IAA Oxidase Research Articles

PoARRO-1 regulates adventitious rooting through interaction with PoIAA27b in Paeonia ostii

Adventitious root (AR) formation is a limiting factor in the vegetative propagation of tree peony (Paeonia suffruticosa Andr.). PoARRO-1, which encodes an auxin oxidase involved in AR formation, plays a role in the root development of P. ostii, but its associated molecular regulatory mechanisms are not yet understood. In this study, we examined the role of PoARRO-1 in AR formation in P. ostii. The overexpression of PoARRO-1 in P. ostii test-tube plantlets led to a notable enhancement in both the rooting rate and the average number of ARs in vitro, as well as increased activities of peroxidase (POD), superoxide dismutase (SOD), and indoleacetic acid oxidase (IAAO). PoARRO-1 was involved in the conversion of IAA-Asp and IAA-Glu to OxIAA and promoted IAA oxidation. RNA sequencing analysis revealed that PoARRO-1 overexpression led to upregulation of enzyme activity, auxin metabolism related genes. Further analyses showed that PoARRO-1 interacted with the 1–175 aa position of PoIAA27b to regulate the formation of ARs. We therefore propose that PoARRO-1 interacts with PoIAA27b to promote AR formation, and it may be useful targets for enhancing the in vitro propagation of P. ostii.

NnARF17 and NnARF18 from lotus promote root formation and modulate stress tolerance in transgenic Arabidopsis thaliana

Auxin response factors (ARFs) play a crucial role in regulating gene expression within the auxin signal transduction pathway, particularly during adventitious root (AR) formation. In this investigation, we identified full-length sequences for ARF17 and ARF18, encompassing 1,800 and 2,055 bp, encoding 599 and 684 amino acid residues, respectively. Despite exhibiting low sequence homology, the ARF17- and ARF18-encoded proteins displayed significant structural similarity and shared identical motifs. Phylogenetic analysis revealed close relationships between NnARF17 and VvARF17, as well as NnARF18 and BvARF18. Both ARF17 and ARF18 demonstrated responsiveness to exogenous indole-3-acetic acid (IAA), ethephon, and sucrose, exhibiting organ-specific expression patterns. Beyond their role in promoting root development, these ARFs enhanced stem growth and conferred drought tolerance while mitigating waterlogging stress in transgenic Arabidopsis plants. RNA sequencing data indicated upregulation of 51 and 75 genes in ARF17 and ARF18 transgenic plants, respectively, including five and three genes associated with hormone metabolism and responses. Further analysis of transgenic plants revealed a significant decrease in IAA content, accompanied by a marked increase in abscisic acid content under normal growth conditions. Additionally, lotus seedlings treated with IAA exhibited elevated levels of polyphenol oxidase, IAA oxidase, and peroxidase. The consistent modulation of IAA content in both lotus and transgenic plants highlights the pivotal role of IAA in AR formation in lotus seedlings.

Effect of ethrel and gibbrellic acid on bio-chemical changes and productivity of sugarcane (Saccharum species hybrid complex)

The present study was conducted during the spring seasons of 2015–16 to 2017–18 to investigate the effects of application of ethrel and gibbrellic acid on growth, yield and sucrose content of spring planted sugarcane in order to work out its potential to be used as germination and growth enhancer in subtropical region. The treatments viz., planting of setts after overnight soaking in water, T2 ; planting of setts after overnight soaking in 50 ppm ethrel solution, T3 ; planting of setts after overnight soaking in 100 ppm ethrel solution, T4 ; T1 + GA3 spray @ 35 ppm at 90, 120 and 150 DAP, T5 ; T2 + GA3 spray @ 35 ppm at 90, 120 and 150 DAP, T6 ; T3 + GA3 spray @ 35 ppm at 90, 120 and 150 DAP, T7 and T4 + GA3 spray @ 35 ppm at 90, 120 and 150 DAP, T8 were compared with T1 (conventional planting/farmers practice treatment). Sugarcane growth, yield, and quality parameters were significantly influenced by various treatments. Owing to enhanced reducing sugars, acid invertase (AI), indole acetic acid oxidase (IAAO) and superoxide dismutase (SOD) activity in treated setts, planting of setts after overnight soaking in 50 ppm ethrel solution resulted in higher germination count at 10, 20, 30, 40 and 50 days after planting (DAP). Planting of setts after overnight soaking in 50 ppm ethrel solution + GA3 spray @ 35 ppm at 90, 120, and 150 DAP resulted in a greater plant population at all stages of growth, which was responsible for a higher number of millable canes at harvesting. Treatment planting of setts after overnight soaking in 50 ppm ethrel solution + GA3 spray @ 35 ppm at 90, 120 and 150 DAP recorded higher leaf area index at 180 and 240 DAP. Similarly, treatment (T7 ) also recorded higher shoot and root dry weight at 120, 180, 240 and 300 DAP. Net assimilation rate during 120–180 DAP (5.78 g/m2 /day) and 180–240 DAP (3.95/m2 /day) were also recorded highest in treatment T7 . Similarly, planting of setts after overnight soaking in 50 ppm ethrel solution + GA3 spray @ 35 ppm at 90, 120 and 150 DAP recorded higher cane yield (101.2 t/ha) and net returns (166.25 × 103 `/ha) with a benefit: cost ratio of 1.31 which was significantly higher than farmers practice and planting of setts after overnight soaking in water. Thus, planting of setts after overnight soaking in 50 ppm ethrel solution + GA3 spray @ 35 ppm at 90, 120 and 150 DAP should be adopted to obtain the maximum productivity and profitability by spring sugarcane.

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.

Spirulina platensis improves growth, oil content, and antioxidant activitiy of rosemary plant under cadmium and lead stress

In the present study, a pot experiment was conducted to investigate the response of rosemary (Rosmarinus officinalis L.) plants to foliar application of Spirulina platensis at 0.0, 0.1, 0.2, and 0.4%; soil irrigation with heavy metals (Cd nitrate, Pb acetate, and Cd + Pb, each at 100 ppm), and Spirulina platensis at 0.1% + heavy metals. Spirulina platensis significantly improved growth parameters, oil yield/fed, photosynthetic pigments, and activity of superoxide dismutase (SOD), glutathione reductase (GR), catalase (CAT), and polyphenol oxidase (PPO) with a maximum promoting effect at 0.2% algal extract. On the other hand, heavy metal stress reduced growth criteria, photosynthetic pigments, and oil yield, while, significantly increased levels of antioxidant enzymes (SOD, CAT, GR) and corresponding non-enzymatic antioxidants (ascorbic acid, total antioxidant capacity, phenolics and flavonoids). Bioaccumulation factor (BF) and translocation factor (TF) indicated that Cd and Pb accumulated largely in the roots, with little transfer to the shoots. Nevertheless, compared with heavy metal treatments, S. platensis at 0.1% significantly increasing growth parameters, oil content, photosynthetic pigments, and the activity of non-enzymatic and enzymatic antioxidants, while, slightly reduced TF of Cd and Pb, alleviated membrane lipid peroxidation, and significantly lowered the content of malondialdehyde, hydrogen peroxide, and indole acetic acid oxidase (IAAO) activity in heavy metal (Cd, Pb, and Cd + Pb)-treated rosemary plants.

TRITERPENE GLYCOSIDES AS PLANT GROWTH REGULATORS: POTENTIAL AND PROSPECTS FOR USE (RE-VIEW)

The increased interest in the study of the growth-regulating activity of triterpene glycosides (TG) in recent years is largely due to the need to create new highly effective environmentally friendly plant growth biostimulants, the use of which is considered as an important strategy in managing the productivity and stress resistance of agricultural crops. Тhe review presents information available in the literature on phytoregulatory activity TG with an emphasis on their growth-stimulating properties. The physiological effects of TG in bioassays on phytohormonal activity are considered. The auxin- gibberellin- and cytokinin-like effect of TG on growth and metabolism (changes in the activity of enzymes: α-amylase, peroxidase, catalase, polyphenol oxidase, IAA oxidase, nitrate reductase, chlorophyll and protein content), was shown depending on the structure of TG, concentration and the tested plant. The issues of the mechanism of the growth-stimulating action and the possible involvement of TG and free triterpenes in physiological processes in plants are discussed. The relationships between the structure and phytoregulatory activity of TG was analyzed. The effect of exogenous TG and triterpenoids on plants under abiotic stresses, as well as the possibility of using some TG, extracts of saponin-bearing plants (Сamellia sp., Silphium perfoliatum, Medicago sativa, Glycine max, Vigna radiata, Glycyrrhiza glabra, Moringa oleifera, Solidago gigantea, Centella asiatica, Eclipta alba, Quillaja saponaria, Bacopa monnieri et al.) and plant extracts containing triterpenoids (Abies sibirica, Betula sp.) in crop production as plant growth regulators, is considered.

Analysis of oxidase activity and transcriptomic changes related to cutting propagation of hybrid larch

Hybrid larch is the main timber and afforestation tree species in Northeast China. To solve the problem of rooting difficulties in larch cutting propagation, enzyme activity determination and transcriptome sequencing were carried out on the rooting tissues at five timepoints after cutting. peroxidase (POD), indole acetic acid oxidase (IAAO) and polyphenol oxidase (PPO) play important roles in the larch rooting process after cutting. A total of 101.20 Gb of clean data was obtained by transcriptome sequencing, and 43,246 unigenes were obtained after further screening and assembly. According to GO analysis and KEGG enrichment analysis, we think that plant hormones play an important role in the rooting process of larch stem cuttings. in the plant hormone signal transduction pathway, a larch gene c141104.graph_c0 that is homologous to the Arabidopsis AUX1 was found to be significantly up-regulated. We suggest that AUX1 may promote IAA transport in larch, thus affecting adventitious root development. According to the results of POD, PPO IAAO indexes and GO analysis, we think s1 and s2 periods may be important periods in the rooting process of larch stem cuttings, so we built a gene regulatory network, a total of 14genes, including LBD, NAC, AP2/ERF, bHLH and etc., may be important in different stages of cutting propagation. As the rooting rate after cutting inhibits the development of larch clone propagation, identifying the genes that regulate rooting could help us to preliminarily understand the molecular mechanism of adventitious root formation and select a better treatment method for cutting propagation.

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.

ABA-responsive AREB1/ABI3-1/ABI5 cascade regulates IAA oxidase gene SlDAO2 to inhibit hypocotyl elongation in tomato.

Hypocotyl elongation is dramatically influenced by environmental factors and phytohormones. Indole-3-acetic acid (IAA) plays a prominent role in hypocotyl elongation, whereas abscisic acid (ABA) is regarded as an inhibitor through repressing IAA synthesis and signalling. However, the regulatory role of ABA in local IAA deactivation remains largely uncharacterized. In this study, we confirmed the antagonistic interplay of ABA and IAA during the hypocotyl elongation of tomato (Solanum lycopersicum) seedlings. We identified an IAA oxidase enzyme DIOXYGENASE FOR AUXIN OXIDATION2 (SlDAO2), and its expression was induced by both external and internal ABA signals in tomato hypocotyls. Moreover, the overexpression of SlDAO2 led to a reduced sensitivity to IAA, and the knockout of SlDAO2 alleviated the inhibitory effect of ABA on hypocotyl elongation. Furthermore, an ABA-responsive regulatory SlAREB1/SlABI3-1/SlABI5 cascade was identified to act upstream of SlDAO2 and to precisely control its expression. SlAREB1 directly bound to the ABRE present in the SlDAO2 promoter to activate SlDAO2 expression, and SlABI3-1 enhanced while SlABI5 inhibited the activation ability of SlAREB1 by directly interacting with SlAREB1. Our findings revealed that ABA might induce local IAA oxidation and deactivation via SlDAO2 to modulate IAA homoeostasis and thereby repress hypocotyl elongation in tomato.

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.

Response of Castor Seedling Roots to Combined Pollution of Cd and Zn in Soils

Castors are used to remediate heavy-metal-polluted soils due to their good ability to accumulate heavy metals. However, only limited studies addressed the interaction between heavy metals and castor seedling roots. In this study, the physiological response of castor seedling roots to Cd and Zn stress, and the change in trace elements in rhizosphere and non-rhizosphere soils were investigated. The results showed that, with an increase in Cd concentration, the accumulation of Zn in roots decreased by 20%, indicating a competition between Cd and Zn accumulation. The increase in Cd content enlarged the difference in nutrient contents at different depths: the amounts of P, Fe, and Mn were more in rhizosphere soils than in non-rhizosphere soils, while the amount of K showed an opposite trend. The addition of Cd and Zn stimulated root growth, but root activity was reduced. The addition of Cd and Zn affected the root cell morphology, including increases in the root cortex thickness and the root xylem area. The contents of the enzymes SOD, POD, and MDA increased with the addition of Cd and Zn, while the activity of CAT first increased and then decreased. There was no significant change in the soluble protein content. The decrease in IAA oxidase content, from 40.1% to 72.7%, was conducive to plant growth. To sum up, high contents of Cd and Zn in soils not only affect the root morphology and increase the gap in the contents of K, P, Fe, and Mn between rhizosphere and non-rhizosphere soils but also change the SOD, POD, MDA, and IAA contents in the root, so as to reduce the amount of root damage caused by the external environment.

Allelopathy and Allelochemicals of Leucaenaleucocephala as an Invasive Plant Species.

Leucaena leucocephala (Lam.) de Wit is native to southern Mexico and Central America and is now naturalized in more than 130 countries. The spread of L. leucocephala is probably due to its multipurpose use such as fodder, timber, paper pulp, shade trees, and soil amendment. However, the species is listed in the world’s 100 worst invasive alien species, and an aggressive colonizer. It forms dense monospecific stands and threatens native plant communities, especially in oceanic islands. Phytotoxic chemical interactions such as allelopathy have been reported to play an important role in the invasion of several invasive plant species. Possible evidence for allelopathy of L. leucocephala has also been accumulated in the literature over 30 years. The extracts, leachates, root exudates, litter, decomposing residues, and rhizosphere soil of L. leucocephala increased the mortality and suppressed the germination and growth of several plant species, including weeds and woody plants. Those observations suggest that L. leucocephala is allelopathic and contains certain allelochemicals. Those allelochemicals may release into the rhizosphere soil during decomposition process of the plant residues and root exudation. Several putative allelochemicals such as phenolic acids, flavonoids, and mimosine were identified in L. leucocephala. The species produces a large amount of mimosine and accumulates it in almost all parts of the plants, including leaves, stems, seeds, flowers, roots, and root nodules. The concentrations of mimosine in these parts were 0.11 to 6.4% of their dry weight. Mimosine showed growth inhibitory activity against several plant species, including some woody plants and invasive plants. Mimosine blocked cell division of protoplasts from Petunia hybrida hort. ex E. Vilm. between G1 and S phases, and disturbed the enzyme activity such as peroxidase, catalase, and IAA oxidase. Some of those identified compounds in L. leucocephala may be involved in its allelopathy. Therefore, the allelopathic property of L. leucocephala may support its invasive potential and formation of dense monospecific stands. However, the concentrations of mimosine, phenolic acids, and flavonoids in the vicinity of L. leucocephala, including its rhizosphere soil, have not yet been reported.

Characterization of the antagonism of the mycorrhizal fungus Waitea circinata against Magnaporthe oryzae, Cochliobolus miyabeanus, Monographella albescens and Sarocladium oryzae rice pathogens

Rice production is affected by important pathogens such as Magnaporthe oryzae, Cochliobolus miyabeanus, Monographella albescens and Sarocladium oryzae, and orchid mycorrhizal fungi can contribute to the biocontrol of these diseases. The aim of this study was to characterize the antagonism mechanisms of W. circinata against rice pathogens. The indoleacetic acid (IAA) and lytic enzymes of W. circinata were quantified. The effectiveness of the bioagent and its metabolites was assessed in vitro. Antagonism in vivo against rice blast was also investigated. Waitea circinata produced IAA (2.3 µg ml-1), cellulase and polyphenol oxidase in a qualitative test. Glucanase, chitinase and protease were also produced in culture with cell walls and in co-culture with pathogens to explain antibiosis. W. circinata acts on direct antagonism by antibiosis and volatile metabolites. Mycelial suspension reduced M. oryzae conidial germination, appressorium formation, and rice blast by 61, 82 and 84%, respectively. W. circinata, a unique bioagent, controls four rice pathogens from mechanisms of parasitism and antibiosis. The results could contribute to new formulations containing this fungus, enzymes as well as its volatile metabolites.

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.

Comparing Rooting Ability and Physiological Changes of Two Eucommia ulmoides Improved Varieties

Eucommia ulmoides (E. ulmoides) is a significant national strategic resource in China. It is a natural high quality rubber resource, with great development potential. We found large differences in rooting ability during adventitious root (AR) formation in two E. ulmoides improved varieties. Therefore, we used two improved varieties of E. ulmoides, ‘Huazhong 6’ (H6, with rooting rate 85.3%) and ‘Huazhong 8’ (H8, with rooting rate 22.5%) to explore the cutting rooting mechanism. In this study, we mainly determined the morphological development process of E. ulmoides cutting rooting, and compared the rooting-related indexes of the two improved varieties, and the changes in physiological indexes closely related to rooting, which include endogenous hormones, oxidases and nutrients in the phloem of the basal stem. The results showed that indole–3–acetic acid (IAA), zeatin riboside (ZR), IAA/ZR and indoleacetic acid oxidase (IAAO) were the key factors that caused big differences in rooting ability between the two E. ulmoides improved varieties. The increase in endogenous hormone IAA content and IAA/ZR value were necessary for the formation of AR. The increase in IAA content was beneficial to AR formation. The activity of IAAO was significantly negatively correlated with the rooting ability of the E. ulmoides cuttings. The high IAAO activity of the H8 cuttings led to the consumption of IAA. Although the content of IAA increased, the rooting conditions were not reached. The accumulation of nutrients before rooting also has an important effect on rooting; it is easy for cuttings to root when the carbon–nitrogen ratio (C/N) value is high. This research provides an improved understanding of the cellular and physiological underpinnings of the AR process in woody plants. In addition, it provides a theoretical basis and foundation for subsequent research on E. ulmoides cuttage technology.

Endophytic Aspergillus niger reprograms the physicochemical traits of tomato under cadmium and chromium stress

This study aimed to evaluate the effect of endophytic fungi isolated from Cucurbita roots on growth, physiological, biochemical and molecular attributes of Solanum lycopersicum L. under Cd and Cr stress. The initial screening experiments on Oryza sativa L. seedlings revealed a plant growth promoting endophyte (Cu-17) out of the 17 isolated strains. The strain was identified as Aspergillus niger by amplifying ITS region of 18 S rDNA. A pot experiment was set to evaluate the effect of A. niger on S. lycopersicum exposed to two different concentrations (100 μg/g and 500 μg/g) of Cd and Cr. A. niger alleviated Cd and Cr stress in S. lycopersicum by reducing its translocation to the aerial parts of the host plant. A. niger also enabled the S. lycopersicum to produce significant amounts of IAA, proline, flavonoids, phenols, catalase (CAT) and ascorbic acid oxidase (AAO), in addition to sugar and proteins. Moreover, A. niger facilitated the S. lycopersicum to induce stress responsive genes (SlGSH1 and SlPCS1) in order to develop tolerance against the Cd and Cr stress. Both SlGSH1 and SlPCS1 genes helped the S. lycopersicum to chelate Cd and Cr and thus mitigate their toxicity. The results, therefore, conclude that A. niger might be used as biofertilizer for healthy and safe crop production in Cd and Cr contaminated soils.

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.