal explants on Murashige and Skoog’s (MS) medium containing 1.0 mg L−1 meta-Topolin (mT). The MS medium supplemented with 0.5 mg L-1 mT and 0.25 mg L−1 α-naphthalene acetic acid (NAA) exhibited maximum shoot proliferation potential (135 shoots with 7.9 cm length per explant) after the 3rd subculture. Further, the combination of mT and NAA resulted in the production of higher levels of free amino acids [33.6 mg g-1 dry weight (DW)], soluble sugar (37.4 mg g-1 DW), and reducing sugar (45.0 mg g-1 DW) in the leaves than the BAP and NAA combinations. The efficiency of mT has also been highlighted in the foliar structural developments. Comparative anatomy of leaves showed the presence of structural variations influenced by the type of cytokinins used. BAP and NAA-derived leaves revealed the presence of under-developed cuticle, unorganized tissue systems, undifferentiated mesophyll tissues, and under-developed mechanical and vascular tissues. Whereas, mT and NAA-derived leaves exhibited comparatively thick cuticle, collenchymatous hypodermis, well-differentiated mesophylls, and increased vascular elements. Roots were induced ex vitro under the greenhouse conditions when the shoot-bases were treated with 500 mg L−1 indole-3-butyric acid (IBA) for 10 min. These plantlets were hardened in soilrite® and cocopeat (1:1) mixture and a 100 % survival rate was achieved in the field. Additionally, the Start codon targeted (SCoT) markers analysis demonstrated that the genetic homogeneity was maintained during in vitro development of plantlets. The application of mT can be an effective growth regulator for in vitro propagation of S. album, as it favoured enhanced and quick production of genetically uniform clones.

Effects of kinetin on arsenic speciation and antioxidative enzymes in fronds of the arsenic hyperaccumulator Pteris cretica var. nervosa and non-hyperaccumulator Pteris ensiformis

Cytokinins (CTKs) enhance plant tolerance to heavy metals, but the associated mechanisms are not yet fully understood. Here, we investigated the effects of kinetin (KT, a type of CTKs) on arsenic (As) speciation and antioxidative enzymes in plant fronds, by comparing Pteris cretica var. nervosa (As hyperaccumulator) and Pteris ensiformis (non-hyperaccumulator). A hydroponic test was carried out and the two plant species were treated with 2 mg L−1 arsenite [As(III)], arsenate [As(V)] or dimethylarsinate (DMA), and then 0–1.0 mg L−1 KT was exogenously applied for 14 days. The maximum As uptake of the two experimental plants was 0.5 mg L−1 KT. Fresh plant biomass was also significantly increased, except in P. cretica var. nervosa under DMA stress. The frond superoxide dismutase (SOD) and catalase (CAT) activity in the two plant species was significantly increased by 0.5 mg L−1 KT. Additionally, a significant decline in frond peroxidase (POD) activity was observed in P. ensiformis at 1.0 mg L−1 KT under As(III) stress. However, POD activity was significantly increased in P. cretica var. nervosa, at 0.1 mg L−1 KT, under As(III) or DMA stress, and at 1.0 mg L−1 KT, under As(V) stress. Therefore, KT promoted As transport and increased frond POD activity in P. cretica var. nervosa, which contributed to its As tolerance under stress from different As species.

Beyond transport: cytokinin ribosides are translocated and active in regulating the development and environmental responses of plants.

Riboside type cytokinins are key components in cytokinin metabolism, transport, and sensitivity, making them important functional signals in plant growth and development and environmental stress responses. Cytokinin (CKs) are phytohormones that regulate multiple processes in plants and are critical for agronomy, as they are involved in seed filling and plant responses to biotic and abiotic stress. Among the over 30 identified CKs, there is uncertainty about the roles of many of the individual CK structural forms. Cytokinin free bases (CKFBs), have been studied in great detail, but, by comparison, roles of riboside-type CKs (CKRs) in CK metabolism and associated signaling pathways and their distal impacts on plant physiology remain largely unknown. Here, recent findings on CKR abundance, transport and localization, are summarized, and their importance in planta is discussed. The history of CKR analyses is reviewed, in the context of the determination of CK metabolic pathways, and research on CKR affinity for CK receptors, all of which yield essential insights into their functions. Recent studies suggest that CKR forms are a lot more than a group of transport CKs and, beyond this, they play important roles in plant development and responses to environmental stress. In this context, this review discusses the involvement of CKRs in plant development, and highlight the less anticipated functions of CKRs in abiotic stress tolerance. Based on this, possible mechanisms for CKR modes of action are proposed and experimental approaches to further uncover their roles and future biotechnological applications are suggested.

Effects of P<sub>SAG12</sub><italic>-IPT </italic>gene expression on leaf senescence, yield, and fiber quality in cotton

<p indent="0mm">A chimeric gene of bacterial <italic>IPT</italic> and the senescence-specific SAG12 promoter from <italic>Arabidopsis</italic> (P_SAG12-<italic>IPT</italic>) was overexpressed in cotton, and nine independent transgenic lines were obtained. To identify the leaf senescence characteristics, yield, and fiber quality of P_SAG12-<italic>IPT</italic> cotton plants, we performed the experiments at the Shangzhuang Experimental Station of China Agricultural University in 2011 and 2012. The results showed that the expression of <italic>IPT</italic> genes in transgenic lines was dramatically up-regulated at leaf aging stage, and the content of Z+ZR-type cytokinin was significantly higher than that of wild type Jihe 321. According to the content of Z+ZR-type cytokinin, nine transgenic lines were clustered into three categories with strong, weak, and moderate anti-aging ability. During leaf senescence period, the contents of chlorophyll and soluble proteins in transgenic lines were positively related to the content of Z+ZR-type cytokinin. Compared to wild type, transgenic lines had a higher or equal number of bolls (diameter ≥ <sc>2 cm)</sc> per plant and boll weigh, but their boll-opening rate at the first harvest was significantly decreased, and the extent of reduction was positively related to the anti-aging ability. Consequently, the seed cotton yield of P_SAG12-<italic>IPT</italic> lines (<italic>OE</italic>-37 and <italic>OE</italic>-38) with strong or moderate anti-aging ability decreased due to less opened bolls, while the line (<italic>OE</italic>-30) with weak anti-aging ability had a comparable yield to that of wild type. The fiber length uniformity of P_SAG12-<italic>IPT</italic> cotton lines was significantly higher than that of wild type. Compared with wild type, the micronaire results of transgenic lines revealed an increasing trend, and fiber length, breaking strength, and breaking elongation was not significantly different from that of wild type.

Cytokinin Mediated Increased In Vitro Production of Secondary Metabolites with Special Reference to Solasodine in Solanum erianthum

AbstractSteroid alkaloid solasodine is a nitrogen analogue of diosgenin and has great importance in the production of steroidal medicines. Solanum erianthum D. Don (Solanaceae) is a good source of solasodine. The aim of this study was to evaluate the effect of different cytokinins on the production of secondary metabolites, especially solasodine in the in vitro culture of S. erianthum. For solasodine estimation, field-grown plant parts and in vitro tissues were extracted thrice and subjected to high-performance liquid Chromatography. Quantitative analysis of different secondary metabolites showed that the amount was higher in the in vitro regenerated plantlets compared to callus and field-grown plants. The present study critically evaluates the effect of the type of cytokinin used in the culture medium on solasodine accumulation in regenerated plants. The highest solasodine content (46.78±3.23 mg g-1) was recorded in leaf extracts of the in vitro grown plantlets in the presence of 6-γ,γ-dimethylallylamino purine in the culture medium and the content was 3.8-fold higher compared to the mother plant.

In vitro growth of Sempur (Dillenia philippinensis Rolfe) shoots in response to different types of plants growth regulators supplemented on MS medium

Plant tissue culture of Sempur (Dillenia philippinensis Rolfe) has not been widely reported. The previous study showed that BAP added to Murashige & Skoog (MS) basal medium promoted the growth of D. philippinensis shoot culture. This research aimed to investigate the growth of D. philippinensis shoot tip cultures on MS medium containing three types of cytokinins namely BAP, Kinetin, and 2-iP compared with Gibberelic acid (GA3). The results showed that the type and concentrations of cytokinins significantly affected all growth parameters observed except the number of roots which was only influenced by cytokinin concentrations alone. However, different levels of GA3 did not significantly affect all growth parameters observed. After eight weeks of culture, MS medium containing 1 mg/l 2-iP gave the best response for plant height, (3.68± 0.26 cm). The highest number of leaves (20.33±3.14) and nodes (6.67± 0.21) were found in MS medium containing 0.5 mg/l BAP. While the highest number of roots (1.83±0.17) was found in MS medium without the addition of cytokinins. The range of average values of plant height at different levels of GA3 was 3.08-3.74 cm; the number of leaves was 5.1-7.5; the number of nodes was 3.9-5.4 and the number of roots was 1.0-2.8.

Micropropagation of diploid and tetraploid Plectranthus amboinicus (Lour.) Spreng

Plectranthus amboinicus (Lour.) Spreng is commonly consumed by people in North Sumatra, Indonesia, as a vegetable, which is commonly called Torbangun. Plant tissue culture is an alternative method for the mass-production of transplants. Genetic improvement by somatic cell manipulation such as induction of polyploid plants is needed to improve biomass production as well as their secondary metabolite products. This research aimed to conduct in vitro micropropagation of diploid and tetraploid P. amboinicus on Murashige and Skoog (MS) medium containing BAP or Kinetin. Shoot tips were used as explants and cultured on MS medium containing BAP or Kinetin at 0, 0.5, 1 and 2 mg/l given as single concentration. The experiment used a completely randomized design with four replications. Each replication consisted of three explants. The results showed that height of shoots was affected by type of cytokinins. Kinetin at 0.5 mg/l gave the highest shoots of tetraploid plants significantly different with addition of BAP both to diploid and tetraploid plants. The number of multiple shoots and leaves varied in both diploid and tetraploid plants. Root formation was best on the medium without addition of cytokinins. Both diploid and tetraploid plantlets had a high survival rate after acclimatization in the greenhouse.

Effects of Cytokinin in Enhancing the Multiplication of Vegetative &lt;i&gt;Hylocereus polyrhizus&lt;/i&gt;

Hylocereus polyrhizus is a climbing vine cactus species that grows in tropical area. Recently, it has attracted the attention of public as it provides numerous benefits to humans in term of health especially for those who prioritize health over mostly anything. The objective of this research was to assess the effects of different type of cytokinins which were 6-Benzylaminopurine (BAP) and Kinetin in different concentration with combination of waste coconut water and sucrose on enhancing the in vitro multiplication of H. polyrhizus. It was found that BAP had higher effect in shoot multiplication than Kinetin as the highest number of shoots was produced at 3.67± 0.67 when supplemented with 3.0 mg/L of BAP whereas for Kinetin, it only produced 1.75±0.38 shoots and without cytokinin was 1.17±0.01. However, Kinetin had a slightly better effect in shoot elongation than BAP as Kinetin produced shoots with longer length than BAP. It was found that the longest length produced by Kinetin was 2.51±0.06 while BAP was 2.43±0.05 cm and without cytokinin was 2.18±.0.01.For the production of roots, low concentration of cytokinin in range 0.3 mg/L to 1.0 mg/L provides the best number of roots. In conclusion, addition of cytokinin has significant effect in enhancing the growth and multiplication of vegetative H. polyrhizus.

Diversified Regulation of Cytokinin Levels and Signaling During Botrytis cinerea Infection in Arabidopsis.

Cytokinins (CKs) can modulate plant immunity to various pathogens, but how CKs are involved in plant defense responses to the necrotrophic pathogen Botrytis cinerea is still unknown. Here, we found that B. cinerea infection induced transcriptional changes in multiple genes involved in the biosynthesis, degradation, and signaling of CKs, as well as their contents, in pathogen-infected Arabidopsis leaves. Among the CKs, the gene expression of CYTOKININ OXIDASE/DEHYDROGENASE 5 (CKX5) was remarkably induced in the local infected leaves and the distant leaves of the same plant without pathogen inoculation. Cis-zeatin (cZ) and its riboside (cZR) accumulated considerably in infected leaves, suggesting an important role of the cis-zeatin type of CKs in the plant response to B. cinerea. Cytokinin double-receptor mutants were more susceptible to B. cinerea infection, whereas an exogenous CK treatment enhanced the expression levels of defense-related genes and of jasmonic acid (JA) and ethylene (ET), but not salicylic acid (SA), resulting in higher resistance of Arabidopsis to B. cinerea. Investigation of CK responses to B. cinerea infection in the JA biosynthesis mutant, jar1-1, and ET-insensitive mutant, ein2-1, showed that CK signaling and levels of CKs, namely, those of isopentenyladenine (iP), isopentenyladenine riboside (iPR), and trans-zeatin (tZ), were enhanced in jar1-1-infected leaves. By contrast, reductions in iP, iPR, tZ, and tZ riboside (tZR) as well as cZR contents occurred in ein2-1-infected leaves, whose transcript levels of CK signaling genes were likewise differentially regulated. The Arabidopsis Response Regulator 5 (ARR5) gene was upregulated in infected leaves of ein2-1 whereas another type-A response regulator, ARR16, was significantly downregulated, suggesting the existence of a complex regulation of CK signaling via the ET pathway. Accumulation of the cis-zeatin type of CKs in B. cinerea-infected leaves depended on ET but not JA pathways. Collectively, our findings provide evidence that CK responds to B. cinerea infection in a variety of ways that are differently modulated by JA and ET pathways in Arabidopsis.

Silver birch (Betula pendula Roth.) culture initiation in vitro and genotype determined differences in micropropagation

Micropropagation has several advantages over conventional vegetative propagation methods, but it is limited by genotype responsiveness. We assessed the effect of age of the mother-tree and the time of explant collection on culture initiation, as well as the multiplication ability and effect of different nutrient media and plant growth regulators on silver birch genotypes. Explants collected from 1‐year‐old trees (66%) and explants collected in spring (64–67%) developed a significantly (both p < 0.001) higher proportion of shoots than those from 15‐year‐old trees (39%) and those collected in mid-summer (31%) and autumn (29%), respectively. In a stabilised culture, the length of the main shoot varied from 1.3 to 7.8 cm between genotypes, and the multiplication rate ranged from 1.0 to 6.8 shoots per explant. Hyperhydrated shoots were present in 17 out of 50 clones, and, among the clones, ranged from 14 to 50%. Cultures on the Murashige and Skoog basal medium had a higher multiplication rate than cultures on a Woody Plant Medium, and the application of zeatin provided better results than 6‐benzylaminopurine. The difference between cytokinin types was 11–29% for the multiplication rate and 21–29% for the length of the main stem. The highest multiplication rate was obtained using a zeatin concentration of 0.5 mg L−1. However, better shoot growth and proliferation had a significant positive relation to shoot hyperhydration (all p < 0.001). Therefore, a medium with an optimal balance between the multiplication rate and the number of hyperhydrated shoots should be carefully selected.