IAA-oxidase Activity Research Articles

Effect of Exogenous Plant Growth Regulators and Rejuvenation Measures on the Endogenous Hormone and Enzyme Activity Responses of Acer mono Maxim in Cuttage Rooting.

The cuttage rooting method for Acer species is difficult to achieve a good efficacy as trees maintain good characteristics at the rejuvenation stage, thus improving the rooting of Acer species. The addition of exogenous hormones and rejuvenation can improve the rooting effect of cuttings; however, the specific regulatory mechanism is still unclear. Here, Acer mono Maxim rejuvenation and non-rejuvenation cuttings were used as test subjects, to investigate the effects of exogenous hormones on the activities of endogenous hormones and antioxidant enzymes in the rooting process of young cuttings. The results showed that exogenous growth-regulating substances significantly improved the rooting rate of A. mono. Exogenous hormones naphthylacetic acid (NAA) + indolebutyric acid (IBA) increased the initial levels of the endogenous hormones, indoleacetic acid (IAA) and abscisic acid (ABA), and the enzyme activities of peroxidase (POD) and polyphenol oxidase (PPO). Rejuvenation treatment prolonged the time of increase in ABA content and indoleacetic acid oxidase (IAAO) activity at the root primordium induction stage, while increasing trans-zeatin riboside (ZR) content and decreasing POD enzyme activity in cuttings. These results demonstrate that A. mono cuttings can achieve the purpose of improving the rooting rate by adding the exogenous hormone (NAA + IBA), which is closely related to the changes of endogenous hormone content and enzyme activity, and these changes of A. mono rejuvenation cuttings are different from non-rejuvenation cuttings.

Morphological, Anatomical, Physiological and Biochemical Changes during Adventitious Roots Formation of Bougainvillea buttiana ‘Miss Manila’

Bougainvillea, a widely used ornamental plant, is mainly propagated by cuttings and tissue culture. Still, large-scale production of Bougainvillea is often difficult because of rooting issues. Therefore, based on an early establishment of the regeneration system for tissue culture in Bougainvillea by our research team, we further studied its rooting mechanism. It was observed that the morphology and anatomical structure of Bougainvillea buttiana ‘Miss Manila’ contained endogenous hormones, such as indole-3-acetic acid (IAA), abscisic acid (ABA), gibberellic acid (GA3), and zeatin-riboside (ZR), including peroxidase (POD), polyphenol oxidase (PPO), and IAA-oxidase (IAAO) activities. Following the culture, Days 0–15 consisted of the induction and initiation stages, while Days 15–25 included the expression stages. No latent root primordium was found in the Bougainvillea plantlet, which belonged to the induced rooting type. The root primordium was derived from callus cells generated by divisions of parenchyma cells in the basic tissues. It was found that the changes in the POD, PPO, and IAAO activities were closely related to the formation of adventitious roots (AR), in which the highest rooting values occurred during the transition from the initiation stage to the expression stage, whereas the endogenous IAA and ABA contents had negative and positive correlations during the induction, initiation, and expression stages.; The values of GA3 and ZR also peaked during the transition from the initiation to the expression stage. ZR and GA3 were found to promote adventitious root formation, while ABA inhibited it. The IAA/ABA, ABA/ GA3, and IAA/ZR ratios also shifted at the onset of the expression stage of AR, indicating these values were closely related to their occurrence. Overall, this study provides the basis for further research considering AR formation in Bougainvillea, and the propagation of various Bougainvillea varieties.

BIOCHEMICAL PROFILE OF EMBRYONIC AND NON-EMBRYONIC CALLUS OF CLERODENDRUM PHLOMIDIS L.

Clerodendrum phlomidis L. (Arani) is a medicinal plant used in the treatment of Diabetes mellitus. Enzymatic studies helps to differentiate between embryonic and non-embryonic callus at very early stage. In vitro experiments were conducted using leaf, stem, node, internode, apical bud as an explant. Callus cultured on MS basal medium supplemented with various combinations of 2, 4-D and Kinetin (1 : 1, 2 : 2, 3 : 3, 4 : 4, 5 : 5 mg/l 2,4-D : Kinetin). Large variations were observed in the callus cultures owing to hormonal variations. Higher hormonal concentration 5 mg/l 2, 4-D + 5 mg/l kinetin resulted in somatic embryoids while lower concentrations 1:1, 2:2, 3:3 mg/l, 2,4-D : kinetin resulted in non-embryonic cells. Enzymatic activities of peroxidase, IAA- oxidase, invertase, protease,  and  amylase, polyphenol oxidase (PPO), catalase and enzyme protein were estimated from cytoplasmic as well as wall-bound fractions of 2, 4, 6and 8 week old callus using standard methods. In two week old culture peroxidase and polyphenol oxidase (both wall bound and cytoplasmic) activity increases in non-embryonic callus and decreases in embryonic callus while IAA oxidase and Protease (both wall bound and cytoplasmic) activity decreases in non-embryonic callus and increases in embryonic callus. Total amylase and α-amylase activity of wall bound enzymes increases in non-embryonic callus and decreases in embryonic callus while cytoplasmic activity decreases in non-embryonic callus and increases in embryonic callus. On the basis of the above study enzymes could serve as a biochemical marker to determine the embryonic and non-embryonic callus at very early stage.

Metabolites in galls induced on the leaves of Trewian udiflora (L.) (Euphorbiaceae) by Trioza fletcheri Crawford (Hemiptera: Triozidae)

Trioza fletcheri Crawford is a sap-sucking psyllid that induces galls on Trewia nudiflora leaves. Early stages of T. fletcheri feed on parenchyma, whereas late-stages and adults feed on phloem, causing galls which arise in an isolated, agglomerated mass and rosette form only on the abaxial surface of T. nudiflora leaves. The feeding action of immature stages induces changes in metabolites of host tissue and creates a nutrition sink for feeding. The biochemical study revealed that galled tissues had higher levels of metabolites (total soluble sugars, reducing sugars, total protein and free amino acids) than ungalled tissues, with average values measuring 3.4±0.09, 1.4±0.1, 0.63±0.03, 1.9±0.23, 3.0±0.72mg/gdw in ungalled leaves; 4.3±0.02, 2.9±0.3, 1.9±0.47, 3.7±0.36, 4.7±0.53 mg/g dw in young galls; 3.8±0.50, 3.7±0.3, 1.03±0.04, 2.9±0.35, 5.4±0.31 mg/g dw in mature galls; and 2.7±0.23, 2.4±0.3, 0.83±0.03, 2.6±0.34 and, 4.3±0.22mg/g dw in old galls, respectively. Enhanced activities of IAA-oxidase, á-amylase, peroxidase, and invertase were observed in galled infested leaves than in ungalled leaves, and their values were measured to be 2.45±0.53, 2.4±0.3, 0.9±0.2, and 3.7±0.5 in ungalled leaves, 2.92±0.32, 3.2±0.2, 1.9±0.5 and 4.5±0.3in young galls, 3.7±0.43, 3.6±0.4, 1.4±0.4, 4.3±0.2 in mature galls, and 2.51±0.03, 2.9±0.4, 1.4±0.4, 3.8±0.1 in old galls respectively.

Nitric oxide is involved in hydrogen sulfide-induced adventitious rooting in tomato (Solanum lycopersicum).

Nitric oxide (NO) and hydrogen sulfide (H2 S) are signalling molecules that regulate adventitious rooting in plants. However, little is known about the cross-talk between NO and H2 S during adventitious rooting. Tomato (Solanum lycopersicum L.) explants were used to investigate the roles of and relationships between NO and H2 S during rooting. Effects of the NO donor sodium nitroprusside (SNP) and the H2 S donor sodium hydrosulfide (NaHS) on adventitious rooting were dose-dependent, and the greatest biological responses were observed under 25μM SNP and 50μM NaHS. The positive effect of NaHS was reversed by the NO scavenger 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), indicating that the H2 S-induced response was partially NO-dependent. Peroxidase (POD), polyphenol oxidase (PPO), and superoxide dismutase (SOD) activities significantly increased by SNP and NaHS treatment, and indoleacetic acid oxidase (IAAO) activity and the O2 - and H2 O2 content significantly decreased by SNP and NaHS treatment. SNP and NaHS treatment also increased the content of soluble sugar and protein and indole-3-acetic acid (IAA). cPTIO significantly mitigated the increases in POD, PPO and SOD activity and soluble sugar, protein and IAA content induced by NaHS. SNP and NaHS upregulated the expression of auxin-related genes (ARF4 and ARF16 ), cell cycle-related genes (CYCD3 , CYCA3 and CDKA1 ), and antioxidant-related genes (TPX2 , SOD and POD ); whereas cPTIO significantly inhibited the increase in the expression of these genes induced by NaHS. Overall, these results show that NO may be involved in H2 S-induced adventitious rooting by regulating the activity of rooting-related enzymes, the expression of related genes, and the content of various nutrients.

Starving longan fruit sends weakened abscission-suppressing signal rather than enhanced abscission-triggering signal to the abscission zone

Fruit abscission is largely governed by carbohydrate supply, and carbohydrate shortage intensifies fruit abscission. Understanding cues from the starving fruit that activate the abscission zone (AZ) is an intriguing research subject and important for control fruit abscission. In this study, starvation stress generated by girdling and defoliating the bearing shoots was used to explore the cues from the starving fruit that triggers abscission in longan. The starving fruit abscised quickly within 5 days. However, removing the starving fruit induced even faster AZ activation with greater ethylene production in the pedicel. Abscission of the defruited pedicel was strongly suppressed by IAA, slightly by ethylene action inhibitor, silver thiosulfate (STS), but not by GA3 or zeatin. Both IAA and ABA concentrations in the starving fruit and the pedicel were significantly reduced compared with the control. IAA exudation from the starving fruit was significantly lower, while IAA oxidase activity in the fruit was higher. The activity of plasma membrane H+-ATPase (PM H+-ATPase) in the fruit and the pedicel was not significantly affected by carbohydrate starvation, while that of PM Ca2+-ATPase in both organs was significantly reduced by starvation. The results suggested that the starving fruit seems not send abscission-promoting signal e.g. ABA or ethylene, but sends weakened abscission-suppressing signal, IAA, to the AZ. The weakened capacity of starving fruit to export IAA is related to increase in IAA deactivation and reduction in PM Ca2+-ATPase activity. The reduced IAA in the AZ leads to increased sensitivity to ethylene synthesized in situ in the pedicel, which activates the AZ under starvation.

Effect of mulching, drip irrigation and fertigation on flowering, physiological and biochemical parameters of nerium (Nerium oleander L.)

A study was conducted to study the effect of mulching, drip irrigation and fertigation on flowering, physiological and biochemical parameters of nerium (Nerium oleander L.) at Department of Floriculture and Landscape Architecture, Horticultural College and Research Institute, Tamil Nadu Agricultural University, Periyakulam in the year 2017. The experiment was laid out in a split split plot design consisting of three factors, viz., factor - I (Black polythene mulch - M1, coir waste - M2 and without mulch - M3), factor - II three levels of drip irrigation (I1- 75 % WRc through drip irrigation, I2 - 100 % WRc through drip irrigation and I3 - 125 % WRc through drip irrigation) and factor - III three levels of fertigation (75 % RDF through fertigation - F1, 100 % RDF through fertigation - F2, 125 % RDF through fertigation - F3 with twenty seven treatment combinations. The results of the study indicated that the treatment M1I2F3 (black polythene mulch + 100 % WRc through drip irrigation + 125 % RDF through fertigation) recorded highest number of inflorescence plant-1and numbers of flowers inflorescence-1, increased chlorophyll content, total phenol content and IAA oxidase activity.

Mechanical stimulation affects growth dynamics, IAA content and activity of POD and IAA oxidase in Petunia x atkinsiana

Ornamental plants are bred and purchased for their aesthetical features such as colorful flowers and leaves, as well as compact and elegant stature. Petunia is one of the most popular bedding plants for urban areas and gardens, therefore, control of its growth and branching is essential. In commercial horticulture, the most common method to control growth dynamics is via growth regulators. Mechanical stimulation is proposed as an environmentally friendly alternative to chemical regulators. In this study, the efficiency of MS was tested on two cultivars of Petunia x atkinsiana. A brushing apparatus was set to stroke apical parts of young plants 40, 60 or 80 times per day between 14 March and 25 April. Several parameters, such as stem length, the number of branches, mature leaf area, the number of open flowers, were measured four times during the whole experiment: three times during the stimulation period, on 20 March, 4 and 25 April, and the last time on 18 May, three weeks after the stimulation stopped. For biochemical analyses, 1 cm apical stem fragments were collected on 20 March, 25 April and 18 May. The results show that MS affects the growth dynamics in petunia, but the response appears to be cultivar specific. In both cultivars, brushing with 80 strokes per day produced the most spectacular effects in growth reduction. On the last day of brushing the POD and IAA oxidase activities in the strongly reacting cultivar were the highest in plants rubbed 80 x per day. The results indicate that MS can be very effective in controlling stem growth in at least some cultivars of petunia, replacing hormonal treatments.

Stress Ameliorative Effects of Indole Acetic Acid on Hordeum vulgare L. Seedlings Subjected to Zinc Toxicity

The heavy metals present in the environment accumulate in the plants and affect their productivity and yield. By entering the food chain, metals cause several serious health problems in human beings as well as in other organisms. Indole acetic acid (IAA) is known to act as a signaling molecule between symbiotic association of metal accumulating plants and plant growth promoting rhizobacteria (PGPR). Present study demonstrated a protective role of IAA against surplus Zinc (Zn)-induced toxicity to Hordeum vulgare seedlings. Elevated Zn concentrations suppressed the plant growth, caused a reduction in leaf relative water contents (RWC) and elevated free proline and non-protein thiols (NPT) accumulation. Zinc treatment also led to enhanced lipid peroxidation (MDA contents) as well as the activity of ascorbate peroxidase (APX), showing the involvement of antioxidative defense mechanism to reduce Zn induced toxicity. IAA oxidase activity was also observed to increase due to Zn treatment. IAA pretreatment of H. vulgare caryopsis could partly revert the Zn-induced toxicity in seedlings.

Rooting and Related Physiological Characteristics Responses to Stolon Cuttings Pre-treatment by Cold Plasma in Centipedegrass (Eremochloa ophiuroides (Munro.) Hack.)

Cold plasma is a new agricultural technology demonstrating wide potential application in plants. Previous studies have elucidated that the cold plasma pre-treatment of seeds improves seed germination and early growth. However, the effects of cold plasma treatment on vegetative propagation, including rooting, remains unclear. In this study, effects of cold plasma treatment on rooting percentage, physiochemical properties in stolon cuttings and physiological characteristics in the rooting process of centipedegrass (Eremochloa ophiuroides (Munro.) Hack.) stolon cuttings were investigated. The centipedegrass stolon cuttings were pre-treated with 0, 150, 300 and 450 W of cold plasma for 15 s. Cold plasma treatments positively stimulated rooting of stolon cuttings, and the 300 W treatment yielded the best effect. Rooting percentage, numbers of adventitious roots, total root length, total root surface area, total root volume, average root diameter, and dry weights of roots were significantly improved by cold plasma treatments. The conductivity and water uptake increased by cold plasma treatments; the auxin (IAA) content and activities of polyphenol oxidase and peroxidase activities improved, and the IAA-oxidase activity decreased; the soluble sugar and protein contents increased after cold plasma treatment. The results of this study not only showed that cold plasma pre-treatment may improve rooting of vegetations but also provided inspiration and support for the application of cold plasma in vegetative propagation of plant.

Hydrogen gas promotes the adventitious rooting in cucumber under cadmium stress.

Hydrogen gas (H2) plays an important role in plant development and stress responses. Here, cucumber (Cucumis sativus L.) explants were used to investigate the roles of H2 in adventitious root development under cadmium (Cd) stress and its physiological mechanism. The results showed that hydrogen-rich water (HRW) promoted adventitious rooting under Cd stress and 50% HRW obtained the maximal biological response. Compared with Cd treatment, HRW + Cd treatment significantly reduced the content of malondialdehyde (MDA), hydrogen peroxide (H2O2), superoxide radical (O2-), thiobarbituric acid reactive substances (TBARS), ascorbic acid (AsA) and reduced glutathione (GSH), as well as relative electrical conductivity (REC), lipoxygenase (LOX) activity, AsA/docosahexaenoic acid (DHA) ratio, and GSH/oxidized glutathione (GSSG) ratio, while increasing DHA and GSSG content. HRW + Cd treatment also significantly increased in the activity and related gene expression of ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR). Additionally, HRW + Cd treatment increased the contents of osmotic adjustment substances, as well as the activities of peroxidase (POD) and polyphenol oxidase (PPO), while significantly decreasing indoleacetic acid oxidase (IAAO) activity. In summary, H2 could induce adventitious rooting under Cd stress by decreasing the oxidative damage, increasing osmotic adjustment substance content and regulating rooting-related enzyme activity.

Endogenous hormone levels and activities of IAA-modifying enzymes during adventitious rooting of tree peony cuttings and grafted scions

During rooting of both cuttings and grafted scions of tree peony (Paeonia suffruticosa Andr.) cultivar ‘Fengdanbai’, the anatomical structure, the contents of endogenous hormones (indole acetic acid, IAA; zeatin, ZT; gibberellin, GA3; and abscisic acid, ABA), and the activities of IAA oxidase (IAAO), peroxidase (POD), and polyphenol oxidase (PPO) were observed. The results showed that the rooting processes in cuttings and grafted scions were similar, but that the critical period of rooting in cuttings was earlier than in grafts (cuttings: 18–20 days; scions: 38–40 days). IAA content showed a direct correlation with rooting, with the peak value appearing as the adventitious roots were breaking through the epidermis in both cuttings and grafts (cuttings: 20 days; scions: 38 days). ZT and GA3 promoted adventitious rooting, and ABA inhibited it. The peak values of the IAA:ABA and IAA:ZT ratios appeared at the same time as the IAA peak (cuttings: 20 days; scions: 38 days), which indicated that these values were closely related to the occurrence of adventitious roots. Changes in the activities of IAAO, POD, and PPO, which modify IAA levels, indicated that there were no direct relationships between these three enzymes and adventitious root formation in cuttings or grafts. These results provide a basis for further study of adventitious root formation in the ornamental tree peony.

Effects of chitosan nanoparticles on seed germination and seedling growth of wheat (Triticum aestivum L.)

To investigate the effect and mechanism of chitosan nanoparticles (CSNPs) on the germination and seedling growth of wheat (Triticum aestivum L.), we conducted systematic research on the impact of different concentrations (1–100 μg/mL) of CSNPs and chitosan (CS). The result of energy-dispersive spectroscopy (EDS) and confocal laser scanning microscopy (CLSM) showed that adsorption of CSNPs on the surface of wheat seeds was higher than that of CS. CSNPs had growth promoting effect at a lower concentration (5 μg/mL) compared with CS (50 μg/mL). In addition, the application of 5 μg/mL CSNPs induced the auxin-related gene expression, accelerated indole-3-acetic acid (IAA) biosynthesis and transport, and reduced IAA oxidase activity resulting in the increase of IAA concentration in wheat shoots and roots. The results suggest that CSNPs have positive effect on seed germination and seedling growth of wheat at a lower concentration than CS due to higher adsorption on the surface of wheat seeds.

Root promoting effect and its regulation mechanisms of endophytic Bacillus amyloliquefaciens YTB1407 in sweet potato

We isolated the endophytic Bacillus amyloliquefaciens YTB1407 from the root of Panax quinquefolium, which has both biological control and growth promoting effects. To investigate its potential applications, a pot experiment of sweet potato was tested to assess the capacity of endophytic colonization of YTB1407 and the selection of its optimum concentration by investigating the performance of root characteristics on three time points in the whole early growth phase after irrigating with different concentrations of bacterial suspensions with treatment of sterile water as control. The activities of endogenous hormone IAA, ZR, t-ZR and IAA oxidase (IAAO, PPO, POD) were analyzed. The results showed that YTB1407 promoted the specific colonization of root system, the elongation of adventitious root and branch roots, and root activity in the early growth stage of sweet potato. At later growth stage, it formed greater fresh mass of absorption root and lower aboveground/root system mass ratio. YTB1407 suspensions with OD600 of 0.50 (T0.50) had more significant effect, which induced the highest fresh tuber mass and the largest effective tuber numbers of per plant at top cover stage. YTB1407 promoted the differentiation of adventitious roots into tubers at initial point of tuberization by increasing IAA content and the ratio of (t-ZR+ZR)/IAA, decreasing IAAO activity and enhancing PPO activity. Moreover, it promoted the differentiated roots into tubers at tuberization stage by keeping the higher content of IAA, lower ratio of (t-ZR+ZR)/IAA, and decreasing IAAO and PPO activities.

Mycorrhiza-induced change in root hair growth is associated with IAA accumulation and expression of EXPs in trifoliate orange under two P levels

Abstract Root hair growth can be regulated by substrate nutrient levels, phytohormones, and arbuscular mycorrhizal (AM) fungi. However, the information about effects of AM fungi and substrate phosphorus (P) levels on root hair features is scarce. This study evaluated the effect of an AM fungus, Funneliformis mosseae, on root hair morphology, root indole-3-acetic acid (IAA) level, indole-3-acetic acid oxidase (IAAO) activity, and expressions of auxin-related genes and expansins (EXPs) in trifoliate orange (Poncirus trifoliata) seedlings under 0.1 mM (P0.1) and 1.0 mM (P1) P levels for 16 weeks. AM seedlings showed better root colonization under P0.1 than under P1. Under P0.1 and P1, mycorrhizal seedlings recorded higher concentrations of P and IAA and lower IAAO activity in roots than non-mycorrhizal seedlings. Root hair density was significantly higher in AM seedlings under P0.1 but dramatically lower under P1 than non-AM seedlings. Root hair length and diameter of AM seedlings were significantly increased under P1 only, relative to non-AM seedlings. Indole-3-pyruvate monooxygenase (PtYUC2) and auxin transporter-like protein 3 (PtLAX3) expressions in roots were significantly up-regulated by mycorrhizal treatment under both P0.1 and P1. The transcript levels of root auxin efflux carrier component 2 and 8 (PtPIN2 and PtPIN8) were dramatically down-regulated by mycorrhizal inoculation, irrespective of P levels. Root PtEXPB2, PtEXPA2, and PtEXPA4 expressions were notably up-regulated by mycorrhiza under P0.1 but down-regulated under P1. These results indicated that mycorrhiza-induced changes in root hair growth is closely related with up-regulated expressions of EXPs and simultaneous IAA accumulation in roots.

Cadmium stress inhibits the growth of primary roots by interfering auxin homeostasis in Sorghum bicolor seedlings

Phytotoxic effects of cadmium (Cd), a heavy metal pollutant, on plants have been extensively examined. Auxin plays vital roles in many aspects of plant development. The association between root growth and auxin signaling in Cd-stressed Sorghum bicolor was analyzed in our study. Root elongation, shoot length and the maximal photochemical efficiency (Fv/Fm) in S. bicolor seedlings were dramatically reduced after Cd stress treatment. Cd was found to be predominantly confined in the meristematic zone using a Cd-staining method. Cd stress remarkably influenced the cell cycle progression at the root tip as shown by EdU (ethynyl deoxyuridine) assay. The content of IAA was markedly diminished in the roots of Cd-stressed S. bicolor, which was along with the increase of IAA oxidase activity. Auxin transport inhibitors, 1-naphthoxyacetic acid (1-NOA) or 1- naphthylphthalamic acid (NPA), greatly reduced plant tolerance to Cd stress, whereas exogenous application of 1-naphthaleneacetic acid (NAA) improved Cd tolerance in S. bicolor seedlings. Cd stress altered the transcript level of some putative auxin biosynthetic genes. In addition, NAA interfered with the homeostasis of Cd-induced reactive oxygen species (ROS). These results revealed that Cd stress disturbed the growth of S. bicolor seedlings by affecting the homeostasis of auxin and ROS.

The metabolic constituent and rooting-related enzymes responses of marigold explants to hydrogen gas during adventitious root development

Recent evidence suggests that hydrogen gas is involved in multiple physiological process in plants. However, the physiological mechanism of hydrogen gas on adventitious rooting is largely unknown. In this report, marigold (Tagetes erecta L.) was used to determine the effect of hydrogen gas on physiological changes during adventitious root development. The results showed that 50% hydrogen-rich water significantly increased root number and length of marigold explants. Hydrogen-rich water treatment provoked a significant reduction of stomatal aperture which might be associated with the increase of relative water content. Hydrogen-rich water decreased electrolyte leakage during adventitious rooting. The content of water-soluble carbohydrate, starch and soluble protein were higher in normal water-treated controls than in hydrogen-rich water-treated explants. Compared with the control, the application of hydrogen-rich water increased peroxidases, polyphenol oxidase and indoleacetic acid oxidase activity. Results indicated that hydrogen gas promotes adventitious root development through the increase of relative water content, metabolic constituents, rooting-related enzymes and simultaneously keeping cell membrane integrity.

Effects of IBA on adventitious root development and the associated metabolic changes during softwood cutting rooting of sweet cherry rootstocks Gisela 6

In order to study the physiological mechanism underpinning the success of softwood cutting of sweet cherry rootstock Gisela 6 (Prunus cerasus × Prunus canescens), the effects of indole-3-butyric acid (IBA) on adventitious root development and changes of activities of peroxidase (POD), polyphenol oxidase (PPO), indoleacetic acid oxidase (IAAO), total soluble sugar content, total nitrogen content, and C/N ratio during rooting were investigated. The results showed that the rooting percentage, root numbers and the average root length increased significantly when treated by IBA. The treatment of 1000 mg L-1 IBA exhibited the best rooting responses. The rooting percentage, root numbers and the average root length were 81.2%, 10.5 and 2.95 cm, respectively. Compared with the control, they increased by 133.3, 262.1 and 45.3%, respectively. The activities of PPO and POD increased more significantly during the rooting period when treated by IBA. It also induced more total soluble sugar accumulation and increased C/N ratio. However, the total nitrogen content did not changed significantly. These results indicated that IBA increased rooting activities of Gisela 6 softwood mainly owing to the increase of the activities of PPO and POD, the total soluble sugar content and C/N ratio and the reduction of the IAAO activity.

Effect of Auxins and Associated Metabolic Changes on Cuttings of Hybrid Aspen

In the present study, an attempt was made to induce rooting from single-node cuttings of hybrid aspen (Populus tremula L. × P. tremuloides Michx.) with different concentrations of Indole-3-acetic acid (IAA), Indole-3-Butytric acid (IBA) and 1-Naphthylacetic acid (NAA). Among the three auxins used, 0.54 mM NAA showed more effective induction on rooting as compared to IAA and IBA at the whole level. Thereafter, 0.54 mM NAA was used further for the anatomical and biochemical investigation. The results showed that it took 12 days from the differentiation of primordium to the appearance of young adventitious roots under NAA application. It was found that endogenous IAA, Zeatin riboside (ZR) and Gibberellic Acid (GA3) levels increased, but Abscisic acid (ABA) decreased in cuttings with NAA treatment. In contrast to the endogenous IAA level, NAA resulted in a decrease in IAA-oxidase (IAAO) activity. Similarly, the decreased peroxidase (POD) activity, consistent with down-regulation of expressed levels of POD1 and POD2, was observed in NAA-treated cuttings. Moreover, NAA resulted in a higher activity in polyphenol oxidase (PPO) compared with control cuttings. Collectively, the study highlighted that 0.54 mM NAA is efficient on rooting in hybrid aspen, and its effect on metabolic changes during rooting was discussed, which can provide valuable information for propagating hybrid aspen.

Inhibition of IAA oxidase activity of wheat anionic peroxidase by chitooligosaccharides

The study demonstrated that chitooligosaccharides with a molecular weight of 5–10 kDa and a degree of acetylation of 65% exhibited an auxin-like effect in wheat plants and also played an important role in regulating the activity of polysaccharide (chitin)–specific anion isoenzymes of peroxidase oxidizing indole acetic acid. Changes in the kinetic parameters of the interaction of the wheat anionic chitin-specific peroxidase with pI ∼3.5 with chitin oligomers in the presence of indoleacetic acid were pH-depended and indicated that chitooligosaccharides significantly impair the ability of the enzyme for oxidation at pH levels of 4.2 and 6.0. It can be assumed that chitooligosaccharides not only induce protective plant systems but also increase the accumulation of auxin in plant tissues, thus adversely affecting a number of components of the plant protective system against pathogens.