Zeatin Research Articles

Effects of Arbuscular Mycorrhizal Fungi on Growth and Physiological Performance of Catalpa bungei C.A.Mey. under Drought Stress

Catalpa bungei C.A.Mey. is a common ornamental timber species. Its survival and growth are greatly affected by water scarcity in arid and semi-arid areas of Northwest China. Evidence suggests arbuscular mycorrhizal fungus (AMF) may improve plant drought resistance. However, there is limited information on the systematic effects of AMF on drought resistance in C. bungei seedlings. Here, a pot experiment was used to explore the effects of inoculation with the AMF Rhizophagus intraradices on the growth and physiological performance of C. bungei under different water treatment conditions. Three water levels and two mycorrhizal inoculation treatments were used with factorial design. The results showed that drought stress noticeably affected the growth and physiological performance of C. bungei seedlings. However, inoculation with R. intraradices significantly ameliorated the growth, and alleviated the effects of drought stress. The growth parameters of AMF-inoculated seedlings significantly increased regardless of water status. AMF changed the biomass allocation in seedlings by reducing the root mass ratio (RMR) and root/shoot ratio. AMF-inoculated seedlings displayed higher gas exchange parameters, photosynthetic pigment concentrations, specific leaf area (SLA), but lower specific leaf weight (SLW), regardless of water status. AMF alleviated drought-induced oxidative stress by attenuating the excess generation of reactive oxygen species (ROS), especially H2O2 and O2−, in leaves. Inoculation with AMF under drought stress also dramatically augmented indole-3-acetic acid (IAA) and gibberellins (GA3) levels and the IAA/abscisic acid (ABA) and GA3/ABA ratios, but reduced ABA and zeatin (ZT) levels in leaves. AMF symbiosis improved root morphology and promoted the absorption of nitrogen (N) and phosphorus (P) in seedlings. We conclude that inoculation with R. intraradices is potentially useful for afforestation and cultivation of C. bungei in Northwest China. Furthermore, AMF improved soil structure by increasing the glomalin-related soil protein (GRSP) contents and the proportion of macro-aggregates (0.25–0.5 mm) in the rhizosphere soil.

Transcriptome sequencing and endogenous phytohormone analysis reveal new insights in CPPU controlling fruit development in kiwifruit (Actinidia chinensis).

Kiwifruit (Actinidia chinensis) is a rich nutritious fruit crop owing to a markedly higher content of vitamin C and minerals. To promote fruit set and to increase the yield of kiwifruit, forchlorfenuron (CPPU) has been widely applied. However, the molecular details regarding CPPU controlling kiwifruit development, especially at the fastest fruit growth stage, remain unknown. In the present study, we measured the effect of CPPU on developmental regulation in red-fleshed kiwifruit (Actinidia chinensis ‘Hongyang’). Additionally, a cytological analysis was performed to clarify the precise changes in the cell structure of the CPPU-treated kiwifruits. Moreover, the concentration of endogenous phytohormones, including indoleacetic acid (IAA), zeatin (ZT), gibberellic acid 3 (GA3), and abscisic acid (ABA), were measured by Enzyme-linked Immunosorbent Assay (ELISA). Furthermore, RNA-Seq was performed to dissect the complicated molecular mechanisms, with a focus on biosynthesis, metabolism, and signaling compounds, such as endogenous hormones, sugars, and L-ascorbic acid. Our results demonstrated that CPPU treatment not only regulates the size and weight of a single fruit but also improves the quality in ‘Hongyang’ kiwifruit through the accumulation of both soluble sugar and vitamin C. It was also seen that CPPU regulates kiwifruit development by enhancing cell expansion of epidermal cells and parenchyma cells, while, promoting cell division of subepidermal cells. Additionally, CPPU significantly increased the gibberellin and cytokinin biosynthetic pathway and signaling, while repressing auxin and ABA biosynthetic pathway; thus, signaling plays an essential role in CPPU controlling kiwifruit development. Notably, transcriptomic analysis revealed that a total of 2244 genes, including 352 unannotated genes, were differentially expressed in kiwifruits because of CPPU treatment, including 127 transcription factors. These genes are mainly enriched in plant hormone signal transduction, photosynthesis, MAPK signaling pathway, starch and sucrose metabolism, and phenylpropanoid biosynthesis. Overall, our results highlight that CPPU regulation of kiwifruit development is mainly associated with an antagonistic and/or synergistic regulatory role of endogenous phytohormones, and enhancing the energy supply. This provides new insights into the molecular details of CPPU controlling kiwifruit development at the fastest fruit growth stage, which is of agricultural importance for kiwifruit breeding and crop improvement.

Comparative transcriptome analyses provide novel insights into etiolated shoot development of walnut (Juglans regia L.).

In general, genes promoting IAA, CTK GA and ethylene biosynthesis were upregulated, while genes participating in ABA, chlorophyll and starch biosynthesis pathways performed opposite tendency during etiolation. Etiolation as a method for rejuvenation plays an important role in the vegetative propagation of woody plants. However, the molecular mechanism of etiolated shoot development remains unclear. In this study, we investigated changes at different etiolation stages of Juglans regia. The histology and transcriptome of J. regia were analysed using etiolated stems, which were treated in darkness for 30, 60, 90days. The results showed that the ratios of pith (Pi) diameter/stem diameter (D), cortex (Co) width/D, and phloem (Ph) width/D increased, while the ratio of xylem (Xy) width/D decreased after etiolation, and the difference in these ratios between etiolated stems and the control was more significant at 60 days than 90 days. Differentially expressed genes (DEGs) were significantly enriched in pathways such as plant hormone biosynthesis and signal transduction, chlorophyll biosynthesis and degradation, and starch and sucrose metabolism. The difference in the contents of indole-3-acetic acid (IAA), abscisic acid (ABA), sugar and chlorophyll between etiolated stems and the control increased with increasing treatment duration; in contrast, the concentrations of gibberellin (GA), zeatin (ZT), and starch, as well as the difference between the etiolated stems and control were lowest at 60 days among the three stages. On the whole, the positive effect of etiolation on the rejuvenation of walnut stems changed as the treatment period increased. The present investigation lays a foundation for future studies on the effect of etiolation on rejuvenation and for promoting the efficiency of vegetative propagation.

Seed germination, micropropagation from adult and juvenile origin explants and address of hyperhydricity of the Cretan endemic herb Calamintha cretica

The optimum range of temperature for germination (96-100%) of Calamintha cretica, an herb with potential pharmaceutical and horticultural uses, was 15 to 20 °C, with 10 and 30 °C cardinal temperatures. Storage up to one year did not affect germination. The effect of zeatin (ZEA), 6-benzyladenine (BA), kinetin, and 6-γ-γ-(dimethylallylamino)-purine added in MS medium at concentrations from 0.0 to 8.0 mg L-1 was tested for shoot proliferation of both adult- and seedling-origin nodal explants at first- and sub-culture. Both explant types responded similarly during in vitro culture. At cytokinin concentrations up to 1 mg L-1 explant response was high (over 85%) but shoot number per explant was low (1.2-2.2). Increasing cytokinin from 2.0 to 8.0 mg L-1 resulted to an analogous decrease of explant response and shoot length, and an increase of shoot number, particularly when ZEA or BA was used (5.0-6.6 shoots per explant, 0.5-1.0 cm long) with simultaneous though increase of hyperhydricity (up to 50%). The addition of 0.1 mg L-1 naphthaleneacetic acid into the 8.0 mg L-1 BA medium almost eliminated hyperhydricity and increased explant response, while the increase of agar concentration from 8.0 to 12.0 g L-1 eliminated hyperhidricity and induced the highest shoot proliferation (93-95% explant response, 11.2-12.3 shoots per explant, 0.8-1.0 cm long). Microshoots and microshoot clusters rooted (88-96%) on half-strength MS medium either hormone free or supplemented with 1 to 4 mg L-1 indole-3-butyric acid. Plantlets survived at 80% to 100% after ex vitro acclimatization in peat: perlite 1:1 (v/v).

Endogenous phytohormones and the expression of flowering genes synergistically induce flowering in loquat

Flowering is an important process for the reproduction of higher plants. Up to this point, the studies on flowering have mostly focused on the model plant Arabidopsis thaliana, and the flowering mechanism of fruit trees remains mostly unknown. The diversity of the flowering time of loquat (Eriobotrya japonica Lindl.) makes it an ideal material to study the regulation of flowering. In this study, we first observed the inflorescence bud differentiation in two varieties of loquat that had different blooming times (cv. Dawuxing (E. japonica), that blooms in the fall and cv. Chunhua (E. japonica×Eriobotrya bengalensis Hook. f.) that blooms in the spring) and found that the starting time of inflorescence bud differentiation and the speed of inflorescence development were responsible for the difference in blooming times. The determination of endogenous phytohormones by high performance liquid chromatography (HPLC) indicated that abscisic acid (ABA), zeatin (ZT), and gibberellin (GA3) promoted flowering in loquat, while indole-3-acetic acid (IAA) was mainly involved in inflorescence bud differentiation in Chunhua. A transcription level analysis illustrated that multiple flowering-related genes could respond to different signals, integrate to the TFL1, AP1 and FT genes, and then synergistically regulate flowering in loquat. Thus, this study provides a new insight into flowering regulation mechanisms in loquat.

An efficient protocol for Agrobacterium-mediated genetic transformation of Antirrhinum majus

Snapdragon (Antirrhinum majus L.) is a popular ornamental and model plant species, and the recently released reference genome could greatly boost its utilization in fundamental research. However, the lack of an efficient genetic transformation system is still a major limiting factor for its full application in genetic and molecular studies. In this study, a simple method for quick regeneration and efficient Agrobacterium-mediated transformation of snapdragon was developed. Cotyledon petiole and hypocotyl explants derived from two-week-old seedlings were cultured on MS media supplemented with 2 mg/L zeatin (ZT), 0.2 mg/L 1-naphthaleneacetic acid (NAA), and 2 mg/L AgNO3, and adventitious shoots were regenerated through organogenesis with an average regeneration of 48.00% and 41.33%, respectively. By contrast, the regeneration frequency was only 22.67% for cotyledon petiole and 25.67% for hypocotyl explants in the absence of AgNO3. Moreover, the application of AgNO3 promoted indirect shoot organogenesis, while direct shoot organogenesis occurred in the absence of AgNO3 from both hypocotyl or cotyledon petiole explants. Agrobacterium-mediated genetic transformation systems were developed with this high-efficient regeneration system. The transformation efficiency has been improved from 0 to 1% through the direct shoot organogenesis to 3 to 4% via the indirect shoot organogenesis. This efficient regeneration and genetic transformation method could be important for future use of snapdragon as a model plant to address some fundamental questions which are hard to be solved by using other model plant species, and to accelerate the breeding process through CRISPR/Cas9 genome editing. Genetic transformation of snapdragon was significantly improved by applying AgNO3 to induce indirect organogenesis, which will substantially facilitate its fundamental research as well as molecular breeding.

Abundance and Extracellular Release of Phytohormones in Aero-terrestrial Microalgae (Trebouxiophyceae, Chlorophyta) As a Potential Chemical Signaling Source1.

Phytohormones are pivotal signaling compounds in higher plants, in which they exert their roles intracellularly, but are also released for cell‐to‐cell communication. In unicellular organisms, extracellularly released phytohormones can be involved in chemical crosstalk with other organisms. However, compared to higher plants, hardly any knowledge is available on the roles of phytohormones in green algae. Here, we studied phytohormone composition and extracellular release in aero‐terrestrial Trebouxiophyceae. We investigated (a) which phytohormones are produced and if they are released extracellularly, and if extracellular phytohormone levels are (b) affected by environmental stimuli, and (c) differ between lichen‐forming and non‐lichen‐forming species. Three free‐living microalgae (Apatococcus lobatus, Chloroidium ellipsoideum, and Myrmecia bisecta) and three lichen‐forming microalgae (Asterochloris glomerata, Trebouxia decolorans, and Trebouxia sp.) were studied. Algae were grown on solid media and the following cellular phytohormones were identified by ultra‐high‐performance liquid chromatography coupled with tandem mass spectrometry (UHPLC‐MS/MS): indole‐3‐acetic acid (IAA), indole‐3‐butyric acid (IBA), abscisic acid (ABA), gibberellin A4 (GA4), and zeatin (ZT). Furthermore, IAA, IBA, ABA, jasmonic acid (JA), gibberellin A3 (GA3), and GA4 were found to be released extracellularly. IAA and ABA were released by all six species, and IAA was the most concentrated. Phytohormone release was affected by light and water availability, especially IAA in A. glomerata, Trebouxia sp., and C. ellipsoideum. No clear patterns were observed between lichen‐forming and non‐lichen‐forming species. The results are envisaged to contribute valuable baseline information for further studies into the roles of phytohormones in microalgae.

Cucumber Fruit Size and Shape Variations Explored from the Aspects of Morphology, Histology, and Endogenous Hormones

Fruit size and shape are important qualities and yield traits in cucumber (Cucumis sativus L.), but the factors that influence fruit size and shape remain to be explored. In this study, we investigated the dynamic changes of fruit size and shape from the aspects of morphology, cellular levels and endogenous hormones for nine typical cucumber inbred lines. The results show that fruit length had a strong positive correlation to the cell number in the longitudinal section of fruit throughout the four stages of 0, 6, 12, and 30 DAA (days after anthesis). However, the significant negative correlations were found between fruit length and the fruit cell size at 12 and 30 DAA. Furthermore, fruit diameter was positively correlated to the cell number in the cross section at all the investigated fruit growth stages. The indole-3-acetic acid (IAA) content showed significant positive correlations to the fruit length at all fruit growth stages of −6, −3, 0, 3, 6, 9 and 12 DAA, but IAA content and fruit diameter showed significant negative correlations for all the stages except for at −6 DAA. The trans-zeatin riboside (tZR), zeatin (ZT), gibberellic acid (GA3) and jasmonic acid (JA) content had a positive or negative correlation with fruit length or diameter only at certain stages. Neither fruit length nor diameter had significant correlations to abscisic acid (ABA) content. These results indicate that variations in fruit size and shape of different cucumber inbred lines mainly result from the differences in fruit cell number and endogenous IAA content. The present work is the first to propose cucumber fruit size and shape changes from the combined aspects of morphology, cellular levels, and endogenous hormones.

Transcriptome profiling of the flowering transition in saffron (Crocus sativus L.)

Saffron, derived from the stigma of Crocus sativus, is not only a valuable traditional Chinese medicine but also the expensive spice and dye. Its yield and quality are seriously influenced by its flowering transition. However, the molecular regulatory mechanism of the flowering transition in C. sativus is still unknown. In this study, we performed morphological, physiological and transcriptomic analyses using apical bud samples from C. sativus during the floral transition process. Morphological results indicated that the flowering transition process could be divided into three stages: an undifferentiated period, the early flower bud differentiation period, and the late flower bud differentiation period. Sugar, gibberellin (GA3), auxin (IAA) and zeatin (ZT) levels were steadily upregulated, while starch and abscisic acid (ABA) levels were gradually downregulated. Transcriptomic analysis showed that a total of 60 203 unigenes were identified, among which 19 490 were significantly differentially expressed. Of these, 165 unigenes were involved in flowering and were significantly enriched in the sugar metabolism, hormone signal transduction, cell cycle regulatory, photoperiod and autonomous pathways. Based on the above analysis, a hypothetical model for the regulatory networks of the saffron flowering transition was proposed. This study lays a theoretical basis for the genetic regulation of flowering in C. sativus.

Effects of Plant Growth Regulators, Soil Moisture Contents, and Carbon/Nitrogen Ratios on Sex Differentiation in Persimmon (Diospyros kaki Thunb.) Flowers

The sex types of persimmon (Diospyros kaki Thunb.) flowers are occasionally alterable. The feminizing agents such as ethrel, 5-azacytidine, a mixture of exogenous zeatin (ZT), abscisic acid (ABA), and indole-3-acetic acid (IAA) were injected into androecious wild persimmon trees. Different concentrations of masculinizing exogenous gibberellin (GA3) were injected into gynoecious ‘Jiro’ cultivar trees. ‘Jiro’ trees were also grown in soils differing in moisture content and carbon/nitrogen (C/N) ratio, to determine their effects on floral development and sex differentiation in persimmons. Injection of ethrel significantly decreased the diameter of pollen grains and the length of pollen tubes, thereby demonstrating a feminizing effect. Injection of GA3 significantly increased the length of arrested stamens in gynoecious trees, demonstrating a masculinizing effect. High soil moisture levels (55% and 45% volumetric moisture contents) significantly increased the length of pistils compared to the control (20% moisture content) in gynoecious trees; a high C/N ratio markedly increased the length of both pistils and arrested stamens. Many of the treatments also significantly changed the expression patterns of crucial genes, the contents of assimilates and stress markers, and the activities of antioxidative enzymes in floral buds. These treatment responses may relate to changes in phenotypes. Although the sex types of persimmon flowers were not completely transformed in our study, the treatments significantly influenced pistil and stamen length. Improved artificial treatments may be used to control sex type in persimmons in the future.

Response of hormone in rice seedlings to irrigation contaminated with cyanobacterial extract containing microcystins

Microcystins released by cyanobacteria affect crop growth and productivity, and even food safety. Plant hormones play a vital role in regulating growth, development and stress response in plants. Therefore, we studied the response of hormones including abscisic acid (ABA), indole-3-acetic acid (IAA), Zeatin (ZT) and gibberellin (GA3) as well as hormone balances (IAA/ABA, ZT/ABA and GA/ABA) to cyanobacterial extract containing microcystins (1, 10, 100 and 1000 μg/L) during stress and recovery periods. Low concentration microcystins (1 μg/L) promoted growth of rice seedlings by increasing levels of IAA, ZT and GA3 and maintaining hormone balances. In addition, the up-regulation of OsYUCCA1 increased IAA level in rice roots by promoting IAA biosynthesis. High concentrations microcystins (10, 100 or1000 μg/L) inhibited growth of rice seedlings by reducing levels of IAA, ZT and GA3 and ratios of IAA/ABA, ZT/ABA and GA/ABA due to increased ABA level. The increase in ABA in rice seedlings induced by high concentrations MCs was resulted from up-regulation of OsNCED1, OsNCED3, OsNCED4 and OsZEP to enhance ABA biosynthesis, and was controlled by up-regulating expression levels of OsABAox1-3 for enhancing ABA catabolism as negative feedback. The highest concentration of MCs (1000 μg/L) caused irreversible damage to metabolisms of IAA and ABA, partly resulting in unrecoverable inhibition on rice growth. All results demonstrate that “low-concentration promotion and high-concentration inhibition” of microcystins was associated with changes in hormone levels and balances by affecting their metabolisms, and could be helpful for guiding agricultural irrigation with microcystin contaminated water.

Exogenous Brassinolide Enhances the Growth and Cold Resistance of Maize (Zea mays L.) Seedlings under Chilling Stress

This paper aims to elucidate the effects of exogenous brassinolide (BL) on maize germination and seedling growth under chilling stress. The cold-resistant maize hybrid Tiannong 9 and the cold-sensitive hybrid Tianhe 1 were soaked at the germination stage (6 °C) and leaves were sprayed at seedling stage (4 °C), with BL at concentrations of 0, 0.01, 0.1, and 1 mg/L. The germination rate of the maize seeds and the changes in seedling biomass, antioxidant, photosynthetic, and plant endogenous hormone systems and chloroplast ultrastructures were determined. The results showed that the optimum concentration of BL to alleviate chilling stress in maize seedlings was 0.1 mg/L. This rate effectively increased the germination rate and plant biomass of maize and significantly increased the superoxide dismutase (SOD) peroxidase (POD) and catalase (CAT) activities, the net photosynthetic rate (Pn), stomatal conductance (gs) and transpiration rate (Tr), and seedling auxin (IAA), gibberellin (GA3) and trans zeatin nucleoside (t-ZR) contents under chilling stress. In addition, BL significantly reduced the malondialdehyde (MDA) content, abscisic acid (ABA) content, and intercellular carbon dioxide concentration (Ci). In the comparison of mesophyll cells, the chloroplast membrane of the treatment group was tightly attached to the stroma, and some of the plasma membranes were dissolved, but the overall structure of the chloroplast was relatively complete, and the osmiophilic granules were relatively few. The exogenous application of BL can effectively alleviate the damage caused by a low temperature in maize, maintain the normal characteristics of seedlings in chilling environments, and ensure the development and growth of plant tissue in the later stage.

Effect of Drought Stress and Thermal Pre-treatment on the In vitro Shoot Development of Solanum lycopersicum L.

Tomato is one of the popular vegetables in the world. However, drought has become more serious in recent years. Drought strongly reduced the development and yield of tomato. Thus, the effect of drought stress condition (½ Murashige and Skoog’s medium supplemented with 35 g.L-1 mannitol) and thermal pre-treatment (45 (C for 120 min) on in vitro shoot development of Solanum lycopersicum L. were studied to improve the drought-tolerant of tomato. Morphological, physiological and biochemical changes during the development of in vitro shoot in the drought stress condition were analyzed. Then, leaves of the shoot that pre-treated at 45 (C for 120 min and developed on the drought stress condition were cultured on ½ MS medium supplemented with 20 g.L-1 sucrose, 0.1 mg.L-1 Indole acetic acid, 2 mg.L-1 zeatin and 35 g.L-1 mannitol to regenerate the drought-tolerant shoots. In the drought stress condition (½ MS medium with 35 g.L-1 mannitol), the height of shoot, the number of leaves, and the total leaf area were decreased by approximately 50 % compared to control (½ MS medium without mannitol). Besides, the leaf midrib thickness and the vascular bundle width of the leaf in drought stress were smaller than those of the control. The leaf midrib thickness and the leaf vascular bundle width in drought stress condition were 953.30 (m and 320.21 (m, compared to 1243.80 (m and 410.15 (m in that of control. Chlorophyll fluorescence occurs in some parenchyma cells near the midrib vascular bundle of treated leaves instead of all parenchyma cells in control leaves. Under the drought stress condition, chlorophyll content, photosynthetic intensity and cytokinin activity of leaf were strongly decreased but respiration intensity, the content of carotenoid and proline, especially the activity auxin and abscisic acid were increased. Thermal pre-treatment stimulated shoot regeneration (2.53 shoots/leaf explant) while there was no shoot regenerated from the leaf of the control plant. The shoots regenerated by this method grew well in the drought stress condition.

Hydrogen cyanamide induces grape bud endodormancy release through carbohydrate metabolism and plant hormone signaling

BackgroundGrape buds exhibit non-uniform, or delayed, break in early spring in subtropical regions because the accumulation of chilling is insufficient. Hydrogen cyanamide (H2CN2, HC) can partially replace chilling to effectively promote bud sprouting and is used widely in warm winter areas. However, the exact underlying mechanism of grape bud release from endodormancy induced by HC remains elusive.ResultsIn this study, the transcriptome of grape winter buds under in vitro conditions following HC and water treatment (control) was analyzed using RNA-seq technology. A total of 6772 differentially expressed genes (DEGs) were identified. Furthermore, the gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that starch and sucrose metabolism and plant hormone signaling transduction were most enriched out of the 50 total pathways. HC treatment induced the upregulated expression of sucrose synthase (SUS), sucrose phosphate synthase (SPS), α-amylase (AM), and β-amylase (BM) and downregulated expression of sucrose invertase (INV), hexokinase (HK), fructokinase (FK), soluble starch synthase (SS), and granule-bound starch synthase (GBSS). Hence, the starch concentration in the HC-treated group was significantly lower than that in control, whereas soluble sugar content in the HC-treated group increased quickly and was higher than that in control between 0 and 8 d. The concentration of indoleacetic acid (IAA) and zeatin (ZT) increased, whereas that of abscisic acid (ABA) and gibberellin (GA) decreased in HC treated group, which coincided with the expression level of genes involved in above hormone signals. The content of hydrogen peroxide (H2O2) and enzyme activity of superoxide dismutase (SOD) and peroxidase (POD) were increased in grape buds with HC treatment, whereas catalase (CAT) activity was decreased. HC treatment increased the expression of POD, SOD, primary amine oxidase (PAO), polyamine oxidase (PAOX), and glutathione peroxidase (GSH-Px).ConclusionBased on these results, it is possible to propose a mechanistic model that underlies the regulation of endodormancy release in grapevine buds by exogenous HC application.

Micropropagation and prevention of hyperhydricity in olive (Olea europaea L.) cultivar ‘Gemlik’

Olive (Olea europaea L.) is an economically important crop because of its fruit and oil. Successful olive micropropagation is highly dependence on cultivar, shoot proliferation rate, which is generally low, the rooting of micropropagated olive plantlets is difficult, and the rate of post-transplanting losses is high. In addition, hyperhydricity, a common problem in vitro culture was found to be prevalent. The aim of this study was to establish a micropropagation system for the Turkish O. europaea L. cv. Gemlik. Initially, five different basal media were tested to determine appropriate medium for establishment of in vitro culture and Woody Plant Medium (WPM) was the most efficient. Nodal explants were cultured on WPM containing different plant growth regulators (PGRs) for shoot regeneration. Maximum regeneration frequency and number of shoots per explant were achieved from nodal explants cultured on WPM supplemented with 4.0 mg/L 6-benzyladenine (BA). However, all cultures showed high hyperhydricity and an experimentation was also conducted to resolve the hyperhydricity problem. Hyperhydricity was prevented by changing the gelling agent to Agar-Agar. The shoots regenerated from nodal explants and still attached to initial woody nodal explant were transferred to four different medium formulations each containing 2.0 mg/L zeatin (ZEA) for shoot elongation. Modified Olive Medium (MOM2: OM with three times the concentrations of KNO3) fortified with 2.0 mg/L ZEA was found to be the best for shoot elongation. The elongated shoots were rooted on Olive medium (OM) containing 160 mg/L Putrescine, 1.5 mg/L naphthaleneacetic acid (NAA), 30 g/L mannitol and solidified with 0.65% (w/v) Agar-Agar. Finally, all plantlets were successfully acclimatized in a climate chamber and the plants were transferred to greenhouse conditions.

Carbon dioxide and precipitation alter Reaumuria soongorica root morphology by regulating the levels of soluble sugars and phytohormones

Significant increases in the concentration of carbon dioxide (CO2) have been shown to cause changes in precipitation patterns. These changes can severely affect the desert ecosystem. Therefore, it is important to investigate the impacts of CO2 concentration and precipitation on root morphology, so as to better predict the responses of desert ecosystems to the global climate change. For this purpose, we studied Reaumuria soongorica that is a dominant plant in the desert. Open top chambers were used to simulate changes in CO2 concentrations (350 μmol mol−1 and 700 μmol mol−1), to study the effects of 30% reduction in precipitation (W−), natural precipitation (W), 30% increase in precipitation (W+), and to study the synergistic effects of precipitation with CO2 on R. soongorica root morphological characteristics, endogenous hormones, and soluble sugars. Higher CO2 levels caused a significant increase in root length, mean root diameter, root biomass, total root surface area and total root volume regardless of alterations in precipitation; whereas the root–shoot ratio increased only with increased precipitation. Elevated concentrations of CO2 and decreased precipitation significantly increased the contents of fructose, sucrose, glucose and other soluble sugars in the R. soongorica root system. Meanwhile, the two environmental factors showed significantly synergistic effects on R. soongorica root morphology. With elevated concentrations of CO2, R. soongorica roots showed increased levels of endogenous hormones, including abscisic acid (ABA), indole-3-acetic acid (IAA) and gibberellin (GA). The effect of precipitation on hormone levels varied among hormones. IAA and GA levels were increased, regardless of changes in precipitation; ABA decreased with higher precipitation, whereas zeatin (ZT) increased with more precipitation. Correlation analyses indicated a significant correlation between root morphology and the levels of soluble sugars and endogenous hormone, as well as between the level of soluble sugars and the level of endogenous hormones. We conclude that future changes in climate conditions such as CO2 levels and precipitation will synergistically induce the root system of R. soongorica to undergo morphological and physiological alterations.

The miRNA-mRNA Networks Involving Abnormal Energy and Hormone Metabolisms Restrict Tillering in a Wheat Mutant dmc.

Tillers not only determine plant architecture but also influence crop yield. To explore the miRNA regulatory network restraining tiller development in a dwarf-monoculm wheat mutant (dmc) derived from Guomai 301 (wild type, WT), we employed miRNome and transcriptome integrative analysis, real-time qRT-PCR, histochemistry, and determinations of the key metabolites and photosynthesis parameters. A total of 91 differentially expressed miRNAs (DEMs) were identified between dmc and WT. Among them, 40 key DEMs targeted 45 differentially expressed genes (DEGs) including the key DEGs encode growth-regulating factors (GRF), auxin response factors (ARF), and other proteins involved in the metabolisms of hormones and carbohydrates, etc. Compared with WT, both the chlorophyll contents and the photosynthesis rate were lower in dmc. The contents of glucose, sucrose, fructose, and maltose were lower in dmc. The contents of auxin (IAA) and zeatin (ZA) were significantly lower, but gibberellin (GA) was significantly higher in the tiller tissues of dmc. This research demonstrated that the DEMs regulating hormone and carbohydrate metabolisms were important causes for dmc to not tiller. A primary miRNA–mRNA regulatory model for dmc tillering was established. The lower photosynthesis rate, insufficient energy, and abnormal hormone metabolisms restrict tillering in dmc.

Studies on Seed Germination and Micropropagation of Clinopodium nepeta: A Medicinal and Aromatic Plant

Seed ecophysiology and micropropagation of Clinopodium nepeta, an aromatic Mediterranean plant with pharmaceutical and horticultural uses was investigated. The optimum germination temperature of seeds stored at room temperature for 0, 6, or 12 months was 15 to 20 °C (100% germination completed in 10 to14 days) and cardinal temperatures were defined at 10 and 30 °C (80% to 82% and 62% to 76% germination, respectively). Six or 12 months of storage did not seem to affect germination, although 12-month-old seeds germinated at higher percentage and completed germination earlier at 15 °C than at 20 °C. Concerning micropropagation, shoot multiplication at subcultures of both adult plant- and seedling-origin nodal explants was tested on Murashige and Skoog (MS) medium supplemented with various cytokinin types, i.e., zeatin (ZEA), 6-benzyladenine (BA), kinetin (KIN), and 6-γ-γ-(dimethylallylamino)-purine (2IP), at various concentrations from 0.0 to 8.0 mg·L−1. Both explant types presented a rather similar response during in vitro culture. Increasing concentration of all cytokinin types resulted in an increase in shoot number per responding explant (1.1–5.3) and in most cases a decrease in shoot length (0.6–3.4 cm). Increasing cytokinin concentration induced hyperhydricity to a number of shoots (0.1–6.5) per explant, mostly when ZEA and BA were used. Supplementing the MS medium with 8.0 mg·L−1 BA combined with 0.1 mg·L−1 1-naphthaleneacetic acid (NAA) led to almost elimination of hyperhydricity and very satisfactory shoot production (80%/88% explant response and 6.5/7.5 shoot number per responding explant for seedling- / adult-origin explants, respectively). Alternatively, increasing the agar concentration to 12.0 g·L−1 and supplementing the medium with 8.0 mg·L−1 BA only, resulted in the same effect on eliminating hyperhydricity, such as the addition of NAA, and in the best shoot multiplication response achieved in this study (100% explant response, 9.4/9.9 shoots per explant for seedling-/adult-origin explants, respectively). Microshoots rooted abundantly (92% to 100%) on half-strength MS medium, either Hf or supplemented with 0.5 mg·L−1 to 4.0 mg·L−1 indole-3-butyric acid (IBA). The addition of IBA to the rooting medium, regardless of its concentration, affected only the root length by increasing it 2- to 3-fold. Microshoot clusters produced on multiplication media rooted at 96% when cultured on Hf half-strength MS medium. Rooted microshoots and shoot clusters survived at 80% to 100%, respectively, after ex vitro acclimatization in peat:perlite 1:1 (v/v).

Sucul Bitki Bacopa monnieri (L.) Wettst.’nin Yaprak Eksplantlarından Çoklu Sürgün Rejenerasyonu Üzerine Zeatin Ön Uygulamasının Etkisi

Bacopa monnieri (L.) Wettst su ortamının iyileştirilmesinde ve geleneksel tıp sisteminde önemli bir bitkidir. Bu çalışmada, B. monnieri’nin doku kültürü teknikleri ile üretimi hedeflenmiştir. B. monneri’nin yaprak eksplantları farklı dozlarda Zeatin (ZEA)’li solüsyonlarda (0,5-8,0 mg/L) bir saat bekletilmiş ve ardından bitki büyüme düzenleyici içermeyen kültür ortamına aktarılmıştır. Yaprak eksplantlarından ilk sürgün çıkışları 16. günde 4 mg/L ZEA ön uygulamasında gözlenmiştir. Sürgün rejenerasyon frekansı %16,66-88,89 arasında sıralanmıştır. En yüksek sürgün rejenerasyon frekansları 4 ve 8 mg/L ZEA ön uygulamasında elde edilmiştir. Genel olarak ZEA konsantrasyonu arttıkça sürgün sayısı ve sürgün uzunluğu da artmıştır. Eksplant başına maksimum sürgün sayısı (10,31 sürgün/eksplant) 4 mg/L ZEA ön uygulamasında, en uzun sürgünler ise (2,02 cm) 8 mg/L ZEA ön uygulamasında tespit edilmiştir. Rejenere sürgünler 0,25 mg/L indol-3-butirik asit (IBA) içeren kültür ortamında köklendirildikten sonra dış koşullara başarıyla alıştırılmıştır. Sonuç olarak, ZEA ön uygulamasının B. monnieri’nin in vitro üretimindeki etkinliği kaydedilmiştir.

Strip rotary tillage with a two-year subsoiling interval enhances root growth and yield in wheat

Excessive tillage and soil compaction threaten the sustainable farmlands in the Huang-Huai-Hai Plains of China. Our study explores tillage practices to improve soil and root ecology and promote productivity in the winter wheat fields. We tested the impact of plowing, rotary, strip rotary tillage and strip rotary tillage with a two-year subsoiling interval (SRS) on wheat yield and root quality. SRS decreased soil bulk density compared with other treatments, resulting in lower soil penetration resistance. Root morphology and weight density decreased with the increased soil depth and was higher in SRS. Moreover, SRS increased the indoleacetic acid and trans zeatin riboside levels corresponding to greater TTC reduction activities, the total and active absorption root area. SRS increased the superoxide dismutase and catalase activities and soluble protein concentration and decreased the malondialdehyde concentration. The first two factors extracted using 11 root attributes in various soil layers through principal component analysis were selected as the integrated indicators for the minimum data set, and their integrated score was calculated to quantify the root quality. Our study suggests that SRS could significantly improve root morphology and enhance the root activity in subsoil layers, thus, delaying root senescence and increasing winter wheat yield.